# Will the size of my ducts have to be changed?



## beenthere (Oct 11, 2008)

Doubt your neighbor needs 4 tons, and doubt you need 5 tons.

Might want to do a load calc and find out what size you really need, can save you a lot of money. 

http://www.hvaccomputer.com/gtarget1.asp?kwx=38&adx=4&gclid=COr9k9X0qbUCFQSqnQodVmgAsQ

49 dollar fee to use for 60 days as I recall.


----------



## TarheelTerp (Jan 6, 2009)

beenthere said:


> Doubt your neighbor needs 4 tons, and doubt you need 5 tons.
> Might want to do a load calc...


Pawl... don't start multiple threads to discuss the same issues.

Mostly the same people are reading them all and they will mostly the same advice will be given... but details will tend to be lost by dividing the flow.


----------



## sammy37 (Dec 9, 2008)

Your neighbor would have probably been better off in the 2 to 2.5 ton range. Please make sure the contractor you hire performas a load calculation. You say you've added insualtion and replaced windows? That will help quite a bit in reducing the tonnage needed.


----------



## digitalplumber (Jul 8, 2011)

Pawl, as another homeowner, let me tell you my experience. My home was built in 98 and soon after we moved in. It was an energy star rated home by the local utility, which was suppose to mean it had a lot of sealing, double pane windows and insulation, etc. I only say this because I know yours is not and to point this out. I live in Houston Texas.

I have 3600 square feet with 1800 up and down. The load calc done on this home said it needed 2 3 ton units. (unofficial rule of thumb is 400 sq feet per ton) While the 3 ton downstairs was ok, it certianally was not for the upstairs. So we argued and fought with the builder and the AC company and after letting them do balancing and checking over and over, with no good results, we gave them a choice: replace the units with 4 tons, or go to court.

They replaced both units with 4 ton units. Yes my electric bill went up some, but we accomplished the comfort levels and operations that we wanted from the units, especially upstairs.

So my point to you is as one homeowner to another is this: you are in a very old home, in contrast to mine which has a lot of insulation and energy efficient stuff. If you want comfort on the days when it gets tough outside, you probably will need to go bigger than what the load calc suggests. I base this on the old age of your home and poor insulation and sealing in walls and attic.

So based on the 400 per square foot unofficial theory and poor insulation and sealing, 5 tons could be what you want. Would the experts here agree, probably not because they prefer to build based on a load cals. But I have seen more and more where some experts have said that sometimes they need to re-evaluate the load calc and listen more to the customer.

In my case, the smaller 3 ton unit upstairs would run and run on extremely hot days. I know that a unit needs to run a ceertian amount of time in order to remove humidity. Cycling too fast is not good. Once we put the 4 ton in, not only would it cycle on the challenging days, but it felt more comfortable.

One other thing that you need to consider for comfort that also assisted us was the addition of more return airs, especially upstairs. This assisted in comfort, in my opinion, but adding these alone would not have resolved the long run times on hot days.

I am not an expert, there a lot of great ones here for those opinions! I can only tell you that from a homeowners standpoint, you may have to be ready to put your foot down on what gets installed. I think load calcs are great on new built tight and sealed homes.

JMO.


----------



## beenthere (Oct 11, 2008)

Load calc doesn't have ability to account for heat rising from first floor to second floor. Your first floor unit probably should have stayed a 3 ton, as the upstairs cool air also falls down to the first floor. If you had kept the first floor 3 tons. It would probably have a much better humidity level.

The second floor probably would have been fine with a 3.5 ton. Splitting hairs? maybe, but often a 1/2 ton increase in size will reduce temp by 6 to 8 degrees, and keep the humidity in much better check.

Your also forgetting your location compared to other posters. Your area is a hotter area.


----------



## digitalplumber (Jul 8, 2011)

beenthere said:


> Load calc doesn't have ability to account for heat rising from first floor to second floor. Your first floor unit probably should have stayed a 3 ton, as the upstairs cool air also falls down to the first floor. If you had kept the first floor 3 tons. It would probably have a much better humidity level.
> 
> The second floor probably would have been fine with a 3.5 ton. Splitting hairs? maybe, but often a 1/2 ton increase in size will reduce temp by 6 to 8 degrees, and keep the humidity in much better check.
> 
> Your also forgetting your location compared to other posters. Your area is a hotter area.


Thanks and you are probably right about the 3 .5 .

Thanks for the info on heat calc, see after many years I have learned again how wrong they were in what they told me!

Thanks


----------



## Pawl (Mar 5, 2008)

I am going to be talking about a lot of things on here because I value everyone's opinion so be patient. I am all over the place trying to get questions answered. I am looking into the suggestion for a do it yourself $49 load calculation as we speak. I feel I can do the load calculations myself and maybe a more thorough job because its my house and I have more time. 

I have popped a piece of drywall out on the 2nd floor where the original ducting in the 1st floor attic changes in size from 8" round to rectangular (5'h x 14"w x 3"d) to fit into the vertical wall going up and comes back out in the 2nd floor attic 6" round in diameter. And my hunch was right --->>>. After cutting away the drywall I could see the original installer did not seal all joints properly so heat has been leaking out of this rectangular ducting in the wall since the house was built in 1965.

I needed to open the wall anyway because I am going to have to run return air ducts from the 2nd floor ceilings to the 1st floor attic.There are no return air ducts because the house has never had air conditioning. I will just position the return air ducting in between the wall studs right next to the existing rectangular duct.

Is it true that each room should have the ceiling register where air is coming out of positioned in each room closer to the area where the heat is the highest? Say for example near a window that brings in more heat from the sun as opposed to an interior wall in the same room. I just figured the middle of the room. 

After determining where to put the ceiling registers where or how far away does the return air vents go in the same room. On the 2nd floor would I include return air ducts in the bathroom and the small area at the top of the stairs with the walkway to each bedroom?


----------



## beenthere (Oct 11, 2008)

Bathrooms don't get returns. Don't want all the odor spread through out the house.

Return in the ceiling of the second floor landing will help a lot in cooling season.

The supplies should throw the air toward the highest heat gain/loss area. Returns should not be in any direct line of throw from the supply register. So if the supply is in the middle of the room. The return should then be near the inside wall.


----------



## Pawl (Mar 5, 2008)

1.) Does the area at the top of the stairs need a return or supply duct? The square footage of floor area on the 2nd floor landing is 51 sq.ft

2.) Do you feel that using rigid duct is the best way to go? Original duct is rigid,pretty dirty inside and 48 years old so I am going to change it.

3.) Just for my education today is their a rule of thumb when talking about return ducts. Are they the same size as supply or 75%,50% or 25%. 

4.) I am going to run new ducting so I can move supply registers closer to heat gain/loss (window). Are there ceiling register configurations you feel are better than others? It sounds like a rectangular one placed in the ceiling dispursing air four ways is the way to go.

5.) Upstairs there is a total of 381sq.ft in both bedrooms plus 40 sq.ft in bathroom. Is it worthwhile or even possible to try and isolate the 2nd floor when using only one ac/heating unit for the whole house?

6.) Is it possible to put something in the duct system that gives me a choice to direct air only to first floor? I rarely go upstairs. Most of my time I spend downstairs. I saw this clip on the internet where this family would shut down certain areas of the house but it was causing a whistle in the floor registers from too much pressure in one zone area so they placed a weighted damper in the supply duct routing the additional pressure back into the return duct.


----------



## bobinphx (Nov 25, 2011)

hope this helps... 

1. supply us with a drawing, including windows and all here can help you locate the supplies and returns for you. 

2. I believe that the best choice for duct work is rigid steel. Note that old ducts can be cleaned, so dirt is not the issue. Air leaks (sealing), izing and rust are issues that could be corrected with new ductwork. 

3. Standards for returns are tied to the size of the supply ductwork size and air handler sizes. Supply ductwork sizes are tied to the room size and calculated hot and cold expectations based on windows, insulation, air tightness, air handler size, throw of air from the register, noise and orientation of the room to the sun. static pressure within the system is the form of measurement you need to test, along with FPM air flow at the air filter. There is lots and lots of math and science that goes into design of the ductwork. In order to get it right you have to have a real pro design it or do the homework information gathering on the internet. Dont mean to scare you away from doing your own work, it is possible!!!!! (I did it !!)

4. drawings of the floor plan would help the forum tell you the best placement of supplies and returns!! even a napkin drawing would be good!!

5. zoning is what you are thinking of.... yes, zoning is good and possible, but it has some drawbacks. its my understanding that a correctly built zone system can do what you want, but with anything, that extra ablility to control things comes at a cost. Time, money, complexity and maintiance. But it can be done!!!!!!!!!

6. it is possible... but the supply to return pressure bleed off sure seems like a hack job to me.. I think what you are looking for is a single hvac unit and two duct (supply and return) systems tied to the single unit, with the ability to switch between the two, given the need. This is great and would be really neat if it was all automatic and all designed to provide the correct air flow into the two zones in all circumstances. given the proper controls and sizing everything is possible.. but cost and complexity enter into the idea... as well as effency.. as I would guess there is no insulation and air sealing between your floors so keeping the heat or cool between the floors might be tough. but it could be done...

again, this is just one guys opinions and self taught knowledge.


----------



## Pawl (Mar 5, 2008)

I did the $49 residential load calculation myself. Under the Whole House totals it showed The Total Heat Loss BTUH was 39,758 & Total Heat Gain BTUH was 17,631. The Latent Heat Gain BTUH was 1,495 and Sensible Gain BTUH was 16,136. Below the Total Heat Gain column it listed (1.5 tons). The square footage totaled 1626. 
Maybe someone can give an explanation of these numbers to better educate me. Thanks


----------



## TarheelTerp (Jan 6, 2009)

Pawl said:


> I did the $49 residential load calculation myself.
> Maybe someone can give an explanation of these numbers to better educate me.


They're saying that your 1626SF house in mild California...
doesn't much help to maintain a comfortable temperature. 

Some additional reading:
http://www.engineeringtoolbox.com/latent-sensible-cooling-load-d_245.html


----------



## Pawl (Mar 5, 2008)

These are the Design Conditions that the program used for my area in Cypress,Calif. 
Indoor: Summer Temperature: 75 - Winter Temperature: 72 - Relative Humidity: 50
Outdoor: Summer Temperature: 80- Winter Temperature: 43 - Summer grains of moisture: 84 - Daily Temperature Range: Medium

1.) Under Total Heat Gain (BTUH) they listed 19,238 (1.5 tons) - Are they saying I need a 1.5 ton A/C unit under these Design Conditions listed at the top to maintain those temperatures?


----------



## beenthere (Oct 11, 2008)

Pawl said:


> These are the Design Conditions that the program used for my area in Cypress,Calif.
> Indoor: Summer Temperature: 75 - Winter Temperature: 72 - Relative Humidity: 50
> Outdoor: Summer Temperature: 80- Winter Temperature: 43 - Summer grains of moisture: 84 - Daily Temperature Range: Medium
> 
> 1.) Under Total Heat Gain (BTUH) they listed 19,238 (1.5 tons) - Are they saying I need a 1.5 ton A/C unit under these Design Conditions listed at the top to maintain those temperatures?


Yes, that is what they are saying.


----------



## Pawl (Mar 5, 2008)

I was watching the sun today relating it to my house. The rear faces east. Sun hits the clear glass patio door & windows around 7am to 11am. Neighbor behind me and over one has a two story house blocking the sunrise a little longer. Southside has no windows/doors. Northside gets no sun. West side (front) starts seeing sunlight on windows around 2 pm to sunset. Entry door is set back 2 ft in so door gets no sun exposure. No wonder my house is so cold when the heater is not on. Duh?

Attached garage is on northwest side blocking half the west side sun exposure. Eaves all the way around 1st and 2nd story are 3' deep with 2x8 facia so it blocks some sun. Two small 14x33 windows at the top of stairs are blocked from the sun partially by facia. I have a 95x33 window on southside 2nd story that gets sun all day. My point to all of this is that for a residential house I think it is positioned pretty good to ward off sunlight. 

I have to figure out my next move to get this rolling. I have to find someone to work with me designing a ducting system,where to place supply/returns and an A/C unit. Just randomly calling a contractor is not going to work because most want to come in, do it all in a few days and be gone. I am trying to do as they say," Measure twice and cut once". 

I just cant believe my neighbors have a 3 bedroom house with a 3 ton unit, one has a two story with a 4 ton unit and the last one is a two story with a 5 ton unit. Mine calculates out at 1.5 tons?


----------



## bobinphx (Nov 25, 2011)

1.5 tons.... yup,,, its hard to believe... 

but its all about the target temps and run times at the target temps. 


so lets look at the hottest day and what your hvac system will be doing. 

lets say that between 2pm and 4pm it is 80 degrees outside (your summer outdoor target temp) and 75 degrees inside. Your system is designed to run 100 percent of the time with these conditions (in this case between 2 and 4 pm). so you are saying... I dont want my ac running all the time!!!! well, thats the misconception. HVAC systems do not become effecent until at least 10 minutes has passed while they are running. The initial start up is a huge rush of current, but after that the pressures etc equalize and the amount of energy levels off at a fairly reasonable rate. so yes, your ac system will be running a lot at your target temp. but you will be saving the start and stop costs that others are paying.

The next idea to get your head around is when the outside temp is not at 80, but lets say 78. At this point, you should start to hear the system cycle, still more on then off, but the run times should still be fairly long. with an oversized system you will be running very short times, never long enough to get into the economy zone and believe it or not that start stop process is hard on the equipment.

the closer you get to your indoor and outdoor target temps matching, the shorter your run times will get until you dont need the hvac (temps indoors and outdoors the same)... .

so what if the outside temp is 82 (2 degrees above your design temp)..well your system will not be able to keep the house at 75 degrees for the time period that it is 82 degrees outside. it may only keep the inside 76 degrees. +-


so now lets look at your neighbor with the 4 ton system. His system, at the 80 degree outdoor target temp and 75 indoor temp, will run a very short time. chances are it will never get past the 10 minutes of hard running. His bill will be higher. The energy to start it and then stop it and then start it etc will be more then yours which ran for 2 hours in the heat of the day. His system will not last as long as yours will. 

so now comes a bit of the magic and your input into the design.... the question becomes, is 75 degrees enough to keep you cool?? if not, change that number in your calculations... maybe 78 is cool enough for you... you could put that numnber in.. also think about other heat loads... do you have massive parties in the afternoons with kids and friends running in and out... well, your hvac system may not be able to keep the house at 75 degrees.. but do you want to oversize your system for that occasion??? there are lots of pieces to this, but its my understanding that the manual j is very well done and will work for you!!! 

now lets look at my system 

2500 sq feet, 115 outdoor design temp, 75 degree inside temp, design calcs say 3.5 to 4 tons.. I have 5 tons and the longest run I have is about 30 minutes when its 119 out. so my system is oversized (I joke to my family that our ac system will keep the house cool when its 146 degrees outside as per the manual J!!)it also costs me more to run then it should.. I found all this information after I had a new system put in. We went from a seer 10 to 14 and the utilities increased!!! 

Have fun and remember this is not rocket science, you will have to make compromises and in the end, you will sleep well at night being an informed consumer.


----------



## Pawl (Mar 5, 2008)

Thanks for that explanation bobinphx! Trying to understand something here. When I did the Manual J calcs I just inserted the name of my city where I live and the program gave me the Design Conditions. 

1.) So are these the recommended temperatures to keep the inside of my house comfortable and to have a 1.5 ton unit run the most efficient? 

And as far as having fun I am like you. I have a mechanical brain. For instance with my house I kept wondering where I could run return ducts because this house has never had air. So the old heating duct that transitioned up to the 2nd floor attic is set between the vertical studs so the return can just go up between the studs right next to it. I had a feeling that the existing vertical duct probably was leaking just because work that cant be seen is usually hurried and the drywall covers it. Sure enough the duct was never sealed from day one so heated air has been coming out since 1965 when it was built. I wonder how much. The ducts are 48 years old. Time to throw them out. 

For me personally the challenge is more fun than the end result but in this case I will come out of this very comfortable during the hot weather. 

2.) If you have any recommendations on what brands a/c - heater units to buy I am all ears. I dont know if you have an extensive background in this area but it sure sounds like it. I cant wait to tell someone I need a 1.5 ton for my two story house.

3.) I intend on using rigid supply duct again. Is it also better to run the rigid return duct? 

I also learned from the Manual J calcs I can add some batts in my attics to go from R 11 to R 19. Every little bit helps. I cant believe your summer temps in Arizona.


----------



## Pawl (Mar 5, 2008)

1st floor drawings of my floor plan


----------



## Pawl (Mar 5, 2008)

2nd story floor plan - "W" stands for windows - "S" is for existing heating supply registers. 1st floor attic entry is small entrance door in right upstairs bedroom. I was thinking of putting new rectangular supply registers closer to windows which seem to get the most heat coming through the glass.The bedroom on the right gets full sun exposure all day long being its on the south side. East window in the other room gets full sun from sunrise until 11 am. Two small windows side by side on west side get very little direct sun but exposure is from about 2pm until sunset.


----------



## Missouri Bound (Apr 9, 2011)

I too think that is oversized. I have a two level 2800 sq. ft. home and I have a 3 ton heat pump. I do live in a warmer climate though, Southern Missouri, and the winters are not very cold. (it's 62 here today)


----------



## Pawl (Mar 5, 2008)

west side (front). ridge vents for roof,turbine vents which I have been told need to be removed, skylight, solar tube, front door is set back 2' from west wall,eaves are 3' deep underneath, 2 x 8 facia and double pane windows. The 2 bd rm windows and window by porch start getting sun exposure around 2pm until sunset, 2 small windows up on 2nd story dont get much sun.


----------



## Pawl (Mar 5, 2008)

east side - all windows/patio door get sun from sunrise to 11am. Window up above on west side gets full sun all day long. Patio door is dbl pane too. I took this picture at 1130am and you can see everything is already in the shade. My 1st brick planter job at my house in 1986. Not bad for reading a book to learn how to do it.Those bricks fell off a bldg in a Calif earthquake and they were giving them away if you just came and got them. 27 years later I wish I had left them. Ha ha


----------



## Pawl (Mar 5, 2008)

1965 pull chain dampers


----------



## Pawl (Mar 5, 2008)

You are looking in the attic through 2nd story bedroom attic door. You are looking at 24" plenum with one 8" branch running around 1st floor attic feeding several 6" supply registers. 

When I 1st moved into this house the top of that 24" plenum was open like a can of tuna where the lid starts lifting when you have a couple more turns before its open. I had to push lid back down and seal it. How long did those people I bought my home from wonder why the house was not getting warm? 

The one that is capped off was another 8" duct that fed the 2nd story but I am replacing all the duct so I took it out. I live alone so I dont need heat on the 2nd floor right now. The next picture is the closet of the 2nd story bd rm. I had to open the wall to take out the rectangular duct that was never sealed right from the moment they installed it in 1965 so it has been leaking heat FOREVER. 

In the next picture u will be able to see where I will be running the new return ducts in between studs right next to where old supply duct ran. I love this kind of work. 

I want the new unit right where the 24" plenum is. I dont want it closer to this 2nd story bd room in case it makes any kind of noise


----------



## Pawl (Mar 5, 2008)

2nd story closet - where the pink foil is the old duct ran there and rose vertically. To the right is where the foil is showing and the return will go in between those studs. I will have new ducts and a new unit = a happy man


----------



## sammy37 (Dec 9, 2008)

What a beautiful house! I wish more people in Vegas would take pride in older homes like that but it just doesnt happen here, its a dump.

Your neighbors may not have had a manual j ran when they did their systems, hence the wide range of sizing, many people are affraid to go too small.

Many people here have told me that 3 tons will not cool my 1835 sq ft home in Vegas, we currently have a 4 ton unit but it will work. I have a crane scheduled for this weekend and will be doing the swap. I also blew a ton of insulation into the attic and completely sealed all of the ductwork.


----------



## Pawl (Mar 5, 2008)

Thanks for the compliment. I bought this house in 1986 as a fixer upper. I did everything you see in the pictures,landscape,windows,lighting,roof,skylight,solar tubes,painted it twice and on and on. I just stole all the ideas of the newer houses in the area,took off the old looking design and now it has great curb side appeal.

If I did not know how to do something I kept asking questions. Most everything is paid for because I did the work. I have some things to still do to seal my house up tighter like fireplace,more batts in the attic,front door seal,etc,.. All the things I should have done long ago.

1.) Are you changing 4 ton to 3 ton because the 4 ton needs replacing?

2.) I put a swamp cooler in here years because I could just never afford a complete AC unit, That cooler kept this house very comfortabe unless it was a humid day. We don't get humidity that often. But for $350 I used that unit for 10 years. And my electric bill did not go up much.So I am pretty certain a 1.5 ton unit will work fine. My kids are grown and gone. It is 99.5% of the time me just living here so I should be fine.


----------



## Pawl (Mar 5, 2008)

If I am going to go where most people in my neighborhood are afraid to go meaning a smaller unit I need to:

1.) Find me the best 1.5 ton unit that is out there.

2.) Place those return and supply registers in the most optimum place.

3.) Seal up all the leaks I can find because that will make a big difference.

4.) Put more insulation in the places I can access.

5.) Trust that I have done my homework.

6.) Any input would be greatly appreciated on anything,placement of registers, what brand ac/heater unit to go with. Anything...............

7.) Any thoughts on how big the heater should be?


----------



## sammy37 (Dec 9, 2008)

Pawl said:


> Thanks for the compliment. I bought this house in 1986 as a fixer upper. I did everything you see in the pictures,landscape,windows,lighting,roof,skylight,solar tubes,painted it twice and on and on. I just stole all the ideas of the newer houses in the area,took off the old looking design and now it has great curb side appeal.
> 
> If I did not know how to do something I kept asking questions. Most everything is paid for because I did the work. I have some things to still do to seal my house up tighter like fireplace,more batts in the attic,front door seal,etc,.. All the things I should have done long ago.
> 
> ...


The 4 ton unit is only 6 years old but when I replaced it, I changed it out from the original unit which was also a 4 ton unit. I was always taught in the old days to change equipment like for like, or go on 400 sq ft per ton, which I've learned over the last few years is a no no.

We also originally had a gas unit and by some stupid brainstorm, I thought going heat pump would be the better way but lately I'm not sure in comparing our power bill with the neighbors gas bill. I think gas has dropped in price here over the last few years.

Anyway, I'm going back in with a 3 ton gas packaged unit. 

You say you've been running a swamp cooler down there? We have also for years but my Mrs hates them and when I put the new unit up, the swamp cooler which is up there on the roof also, will be coming down for good.


----------



## Pawl (Mar 5, 2008)

Check out my decorative looking swamp cooler. I set it up (1st floor outside) on the north side where its pulling in the coolest air, I cut a hole in the house to set the opening in,set it on some wall blocks. I can't turn it on high or it will blow your hairpiece off but on low I can live with it. I divert the air to the right so it bounces off the wall away from me. 

Once a person understands the concept of how it works it really cools the house. It's worthless on humid days but we don't have many. I just close all the doors of all the rooms I am not using to make the area to be cooled smaller and I am set. We used the same concept to clear smoke out of a house after a fire when I was working. But those days are over cause I am moving on up to a deluxe air conditioner.


----------



## Pawl (Mar 5, 2008)

$20 decorative cover for the off season when not in use to keep the cold air out of the house. I probably use this cooler 3 to 4 months of the year. Its just not like having air conditioning but it was better than nothing when I could not afford an air conditioning unit. For that I am grateful.


----------



## Pawl (Mar 5, 2008)

could anyone tell me from my drawings where the best place to put the return vents in the ceilings? Is it basically as far away from supply registers as possible?


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> could anyone tell me from my drawings where the best place to put the return vents in the ceilings? Is it basically as far away from supply registers as possible?


 
We put ours as you describe, an opposite corner away from vent and its throw.


----------



## Pawl (Mar 5, 2008)

1.) I read about the pros and cons on rigid duct and flex. As far as return ducting is concerned does rigid or flex come into the conversation?

2.) Is it beneficial to make the return ducts length back to unit as short as possible? meaning every little bit helps


----------



## Pawl (Mar 5, 2008)

Click here: Big Air Heating & Air Conditioning 

>>>>> from the article -To prevent having to call a repairman, Consumer Reports says invest in a more reliable brand, including ones from American Standard, Rheem, or Trane. Any thoughts?


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> 1.) I read about the pros and cons on rigid duct and flex. As far as return ducting is concerned does rigid or flex come into the conversation?
> 
> 2.) Is it beneficial to make the return ducts length back to unit as short as possible? meaning every little bit helps


 
I would think the answer to this is yes, especially if using flex duct. Also curves and turns should be minimal.

I would think that resistance, like in a supply line made of flex, would also be found in a return with flex, but will wait to hear from the experts.


----------



## TarheelTerp (Jan 6, 2009)

Pawl said:


> To prevent having to call a repairman... Any thoughts?


Like with cars... there are two levels to repair work.

One is the basic mechanical components themselves which with few exceptions are essentially the same as they have always been for almost 100 years. The second level is the whiz bang controls and electronics laid over top of those basic components.

The savings from operating efficiencies (X fewer CF of gas, Kwh of electricity, etc) are quickly lost let alone when more than a $5 DIY thermocouple replacement is keeping the furnace from heating the house.. let alone a really expensive controller is needed.


----------



## beenthere (Oct 11, 2008)

Pawl said:


> Click here: Big Air Heating & Air Conditioning
> 
> >>>>> from the article -To prevent having to call a repairman, Consumer Reports says invest in a more reliable brand, including ones from American Standard, Rheem, or Trane. Any thoughts?



Bet big Air Heating and Air Conditioning is a Trane or A/S dealer. Consumer reports ratings on A/C and heating brands is very flawed. But they admit the difference of their rating from best to worse, is so slight, it makes no difference.

The brand is really of little importance. The installation is of major importance.

I just condemned a Trane gas furnace, 8 years old, has a bad heat exchanger. While Trane will supply the heat exchanger for free. The customer will be paying a good amount of money for me to change it out.


----------



## Pawl (Mar 5, 2008)

1.) With a design layout if there are sections that are longer than a 3' or 4' say like 6' would you recommend making the ducts as long as possible that will fit in the attic to reduce joint leaks and ultimately turbulence/friction? 

2.) Would you expand on this statement? >>>>>>> The brand is really of little importance. The installation is of major importance

When you say "installation" do you mean getting the right size unit for my house through a load calc, getting the new ducts engineered right and installed with no leaks, getting the right thermostat for my house? Maybe you could suggest the other things you would identify as the necessary things to complete the installation right.

Here is what I think you mean when I interpret that statement that "the installation is of major importance". 

I have been a backyard auto mechanic for 45 years. I currently maintain 4 Hondas for my 3 daughters and myself. When I do preventative maintenance on these cars I buy the best replacement parts available because my family is driving these cars. I only stayed with Honda because the 1st car I bought my oldest daughter was a Honda in 1998 so it made my life easier and I had the Honda tools to keep duplicating the same preventative measures all these years. I could have easily started with a Toyota. And what I think you are saying is the different brands are nearly all the same its putting it all together correctly that makes it or breaks it.


----------



## Pawl (Mar 5, 2008)

The fact that I am installing A/C in a house that only had forced heating I would think I need an engineer to crush the numbers to create the size ducts based on the size unit I go with. Yes? 

I have drawings of all the rooms in my house as seen on here. I have the load calculations for him. He probably just needs to walk through my house to get a look - see while I point out to him where I think vents should be based on the calculations. What is this persons actual title and where do I find a patient one. Maybe late 50s like me? Retired would be even better. One with lots of experience. What if I went to my local sheet fabricating metal guy near my home? I actually have one I use.


----------



## beenthere (Oct 11, 2008)

Sections of what longer then 3 or 4 foot? If you mean sections of a trunk line, sealing joints is part of corrct installation.

By installation. I mean unit sized sized right, ducts sized right, correct type registers for the volume and air through you need.


----------



## digitalplumber (Jul 8, 2011)

for 300 you can have these folks design

http://www.audubonsupply.com/browse.cfm/complete-hvac-ductwork-design-layout/4,10010.html


----------



## Pawl (Mar 5, 2008)

1.) Thanks I figured this one out ----> Sections of what longer then 3 or 4 foot? If you mean sections of a trunk line, sealing joints is part of corrct installation.

2.) By installation. I mean unit sized sized right, ducts sized right, correct type registers for the volume and air through you need. ------ Will the correct type registers be based on unit size,duct size,etc,....?


----------



## Pawl (Mar 5, 2008)

I went to a guy named Steve who I have been using for years who fabricates sheet metal for all sorts of applications. He has made ducts for me in the past. Its funny he never talks much when I do business with him but today I had more knowledge about my goal and I was able to talk shop with him. I also asked him if he knew anyone in the HVAC business who knew their stuff and would patiently work with me putting a system in my house with me doing some of the grunt work to cut cost.
He said he had only one guy he would ever let work on anything for his home so he gave me the phone # and Monday I am going to see if I can meet with him. Lets keep our fingers crossed. If I am not comfortable with him I will look for someone else. I have worked hard to get to this point and this forum has taught me alot I dont intend on settling for less than almost perfect. Thanks Gentlemen - I will update next week - the harder you work the luckier you get!


----------



## Pawl (Mar 5, 2008)

I fine tuned this load calculation program today and found a few mistakes I made. But I was really surprised when the total results today ended up recommending only 1 ton when the 1st one I did recommended 1.5 ton.

How I figured out how this happened was when I was inputting living 
room numbers the selection for ceiling type in living rooms gave 4 choices: 1.) under ventilated attic 2.) under unheated room 3.) roof on exposed beams/rafters 4.) roof-ceiling combinations. 

My living room ceiling is under the 2nd story. There are two bedrooms above the living room ceiling.So there is no choice to make with the program so I assume I just dont put anything regarding the living room ceiling. 

I realized when I got the 1.5 ton recommendation on my 1st calculation that it was because I put the living room ceiling information into the program. I had inputted one of those 4 choices when in fact I should not have put anything. When I leave the ceiling type out of the calculations the program recommends 1 ton.

The total on the sheet of 1600 plus sq feet is the right square footage for my house. I just want to make sure my load calculations are right before I walk into to meet HVAC guy and he thinks I am crazy. I entered all exterior walls,window sizes,patio door,ceiling sq ft where it is applicable,doors,etc,... I dont look at these sheets with the results everyday but once a person goes over this program a couple of times its not that hard. The recommendations are also based on outdoor temperatures which are listed on the front of this sheet. Any thoughts?


----------



## beenthere (Oct 11, 2008)

Since they don't make a 1 ton, you'll still get a 1.5 ton. id you enter a value for additional heat gain for kitchen appliances.


----------



## digitalplumber (Jul 8, 2011)

Your at 13,800 with no heat load consideration as BT said, I would do the 1.5, even if they had a 1.0.







Pawl said:


> I fine tuned this load calculation program today and found a few mistakes I made. But I was really surprised when the total results today ended up recommending only 1 ton when the 1st one I did recommended 1.5 ton.
> 
> How I figured out how this happened was when I was inputting living
> room numbers the selection for ceiling type in living rooms gave 4 choices: 1.) under ventilated attic 2.) under unheated room 3.) roof on exposed beams/rafters 4.) roof-ceiling combinations.
> ...


----------



## Pawl (Mar 5, 2008)

1.) I included 1200 btuh's for the kitchen appliances and another 1000 btuh's as suggested by this program for the computer in the family room.

2.) Is it also safe to say that under Design Conditions the outdoor temperature given by the program for summer temperatures is correct? I assume those numbers are the most update average over a lot of years. 

3.) Is a 1.5 ton unit large enough to cool my house during a heat wave where we are up the high 90s and even higher. I understand heat waves are not an everyday normal temperature I am just asking how a 1.5 ton unit will handle a heat wave. Southern Calif in notorious for high temps.

4.) How does a 1.5 ton unit handle keeping my house warm during the winter. Is a 1.5 ton recommended size for a unit from a load calculation a measurement for air conditioning only or is it for both heating and air conditioning? My current 1975 heating unit is rated @ 100,000 btuh and 80,000 btuh (bonnet capacity).


----------



## Pawl (Mar 5, 2008)

I need help with this:

When I first filled out the Manual J Calculations online program I inputted under "Design Conditions" the name of my city (Cypress,Ca) it automatically showed for my city a Summer temperature of 80 and a Winter temperature of 43, Summer grains of moisture @ 84,and a daily temperature range was Medium.

When I look at neighboring cities on these tables I see Summer temperatures of 88/89 so I felt something was not right. So I brought up the Manual J Load Calculations chart which shows a California Micro Climate table on page 32 that lists my city of Cypress. For Cypress this table shows a Summer Temperature of 89 and a Winter temperature of 38.

Now when I manually input this Summer Temperature of 89 and Winter Temperature of 38 it now shows I need a 2 ton unit. 

1.) Does this sound right to everybody?

2.) If that in fact is right does the "Summer grains of moisture 84" change and does the "Daily temperature range of Medium" change?

Click here for Manual J load calculations chart: http://www.energystar.gov/ia/partners/bldrs_lenders_raters/downloads/Outdoor_Design_Conditions_508.pdf


----------



## TarheelTerp (Jan 6, 2009)

Pawl said:


> Now when I manually input this Summer Temperature of 89 and Winter Temperature of 38...
> 
> Does this sound right to everybody?


You're the one who lives there. You tell us if it sounds right.

Thirty five years ago lived up the coast a bit in Newport (and Costa Mesa) 
I don't recall it being that cold (or warm).
http://en.wikipedia.org/wiki/Newport_Beach,_California#Climate


----------



## digitalplumber (Jul 8, 2011)

Will a 1.5 work, dont know sounds like my scenario with the 3 ton. It worked mostly, but would run a very long time on the hot days and just be ok. If that bothers you, then I suggest you go to 2 tons and make sure you can be comfortable on the extreme days.

REMEMBER i am speaking to you as a homeowner to another homeowner, I am not an expert.




Pawl said:


> I need help with this:
> 
> When I first filled out the Manual J Calculations online program I inputted under "Design Conditions" the name of my city (Cypress,Ca) it automatically showed for my city a Summer temperature of 80 and a Winter temperature of 43, Summer grains of moisture @ 84,and a daily temperature range was Medium.
> 
> ...


----------



## beenthere (Oct 11, 2008)

An almost 10 degree increase in outdoor summer design temp would easily increase size by 1/2 ton. What was the new sensible load it gave you for cooling.


----------



## Pawl (Mar 5, 2008)

I am assuming that the information the Acca Manual J Load calculations program is putting out is accurate but I am a 1st time user of this program and following a lot of recommendations to do a load calculation on my home first. I have not had anyone tell me to be careful about any misinformation coming from this program so I assume it is up to date but that is all I can be certain of until I do some more research.

I am going to try and find out some more sources of information to come to a conclusion on the temperatures in my area. With that said I am going to have to do some more homework on how they are coming up with their numbers. 

1.) Are the summer and winter outdoor temperatures an average of the last 5 years,10,20 or even the last 30? 

2.) What specific months are considered winter months and what months are summer as far as the calculations are concerned?

I looked up Newport Beach and Costa Mesa under the California Micro Climate table shown on the Acca Manual J Load calculations program. 

(Summer/Winter temperatures/Elevation) for N.Beach were S76/W41/E10' --- Costa Mesa were S77/W38/E75' --- both of these cities are right by the ocean.

These next 4 cities including mine are all next to each other. We are approximately 14 miles from the ocean. Summer/Winter temperatures/elevation for Cypress are S89/W38/E75' ----Cerritos are S89/W40/E34' --- Stanton S88/W38/E45' --- Buena Park S89/W38/E75'


----------



## beenthere (Oct 11, 2008)

The summer design temp is the 97 1/2% temp. meaning only 2.5% of the time in a normal summer will the temp get above the design temp.

Not sure how many years the design temp is calculated from.


----------



## Pawl (Mar 5, 2008)

beenthere said:


> An almost 10 degree increase in outdoor summer design temp would easily increase size by 1/2 ton. What was the new sensible load it gave you for cooling.


updated calculation which is 9 degrees higher on the summer temperature than the original calculation of 80 degrees and its saying or recommending a 2 ton unit. If you scroll up the original calculation is at the top of this page


----------



## beenthere (Oct 11, 2008)

A 2 ton will just barely meet your sensible cooling load. A 2.5 ton with the blower set to 350 CFM per ton will meet it with a little to spare. And provide better heat in the winter.


----------



## Pawl (Mar 5, 2008)

beenthere said:


> A 2 ton will just barely meet your sensible cooling load. A 2.5 ton with the blower set to 350 CFM per ton will meet it with a little to spare. And provide better heat in the winter.


I am trying to understand how the CFM works. 1.) Are you saying at 350 CFM per ton a 2.5 ton unit will produce 875 CFM? 

2.) If 875 CFM is true then will the new duct system will be designed to deliver that amount to all the rooms in my house and the HVAC people will balance the system distribute to this amount? 

3.) What specific months are considered winter months and what months are summer as far as the calculations are concerned?

4.) And provide better heat in the winter <<<< did you mean a 2.5 ton versus a 2 ton will provide better heat?


----------



## Pawl (Mar 5, 2008)

From what I have read it sounds like for Design Conditions concerning Outdoor averages regarding Summer and Winter temperatures they are actually tracked over the entire year.


----------



## beenthere (Oct 11, 2008)

The temps are tracked over many full years. How many is what I'm not sure of anymore.

The duct system should be designed for the full 400 CFM per ton(1000CFM for a 2.5), and then the blower set to only move 350 CFM per ton(875CFM). The installers should balance it out to each rooms needs then. With any excess air being equally allotted to each room.

Which months are in what category varies slightly by area. Here Sept is neither winter or summer, since or the most part neither heat or cooling is needed. Look up the heating and cooling degree days for your area, And you be able to see what months are in which category.


----------



## digitalplumber (Jul 8, 2011)

What kind of furnace/heat are you putting in: Electric, Gas or a heat pump with backup strips?

Tons, per se, relates to AC size and BTU's relates to heat. Heat (Gas and Electric) usually requires less cfm to a room, versus AC cfm. I believe and will be corrected, that a heat pump uses same cfm for heat and cool mode.

So your outside AC condensor is rated at 2 tons and your furnace/blower is rated at a number from the manual j, just say 80,000 BTU for heat (80 or 90% efficiency) and will have a fan speed adjustment for the AC size. (As BT has stated above will need to be adjusted.)


----------



## Pawl (Mar 5, 2008)

Is cfm measured by the amount of pressure coming out of each supply register? 
My old heater (1975) uses natural gas and is rated at 100,000 BTUH with a bonnet capacity of 80,000 BTUH. I dont know how much calculating went into homes back in 1975.


----------



## Pawl (Mar 5, 2008)

I found some weather data for my area where the point of meaurement was 2.5 miles away. I was hoping HVAC people I find can use this in figuring out correct tonnage. Maybe you guys can take these numbers and give me some insight. Is 6 years far enough to go back to get some useful averages?

Days over 89 degrees during each year below: 

2007 - (5 days) 91 degrees 2x, 95 degrees 1x, 96 degrees 1x, 97 degrees 1x 
2008 - (20 days) 90 degrees 4x, 91 3x, 92 1x, 93 3x,94 2x, 95 4x, 97 1x, 99 1x, 100 1x 
2009 - (18 days) 90 degrees 3x, 91 1x, 92 3x, 93 5x, 94 2x, 96 1x, 97 1x, 99 1x, 102 1x
2010 - (14 days) 90 degrees 1x, 91 1x, 92 4x, 93 1x, 94 1x, 95 2x, 96 1x, 98 1x, 103 1x, 109 1x
2011 - (9 days) 91 degrees 4x, 92 3x, 94 1x, 100 1x
2012 - (16 days) 90 degrees 2x, 91 1x, 92 3x, 93 3x, 94 2x, 96 2x, 99 2x, 102 1x
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
89 degree days during each year below:

2007 - 6 days
2008 - 5 days
2009 - 4 days
2010 - 1 day
2011 - 3 days
2012 - 5 days

88 degree days during each year below:

2007 - zero
2008 - 2 days
2009 - 1 day
2010 - 3 days
2011 - 3 days
2012 - 10 days

87 degree days during each year below:

2007 - 4 days
2008 - 9
2009 - 1
2010 - 3
2011 - 2
2012 - 6

86 degree days during each year below:

2007 - 10 days
2008 - 11
2009 - 7
2010 - 4
2011 - 4
2012 - 6

85 degree days during each year below:

2007 - zero days
2008 - 3
2009 - 1
2010 - 1
2011 - zero
2012 - 7

84 degree days during each year below:

2007 - 10 days
2008 - 5
2009 - 3
2010 - 3
2011 - 6
2012 - 8

83 degree days during each year below:

2007 - zero days
2008 - 4
2009 - 5
2010 - 4
2011 - 3
2012 - 8

82 degree days during each year below:

2007 - 10 days
2008 - 15
2009 - 11
2010 - 6
2011 - 8
2012 - 6

81 degree days during each year below:

2007 - zero days
2008 - 3
2009 - 12
2010 - 3
2011 - 6
2012 - 10

80 degree days during each year below:

2007 - 9 days
2008 - 11
2009 - 15
2010 - 3
2011 - 4
2012 - 4


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Will a 1.5 work, dont know sounds like my scenario with the 3 ton. It worked mostly, but would run a very long time on the hot days and just be ok. If that bothers you, then I suggest you go to 2 tons and make sure you can be comfortable on the extreme days.
> 
> REMEMBER i am speaking to you as a homeowner to another homeowner, I am not an expert.


As one homeowner to another my issue here is I have never had air conditioning in my house using ducts so I have nothing to compare it too. I just had the smaller/larger window units,box fans,and ceiling fans, I have a much better understanding of what I am looking for after reading everything on this site. That is why I thought I would try to find the weather pattern for where I live and see if that would help add to a more informed decision.

When it comes to leaning one way or the other on tonnage meaning if I have a choice to go up a half a ton after compiling all the information I might hold firm. After doing all this research my house is starting to remind me of that statement that people always make when they say your house is always cold. 
Since 1989 I was a single dad with 3 daughters playing sports,girl scouts,homework and we were always on the go. As funny as this sounds I did not consciously notice on a daily basis how my house felt at different times of the year by whatever was going on.Too busy raising kids all the time. I was always on my feet doing something so some of the tendencies of this house are only being noticed now because I have the time but mostly because I am putting in air conditioning and its part of solving the what size do I need question.
I am noticing that my house seems to stay relatively cool now with the way it faces west,dbl pane windows, 3' deep eaves all around the house up and down insulation,only one window upstairs that gets full sun all day,the rest get 4-6 hrs of sun,I live alone most of the time, I am going to have a new unit with new ducts that are totally sealed and insulated and there are other things I can still do to seal up my house some more from air leaks. I will also have enough information in hand to show an HVAC installer that I have done my homework.


----------



## Pawl (Mar 5, 2008)

beenthere said:


> The summer design temp is the 97 1/2% temp. meaning only 2.5% of the time in a normal summer will the temp get above the design temp.
> 
> Not sure how many years the design temp is calculated from.


On my current Manual J Calculations under "Design Conditions" I set the Outdoor Summer temperature at 89 degrees:

Days over 89 degrees during the 365 day year in my weather data research for my city:

2007 - 5 days = 1.4%
2008 - 20 days = 5.5%
2009 - 18 days = 4.9%
2010 - 14 days = 3.8%
2011 - 9 days = 2.5%
2012 - 16 days = 4.4%

Have I got this right?


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> What kind of furnace/heat are you putting in: Electric, Gas or a heat pump with backup strips?
> 
> I assume I will be using a gas heater.
> 
> So your outside AC condensor is rated at 2 tons and your furnace/blower is rated at a number from the manual j, just say 80,000 BTU for heat (80 or 90% efficiency) and will have a fan speed adjustment for the AC size. (As BT has stated above will need to be adjusted.)


Looking at my Manual J calcs I posted on here what size heater unit would my house require?


----------



## beenthere (Oct 11, 2008)

You don't have that many days over 89, that are much above 89. The tonnage an A/C is rated to have is done at 80°F indoor temp, and 95°F outdoor temp. So a 2 ton will barely meet your load on the hottest days, and may lose ground a little, but not much. if you want to be able to maintain 75 to 70 on the hottest days, you would need a 2.5 ton.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> Is cfm measured by the amount of pressure coming out of each supply register?
> My old heater (1975) uses natural gas and is rated at 100,000 BTUH with a bonnet capacity of 80,000 BTUH. I dont know how much calculating went into homes back in 1975.


 
Your manual j will determine each rooms cfm. then you have to try and match duct size for that requirement.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> Looking at my Manual J calcs I posted on here what size heater unit would my house require?


looks like 40,000 btu?????


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> Looking at my Manual J calcs I posted on here what size heater unit would my house require?


 
the manual j i have from my home lists that information for each room, yours does not apparently.


----------



## Pawl (Mar 5, 2008)

So, I also researched the Winter temperatures in my area.The point of measurement was 2.5 miles away from my house. Any thoughts on what I will need in the way of heating. 

Days under 38 degrees during each year below: 

2007 - ( 6 days under 38 degrees) 32 degrees 2x, 33 degrees 1x, 37 degrees 2x,
2008 - ( 10 days under 38 degrees) 34 degrees 1x, 35 degrees 2x, 36 degrees 2x, 37 degrees 5x,
2009 - ( 7 days under 38 degrees) 35 degrees 2x, 36 degrees 2x, 37 degrees 3x,
2010 - ( 5 days under 38 degrees) 33 degrees 2x, 36 degrees 1x, 37 degrees 2x, 
2011 - ( 15 days under 38 degrees) 31 degrees 1x, 32 degrees 1x, 34 degrees 2x, 35 degrees 5x, 36 degrees 4x, 37 degrees 2x.
2012 - ( 11 days under 38 degrees) 33 degrees 1x, 35 degrees 3x, 36 degrees 2x, 37 degrees 5x, 
2013 - ( 16 days under 38 degrees) 31 degrees 1x, 32 degrees 2x, 33 degrees 3x, 34 degrees 1x, 35 degrees 2x, 36 degrees 3x, 37 degrees 7x,
* the numbers seem to point out that in the last 3 years it is getting colder here
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
38 degree days during each year below:
2007 zero days
2008 - zero days
2009 - 3 days
2010 - 4 days
2011 - 2 days
2012 - 2 days
2013 - 5 days
39 degree days during each year below:
2007 - 8 days
2008 - 6 days
2009 - 4 day
2010 - 2 days
2011 - 16 days
2012 - 6 days
2013 - 3 days
40 degree days during each year below:
2007 - zero days
2008 - 1 
2009 - 7
2010 - 5
2011 - 8
2012 - 3
2013 - 1
41 degree days during each year below:
2007 - 8 
2008 - 5
2009 - 8
2010 - 11
2011 - 13
2012 - 12
2013 - 3
42 degree days during each year below:
2007 - 10
2008 - 9
2009 - 12
2010 - 11
2011 - 10
2012 - 5
2013 - 4
43 degree days during each year below:
2007 - zero
2008 - 3
2009 - 18
2010 - 12
2011 - 9
2012 - 15
2013 - 2


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> the manual j i have from my home lists that information for each room, yours does not apparently.


The program I used for the manual J load calc has some different options for the information I can retrieve. Are you talking about the different items that are measured and inputted into the program for each room with that rooms measurements and square footage? Because I can post that information.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> The program I used for the manual J load calc has some different options for the information I can retrieve. Are you talking about the different items that are measured and inputted into the program for each room with that rooms measurements and square footage?


Not sure as I do not have the program, but you need to know what that report says you need for each room, cfm, so that you can also determine duct size. I would assume that is in there somewhere based on all of the data you entered.

If that program has an expiration, I would print every possible report you can before it expires.


----------



## Pawl (Mar 5, 2008)

This picture shows the existing heating supply register. Just for conversation I feel that the new supply register will have to be moved between this ceiling fan and the window you are looking at. I am just extending the supply ducting toward that window. Moving it will also create distance between supply and return.

That is the east side of my house which gets sun on this window from sunrise until about 11am. That is a small round recessed light in the picture. There are four in the ceiling.

The new return will be installed somewhere right above the entrance to this room in the ceiling. With it located in that spot it will put the return closer to the new AC unit area. The entrance to this room is at the end of the hallway. About 8' back down the hallway is the entrance to the original heater in the closet.

Is their an advantage to having the return ducts as close as possible to the AC unit? For example I would think in a bedroom you can mount these ceiling registers/vents anywhere you want but there is obviously a sweet spot for both which will be the most advantageous in performance.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> This picture shows the existing heating supply register. Just for conversation I feel that the new supply register will have to be moved between this ceiling fan and the window you are looking at. I am just extending the supply ducting toward that window. Moving it will also create distance between supply and return.
> 
> That is the east side of my house which gets sun on this window from sunrise until about 11am. That is a small round recessed light in the picture. There are four in the ceiling.
> 
> ...


 
Again, basing on what I have read. Your supply vents need to be over the windows as you have indicated. All rooms. 

As far as the return air, across the room from them. A short path back to the return, I assume, is a great idea but maybe getting to worrysome to accomplish or not even a worry.. Remember, you are adding this to a room you did not have before so it has to help.

Hopefully the real experts will chime in soon.


----------



## Pawl (Mar 5, 2008)

This is one of the bedrooms on the west side. It gets sun from about 2pm until sunset so on a hot day this room warms up.It looks to me like this supply duct is probably fine in this spot because it is very close to the window and far enough away to create distance from the return vent. I will just be changing the the old registers for new ones unless someone here has a different opinion or HVAC guy tells me something I dont know.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> This is one of the bedrooms on the west side. It gets sun from about 2pm until sunset so on a hot day this room warms up.It looks to me like this supply duct is probably fine in this spot because it is very close to the window and far enough away to create distance from the return vent. I will just be changing the the old registers for new ones unless someone here has a different opinion or HVAC guy tells me something I dont know.


 
Again you need to know what the manual j says for the correct amount of ac cfm should be for that room. (As I recall, you base a rooms cfm on the higher ac number.) Once you know that, you can determine if the current discharge vent and supply duct is still the correct size for the room. 

Remember it takes a larger flex duct size to move the same air as a solid duct of smaller size rated for the same or close to cfm..


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Again you need to know what the manual j says for the correct amount of ac cfm should be for that room. (As I recall, you base a rooms cfm on the higher ac number.) Once you know that, you can determine if the current discharge vent and supply duct is still the correct size for the room.
> 
> 1.) Remember it takes a larger flex duct size to move the same air as a solid duct of smaller size rated for the same or close to cfm..


I plan on using rigid duct. My goal is to get all the information and help I can here and then I am going to meet with a HVAC business that came highly recommended from a friend of mine who has a fabricating sheet metal business. I want him to let me do some of the work meaning the installation of the ducts in my house. I am retired and have worked on many many aspects of my home. I have more time than a company on the clock. 
The HVAC people can do the install of the AC/Heating unit/balancing /thermostat/electrical because thats a specialty. I want the supply/returns and ducts put in correctly. I found the original ducts in my walls not sealed and heat has been blowing in the walls since 1965. They probably will be glad to have someone else crawl around my attic. I will have to have him calculate everything before we can figure out duct sizes etc,... My worry is as of now I am somewhere in the area of needing a 2.5 ton unit. If they start trying to talk me out of it by suggesting a larger unit I will be finding someone else. I will have my load calculations with me, weather data for my area so any good HVAC company should be able to work their magic. I have done a lot of the homework on this website.



(As I recall, you base a rooms cfm on the higher ac number.)<<<<<< - 

2.) Could you explain this statement some more. What is the higher ac number and where are you finding it? Are you saying the results of a Manual J load Calculations should be printing out the AC number?


----------



## Pawl (Mar 5, 2008)

In your opinion will an area at the top of these stairs need a supply or return vent? The door you are looking at is the bathroom door and there are two more bedrooms up there to the right.


----------



## beenthere (Oct 11, 2008)

Those round supplies are terrible for heating.

Switch to 3 way rectangular ones, that will throw the air toward the outside wall, and the 2 perpendicular walls.

Returns near the air handler sometime give more noise. How close or far they are to the air handler has little to no effect.

If you entered each room individually, then you have a room by room load calc, and the program will print out the CFM each room should have.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> In your opinion will an area at the top of these stairs need a supply or return vent? The door you are looking at is the bathroom door and there are two more bedrooms up there to the right.


 
If it were me, I would have a return at the top of the stairs and one in each bedroom.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> I plan on using rigid duct. My goal is to get all the information and help I can here and then I am going to meet with a HVAC business that came highly recommended from a friend of mine who has a fabricating sheet metal business. I want him to let me do some of the work meaning the installation of the ducts in my house. I am retired and have worked on many many aspects of my home. I have more time than a company on the clock.
> The HVAC people can do the install of the AC/Heating unit/balancing /thermostat/electrical because thats a specialty. I want the supply/returns and ducts put in correctly. I found the original ducts in my walls not sealed and heat has been blowing in the walls since 1965. They probably will be glad to have someone else crawl around my attic. I will have to have him calculate everything before we can figure out duct sizes etc,... My worry is as of now I am somewhere in the area of needing a 2.5 ton unit. If they start trying to talk me out of it by suggesting a larger unit I will be finding someone else. I will have my load calculations with me, weather data for my area so any good HVAC company should be able to work their magic. I have done a lot of the homework on this website.
> 
> *I agree knowledge is power and if I were you, I would rather err on the too large side than too small and regret it. BT has been giving you good sound free advice!*
> ...


*Cooling and heat cfm requirements are different, at least when you have a gas furnace for heat. Not sure how it works for full electric and heat pump, but I think they (cfms) are the same. *

*For instance in my home a room calls for 244 cfm cooling and 172 heating cfm. I think the theory is its easier to heat than cool.*

*The manual j should tell you all of this, unless I am mistaken.*

*The one I have for my home given to me by the builders ac company, has all of this info.*


----------



## digitalplumber (Jul 8, 2011)

another website to fuel your knowledge thirst:

http://www.furnacecompare.com/


----------



## Pawl (Mar 5, 2008)

I found the duct sizing tool on the program. I checked all the boxes for a total of 653 CFM. 

459 cfm on the 1st floor:
~~~~~~~~~~~~~
bath rm 16 
master bath 17
living rm 110
kitchen 79
family rm 98
front entry 27
hallway 6
office 42
alexis bed rm 56
dads bed rm 61

148 cfm on 2nd floor:
~~~~~~~~~~~~~~~
allison bed rm 69
extra bed rm 50
bath rm 12
upstairs landing 10

When I click on supply or return it defaults to 16 x 8 duct. There are two other choices for duct: 12" round or 12 x 10.

* my current heating ducts go from a 24" plenum with 8" tapped into plenum reducing to 6" to each room. The two bathrooms downstairs were 5" coming straight off plenum and bathroom upstairs branched off of 6" reducing to 5". 

When I click on return the speed of the air selection defaults to 700. Supply defaults to 900.

1.) Are these numbers based solely on load calculation information I entered into the program? Whatever size unit I pick is separate from these numbers?


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> I found the duct sizing tool on the program. I checked all the boxes for a total of 653 CFM.
> 
> 459 cfm on the 1st floor:
> ~~~~~~~~~~~~~
> ...


 
Are you talking about the CFM, yes its based on your entries. Does it say these are cooling or heating cfm?


----------



## Pawl (Mar 5, 2008)

I played with the duct sizing portion of the program again and here is what the program came up with:

1st floor shows a total need of 459 cfm. For supply they show 4 configurations of ducts to move this amount of cfm. They also show a figure of 512 cfm that is the maximum these 4 configurations will carry. Choices are 10" round, 14x6, 12x7 or 10x8. I also chose rigid duct construction. The program defaulted to 900 on speed of the air.
The return ducts show all the same numbers and same choices of duct sizes as the supply ducts.The speed of the air went to 700 as I was checking the boxes of what rooms to include. Return ducts are same size duct as supply?

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

2nd story shows a total need of 148 cfm. For supply they show 3 configurations of ducts to move this amount of cfm.They also show a figure of 149 cfm that is the maximum these 3 configurations will carry. Choices are 6" round,8x4,or 6x5. Rigid duct construction.Speed of the air defaulted to 900. 
The return ducts show all the same numbers and choices of ducts as the supply ducts except the speed of the air went to 700.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
If the 6" round ends up being the right size for up stairs I have about 37' I used on the 1st floor that is only about 5 years old and a thicker gauge metal.


----------



## Pawl (Mar 5, 2008)

1.) With the right size ducts figured out now for the total amount of cfm needed will the balancing of each room be dependant on the air speed and the dampers? 

2.) If what I just asked is true are the settings for heating and air conditioning based on different speeds for the blower? 

3.) Now that I have figured out my duct size for the layout that will not change if I went with a 2 ton unit or 2.5 ton unit?


----------



## Pawl (Mar 5, 2008)

The duct size for upstairs 149 CFM requires 6" round duct. There is a transition that goes from round to rectangular that passes vertically up the back closet wall from 1st floor attic to 2nd story attic. So the rectangular transitional piece that was in use was 14 x 3 which is 42 sq inches and 6" round is 28 sq inches so the original rectangular transitional duct might have been too big from the start. What do you think?
I would like to do maybe a 10" x 3" = a 30 sq inch rectangular duct and it would leave me room for insulation. I want to be able to have room for insulation around this 9' long two piece duct.The original duct fit so tight there was no room for insulation. Plus the return duct needs to go beside it.I have to figure out how to make that work. I dont think i could find too many companies that would go to this great length to do this right without charging a lot of $$$. And I dont blame them but I can do this.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> 1.) With the right size ducts figured out now for the total amount of cfm needed will the balancing of each room be dependant on the air speed and the dampers?
> 
> 2.) If what I just asked is true are the settings for heating and air conditioning based on different speeds for the blower?
> 
> 3.) Now that I have figured out my duct size for the layout that will not change if I went with a 2 ton unit or 2.5 ton unit?



Yes fine tuning the balance of each room will be by dampers at the supply plenum. Realistically because of leaks, turns and friction you expect the numbers to be off some at the supply vents, as I understand.

Yes and obviously controlled by the thermostat when set to heat or cool mode. A furnace can be made for multiple ac applications: 3, 3.5 or 4 tons for example. The unit should be verified upon install that the correct ac cfm is set. Based on 400 cfm per ton: 3=1200, 2=800 for instance. Also, the furnace will have heating cfm setting, usually much lower than ac cfm. If you are asking will you have to make manual seasonal adjustments in the dampers, I would say no you will find a happy medium.

Not sure what you are asking here? Once again I believe this is decided for you by your entries in the program, heating btu's and ac tonnage.. You have to look at what the program is saying your cooling needs are and further what it is suggesting for duct size relative to the ac size. keeping in mind though, in my opinion, that if your home is older and poorly insulated and sealed coupled with a borderline cooling suggestion say close to 2.5 tons, I would go with the higher number. 

If you go the 2.5 and have a cfm delivery of 1000 cfm and the manual j says you only need 800, you will have the extra to make up for leaks, turns etc. the folks upstairs will be thankful.


----------



## Pawl (Mar 5, 2008)

This is the duct sizing for upstairs. At the bottom of the boxes to be checked I have checked the 4 boxes for the 2nd story CFM. You can see the 3 choices of duct size to accomplish the task. Rigid duct is chosen and the speed of air is at 900.Like I said earlier the speed of air defaults to 900 with the more boxes I checked.This picture is for supply air duct sizing. 

1.) Regardless of whether I choose 2 ton or 2.5 ton this recommended size ducting will not change. Is that correct?

Currently in my house now the heating duct going to the 2nd floor is 8" round and it travels across the attic but the closer bedroom supply register branches off with a 6" fitting and 2ft of 6" round size running to that bedroom supply register. The new register in this room is going to be moved an additional 4 feet.
The farthest bedroom register which is basically at the end of the 8" run has a fitting on it that reduces the 8" round to 2 ft of 6" round with a 5" round branch that travels for 9' to the bathroom supply register. 
2.) My question is the duct sizing on my manual J calcs says I can use 8" round to get the right cfm upstairs but it gives no smaller reducing sizes for branching off to each supply register. Any thoughts?


----------



## Pawl (Mar 5, 2008)

If you go the 2.5 ton and have a cfm delivery of 1000 cfm and the manual j says you only need 800, you will have the extra to make up for leaks, turns etc. the folks upstairs will be thankful.[/QUOTE]

From using the duct sizing portion of this program the total amount of cfm I have for my house is 609. You can see the total in the picture I displayed. 

1.) Is a 2.5 ton too big for this system? 

2.) Is a 2 ton unit cutting it close with 800 cfm if I only need 609? 

A 2.5 ton (1000 cfm delivery) is giving me a 391 cfm cushion if I only need 609 cfm. I have no problem with either size I am just trying to keep from having the short cycling issues and humidity.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> This is the duct sizing for upstairs. At the bottom of the boxes to be checked I have checked the 4 boxes for the 2nd story CFM. You can see the 3 choices of duct size to accomplish the task. Rigid duct is chosen and the speed of air is at 900.Like I said earlier the speed of air defaults to 900 with the more boxes I checked.This picture is for supply air duct sizing.
> 
> 1.) Regardless of whether I choose 2 ton or 2.5 ton this recommended size ducting will not change. Is that correct?
> 
> ...


 
Interesting, I would have assumned this program would have told you what individual room size duct to use.


*You need a Air Duct Calculator:* 

If I am reading mine right and using .10 for friction (Its recommendation):

I used 70 cfm for allisons bedroom and I get 5" rigid and 6 with a flex.

Extra Bedroom is 5 (4.5 actual) rigid and 5 on my flex.

Bathroom have to use 15 cfm which is 3 rigid and 3 flex

Landing is 3 and 3

Again take these with a grain of salt, hopefully somone will chime in and same I am close, right or wrong!


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> If you go the 2.5 ton and have a cfm delivery of 1000 cfm and the manual j says you only need 800, you will have the extra to make up for leaks, turns etc. the folks upstairs will be thankful.


From using the duct sizing portion of this program the total amount of cfm I have for my house is 609. You can see the total in the picture I displayed. 

1.) Is a 2.5 ton too big for this system? 

2.) Is a 2 ton unit cutting it close with 800 cfm if I only need 609? 

A 2.5 ton (1000 cfm delivery) is giving me a 391 cfm cushion if I only need 609 cfm. I have no problem with either size I am just trying to keep from having the short cycling issues and humidity.[/QUOTE]


Again earlier I believe BT recommended that you go the larger unit based on your numbers. I would for the peace of mind, but thats me.


----------



## Pawl (Mar 5, 2008)

*Central Air: Figuring out duct size for supply/return trunks* 
The easiest way to size your duct work is with a ductulator, but most people don't have one so heres another easy way you can do with a calculator.
the formula is V X A = CFM.

V stands for velocity like in feet per minute, the standard residental design for trunk ducts is 900 fpm so V = 900
A is the area of the duct in sq ft and CFM is cubic feet per minute.

so like you said 400 cfm per ton (another industry standard) 2.5 tons = 1000 cfm.
the equation looks like this.....1000/900= A in sq feet
so 1000/900= 1.1 sq feet is the area of your trunk duct at the unit.
1.1 x 144 (144 to change to sq inches) = 160 sq inches so you can pick any multiple of sizes 20x8=160 16x10=160 etc.
start out with 20x8 pick up half your run outs and and do the cals again and pick a new size for the rest of the supply trunk. (500/900=.55 etc)
few tips when you pick the last size make it a little larger the air cools of as you get near the end of the run so you need more of it.
no run outs smaller than 6" dia., all with dampers
insulate everything in the attic
make the return the same size as the supply (the air don't know which way its going)

if you want make the sizes a little bit bigger you can't get hurt making them larger. but 25 x10 seems a little large for 2.5 tons

here's the table we used for years sizing run outs.
6" dia. 150 cfm or less
8" dia. 250 cfm or less
10" dia. 450 cfm or less
12" dia. 650 cfm or less


----------



## beenthere (Oct 11, 2008)

That table will give you a high static pressure in you system. 

6" less then 100CFM
7" less then 130CFM
8" less then 180CFM
The above is for room supplies.
The below is trunk lines.
8" up to 250 CFM
9" up to 310 CFM
10" up to 390 CFM
12" up to 580 CFM


----------



## Pawl (Mar 5, 2008)

beenthere said:


> That table will give you a high static pressure in you system.
> 
> 6" less then 100CFM
> 7" less then 130CFM
> ...


beenthere,

1.) What about a bathroom that calls for 13 cfm (38 sq ft room) from the load calculation? Can you give me some smaller diameter sizes to get closer to 13 CFM? The old duct leading to that bathroom is 5".

2.) I have a total of 154 cooling CFM/141 heating CFM needed for 2nd floor that will be running from 1st floor AC unit up to 2nd floor. An 8" trunk line running through 1st floor attic is going to transition to a 9' rectangular duct going vertically up wall into 2nd story attic and then back to 8" round across ceiling joists branching across over bedrooms to each register. The original vertical rectangular duct is 14"x 3" and there was no room for insulation because it would only fit 14" wide between roof rafters/wall stud. I was thinking maybe 12" x 4" duct (48 sq inches) giving me 1" on each side for insulation and then just bring the wall out an extra inch to make this fit. And 8" duct measures 50 sq inches.

3.) Are those numbers shown here for supply/trunk lines above also used for the return ducts back to ac unit?

4.) Is there any advantage to trying to run one larger return duct versus two separate return ducts (1st flr/2nd flr) back to ac unit? The obvios is less material to install or is it not a good idea?


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> beenthere,
> 
> 1.) What about a bathroom that calls for 13 cfm (38 sq ft room) from the load calculation? Can you give me some smaller diameter sizes to get closer to 13 CFM? The old duct leading to that bathroom is 5".
> 
> ...


Having returns in at least all bedrooms allows the door to be closed. Having one up and one down is good but more makes for more comfort.


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Having returns in at least all bedrooms allows the door to be closed. Having one up and one down is good but more makes for more comfort.


I just realized I didnt say that right. I plan on putting returns in both upstairs bedrooms and at the top of the stairs. I will have to bring all the upstairs return ducts/vents into one 8" return duct in the 2nd story attic and run that duct back to the ac unit.
But I was asking if when I bring that 2nd story 8" return duct down into that open wall in the closet and send it back into the 1st story attic could I tie that duct at that point into the 1st story 12" return duct and just send one duct back to the ac unit for both floors.Might save some work,some material,some space in the attic. 
I would probably have to run an 8" return duct in the 2nd floor and transition on the 1st floor into a 12' return duct to handle 610 cfm for the whole house.
If I have to run separate return ducts back to the ac unit for each floor than I need one 12' round duct for 1st floor and one 8" duct for 2nd floor. Maybe separate ducts is better because "beenthere" said the 12" duct is rated up to 580 cfm and my whole house adds up to 609cfm.


----------



## beenthere (Oct 11, 2008)

Pawl said:


> beenthere,
> 
> 1.) What about a bathroom that calls for 13 cfm (38 sq ft room) from the load calculation? Can you give me some smaller diameter sizes to get closer to 13 CFM? The old duct leading to that bathroom is 5".
> 
> ...


I use a 5", with a damper in it. So it can be throttled down. You can use a 4" if you want for that low of a CFM.

I believe the CFMs the software is saying you need, is based on a 1.5 ton unit still. Correct it to the size you are going to install.


----------



## Pawl (Mar 5, 2008)

beenthere said:


> I use a 5", with a damper in it. So it can be throttled down. You can use a 4" if you want for that low of a CFM.
> 
> I believe the CFMs the software is saying you need, is based on a 1.5 ton unit still. Correct it to the size you are going to install.


The 13 CFMs for my upstairs bathroom is based on a total of 600 total cfm which I believe is equivalent to a 1.5 ton unit. A total of 800 cfm (2 ton?) raises the upstairs bathroom cfm requirements to 18 cfm and a total of 900 cfm raises it to 20 cfm. The program only allows me to enter between 300 cfm and topping out at 900 cfm with 50 cfm increments.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> The 13 CFMs for my upstairs bathroom is based on a total of 600 total cfm which I believe is equivalent to a 1.5 ton unit. A total of 800 cfm (2 ton?) raises the upstairs bathroom cfm requirements to 18 cfm and a total of 900 cfm raises it to 20 cfm. The program only allows me to enter between 300 cfm and topping out at 900 cfm with 50 cfm increments.


 
I'm confused, after you enter all of your data are you telling me that you are entering the data for the Total AC CFM manually?

I thought that the program would tell you this after you entered all of the individual room sizes?

Someone correct me if I am wrong, but there should be no manual entry of the total cfms correct? the calc program should tell us this?

The minor increase in CFM would seem to be no big deal to me.


----------



## beenthere (Oct 11, 2008)

digitalplumber said:


> I'm confused, after you enter all of your data are you telling me that you are entering the data for the Total AC CFM manually?
> 
> I thought that the program would tell you this after you entered all of the individual room sizes?
> 
> ...


The program allows manual input so as to obtain the sensible/latent ratio you need. I believe it limits air flow to 450 CFM per ton though.


----------



## beenthere (Oct 11, 2008)

Pawl said:


> The 13 CFMs for my upstairs bathroom is based on a total of 600 total cfm which I believe is equivalent to a 1.5 ton unit. A total of 800 cfm (2 ton?) raises the upstairs bathroom cfm requirements to 18 cfm and a total of 900 cfm raises it to 20 cfm. The program only allows me to enter between 300 cfm and topping out at 900 cfm with 50 cfm increments.


5" will cover your bathroom. Its good for about 55 CFM quietly.


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> I'm confused, after you enter all of your data are you telling me that you are entering the data for the Total AC CFM manually?
> 
> I thought that the program would tell you this after you entered all of the individual room sizes?
> 
> ...


1.) Under tools for the program I clicked on "CFM per room calculation"

2.) Next I have to choose either one air handler for the whole house or one air handler for each zone. 

3.) Next I have to choose the cfm for the equiptment chosen for this house. I assume 1.5 ton equates to 600 cfm for the whole house, 2 ton is 800 cfm and 2.5 ton is 1000 cfm but it tops off at 900 cfm. The choice starts at 300 cfm and goes up in 50 cfm increments 350,400,450 to 900 cfm.

4.) So whatever amount of cfm I chose between 300 and 900 it gives me a breakdown for the whole house room by room with one column for cooling cfm for each room and one column for heating cfm for each room. 

5.) So I chose 600 cfm and got 13 cfm for upstairs bathroom, then I chose 800 cfm and got 18 cfm for upstairs bathroom, then I chose 900 cfm and got 20 cfm.

6.) I did not do what beenthere is talking about with entering manually because I dont know how to do that nor even understand what that would tell me. But I am sure it can be done.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> 1.) Under tools for the program I clicked on "CFM per room calculation"
> 
> 2.) Next I have to choose either one air handler for the whole house or one air handler for each zone.
> 
> ...


 
Thats interesting, I always assumnned that the purpose of a manual j was for it to ultimately tell YOU the total cfm necessary based on the numbers you entered? 

So do you then look at the final Sensible and Latent cooling BTU's and compare these 2 to determine if your original unit size is correct??

Do you have to enter a number there?


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Thats interesting, I always assumnned that the purpose of a manual j was for it to ultimately tell YOU the total cfm necessary based on the numbers you entered?
> 
> So do you then look at the final Sensible and Latent cooling BTU's and compare these 2 to determine if your original unit size is correct??
> 
> Do you have to enter a number there?


Dp--I was just thinking about this when you posted it to me a while back.>>>>>>> But I have seen more and more where some experts have said that sometimes they need to re-evaluate the load calc and listen more to the customer. <<<<<<

I really enjoy the fact that they have an online program for homeowners to do their own load calcs but I have found I have to go over it with a fine tooth comb to hope that I come up with the right size unit for my house.
I am almost like a danger to myself being a green horn. I have no experience in doing this but it is all I can do short of hiring someone. 

Anyway to get to my point I was reading FAQ and they talk about external shading and internal shading. Originally I took credit for windows/patio doors in my house and outside credit for how long the sun is hitting certain windows etc,... 

The program says that on a beautiful summer day I would probably have all the blinds open so they said do not take credit for either external or internal shading. Leave both at 0%. After making the necessary changes (unchecking all the boxes) my total heat gain went from 20,874 BTUH to 24,911 BTUH 

And the laugher is I live by myself and most of the time 80% of the blinds are going to be left closed in my house. But I do understand I am getting "worst case scenario" advice from the program.Now I have to decide what to do with that information. The good part is I understand it where if I hired someone to do the load calc for me I don't think it would register in my mind just looking at a finished load calc on paper. 


The additional BTUHs just from eliminating external/internal shading has bumped me up to a 2 ton unit. But I learned that now I have the knowledge that my 2 ton at this point is plenty when the drapes/blades are closed and still the 2 ton unit will fight the good fight to keep things cool when all the blinds are open.
Not finished reading all the information on the load calc site yet. Not finished with the decision making on the load calc site yet. Still learning things.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> Dp--I was just thinking about this when you posted it to me a while back.>>>>>>> But I have seen more and more where some experts have said that sometimes they need to re-evaluate the load calc and listen more to the customer. <<<<<<
> 
> I really enjoy the fact that they have an online program for homeowners to do their own load calcs but I have found I have to go over it with a fine tooth comb to hope that I come up with the right size unit for my house.
> I am almost like a danger to myself being a green horn. I have no experience in doing this but it is all I can do short of hiring someone.
> ...


 
Check back in with us after all is said and done!


----------



## beenthere (Oct 11, 2008)

digitalplumber said:


> Thats interesting, I always assumnned that the purpose of a manual j was for it to ultimately tell YOU the total cfm necessary based on the numbers you entered?
> 
> So do you then look at the final Sensible and Latent cooling BTU's and compare these 2 to determine if your original unit size is correct??
> 
> Do you have to enter a number there?


The program has no way of knowing the SHR of the equipment you are going to use. Nor does it decide that your going to use a heat pump instead of a gas furnace or vice versa. You could be using a gas furnace, which can't be gotten in the exact size your house needs. So you may be using the next size up. So you have to enter the CFM for both heating and cooling, and then size the duct for the one needing the most air.


----------



## digitalplumber (Jul 8, 2011)

beenthere said:


> The program has no way of knowing the SHR of the equipment you are going to use. Nor does it decide that your going to use a heat pump instead of a gas furnace or vice versa. You could be using a gas furnace, which can't be gotten in the exact size your house needs. So you may be using the next size up. So you have to enter the CFM for both heating and cooling, and then size the duct for the one needing the most air.


 
How can you know what equipment you are going to use if you dont know all of the other data and plug it into a manual j type program? That is what I always hear from you guys?

I'm really confused now????????


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> How can you know what equipment you are going to use if you dont know all of the other data and plug it into a manual j type program? That is what I always hear from you guys?
> 
> I'm really confused now????????


~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Your confused? Just when I think its starting to make sense?

With the load calculation program I clicked on the tools section at the top of the page and then clicked on CFM per room calculation, then I have to choose either one air handler for the whole house or one air handler for each zone. I chose one air handler for the whole house. 
Then I have to enter "the CFM of the equipt chosen for this house" by the cfm numbers the program offers. I dont have an ac unit yet. 
Anyway I think the range of cfm numbers offered by the program are based on the outside design temp (80)/ inside design temp (43) numbers because the range of cfm choices to choose from start at 500 cfm all the way up to 1100 cfm with 50 cfm increments (500,550.600, etc,.... up to 1100 cfm). It seems like this range of cfm increments is based on choosing 80 degrees earlier in Design Conditions.
But if I change from 80 degrees to 89 degrees under Outside Design conditions for Summer and leave the other 3 temperatures as they are the range of cfm increments to choose from change. 
With 89 degrees selected they now go from 700 cfm (previously 500 cfm @80 degrees) to 1300 cfm (previously 1100 cfm @80 degrees) with not a big change in the overall cfm increase per room as you can see in the cooling and heating columns in the pictures I provided. 

Outside Design
80 S -- 43 W
Inside Design
75 S -- 72 W

This is the only way I can start to understand what I am trying to do with not having any experience in this field is going over any reading material I can find many times and reading your feed back to help me see the whole picture and if I am on the right track.
I think from what I see on the cfm calculations paperwork here the duct size I will need for a 2 ton unit or 2.5 ton or 3 ton is not going to change a lot or at all because the amount of cfm increases doesnt seem to change the overall amounts of cfm needed for each room alot.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Your confused? Just when I think its starting to make sense?
> 
> ...


 
But my point is, if you know the equipment you are installing???? why use this program???? This seems like it is backwards??? I know the pros are sitting back LTAO :laughing:, but I am really confused now.

See I thought that this is what this program, everyone raves about needing, did for you. You enter all of the info you have about the home that it needs, then it spits out the BTUS for cooling and heating and you buy based on that.

BTW could you go to that web page I listed and enter some dat and see if it gets close to the program you are using?


----------



## Pawl (Mar 5, 2008)

BTW could you go to that web page I listed and enter some dat and see if it gets close to the program you are using?[/QUOTE]

would you give me that site again? I am going to scroll back through your old posts and look for it again


----------



## beenthere (Oct 11, 2008)

digitalplumber said:


> How can you know what equipment you are going to use if you dont know all of the other data and plug it into a manual j type program? That is what I always hear from you guys?
> 
> I'm really confused now????????


You need to choose equipment that can meet the sensible and latent loads the program list.

You can take 2-2 ton units, one from one manufacturer and another from a different manufacturer, and they won't have the same sensible and latent capacities. One may need its blower slowed down to get the latent a home needs. Or may need the blower sped up to get the sensible the house needs.

The program tells you what capacities, you have to select the equipment.


----------



## beenthere (Oct 11, 2008)

Pawl said:


> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Your confused? Just when I think its starting to make sense?
> 
> ...


If you run a 3 ton A/c at only 800 CFM like you would for a 2 ton. You will end up with a frozen evap coil.

A 3 ton takes much larger duct then a 2 ton.


----------



## digitalplumber (Jul 8, 2011)

http://www.loadcalc.net







Pawl said:


> BTW could you go to that web page I listed and enter some dat and see if it gets close to the program you are using?


would you give me that site again? I am going to scroll back through your old posts and look for it again[/QUOTE]


----------



## Pawl (Mar 5, 2008)

I thought I had everything on my load calc but found a couple more things but hopefully this is the grand total but maybe not. I was reading through all the instructions from the program one more time and they mentioned if I get a low cooling load its because I might have done a couple of things they recommend not to do. The only one I did not do was eliminating all outside shading and inside window covers. They said calculate with inside windows not covered up.So I took them out and the total BTUH on Total Heat Gain went from 15,643 (1.5 tons) with shading,blinds,curtains,roll up shades included to 24,313 BTUH (2 tons) with shading,blinds,curtains,roll up shades NOT INCLUDED.


----------



## Pawl (Mar 5, 2008)

2nd copy


----------



## Pawl (Mar 5, 2008)

I increased that outdoor Summer Temperature on the Manual J program to 86 degrees and it still showed I should use a 2 ton unit. When I increased it to 88 degrees it went to a 2.5 ton unit. I think 2 ton is looking like my choice. What do you think guys?

The Total Heat Loss is 37,849 BTUH. The program says to add 20% to that for a total of 45,419 BTUH. Do they round these amounts to 50,000?

My 1975 heating unit is rated at 100,000 BTUH (input) and 80,000 BTUH bonnet capacity. Of course the house had single pane windows,very little insulation from day one. The house was built in 1965 and this heater says 1975 on it. Maybe the original heater was rated lower and they purchased a larger one or maybe the original one took a dump. Maybe when they bought a new one they told them they wanted a larger one because the original one was not getting it done or the installer sold them a larger one.
My heater is over 30 plus years and it works okay but now I am going from a 100,000 BTUH / 80,000 bonnet capacity to a recommendation of 45,419 BTUH. Is that possible?


----------



## Pawl (Mar 5, 2008)

DP - I tried doing that load calc but I cant read the drop down window choices very well because I dont have right/latest internet explorer.


----------



## Pawl (Mar 5, 2008)

Beenthere - They mention Arizona/Nevada in the program as an example of states located in a dry climate. I am just assuming California is included even though it is not mentioned. We dont have much humidity at all where I live. The program says latent gain is not included in a dry climate so when I am shopping that whatever unit I get is going to be based entirely on sensible gain. Correct?


----------



## beenthere (Oct 11, 2008)

Your Summer grains of moisture is 84, so your not in a dry climate. A 2 ton unit will still just meet your sensible loss. You can use a 50,000 BTU 80% furnace. Or a 40,000 BTU 95% efficient furnace.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> I increased that outdoor Summer Temperature on the Manual J program to 86 degrees and it still showed I should use a 2 ton unit. When I increased it to 88 degrees it went to a 2.5 ton unit. I think 2 ton is looking like my choice. What do you think guys?
> 
> The Total Heat Loss is 37,849 BTUH. The program says to add 20% to that for a total of 45,419 BTUH. Do they round these amounts to 50,000?
> 
> ...


Again, as one homeowner to another, I go back to the scenario I had. Although they claimned 3 ton in my home was adequate, I found that the high summer temp they used wass not realistic and the lessor 3 ton just ok.

Reminds me of software for a computer, it says on the box a "suggested" minimum computer spec for software use. But if you stay with the minimum, it will work but be slow. If you increase, obviously it works better.

I read back thru this and I believe that on at least 2 times, BT has suggested that 2 tons would just barely be enough.

You have to make the decision: do you go 2 tons knowing that if you go out of your design temps in summer, that your unit may run a long time with minor impact. Or do you go to 2.5 knowing that you will be comfortable all of the time.

Me, I am going with the 2.5!


----------



## Pawl (Mar 5, 2008)

beenthere said:


> Your Summer grains of moisture is 84, so your not in a dry climate. A 2 ton unit will still just meet your sensible loss. You can use a 50,000 BTU 80% furnace. Or a 40,000 BTU 95% efficient furnace.


1.) Is the 50,000 BTU 80% furnace the same type I am using now?

2.) Would you explain the 95% efficient furnace? It sounds like I am getting less loss of heat with this style.

3.) Would you recommend one over the other? Pros/Cons

- is one clearly better than the other?
- price?
- anything else?


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> 1.) Is the 50,000 BTU 80% furnace the same type I am using now?
> 
> 2.) Would you explain the 95% efficient furnace? It sounds like I am getting less loss of heat with this style.
> 
> ...


 
The more efficient, the better the unit will be, but you will pay more initially for the furnace. I personally would not install anything less than 90%. 

I would assume that if you bought another new funace the same as you had now lets just say a 50K @ 80%, the only difference would be technology on the mainboard and motor, but efficiency would be the same.

Then again, if you hardly use it the added cost to the higher efficiency may not be worth it.


----------



## JScotty (Jan 14, 2013)

Pawl said:


> 1.) Is the 50,000 BTU 80% furnace the same type I am using now?


It looks to me like an 80% just by calculating input capacity vs. bonnet capacity.



> 2.) Would you explain the 95% efficient furnace? It sounds like I am getting less loss of heat with this style.


Correct the effieciency of a gas furnace is figured simply by what percentage of the heat created goes in your house vs. what percentage goes out the flue pipe. So if your furnace makes 100,000 btu's but 80,000 btu's go into the house then the efficiency is 80%



> 3.) Would you recommend one over the other? Pros/Cons
> 
> - is one clearly better than the other?
> - price?
> - anything else?


Well higher efficiency is obviously better, but there are some things to watch out for with the higher end units. For instance if you go 95% they usually use a variable speed blower, this causes the unit to usually run quieter, but if the motor goes out they are quite expensive to replace. And the savings you get by choosing 95% vs. a lower end 90% unit (usually they aren't exactly 90% usually around 92%) doesn't pay back very quickly because the units cost quite a bit more. Then if you have an expensive motor go out you've spent what savings you did make replacing the motor.

IMO I'd just go with a lower end 90% unit which will get you the savings but not be much more expensive to purchase than the 80% without paying big bucks for the 95%. In other words you get more bang for your buck with a lower end 90% again IMO. 

Also if you're getting a new A/C anyway I would recommend looking at a heat pump. It's basically the same as an A/C with some extra parts which allow it to make heat and it makes heat much cheaper than gas or electric. The cost difference from a A/C to a Heat Pump is usually only about $500.


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Again, as one homeowner to another, I go back to the scenario I had. Although they claimned 3 ton in my home was adequate, I found that the high summer temp they used wass not realistic and the lessor 3 ton just ok.
> 
> Reminds me of software for a computer, it says on the box a "suggested" minimum computer spec for software use. But if you stay with the minimum, it will work but be slow. If you increase, obviously it works better.
> 
> ...


I remember BT said, "a 10 degree increase in outdoor summer design temp would easily increase size of ac unit by 1/2 ton".

I went from 86 degrees with a 2 ton unit recommendation and then put 88 degrees in my outdoor summer design temp and it increased the recommendation to 2.5 ton. So regarding my load calculations if 88 degrees is the low end temperature of going from 2 to 2.5 tons and if what BT is saying is true here in the 1st sentence of my response then theoretically I have a 10 degree cushion for days over 88 degrees. In 2012 my area had 5-89 degree days, 2 days of 90, 91-1x, 92-3x, 94-2x, 96-2x,102 once. Does what I am saying sound right?

Regarding the last paragragh above when I left window coverings and shading out of the program it increased 9000 BTUHs under the Total Heat Gain column. Meaning when those windows are covered on really hot days and with a 9000 BTUH reduction in Total Heat Gain the 2.5 ton unit should keep me comfortable all the time and not have to run a long time with low impact. Sound right?


----------



## Pawl (Mar 5, 2008)

BT - will this information you mentioned on an earlier post apply to my 1000 cfm breakdown below? ------> The duct system should be designed for the full 400 CFM per ton (1000CFM for a 2.5), and then the blower set to only move 350 CFM per ton(875CFM). The installers should balance it out to each rooms needs then. With any excess air being equally allotted to each room.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> BT - will this information you mentioned on an earlier post apply to my 1000 cfm breakdown below? ------> The duct system should be designed for the full 400 CFM per ton (1000CFM for a 2.5), and then the blower set to only move 350 CFM per ton(875CFM). The installers should balance it out to each rooms needs then. With any excess air being equally allotted to each room.


 
Puzzled here as to how an upstairs bedroom can require more heat CFM than cooling?


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> I remember BT said, "a 10 degree increase in outdoor summer design temp would easily increase size of ac unit by 1/2 ton".
> 
> I went from 86 degrees with a 2 ton unit recommendation and then put 88 degrees in my outdoor summer design temp and it increased the recommendation to 2.5 ton. So regarding my load calculations if 88 degrees is the low end temperature of going from 2 to 2.5 tons and if what BT is saying is true here in the 1st sentence of my response then theoretically I have a 10 degree cushion for days over 88 degrees. In 2012 my area had 5-89 degree days, 2 days of 90, 91-1x, 92-3x, 94-2x, 96-2x,102 once. Does what I am saying sound right?
> 
> Regarding the last paragragh above when I left window coverings and shading out of the program it increased 9000 BTUHs under the Total Heat Gain column. Meaning when those windows are covered on really hot days and with a 9000 BTUH reduction in Total Heat Gain the 2.5 ton unit should keep me comfortable all the time and not have to run a long time with low impact. Sound right?


 
Unless you need to pinch pennies and role the dice for non extreme hot days, I would do the 2.5 and be done with it. All of this stuff is "in theory" and could be you install 2.5 tons and have a record heat season!


----------



## beenthere (Oct 11, 2008)

digitalplumber said:


> Unless you need to pinch pennies and role the dice for non extreme hot days, I would do the 2.5 and be done with it. All of this stuff is "in theory" and could be you install 2.5 tons and have a record heat season!


Yep, he could have a record heat season that it can't keep up. no big deal, cause that type of heat wouldn't occur again for 20, 50 or 100 years. you can't plan for the absolute worse extremes, and then have an economical running system.


----------



## beenthere (Oct 11, 2008)

digitalplumber said:


> Puzzled here as to how an upstairs bedroom can require more heat CFM than cooling?


If it has a fair amount more windows then the other rooms, and faces east.


----------



## beenthere (Oct 11, 2008)

Pawl said:


> BT - will this information you mentioned on an earlier post apply to my 1000 cfm breakdown below? ------> The duct system should be designed for the full 400 CFM per ton (1000CFM for a 2.5), and then the blower set to only move 350 CFM per ton(875CFM). The installers should balance it out to each rooms needs then. With any excess air being equally allotted to each room.


Basically yes. You'll find the second floor landing actually needs 50% more air then the program will say. Unless its a landing with a door at the bottom of the steps to prevent heat from the first floor rising.


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Puzzled here as to how an upstairs bedroom can require more heat CFM than cooling?


That one upstairs bedroom window is 8' wide by 34" tall with full southern exposure all day long. Only window in the whole house with full exposure to sun all day. Plus I did not take any credit for window coverings. That is my biggest window.


----------



## digitalplumber (Jul 8, 2011)

Pawl said:


> That one upstairs bedroom window is 8' wide by 34" tall with full southern exposure all day long. Only window in the whole house with full exposure to sun all day. Plus I did not take any credit for window coverings. That is my biggest window.


 
Window Tint!


----------



## sammy37 (Dec 9, 2008)

digitalplumber said:


> Window Tint!


Gotta be careful with window tint. My wife spent a fortune in tinting our front west facing windows, only to find the glass got much hotter.
I peeled the tint and went back in with new solar screens.

Maybe there are other types of tint that would be a better choice but for us, we tried two different kinds and they both doubled window temps.


----------



## digitalplumber (Jul 8, 2011)

sammy37 said:


> Gotta be careful with window tint. My wife spent a fortune in tinting our front west facing windows, only to find the glass got much hotter.
> I peeled the tint and went back in with new solar screens.
> 
> Maybe there are other types of tint that would be a better choice but for us, we tried two different kinds and they both doubled window temps.


 
I think you are right, I believe there is tint rated for double pain glass, etc.....


----------



## Pawl (Mar 5, 2008)

digitalplumber said:


> Window Tint!


thats a good idea DP. Once all the ac/heating is installed I will be doing a lot progressive things to take care of as many leaks as possible, kick up the R vlaues where I can.


----------



## Pawl (Mar 5, 2008)

I used the duct sizing system and this is what I got for the "supply" for upstairs. I entered 1000 cfm and for "speed of air" it defaults to 900 with the word "recommended" beside it which is what BT said (875). The current trunk line is 8" for heating so the 7" round for supply would be great because of a couple of tight spots.
For "return" ducts it says the same thing as "supply" ducts the only difference is they reduce the speed of air to 700 with the word "recommended" next to it. Is that sound right? Then are the "return" "ducts" calculated at 75% the speed of air of the supply ducts?


----------



## Pawl (Mar 5, 2008)

Return ducts


----------



## beenthere (Oct 11, 2008)

Returns are slower then supply to help keep noise down. 

That program unfortunately does not include a way of entering the TEL of the duct. So 7" may be a bit small, if its a long run.


----------



## Pawl (Mar 5, 2008)

beenthere said:


> Returns are slower then supply to help keep noise down.
> 
> That program unfortunately does not include a way of entering the TEL of the duct. So 7" may be a bit small, if its a long run.


2nd flr run - I think to go back from a return register might be 10' across 2nd floor attic, down the wall 9' and 14' across 1st floor attic back to heater = 33 feet.

1st flr run - about 32' to farthest supply duct from heater so it could be closer with a return register.

Are these considered long runs?


----------



## beenthere (Oct 11, 2008)

Thats the linear length. Each bend/elbow has an equivalent length that gets added.

The second floor return run you describe could be 102 foot of total equivalent length. The longest supply run would then get added up for it TEL and added in to the return run's TEL. This could be over 200 foot total. Meaning using the 900 FPM (recommended) will give you a high static pressure and reduce air flow.


----------



## Pawl (Mar 5, 2008)

beenthere said:


> Thats the linear length. Each bend/elbow has an equivalent length that gets added.
> 
> The second floor return run you describe could be 102 foot of total equivalent length. The longest supply run would then get added up for it TEL and added in to the return run's TEL. This could be over 200 foot total. Meaning using the 900 FPM (recommended) will give you a high static pressure and reduce air flow.


The current ducting run for heating from 1st floor closet plenum to 2nd flr has 2-8" 45 degree elbows,1-8" 90, 1-8" t-wye into 5"/6" branches,1-8" t-wye into 6" branch to ceiling register of south bedroom,1- 8" to 6" reducer,1-6" 90 into ceiling register of north bedroom , 8" round transitioning to 9' of 14" x 3" rectangular duct with 5' of that 14" x 3" vertical duct behind the wall of closet in picture and 4' of that 14" x 3" goes over ceiling of that closet transitioning into 8" round running across 2nd floor attic.

Am I able to figure out the runs for my house and have it verified or is too hard?


----------



## Pawl (Mar 5, 2008)

All the duct is round on this run except for the 14" x 3" vertical that runs up behind the closet wall and closet ceiling. 
It seems to me that if the calculations show that 7" round or 8" round is what the trunk lines for supply/return need to be then I would think if I ran 7 or 8" round in place of that 14" x 3" vertical and just build the closet wall out some more. Round duct would have a lot less joints than that piece in the other picture. And isn't that the object for the inside of the ducts. Less drag on the air in the ducts?


----------



## Pawl (Mar 5, 2008)

I was talking to my mailman today. He told me his ac unit runs all day long set at 78 without shutting off and he can't get the temperature in his house to come down to 78. He said even in the evenings he has trouble getting it to come down to 78. He did not know the tonnage. 
I am sure there are many other things he might be able to do to improve his house but I could not help thinking a load calc would have helped. I am also thinking his unit is too small.


----------



## beenthere (Oct 11, 2008)

An 8" isn't going to be a large enough trunk line for your second floor. With all the turns and branches, its gonna be too restrictive. A 9" round, or 10X7 would work better.

Under sized duct work is why many houses don't cool right. And people think they need a bigger system.


----------



## Pawl (Mar 5, 2008)

I am thinking about putting another 22.5" x 5" soffit vent next to the existing vent. The only place I can run the new return duct is in front of that existing vent so there will be some blockage of air flow as the rectangular duct heads up to the 2nd floor attic. But if I put a vent to the left of it where the original heating duct ran the two vents combined should be fine for proper air flow. Right behind where you see the string hanging will be the new supply duct and the far right under existing vent will be return. Anyone see a problem?


----------



## Dog5 (Jan 3, 2011)

Pawl said:


> The current ducting run for heating from 1st floor closet plenum to 2nd flr has 2-8" 45 degree elbows,1-8" 90, 1-8" t-wye into 5"/6" branches,1-8" t-wye into 6" branch to ceiling register of south bedroom,1- 8" to 6" reducer,1-6" 90 into ceiling register of north bedroom , 8" round transitioning to 9' of 14" x 3" rectangular duct with 5' of that 14" x 3" vertical duct behind the wall of closet in picture and 4' of that 14" x 3" goes over ceiling of that closet transitioning into 8" round running across 2nd floor attic.
> 
> Am I able to figure out the runs for my house and have it verified or is too hard?


You know that white coating is probably asbestos, right?


----------



## Pawl (Mar 5, 2008)

Dog5 said:


> You know that white coating is probably asbestos, right?


yes, all the popcorn ceilings and ducts in the homes in my area have it.


----------



## beenthere (Oct 11, 2008)

Pawl said:


> I am thinking about putting another 22.5" x 5" soffit vent next to the existing vent. The only place I can run the new return duct is in front of that existing vent so there will be some blockage of air flow as the rectangular duct heads up to the 2nd floor attic. But if I put a vent to the left of it where the original heating duct ran the two vents combined should be fine for proper air flow. Right behind where you see the string hanging will be the new supply duct and the far right under existing vent will be return. Anyone see a problem?


Can't see the existing vent in that pic.


----------



## Pawl (Mar 5, 2008)

vent picture


----------



## Pawl (Mar 5, 2008)

Quote:

_Can't see the existing vent in that pic._

Supply will be on the left - Return will be on the right. Its easy to place another vent next to the existing vent on the right but just wanted to make sure there is not going to be a problem I am not aware of. I also found that there was insulation right there (previous picture) in front of existing vent when I took the drywall ceiling down so its basically been blocking most of the available air through that vent since 1965.


----------



## beenthere (Oct 11, 2008)

Probably won'y hurt anything since the insulation would have blocked 90% of any air that was coming in.


----------

