# Flex duct connectors



## TREEBARK (Nov 9, 2011)

I understand regular flex duct connectors (splices) have beads allowing for good connections, but what do the pros do when you go from one size either up one or down one (16" to 14" or vice versa) in a trunk run and a wye is not where you want to make the transition? Regular reducers are smooth and aren't they really for metal to metal connecting? Thanks.


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## beenthere (Oct 11, 2008)

Use a regular reducer, duct bands, flat washers and screws, along with mastic.


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## Doc Holliday (Mar 12, 2011)

Not just for metal at all.


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## TREEBARK (Nov 9, 2011)

*More questions about fittings.*

Thanks for the response, I just did not know as I was thinking about code of what is acceptable and not as the splices are specific for flex duct right, but I have been told guys use regular metal pipe and cut it and make it for splicing, but I assume that is against code or maybe not. I have a 12" duct that is just taped up together at the extended 25 ft point and I am sure that is against code also. 

Anyway, my other questions are what do the pros do for example, you have a 6 inch flex duct going to a 6 x 10 boot and you want to, as I do reduce that 6 inch flex duct down to 4 inch. Do you connect a 6 to 4 inch reducer at the wye and again at the boot or do you change the wye and the boot, which would obviously require redoing sheetrock work which I want to avoid. If your wondering why, I have this setup in the tiny toilet room sized 3' X 4' and I see it as being very inefficient and so I want to increase my duct one size in my master closet as it has a 6" duct which I know is 75 CFM, but my manual d calculations says I need 180 CFM and it is always cold in that room. By the way, it also says I need 13 CFM in the toilet room, but I can't find what the CFM of a 4" flex duct is, but 5" is 50 CFM, which is still way more than what I need and I really don't understand why there is a register in the toilet room anyway unless code requires it, but it couldn't require a 6" duct that is for sure. Thanks, RC.


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## beenthere (Oct 11, 2008)

Run 6" all the way to the bathroom, and use a balancing damper at the trunk/wye to control CFM.

Cutting a 6" pipe to use as a splice is fine, and not against code here.


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## TREEBARK (Nov 9, 2011)

I wished I could, but without going more in depth, my system is way over in DSP because of my coil alone. So, which adds more to the static load the damper or the reduction size of the duct. Either way, can you still tell me if you did reduce the duct size, would you replace the boot or not? Thank you again for your time.


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## beenthere (Oct 11, 2008)

The reduction increases pressure drop more. 

If I decreased size, I would replace the boot, as the increase to go from 4 to 6 only adds resistance and creates turbulence.


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## TREEBARK (Nov 9, 2011)

Sorry, if I am making you repeat yourself, but I am planning to do this in my other very small bathroom and want this to be right as it has a 6 x 10 boot also and your saying if I replace the 6" duct with a 4 inch duct, replace the boot with like a 4" x 8" boot? And the boot and the new grille would have less resistance and air turbulance, right? I probably should replace the wye too then to do this more correct as it is a 8 x 6 x 6 and it should be a 8 x 6 x 4 right? I sure like the idea of the damper the more I look at this. Thanks again.


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## beenthere (Oct 11, 2008)

The damper is the better way to go.

Yes, a 4" boot instead of a 6 to 4" increaser. Reducers and increasers all add a lot of resistance/turbulence to air flow.


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## Marty S. (Oct 31, 2009)

Would you put a run in a room that only called for 13 cfm beenthere?


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## TREEBARK (Nov 9, 2011)

You know, the builder did this when we bought the home brand new and seems rather ridiculous, again I was assuming it was code requiring this as I know we may sometimes spend a longer amount of time in that room than we'd like, but being it has a door I figured it is considered a room that must be heated and cooled, tiny but a room. So, if you don't think it is a code requirement I could completely eliminate it all together. There is also an exhaust fan in there and thank god you can't hardly turn around in there, you might as well leave the door open. My wife is 5' 3" and 100 pounds and she avoids it and goes to our guest bathroom 95% of the time. So, I have no idea and I am open for interpertation here.
Thanks.


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## beenthere (Oct 11, 2008)

Marty S. said:


> Would you put a run in a room that only called for 13 cfm beenthere?


If the room(bathroom/half bath) is on an outside wall, yes. Unless the door has a fair amount of under cut on it.


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## TREEBARK (Nov 9, 2011)

It is not on an outside wall it is surrounded by other rooms all the way around and it does have about a half inch under cut. So, being that is the case, do I have to have a branch in there? The other bathroom does have an exterior wall. Thanks again.


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## beenthere (Oct 11, 2008)

nope, inside rooms like that don't need a supply.


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## TREEBARK (Nov 9, 2011)

Great! Thank you so much! That is 75 CFM that I can get over there in that cold closet (about 12 feet away), but being there is a 6 inch duct running over there now and Manual D says 180 CFM is needed, can I move up to a 8 inch or two 6 inch branches. The master closet is the farthest NE corner of the house and is L shaped or trianglar in shape. What would you do there? Again, I am thinking about static pressure and I assume that two 6 inch ducts is a lot less efficient than one 8 inch duct, but I read that report from the environmental building science article that rooms should not have 8 inch duct unless they are high ceilings or are large rooms and this one has a 8 ft. ceiling and @ 90 sq. ft. floor area, but it is a closet and not a bedroom (if that makes a difference to you all). Thank you for your time as I am learning a lot here.


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## beenthere (Oct 11, 2008)

2-6" won't get you 180 CFM. One of them would need to be a 7".

Why does a 90 sq ft room need 180 CFM?


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## TREEBARK (Nov 9, 2011)

I don't know why as I used that HVAC CALC program, in fact if you add up all the CFM it recommmends for all the rooms it calculates over 2,200 CFM using 2,000 CFM as its basis requiring a 5 ton unit. Maybe, because it calculated room by room sq. footage of 2,200. I also told you incorrectly that the master closet faced NE and should have been one wall faces SW and the other wall faces NW, sorry. It also recommends in the master bedroom @240 CFM and I have 11 foot ceiling and it is 14 x 18 feet and I currently have two 6" ducts, which seem way too small in there also. Thanks again.


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## beenthere (Oct 11, 2008)

Go in and change the total CFM to 1800. You'll get more realistic CFM's then.

Post the BTUs for those rooms, both the latent and sensible BTUs.


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## TREEBARK (Nov 9, 2011)

Hello again. I just can't thank you enough for being a little interested here as you don't what it has taken me to get to this point. I have not attached a file before so I tried it and I will keep trying till you can view it. Thank you very much.


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## beenthere (Oct 11, 2008)

Sensible BTU CFM
3996--------168 
584---------- 25 
2621--------110 
3531--------149 
206 ---------- 9 
6815 -------287 
1308 --------55 
7259 -------306 
7457 -------314 
2544 -------107 
2682 -------113 
7193 -------303 
1703 --------72 
345--------- 15 
3326-------140


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## TREEBARK (Nov 9, 2011)

Thank you sir, very much for your time. An air balancing guru guy's philosphy was not to even try to make the duct work more efficient if your coil and filters static pressure exceeds the furnace's design. I understand that, but I look at it as get the duct work as efficient as possible and if and when the coil or furnace has to be changed out, which is not going to happen any time soon, then at that time some minor changes may have to be made, but so be it. For example, I currently have 3-12's and one 10 inch flex duct trunks for supply and the same for the return, no matter what if I have 1 16", 1- 14", and 1-10" there's my 2,000 CFM for supply, right? I also understand in general, you should increase the duct size above that to lower you FPM to @ 450 also for your return, right? I am sure you pros, have other tricks that might accomplish the same task as mentioned earlier using ell's, etc. Yes, I know why not go even larger enough to have less duct runs. Well, it is physical space of the attic and the furnace is at one end of the home requiring this layout. Is there some custom work possible to make it happen? In theory, probably, but my pocket book is not unlimited, so I am working with the best I can. He said to try for 40, 40, 20 for the ratio of the coil, ductwork and last the filter. My coil itself is 0.498" and the furnace is rated at 0.5" @ 2,000 CFM with a 1 hp PSC motor, which I see is a better motor than the average, but it still going to have to work very hard, so I know I don't even have to mention the filter and I should go with all metal ductwork, but again it would all be out of specification. I know there are some coils rated around 0.3" to 0.4" range, but he said that still would not work to keep the system under 0.5".

What is the typical static pressure of flex duct work silimar to what I am describing, just out of curiosity? Again, I know it depends on how many duct fittings, infiltration, grilles, etc. So, I am saying just an average.

Thank you for your time.


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## beenthere (Oct 11, 2008)

3.5 ton and up furnace with A/C often hit .9" TESP. This is mostly due to poor return duct, and borderline supply duct.

Your 3-12s and a 10" are borderline for 2000 CFM. 

On a furnace, a 5 ton A/C system should have the return coming from the bottom, or one side and the bottom, or both sides, to keep the return static as low as possible, and get as close as possible to 2000 CFM.

Your return duct can have 700 to 800 FPM, but the air filter should be down to 300, but 400 is fairly quiet.


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## TREEBARK (Nov 9, 2011)

Thank you again for the insight, so my thoughts are in the same direction and I know without testing this is all general information and there could be lots of reasons why it will be farther off than I forsee and I am willing to risk it. I have an anenometer and a magnehelic gauge (reads up to 1") that I was going to mount in place eventually, but I am using and will use once I make these changes. I am changing the supply to 1-16", 1-14", and one 10", but I would like the 10" be a 12", but that is over 2000 CFM quite a bit, right?

The return I am going with 1- 18", 1-16", and 1-14" to get my FPM down to around 450 and if it is too much, then I will change accordingly. I am bypassing all the returns in the walls and mounting the grilles in the ceilings. I added up all the free area in my grilles and I will have slightly over 900 sq. in. If I understand what I have read and learned you want it to be @ 1,000 sq. in.

I had my contractor add a return and a 2nd 4" filter on the other side of the unit. The run is about 30 feet away mounted in the ceiling and it is just a humming at the grille and I measure @ 750 FPM and about the same on the CFM. I am making them come back and install a plenum that they are making the same size opening as the filter housing, which is about 21" x 20" or so, without me looking it up and they are duplicating it on the other side of the unit. 

Is it better or worse to be a little over in duct size or in available boots for the supply side?

Thanks again for your time.


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## beenthere (Oct 11, 2008)

> I am changing the supply to 1-16", 1-14", and one 10", but I would like the 10" be a 12", but that is over 2000 CFM quite a bit, right?


Won't flow more then what the furnace is able to move.



> Is it better or worse to be a little over in duct size or in available boots for the supply side?


Larger duct is better. only concern on the number of boots, is that you use registers that meet the throw requirements that you have.


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## TREEBARK (Nov 9, 2011)

That's what I thought, but I wanted to hear it, so at least it will be there if the coil gets changed out, etc. The chart shows @ 0.7 or 0.8 the CFM goes down to @ 1,900 or so that is why I wanted larger and less ductwork period as this compounds the TESP, which I know this is not how you pros would setup a system to start with, as you want to know all three factors I mentioned earlier. I see as the friction increases the CFM decreases, but shouldn't current increase? What I don't quite get is what is the advantage of having a 1 hp PSC motor over a 1/2 hp or 3/4 hp in a furnace? I mean even if you had very low TESP a 1 h/p motor is going to operate at a higher current than a smaller motor anyway, right?


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## beenthere (Oct 11, 2008)

A 3/4 HP motor won't move 2000 CFM through a evap coil, unless the evap coils pressure drop is less then .2", need horse power to move 2000 CFM of air. 2000 CFM of standard air is basically moving 9,000 pounds of air an hour. So that is the advantage of the 1 HP motor, it has a better chance of moving the correct amount of air.


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## TREEBARK (Nov 9, 2011)

That's interesting to know, so all those 5 ton units that have 3/4 hp motors are struggling unless, like you say the pressure drop is quite a bit lower, which I noticed the standard coils were very high.

Back to your comment about throw distance out of the registers, I tried to find that information at Truaire and could not, so can you tell me where I can find it. Or maybe I am not looking at the chart right, but it does not display it like Hart and Cooley does. For example, under a 8 x 4 grille at 400 FPM it says 134 CFM and under that it says a value of 20 for one way, but what does that mean nor do they give the AK. which would be nice to know also like Hart and Cooley does. If not minimumly, I would like to know what they would be for truaire 301M grille sizes of 14, 12, 10, and 8 x 6's, and 10 and 8 x 4's. They say one way curved but they do adjust with the outer blades and adjust the opposite direction inside the grille. To me that is two ways, but I guess the blades insides move left or right and the outer curve blades open and close the grille air flow, right?

Also, I have started installing 12 and 14 inch square boots in my ceiling for returns and they are not insulated and they say staple insulation around them right? But, I don't have that kind of staple gun, but I do have a heavy duty staple gun, but not those kind of staples. What are my options to wrap the insulation around those boots correctly? I thought just wrap tape around and around until I get it all done or use 3M 77 spray contact glue, but I want to do it right. Once again, thank you for your time.


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## beenthere (Oct 11, 2008)

Might have to contact truair and ask them for their specs on throw.

I have 2 staple guns for insulation, so i have never tried any other type. You can probably spray glue and tape the insulation.


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## beenthere (Oct 11, 2008)

Ah ha. Think I found it.

http://www.truaire.com/sitemap.html

http://www.truaire.com/124/detailview/details.html

Click on technical data sheet.


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## TREEBARK (Nov 9, 2011)

Man, do I feel dumb, this is what happens when I can't see the trees for the forest or whatever that saying is, but I still don't know what those numbers represent under CFM that are not bold and next to 1 way, 2 way, etc. Surely, an 8 x 4 grille cannot throw air 20 feet away at 134 CFM @ 400 FPM? 

In general, why didn't they use 12 x 8 grilles for 8" supply flex as they used 14 x 6 boots and grilles in my 11 feet ceilings? (esthetics?) Seems like a lot of resistance in itself? The same goes for the 6" supply flex as they used 2- 10 x 6 grilles in 11 feet ceilings in my master bedroom and couldn't they used 12 x 6 grilles there also? I know you probably won't know that, I just thought I would throw that out there. 

The supply house was going to let me borrow their stapler if they had one, but they didn't have one. Those guys have been very generous as compared to another wholesale company down the street.


Thanks for looking up that information again.


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## beenthere (Oct 11, 2008)

A 8X4 grille with 134 CFm going through it can throw air 20 foot. it will also be loud.

Some of your registers m ay have been selected for their throw. Throwing warm/hot air down 11 foot takes a good register, and a fair amount of velocity.


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## TREEBARK (Nov 9, 2011)

Once again, I learned something new. That is why I wonder why they chose a 10 x 6 grill vs. a 12 x 6 grille for 11 feet high ceilings as the 12 x 6 throws slightly farther than the 10 x 6. When they have several 10 x 6 grilles in several much smaller rooms that have only 8 feet flat ceilings. Something tells me economics was factored in here somewhere in all of this. But if you don't do this for a living you wouldn't ever know except, of course discomfort in the room, but that would not be the only possible problem if comfort was an issue. I see it can get to be quite complex and that is when it is time to call the pros in, but in my area they are few and far between that would even think about doing anything other than check the freon and filter and charge you x amount and onward they go. You can't really blame the technician if the company sends someone that just doesn't know, I understand and that is who we should be upset with and not the technician. It would be like calling a mechanic to your home to repair you vehicle and you say it jumps and jerks around and it is the transmission, but the mechanic's expertise is engines, so he can't help you except tell you who to call.

I'll have more questions later as I will let it be this evening. Have a good evening!


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## beenthere (Oct 11, 2008)

You too treebark.


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## TREEBARK (Nov 9, 2011)

Well, sir, I added up the total CFM with your numbers and it totals 2,173 CFM when we know the actual CFM will probably be closer to 1,800 to 1,900 CFM or even lower due to TESP right, which is a very wide range here to aim for. These numbers and the numbers I gave you are all telling me to increase the overall ductwork which is basically, going up one more size on one run and that would cause you to lose more velocity in the system if everything else remained the same, right? What is the CFM you would strive for in this case rather it worked or not? Thanks again for your time.


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## beenthere (Oct 11, 2008)

1850CFM. You regain half of the unused latent capacity. So not meeting the 2173 is not a real problem.

Even if duct velocity is a little low. As long as you choose the registers that give you the throw you need, it won't hurt anything.

Duct velocity and register velocity have no bearing on each other.


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## TREEBARK (Nov 9, 2011)

Okay, now you just went flying over my head on that one, but I'll take your word on it. No, I went and looked it up, you're trying to trip me up there or if you did not think you did, you did. You're referring to air's capacity to retain moisture is what is available to recycle? I'm lost and don't know what I'm saying now. Can you explain it a little better like a glass half full or or half empty kind of way? I did get the rest though.

Thanks again.


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## beenthere (Oct 11, 2008)

latent heat is the heat to change the state from liquid to vapor or vapor to liquid. Your A/C will have X latent capacity. If X is say 10,000 BTUs. And your latent load at desing conditions is 4500 BTUs. Then you will get half of the unused capacity back as sensible capacity, in this example 2,750BTUs. So the sensible capacity increases, causing the air temp from the A/C to be colder. So not as much air volume is required.


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## TREEBARK (Nov 9, 2011)

Thank you for that information, I get it, believe it or not, but you got me wondering what my next move ought to be here. As I mentioned, I am going with three supply ducts, 16", 14", and 10". The problem with the 10" duct, it supplies the three back bedrooms and the bathroom. Your numbers say front bedroom-149 cfm, office-110 cfm, bathroom-25 cfm and the back bedroom-168 cfm. Currently they are all 6 x 10 x 6 boots with 6 x 10 grilles. But, 10" flex suppose to supply 300 CFM at 700 fpm, so if you were wanting to tweak this, what would you do assuming everything else was equal, which we know it is not. My first reaction was make them all 7" each except that back bedroom could be an 8" right (but that just seems too much), and reduce the bathroom down to 4" and now that totals to 330 cfm plus whatever a 4" duct outputs ( I have not found what it does yet). I know 5" is 50 cfm, so I was guessing 25 cfm? These rooms are generally 11' x 11' with 8' ceilings. But I put my anenometer up there and without the grilles in place they all read @ 110 cfm and @ 600 fpm with my current setup giving me fairly close to what I should be looking for already, right? 

I'm saying all this as maybe I should do nothing until I do install the larger returns and get them sealed up and see what I read first? 

Thank you for your time again.


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## beenthere (Oct 11, 2008)

> I'm saying all this as maybe I should do nothing until I do install the larger returns and get them sealed up and see what I read first?


Yep, get your returns in, and then retest those supplies with the grilles in.


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## TREEBARK (Nov 9, 2011)

Thank you sir, you see I am learning something, I hope to get my returns done this weekend, but I am installing can lights, etc. and juggling some contractors coming and going. 

Thank you very much for your time and for responding back.


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## beenthere (Oct 11, 2008)

Sure thing. Yep, renovations can eat up a lot of your time.


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## TREEBARK (Nov 9, 2011)

*mounting register boxes*

It is taking a lot longer to cut those openings and seal them up tight, but I am getting there. My next question is I did get a couple of insulated register boxes, but they are smooth all around and have no flange, so how do you support them if you center them between joists or even against a joist in the ceiling? I had bought other register boxes that had about a 1" flange all the way around and you could buy rails and the metal bent over them for support, but not these. Just smooth rectangular boxes.

Thanks again.


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## beenthere (Oct 11, 2008)

You have to either buy or make your own rails for them.


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## TREEBARK (Nov 9, 2011)

I was making mine out of 1 x 2's for the return boots, but they all have flanges for the rails to fit into if I had wanted to use those rails. I layed my 1 x 2's flat down against the flange, which are against the ceiling and attached the 1 x 2's to the joists. But I have nothing to anchor to other than the box itself, so you must be saying drill holes straight into the side of the boxes and come back seal them up. Seems like more work on us with the potential of air leaks, but I guess it saves money for the supplier not to have flanges on them.

Thank you again for responding.


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## beenthere (Oct 11, 2008)

You can use 1 1/4" long #6 screws(1/4" head) so you can run them in with your drill.

They saved a penny or 2 on not having rails.


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## TREEBARK (Nov 9, 2011)

That's exactly what I used to connect the 1 x 2's to the joist. They were exterior gray painted prime guard drywall screws. I found when you use the interior or black non painted screws they are much more difficult to drive into wood, of course they are not wood screws, but they work well as that is not a lot of weight being applied there. I saw an older listing where you talk about staple guns and I bought a powerfast staple gun and at first I had problems finding the right staples, but I did. 

Do you just pull the insulation on flex duct up and over the wyes all the way up or do you keep them back and use duct insulation and wrap and staple them. I saw a comment once about there being a trick to placing a whole piece over the entire wye, but I haven't figured it out yet without wrapping several pieces. If you know the trick I would like to know otherwise, I have not decided which way to do it. I don't see how you can completely cover the wye with all three coming together, but maybe you can. Thanks again for your time.


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## beenthere (Oct 11, 2008)

I pull it up as far as it will go, and wrap what it doesn't cover.


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## TREEBARK (Nov 9, 2011)

That's what I'll do, KISS-Keep it simple stupid-someone told me of that phrase recently. Okay, I can only imagine every pro has his own way of securing the flex duct and insulation as I have read. I am curious to your method. I was going to tie wrap the inner liner then tape it and then tie wrap around the insulation and then tape it. I have read some people use mastic, especially around the fittings. I had to install a reducer and I used sheet metal screws, then hvac fiberglass tape and then mastic for it, but I don't see the advantage of using mastic, tie wrap, then tape or in the reverse order or any combination thereof connecting flex duct. I'd be all day on just a couple of fittings doing that. Thank you!


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## beenthere (Oct 11, 2008)

Flat washers and screws for the liner, mastic that, and then a duct band to fasten/hold the insulation.

Takes longer, holds better.


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## TREEBARK (Nov 9, 2011)

Okay, I can see no tape needed on the liner, but I assume duct band is the big 3 or 4 ft wire ties as I call it and I assume the 181 thin flex acrylic tape or the more expensive metal 181 approved tape around the insulation and duct band as you call it.


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## beenthere (Oct 11, 2008)

I don't tape the insulation.


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## TREEBARK (Nov 9, 2011)

You know, I can see why you wouldn't, but I thought most codes require it or at least down here in Elvis Land.


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## beenthere (Oct 11, 2008)

In new construction you have to. In existing, its not enforced.


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## TREEBARK (Nov 9, 2011)

Do you mastic the take-offs on the plenums? I read they become un repairable once you do that also. I am just trying to find if you use any tape at all as I see very little need at this point. I know you suggested waiting until I got all the returns in place and I might still yet, but I am pressed for time tomorrow and I have to get these boots and others in place for a reason. So, in general all my bedrooms which are around the perimeter of the house are colder than in the middle of my home by about 4 to 6 degrees. The coldest, referring to this winter right now is my master bedroom, bathroom and walkin closet. So for example, our numbers say @ 303 CFM in my master bedroom. I have two 6 x 10 boots and isn't that way short and the ceiling is 11 feet high by 14 x 16 area and is on the nw side of the house. I want to replace them with 8 inch each, but afraid it will be a little too much. But as miserable as we have been, particularly in the summer, I have to control that urge to get that volume in each and every room. Maybe I should keep it at 7 inch each or 12x 6 x 7 boots and later if it is not then replace them again, but I don't really want to do that either, but I will to get it more right. Either way I should have enough volume. Thanks again for your time.


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## beenthere (Oct 11, 2008)

Yep, mastic on them too. You can use mastic tape/hard cast tape.


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## TREEBARK (Nov 9, 2011)

Can you or do you mastic the wye's first before you connect the flex duct? If you do it all at the same time, seems like it would be messy or it would smear off or not seal right while connecting the flex duct, etc.


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## beenthere (Oct 11, 2008)

Mastic after connecting the flex.


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## TREEBARK (Nov 9, 2011)

#8's or #10's or special washers with standard 1/4" sheet metal screws? How cold can it be and still mastic it all? Thank you!


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## beenthere (Oct 11, 2008)

8's are fine. 

How cold? usually run the heat in the winter, so it dries.


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## TREEBARK (Nov 9, 2011)

I suppose putting mastic on the fiittings and boots prior to installing them is not efficient to you, but I don't see how you can seal the joint at the actual "y" joint in one coat, because you cannot pull the flex beyond it and seal it in one coat. I have put one coat just on the wyes and boots and let it dry and you see holes in various places around the "Y" and around the round duct in the boot as it is not locked in there as there is some movement there. I am even putting mastic on both inside and outside the wyes before I start connecting the flex. Maybe you are not overly concerned of the various holes? Thanks again.


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## beenthere (Oct 11, 2008)

Getting fast at mastic on round pipe(wyes)and flex takes a bit of practice(I'm still not the fastest at it). And I'm not afraid to put it on a bit heavy. 

I don't have any inside with me(to look at the brand name), but all my mastic comes from the same supply house, and it doesn't crack or shrink when it dries. Unless its a large hole that is being covered. In that case, I put mastic down, then mesh tape over that, and then mastic over that again.

Not the best way to leak check your flex duct, but it works for the supply side(and for you will save you money on having someone come in and use a duct blaster). Is to close off at least half of your supply registers, and run the fan at high speed. After 10 minutes or so. If the outer wrap on any run inflates, you got a leak.


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## TREEBARK (Nov 9, 2011)

Thank you for that valuable information. I was starting to wonder how to check them out. I have been buying DP from one hardware store and Masters from another hardware store that we all know. I probably am putting it on too thick, as for example in the "Y" part it is taking at least 2 days to dry and both types crack or holes show up later. So, once it seems completely dry I put another thinner coat over those gaps and holes all in my garage. I have fittings everywhere, it looks like a jigsaw puzzle. In fact, I am losing track which ones go where and I am starting to write on them where they go. I like the idea of suspending the tape, but I bet some would say that is not as strong of a joint as laying the tape directly to the metal. So, I say whatever, either way in that case something is better than nothing filling large gaps. I am telling you though the preinsulated boots I bought, the actual round fitting pulls up and down a sixteenth to an eighth of an inch. To me that is bad period, as I have coated them before mounting them and just accidentally grabbing the round part separates them or I can see once you have it in place and start connecting the flex and pulling it taught it will separate then also. Seems like I need to wait until after I mount them in the ceiling, hang the duct and pull them taught then I need to seal them. Just seems like a no win situation of 100 percent seal, because again, if I do have a leak and start messing around with the duct, bam, the boot will leak. 

About the leak checking, if I have one and I have mastic the liner and not let it completely dry and have come right behind and strapped them tight around the outer insulation, that could be a nightmare to undo. So, again sounds like I should let that dry a day or two before strapping the outer insulation?


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## beenthere (Oct 11, 2008)

A sheet metal screw put in the boot so that the head pushes against the fitting helps to keep them from moving.

On a completely assembled system. If you run the fan, the mastic will dry quicker. Real thick, it will take a day or 2 to dry. Its a practice thing, to gt it thick enough, but not too thick. If you want to wait, no problem, your not under the gun with a start up/finish date.


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## TREEBARK (Nov 9, 2011)

I did just that, ran some screws in there and it worked, thank you and your right about patience, but I have been at this awhile and I am just ready to get it all done.

I should have enough volume and was wondering if it is allowable and if you wanted to add a 4" boot to a kitchen pantry that it backs to our garage and in the summer it gets hot inside the pantry would you add it. I guess the down side as we might get more heat in there than we would care for in the winter. There is a small laundry room on one side of the wall and the refrigerator is on the other side of the wall, which is in the kitchen. I guess it is like a medium size closet. I know it sounds like I am being obsessive here, but before I seal every thing up I thought I would add it. It has an 8 ft ceiling and is about 40 inches wide and 2 feet deep with a recessed light in it. It has a regular 32 inch door with a half inch undercut. The kitchen has one 8" boot and the laundry has a 6" boot, so this would be right in between them (about 10 ft apart) and the laundry is the last and farthest away from the furnace. Thank you for your time.


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## beenthere (Oct 11, 2008)

Usually don't put a supply in a pantry. There is no code against it, just most people don't have it done. Putting a 4" supply in it is fine, and as you said, now is the time to do it.


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## TREEBARK (Nov 9, 2011)

Finally, I have replaced and added all new boots. What is your sequence of running the flex? Start at the boot and working back to the connectors, then to the plenum or vice versa and then hang it all last? Not to beat a dead horse, but your routine is to not put mastic first, but connect the flex liner with screws and washers and then mastic over that (let it dry, I guess?) and no duct strap yet, but then pull the insulation up over the connections and then use the strap and then your done. No tape or other mastic or straps (except strapping the duct to the rafters). I assume to use the same amount of screws to each connector, boot etc. that you would use when connecting reducers, or if you were using metal pipe. Thanks again for your time, as I am slowly progressing.


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## beenthere (Oct 11, 2008)

Varies with the individual run. In basements from start collar/take off to boot most of the time. In attics, from boot to start collar.

3 washers and screws(IMC requirement is 3 mechanical fasteners). Mastic after mechanical fastening and strapping. Then pulling liner over connection after mastic is dry and checked.


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## TREEBARK (Nov 9, 2011)

It's all in the attic, so thank you, I kind of thought that is how it would work. You must be calling the insulation the liner? So, you are using screws and strapping, which sounds good to me, but do you strap the insulation down or leave it loose as I know you don't do tape. Thanks again.


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## beenthere (Oct 11, 2008)

Strap/duct tie.


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## TREEBARK (Nov 9, 2011)

Okay, I have barely connected some returns and I am trying to get a cfm reading using my anenometer. I am not sure you know this, but I understand if you measure your return grilles in place you do not subtract the grille effective area because you are measuring the side that is not restricted as compared to supply registers, correct? I"ll be doing this one step at a time, if you don't mind. Thanks again and boy it has been a struggle connecting these up. If you don't have these 18" and 16" wyes perfectly level you tear the liner easily around those screws and washers moving them, etc.


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## beenthere (Oct 11, 2008)

You still use AK on the returns. As you are measuring the velocity caused by the reduced free area of the grille opening. 

If the washers are spanning across 2 rolls of the wire, it shouldn't tear.

One step at a time is a good way to proceed.


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## TREEBARK (Nov 9, 2011)

I can't believe I did not figure that out. I went out of my way to avoid the wires. I also have a slight tear in the outer reflective foil in one flex. Any suggestions or should I do anything to it. I am disgusted that it happened as it is an 18" duct and was awkward up there trying to rotate it and the wye and put those darn screws and washers in and not even the right way. I still am going to do the screws and in fact I am putting 4 screws in these large fittings. So, now I have strapped and mastic some of them. If I had started with the smaller fittings I could handle it better, so I am not sure what I will do with these. I am just ancy to be sure I haven't oversized this system or just plain did something wrong. I know these readings are inaccurate, but just very curious. This large duct in particular is where my contractor had a 12" directly to this one ceiling return grille and it was very noisy, but that has gone and I am so happy with that in itself and has made my rather proud, but I know there is a lot more to do and I need to take it one step at a time as you say. This project has taken me a lot more time to accomplish and I hope you are willing to give some pointers to the end or when I can't go any farther without some on-site pro advice.


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## beenthere (Oct 11, 2008)

There is a learning cure in everything. I probably should have mentioned that the washers go over the wires. But I'm a bit more use to showing someone first hand. And sometimes I forget that people on the internet have a problem reading my mind. Sorry about that.

Tape the foil, mastic tape/hard cast tape will work, but very expensive for just one tear. May want to use regular 181 foil tape on it. Its the vapor barrier, so its best to seal it, and sealing it helps to prevent the tear from getting bigger.


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## TREEBARK (Nov 9, 2011)

I know it is just second nature to you and you can't always get it all out there and besides, the pros would have known and I am definitely not a pro at this. I understand the vapor barrier and that is what has aggravated me as I was trying to replace several pieces that have gotten torn or chewed on by rats over the years and now I feel I am not getting anywhere related to that. If it wasn't because it is the 18" size I would replace it, but I have spent enough money on this project and as long as it is acceptable to fix it I will, but I will try harder and be more careful though. I have both kinds of that 181 tape and lots of it as I was originally going to tape everything, but you changed my mind on that one. It's the thicker aluminum type and the acrylic type that is specifically for flex duct. But I have plenty of that mastic and fiberglass tape that is just like what sheetrock folks use, but is specifically for HVAC. So, money not being the object here, what would your preference be? The tear is about 3 inches, so would you go all the way around to make the connection or just kind of patch over it with whatever you would use? I guess I could cut a piece from leftovers and staple it with that new stapler I have and tape that and/or mastic over that or let it be with stapling only? Again, thank you so much for your time and I owe you something for all this help, so think about that for later on.


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## beenthere (Oct 11, 2008)

Just patching the torn area works pretty good, as its easier to seal it, then trying to seal the tape the whole way around the flex.

I would use spray glue around the torn area, and make sure the spray glue gets on the exposed insulation. Then use the 181 tape. This makes a good seal. then mastic when the duct is in place and not going to be disturbed again.

And I have never used spray glue, that it didn't get on me also.


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## TREEBARK (Nov 9, 2011)

You see why I asked, as I see the importance of it holding that I know 10 years from now that heat in the attic is wicked on anything that is not solid like wood or metal. I totally see where you are coming from and when you say 181 tape, I'll assume either one, but I personally like the thicker tape as it seems that it would be good for this patching. I hope you say the same about mastic, because I got it on me quite easily while trying to do some underneath the duct the other day and that ain't fun to get off of you either once it dries.


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## beenthere (Oct 11, 2008)

LOL... Yep, mastic too, and roofing cement. 

You can try the thicker tape.


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## TREEBARK (Nov 9, 2011)

What's your opinion on and have you ever ran a run over to an attached garage just to have some conditioned air as I am going to insulate the attic over the garage and I have insulated the outer walls. I know techncially, you can't run a return and I don't want to throw the system out of balance, but I expect to have more than enough to cool our home this summer. It already will smoke you out of there now heat wise and I haven't got the correct size ducts in place yet (larger).


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## beenthere (Oct 11, 2008)

No supplies or returns allowed to go to a garage from the same system that serves the house. Its against code. The garage must be on its own system.


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## TREEBARK (Nov 9, 2011)

Okay, I wondered about code issues. Won't do it. I thought I would ask though. I actually have two 6" exhausts that I had knocked out of my brick wall for two portable AC units 14,000 btu each that ought to work for the summer and one 220 volt 4000 watt in wall heater that my electrician has yet to finish up on. Its a 20 x 20 area. Thank you again.


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## beenthere (Oct 11, 2008)

Your welcome.


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## TREEBARK (Nov 9, 2011)

Well, I am making some progress and I have some major questions and I have a lot of information to share, but I just can't say it all and I won't. But before I go into this, I need to know can you accept not having pulled all the duct tight, strapped and mastic and still make changes to the boot sizes if you suspect it is not or won't be enough? If you can I will just tell you a few things first. The good news is that I have run two out of three supply runs loosely and the third run will have very little change, especially the supply size will be the same, just new. I have run all three return runs also, but they are loose to allow for the moving of the furnace over a foot. 2/3rds of the house is maintaining 70 to 72 degrees (set to 72 degrees) with no noticeable problems. The main concern I have is I have not improved going from the 4 ton unit to the 5 ton unit the temperature in the master bedroom (runs 67 to 68 degrees same problem) and bathroom (68 to 69 degrees same problem), but on the other side of these two rooms is the master closet, that if you recall I went with a 7" run and it runs at 74 degrees, but the colder it gets outside the higher it gets in there. I saw it last night at 78 degrees when it was around 20 degrees outside. You can see the correlation there (longer run times). So, I want to increase the master bedroom runs from 7" to 8" or should I wait. Or do you think pulling an extra 18" slack out of the 16" duct at the plenum will increase everything accordingly. I measured the CFM and FPM on those two particular runs with the grilles in place and the one closer to the unit or the first one you come to walking into the bedroom reads 140 CFM and 420 FPM. The second grille which is nearly the farthest run other than the master closet read 150 CFM and 500 FPM. Back behind the ones in the master bedroom are in our living room and they are two 8" runs and one is about 8 feet from the furnace and the other one is about 15 feet away. The first one reads 600 FPM and 270 CFM and the second one reads 490 FPM and 200 CFM. So, it is two runs running parallel off of the main supply trunk. One goes to the master bedroom and the the other goes to the master bath and closet. The closet reads 440 FPM and 82 CFM and the bathroom a very short 6" run reads 550 FPM and 100 CFM. Back behind these two is our Family room run and it is one 8" and reads 560 FPM and 240 CFM. If you add them up by the Manual D calculations that are suppose to be 810 CFM and I ran a 16" or starts out 16" and after about 5 feet it goes to 14" on downward to the ends. So, there are a total of 7 boots on this one supply, 3- 8" and 3- 7" and 1- 6". I can tell that the staight away runs have higher velocities at the ends than the branching off of the wyes. I later realized I am using regular metal connecting fittings/wyes and not specific flex duct wyes, I hope that was not bad wrong. Should I change the ones that come from the main supply duct and feeds the branches with true flex duct wyes or just go up one size in the bedroom and the bathroom? That means tearing out the the three boots again and I don't want to do that, plus three new grilles but I will in a heartbeat to get it more right. Seems like I will lose more velocity at the sacrifice of maybe increasing the CFM, but maybe that is okay and desireable in this situation. If you understand all this, and I barely do I figured you have a feel for this and I hope I am close and only need to do a little changing, but I wanted to do this before I get it all sealed tight. But, maybe I can't do it that way? Again, I am just asking for your opinion and I know none if it may still work, but I want to prove these guys wrong as they told me if I went up in duct size I could end up back where I started and it is true for these same rooms and it is all my doing 100 percent. Thank you again for your time.


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## beenthere (Oct 11, 2008)

Does the master bedroom have its own return? If so, what size is its return? If it doesn't have enough return, you can end up with a cool room when the door is closed.

May be easier to put a fourth supply into the master bedroom, then to increase the size of the 3 existing supplies.

If you leave the door to the master bath open, then when the MB gets warmer, it should too.

The connectors your using aren't causing the temp problem in your MB. So no need to change them out.

Do you have balancing dampers in all of the supplies? If so, then they can be adjusted to decrease air flow to the room that is over heating, which will cause more air to go to the MB and bath.If not, installing dampers in the supplies for that room, and turning them down will help the MB and bath, and is what I would try first.


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## beenthere (Oct 11, 2008)

If you don't have dampers in your supplies in the attic, and your supply registers in the room that is over heating have dampers in them. try dampering them down first, to see if it helps enough with your MB. If so, then cut in the dampers. 

But I think you'll need to damper down all of the other supplies to get the MB and bath to match temp to the rest of the house.


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## TREEBARK (Nov 9, 2011)

So, please tell me I am not going to have to start all over is all I care about right at this moment because I am partially panicking and disappointed as I did not expect this to occur, but I am ready to deal with it until I can't get it. I have no dampers and to be honest, I did not want to add any as I mentioned earlier, my coil is very restrictive (0.5 IWC) and I just did not want to make it worse. Where exactly would you place a damper or dampers at this point? Can I make something work as a damper to just try as I really don't want to go buy any, but I will if I can find them for the different sizes. 

What is your concern if I increase the boot sizes to 8" in the bedroom? I am thinking about temporarily changing the 10 x 7 x 7 wye to a 10 x 8 x 8 wye that feeds just the MB and running 8" duct to the two 7" boots just to see what happens. Is that a terrible idea?

The other run feeding the MB bathroom and MB closet has a 10 x 7 x 7 wye with a reducer down to a 6" for the bathroom only-FYI. I know ya'll don't like reducers, but which is worse on the system resistance of a damper or a reducer?

Again, according to documentation that I now doubt, a 16" is suppose to supply 1,000 CFM at 700 FPM and adding my boots on paper is 810 CFM, but adding the actual readings of those registers on that one run I am getting 1,260 CFM. Did you get that and that is why you are suggesting damping? Why is it so high, this is heat mode and I know it is suppose to be lower due to it should be on medium or medium high or T4 and that is @ 1,700 CFM @ 0.5 static pressure. So, I am confused about all of this as something is not adding up and maybe a topic for another day. 

Thank you very much for your time again.


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## TREEBARK (Nov 9, 2011)

I am sorry, I missed your first message, but I have one 10" supply feeding two registers in the MB 7" each and I have a 14" return in the ceiling. The MB is open to the bathroom as it is a regular door opening with no door. I have a separate 10" supply run feeding one 6" register in the bathroom and one 7" register in the closet. So, I believe if I did open the closet double doors it would probably warm the bathroom some, but definitel not back through the open door to the bedroom as it is 16 x 18 feet with 11 feet ceiling. It has three double pane windows that are not insulated in the glass. You are now giving me some options that sounds doable plus a lot of hope.

Thanks again, sir.


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## TREEBARK (Nov 9, 2011)

I read the closet incorrectly and it reads 420 FPM and 150 CFM, my fault there. Just in case you are curious the bathroom register reads 420 FPM and 170 CFM. Closet has one 7" register and the bathroom has one 6" register. The closet has an 8 foot ceiling and is triangle in shape 10 x 10 on the back two corner walls and about 15 feet across at the entry width into the closet or about 3 feet in depth, yes quite small, but when we had the 4 ton unit with a 6" run it was always very cold back there, so made I sure took care of that problem didn't I? I know, I probably should have reversed the order and went with 7" in the bathroom and 6" in the closet, but look at the numbers they are almost identical, which I don't understand. I don't know now if I increased to 7" in the bathroom if it would help or cause the closet to get even hotter or what if I went to an 8" in the bathroom? The bathroom has an 11 foot ceiling and is about 10 feet wide by 15 feet long. 

Thanks again, sir.


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## TREEBARK (Nov 9, 2011)

Well, sir I temporarily removed the 7" duct or I cut it at both boots and the wye and slipped the 8" over both ends and it has increased the temperature about 2 degrees in the bedroom and about one degree in the bathroom or 70. 5 degrees and 71 degrees respectively, while not affecting back in the main rooms that the supply is feeding (they are about 73 degrees). So, I also plan to change the 10 x 7 x 7 wye to a 12x 8 x 8 wye and I figure it will put me over the top. I want to wait to see how that affects my bathroom and closet next. But, I am still going to have to tear out those two 7" boots. I wished I had not been afraid to have went with the 8" originally, but every thing I read seems to say don't put 8" in a bedroom, much less two of them and you wouldn't tell me either, which I completely understand why. Also, you remember me telling you about putting a 4 inch in the pantry? I did and it is putting a little too much heat in there (74 degrees) and I have temporarily closed the grille. Do you recommend leaving it that way until summer or install a 4" damper? I was trying to avoid using any dampers, but in this case I think I will have to. The 4" duct is about 8 feet in length and is next to the last boot before the small laundry room on that run. 

Thanks again for your time.


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## beenthere (Oct 11, 2008)

Since its a pantry. Leaving the register damper closed is ok, since it not a room that noise will be an issue. Which is the main reason for not adjusting register dampers.


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## beenthere (Oct 11, 2008)

Dampers, are our friend. They add .03" PD to the TESP of the system. Thats the total, since PD is not accumulative per damper because they are parallel, and not in series with each other.


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## TREEBARK (Nov 9, 2011)

I don't think you were trying to trick me but when you say register damper, I think separate components. When I said closed the register, I meant close the actual register grille in the ceiling. I can install a damper in the 6 x 6 x 4 wye, but I think I have to add some length on that 4 inch because of the way it is made, but maybe not. But, if I understand your statement you are saying just opening and closing this one register grille is okay, not great, but acceptable.


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## TREEBARK (Nov 9, 2011)

About the dampers, I am curious as this same run I had to install a few reducers, since the supply house did not carry for example a 16 x 16 x 8 wye as this is required almost right off from the plenum (4 feet) so I had to go with a 16 x 16 x 10 and I reduced them to a 16 x 14 x 8 and then in another 5 feet went with a 14 x 14 x 8 that they had and went on to the master bedroom, bath, and closet and one more run to our family room. I bet that was disastorous on the PD, but without having a custom wye made, that is what I had to go with. But again, like I said earlier the CFM adds up over 1,200 CFM still out of this one 16" run. The other two are 14" and 10".

Thanks again for your time.


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## beenthere (Oct 11, 2008)

When I say register damper. I am referring to the damper/louver that the register has. not a separate one that you would need to install.

Each reducer in a line adds some PD. You haven't hurt you air flow though, since the last runs are going to the area that is the warmest.


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## TREEBARK (Nov 9, 2011)

Thank you for that information. Well, you got me thinking as I have not ripped out those registers yet, because I have an open floor plan and there are a total of 6 8" boots and one 6" boot that I added, which probably I did not need that the temperature in these different rooms run between 73 and 74 degrees. You could say this is 60 percent of the house floor plan, so I could install some dampers, I guess, but I still feel it won't be enough, but it sure would be a lot easier to do. What bothers me about those dampers is I can't see how you can completely seal the holes that the dampers would mount to without sealing them up with mastic and that makes them non-adjustable at that point.

My question is how and where do you strap the flex duct near the boots, because I was trying to avoid 90 degree bends period, but if you pull them tight and look up through the grill, the side with the tight bend is where the flex krinkles up and is not nice and smooth as on the outer bend, but if you go straight up to take that out youstill have to make a pretty tight bend or you will hit the rafters or the roof decking and you still have the same issue just not at the boot, but where the bend does occur. I saw these straps that supposedly creates a smooth 90 degree bend for flex duct from 4" to 16" that are shaped like the capital I with a bend to them and you use two duct or wire tie staps on each end around the outside of the flex duct. Are these 90 degree bends bad, because I know they are if you use 90 degree metal fittings they are bad for your PD, right?

Thank you for your time.


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## beenthere (Oct 11, 2008)

A 90 ell in sheet metal is equivalent to 15 foot of straight duct.

In a tight area, that the flex may kink, I'll use a sheet metal ell to connect to the boot. I haven't tried those plastic straps that you said about yet, so don't know how well they work.

On a run to a boot, if you need to make a bend,/turn with the flex. Pull it tight to stretch the duct out, and then make your turn/bend as soft as you can, without going to excessive length.

The dampers would be adjusted to the air flow the room needs. and the masticed over the hole.


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## TREEBARK (Nov 9, 2011)

They have them straps on HD website and comments are positive, but they don't seem to come from the pros. It's not that they will kink is just that you see the wires close together on the inside bend versus nice and taught on the outer bend and the only way to spread it out is to be straight as possible and that is impossible unless all duct work could be run straight down to them with about 4 or 5 feet of clearance from the boot to the roof. So, it sounds like to me you just live with not being able to have perfectly smooth inner walls on tighter bends throughout the entire system. One more comment about the dampers, you must go with a happy medium for summer and winter because manual J has two sets of numbers. And to be honest, I am much more concerned about the summer or high speed than I am about winter, but I am trying to be sure I am heating properly right now since I am doing this right now. I guess, I am curious which way do you look at it. Enough air flow for summer or winter, I just don't want to have to readjust dampers, etc. later this summer. I was told by the contractors you have to adjust the dampers twice a year just because, but as I think about it there is a reason for two speeds high for cooling and medium high for heat. I guess that is another reason I wanted to stay away from dampers. Shouldn't I read different CFM and FPM now as compared to high speed in cooling? Maybe not once the coil is condesating creating more PD even though it is on high speed?

Thanks again for your time.


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## beenthere (Oct 11, 2008)

You probably won't find Pros going to HD to buy things like that. At least not too often.

When ever connecting to a boot At an angle, the inside will have the wires close together. just need to make sure its not too harsh.

Damper adjustment is done for the mode that needs the most air. Then as you surmised, as the fan speed changes, the air flow increases or decreases with it. The kitchen could become warm then expected in the winter when cooking. As its cooling air flow is generally high for it area to compensate for cooking during the summer.

It is a bit of a happy medium.

Even in basements, if the dampers aren't sealed, I don't know of anyone that actually adjust them each season every year.


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## TREEBARK (Nov 9, 2011)

Okay, I got it. I guess I should have asked you and I am guessing it is not detrimental, but using those specialty straps to force a nice clean 90 degree bend in the flex duct itself is probably much better on the PD, if there is sufficient room to do it that way rather than buy metal 90's for example at the boots. I also suppose it is the 90 bend that makes it harder on the PD more than the actual fitting itself? I am thinking though, how can this gadget make a 4" duct bend cleanly as compared to a 16" duct, you know. It says it can make that range and create neat 90's I am not convinced, but then again maybe it could. I will try and send you a link to it as I have it saved on my wish list, one of many dreamable (if that is a word) items to have. And over the years, yes my wife would complain all that heat in the kitchen burns her up as it is only one 8" boot there, but yet all these years the 4 ton unit wasn't cooling worth a flip and now I see I could have improved it, but I still feel that it wasn't going to be enough. I hate to say this, but several contractors around here told me you have to move those dampers, but going through all this with you I am seeing it differently. One even said, he hates them as they will loosen and rattle on you over time. You see why I feared them, but now not nearly as much thanks to you explaining the real story on them. Thanks again sir.


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## TREEBARK (Nov 9, 2011)

http://www.homedepot.com/webapp/wcs...eId=10051&catalogId=10053&productId=203164953


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## beenthere (Oct 11, 2008)

Metal ell would probably have less PD.

Looks like those plastic straps just make it so that the flex isn't taken beyond X radius when you attach it to the boot.


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## TREEBARK (Nov 9, 2011)

Thank you sir, so I guess they could be quite useful then if you didn't want to use those hanging straps right at the boots. I assume you probably place those hanging straps about 4 or 5 feet away from the boots, so you have a fairly straight or sloped similarly to the roof pitch if the roof is close to the boots? Now I am beginning to get paronoid about the temperature fluctuations, because I am looking at my thermometers and the problem I am having trouble grasping is at what point do you look at requiring to either use smaller runs or dampers or just do nothing when your temperature overshoots in a room because 2/3rds of my home the temperature will hit on average a couple of degrees over right when the heater cylces off, but when the next cycle starts again the temperature will be within a half to one degree throughout the house of where the thermostat is set at. Now the temperature outside is in the 40's and 50's in the day and around 30 at night right now and it is fixing to get colder over the next couple of days and it might get a little hotter like in the master closet I mentioned to you earlier, but I can live with that as I don't see how if I could keep the temperature within a degree when the furnace turns off because by the time it turns on again it could be 2 or 3 degrees cooler than I'd like. I know more insulation in the attic is needed and I plan to add, but it has about 6.5" loose fill now. I can see if I add more insulation it could cause me to change the air flow again if it holds the temperature in the house longer is my point. Seems like you can't do much better than that. The problem to me is where the thermostat is located in the hallway where three smaller bedrooms and bathroom are located and I have a 10" supply feeding them all and the temperature all in those rooms with returns except in the bathroom are within 1 degree or less on the cooler side as the furnace is located on that end of the house also. In theory, if the thermostat was in the center of the house, which is all open area I would say it would run another degree cooler in this hallway and bedrooms where the thermostat is currently located if you get the bigger picture. So, again I guess you take a happy medium right? What do you shoot for I guess is what I am asking? 

Thanks again for your time!


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## beenthere (Oct 11, 2008)

Code allows 3 degrees while the system is running. I shoot for within 2 degrees of the stat area.

Is there a return in the hall with the thermostat.


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## TREEBARK (Nov 9, 2011)

So, I guess I am not going too over board yet, I hope. I went and bought some dampers ready to try where you think I should try, worst case I try and they don't work, I'll take them right out.

No return or supply in the hallway. I have three 10" returns in the three bedrooms with 8' ceilings connected to 12" square boots, but it starts as a 14" as they and the guest bathoom connect to this hall. I went for it on the returns as you can see. I haven't put my air meter up there yet as I have been working on the other end of the house. I would have went with 10" boots, but they did not have them in stock at the time. I went ahead and went with the 7" boot in the back bedroom and went down to a 4" boot to the bathroom and the other two bedrooms are 6" each all being fed by a 10" supply. At about center of the hall is an open area about 6 feet across that goes into our very open living room, dining room, Family room, breakfast room, kitchen and small foyer (about 30 feet in length and width).

By the way, I meant to tell you I got both 8" boots installed in the bedroom and it was quite a mess as I had caulked and sealed them tight and one of them did not have that flange and it was up against a joist and the one I installed had a flange, so I had to cut more ceiling out so it would fit and I am filling it today and will be repainting, etc. Very time consuming and I see dampers would have been a lot easier. That is what made me go get dampers and so if you think I need them I got them for later. I am kind of expecting to install a damper for the master closet that has the 7". I have a 10 x 7 x 7 feeding the closet and the bathroom, but I had reduced the one 7" to 6" in the bathroom, but I removed it and temporarily put a 7" duct over the boot and it improved in there like the bedroom did so I still might need just a little bit more air. So, my choice is either change this 6" boot to a 7" boot or use a reducer going from a 7" to 6" at the boot and I know what you think about that. If I install the damper for the closet it should help the bathroom right? I bet you might also be thinking I could reduce the air enough to the closet I could have stayed with the 6" in the bathroom too. I could reconnect the reducer and 6" duct back and try it, but I am probably going to still be stubborn in the case. I do think this will be the last boot I tear out though.

Thanks again sir, as I expected a mean response and you haven't done it to me yet, so thank you again.


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## TREEBARK (Nov 9, 2011)

Anything special I need to know about installing a damper that you could pass on? I see that it is threaded on the other end with no wing nut or anything else attached and the handle is on the spring loaded side which seems like that shouldn't matter. I was thinking about getting another wing nut and washer to make it very secure once I lock in on where I want them. It is suppose to get cold tonight so, I'll be running from room to room like a rat running in circles checking the temperature. I sure am nervous about doing this before the cooling season because I don't want to be tearing out insulation and dampers to readjust if it gets too hot in some areas, but if you are fairly sure this will be very close, I will.

Thanks again.


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## beenthere (Oct 11, 2008)

Should be very close for your summer needs.

About half an hour or so after dampering down the rooms that over shoot. the cooler rooms should start to come closer to the temp you want.

Make a before reading, and after reading when adjusting dampers, if you can. This gives you a fair idea how much damper movement reduces how much air flow.


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## TREEBARK (Nov 9, 2011)

I just wanted to let you I am still at it as other projects pulled me off of this major project. I finally completed installing and reinstalling those boots and registers in the ceiling. So, I have started coating that mastic at the boot and flex connections and pulling the insulation around the flex down to the boots and straping them. Unfortunately, I cut one branch long enough, but cut the insulation too short that it doesn't make it to the wye, so I will have to put a much longer length insulation wrap (I have a large roll of R6 4 ft by 75 ft). Can I use this insulation wrap to cover my boots? The boots are already insulated inside (R4), but the problem I am having is rats and squirrels have been getting into the attic, and I am working on minimizing that, but I can tell they are enjoying hanging out on those boots, they are retangular boxes that they can easily sit on and ...... you know as they should go outside and do their thing like a pet, but they don't, even after pulling the insulation down that is around the flex duct. I have a few boxes that are right against the joists either the end or the length or long side and I cannot get that insulation wrap in between. Would that be a case of do the best you can? Or should I just pile the loose fill insulation I already have in the attic around and on top of the boots? Thanks again for your time.


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## beenthere (Oct 11, 2008)

Yep, sometimes, you just gotta make do with what you have to work with.

If the boots are already insulated on the inside, loose fill/insulation will work.

Squirrels, are a pain in the butt.


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## TREEBARK (Nov 9, 2011)

Oh my god, they were going into an opening in the front part of the house between the shingles and the fascia board, so one day I climbed a ladder and one was sticking his head out the corner and I tried to beat the area out to scare him, but he wouldn't come out, so while up on the ladder I went to filling it up with that spray foam insulation. I did it a couple of times to test if he would come out and he still wouldn't, so I just went to filling it up and man he went to scrambling that it scared me that he would do like that squirrel did in Christmas Vacation. That was all I was seeing and I tried to come down the ladder fast, but I missed a step and I went backwards across the ground like I knew gymnastics. It was something else. So, once I got my composure I got back up there slowly and filled it up completely. The next day they chewed away the insulation that was sticking out, but they stopped when they got even with the decking it looked like snow in the front yard where they scattered it all. I am saying all this because they moved to the back patio and peeled my aluminimum gutter screen guards on my gutter back and took chunks of the shingles and the wood to get acces in the attic. I had a roofer do some work and was expecting him to come back and I asked him did he do that work and he said no, so as I examined it closerand I thought I was going to have a stroke. Sunday I screwed down more of that aluminum guard screening, but I am sure they will find another location. So, back in the attic I could tell they were traveling on top of one particular duct, because I could see small little burs sticking up and a small cut in the insulation of that flex duct (another patch job I am going to have to do). I am ready to start performing peramanent removal next, if you know what I mean. I am going to BASS PRO SHOPS!


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## beenthere (Oct 11, 2008)

I've had to use traps to get rid of them.


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## TREEBARK (Nov 9, 2011)

I hope that I don't have to do that, but being we are backed up to some woods, it might never end.


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## beenthere (Oct 11, 2008)

Once they find a "home", they tend to never leave it.


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## TREEBARK (Nov 9, 2011)

I meant to ask you some questions about all the returns I disconnected in the attic that go down the wall as to how if you have done this, what you do with filling them up and/or closing them off permanently. Last night I decided to remove that top sheet metal piece and takeoff to see what I was dealing with on one return. I could not believe this 3 ft x 4 ft area once removed had an opening between the plates of about 2 inches where they chipped away of an opening and it was two stud spaces. I don't see how that was enough opening period, but I thought I would spray some of that foam spray to fill in those gaps and the rest with that loose fill insulation. But, down there on the bottom of the wall are those return grilles are I was thinking about removing the grilles and putting something like 1/4" plywood and painting it white to match the grille back in behind the grilles. If I were to remove the grille completely I would have to do a lot more work as the base board stops there and then there is the sheetrock to replace and then patching and painting. I can do all that, but I will be working on all that all summer. My wife will go nuts. So, what do you normally do, if again you have done this. Remember, I placed all my returns in the ceilings throughout the house. I will never go back to using them for that, but maybe I should think about if we move one day, someone might want to reclaim that or do something with them that I can't think of right at the moment. Thanks, again.


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## beenthere (Oct 11, 2008)

Never had to do something like that.

I would think you can use plywood as you thought.


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## TREEBARK (Nov 9, 2011)

Cool, I'll try it and if it doesn't work I'll try something else. Also, rather it be me or those contractors that moves my furnace over exactly one foot, do I need to make sure the drain still runs straight from the pan out to the eave of the house or can I put two 90's offsetting that one foot distance. I know I would have to drill a new hole outside under the eave, but I won't hesitate to do it, if it needs to remain a straight shot from the overflow drain pan under the furnace exiting the house. Thanks again.


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## beenthere (Oct 11, 2008)

Doesn't have to be a straight shot. As long as it has a 1/4" per foot slope.


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## TREEBARK (Nov 9, 2011)

Thank you sir. Can you take one piece of insulation, if it is large enough and wrap most wyes and cutting it to where you don't have to have separate individual pieces to staple together? Or do you have to cut separate pieces?


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## beenthere (Oct 11, 2008)

Since I was taught by pieces, I always do pieces.


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## TREEBARK (Nov 9, 2011)

Good, because doing it by yourself would be a struggle for me. I won't feel foolish now doing it your way and as long it is not a code breaker that is what I will do. Also, I see less potential waste. I wanted to tell you over these weeks I keep watching the temperature swings and I know I have been over analyzing it because, it is impossible to not see the temperature jump with a very sensitive thermometer because you have at least 90 degree air coming out of those supply grilles even if it is only 5 minutes run time and it overshoots 2 to 4 degrees every time. I think you said wait x amount of minutes before taking that reading, but I do try to time it just before it turns on again or just as it turns on as you can get readings then if your patient. So, throughout the house except for the master bedroom closet, the overall temperature does stay within 2 degrees of the thermostat set point. Again, we can live with it increasing like that in the closet as I would also expect the cooling season will be the opposite and again, we could live with that also. I know you mentioned a damper and I have one, but I am telling you we want it to be able to cool it down this summer. But if you have turned it down to say 68 degrees for several hours and then you manually increase it to say 72 degrees it will overshoot 3 to 4 degrees in some areas of the home and I don't see how you can ever avoid it except not allowing the temperature to swing like that period. After an hour or two of running like this the temperature again stabilizes to within 2 degrees throughout the house. Would you consider this fairly normal? Thanks again.


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## beenthere (Oct 11, 2008)

A 2 degree swing at normal/stabilized temp operation/maintenance. Is allowable and common in many homes. Code allows 3 degrees while system is running.

The higher end thermostats that are sensitive to 1/2 degree temp changes can also minimize that swing.

After your hot season this winter, you'll know which dampers can be choked back, to get a tighter temp control, if you want. Generally(not always) the rooms that over shoot in heating, tend to over shoot in cooling also.


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## TREEBARK (Nov 9, 2011)

I do have that higher end thermostat Honeywell touch screen RCT8101. Where is the best place to place a thermostat? The only reason I see it good in the current location of the hallway is there is no immediate supply or return near it, but that is the only reason to me. Seems like the next best place is in the middle of the home, but there are supplies and returns in that open area, but with 11 and 12 foot ceilings maybe not as much of an affect, where it is now located it is all 8 foot ceilings in the hallway and bedrooms around it.


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## beenthere (Oct 11, 2008)

Best place is near a return.


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## TREEBARK (Nov 9, 2011)

I guess I should not have said near a return if I don't know what I am talking about and I see why you asked me a while back was there one in the hallway. I wished you had suggested moving it, because I can move it towards the center of my home as there are two returns near where I would like to put it and no supplies. My only concern is that it does run about 2 degrees warmer out there compared to where it is located now and I see having to use dampers every where and you know what I am trying not to do. I just have to decide do I want to start into all of that at this point, especially before I start sealing all those wyes with mastic and wrapping the insulation, I need to decide now or I would have a lot more work to do you know.


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## beenthere (Oct 11, 2008)

It might be easier to add a return to the hallway.


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## TREEBARK (Nov 9, 2011)

Without going back and finding my calculation, which I can do I oversized them to begin with. I have net free area close to 1,000 sq inches total for this 5 ton unit. I did some checks about a month ago and I was already concerned of what is too low for CFM and FPM, because I thought I am on the low side or ranges from 250 to 500 FPM velocity wise, but I can easily check it again and let you know as that was the heat mode and not the airconditioning which I know will be a higher speed, but I understand we have to deal with condensation offsetting that with that coil, right? The one return I would want to branch off of is @ 25 feet and I kept it at 10" all the way, so branching from that one run again might also be a problem. I oversized the returns in the three bedrooms around the hallway as I have 12" grilles and 12" square boots, but with 10" duct runs to each. I have 2-6" supplies and one 7" supply in the bedrooms as well. But maybe none of it concerns you yet at this point? Remember, on this side of the house I wanted to go larger with the duct size, but the calculations said otherwise as I went with one 10" supply and one 14" return at the plenums for three bedrooms and one bathroom-it has one 4" supply and no return there all around the hallway. Thanks again.


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## beenthere (Oct 11, 2008)

Can probably wye off the 14" return trunk to the bedrooms to get your return in the hallway.


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## TREEBARK (Nov 9, 2011)

Well, now it is going to be hard to explain. So, what I thought I would do is show you the pictures I took tonight and to put it simply the bucket and really the return is directly over the center of the hallway where the thermostat is located and where the return would go on that end of the hallway. The only other choice is to go the other end of the hallway, but would you branch off of the 14" wye and run a separate run along side the other one you see in the picture or branch off of it at the other end of the hallway? What would you think if I were to move the thermostat around to the other side of the wall which is out in the open area? I see this is going to require a few more messages to get this right. I am having trouble attaching the photos as they are probably too big, so please be patient and hopefully I will get something to you to view. Thanks again.


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## beenthere (Oct 11, 2008)

No problem. Its easy to get a pic that is too large to post.


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## TREEBARK (Nov 9, 2011)

I want to send you several, but they are all too big, is there another way I can send them to you? The more I think about this the more complicated this could be. I already have a 16" and this 14" coming off the one side of the unit, so maybe it would not be as loud as I think, but would the balance be an issue of three runs compared to one on the other side or again is that not an issue for returns? Something tells me your thinking if it pulls the air from the open area it would help increase the temperature in this part of the house. I wish I could put the return right at the opening from the hallway to the living room, but I have a light fixture in the ceiling there that my wife won't go for of removing, but I also think the furnace is directly above that. On the other side of the furnace I have one 18" return and I can't really run off of that as it would take up most of my attic floor space there and is right in front of the attic stairs. But, you can check out the pictures if I can figure out how to get them to you.


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## beenthere (Oct 11, 2008)

Returns are some what self balancing. And although not common to do. You can put a damper(dampered grille) in the one for the hallway, if you think it will draw too much. A return will only draw as much air as is free to it.

You can email the pics to me, email address is in my profile.


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## TREEBARK (Nov 9, 2011)

Give me time about these pictures, I have an Olympus camera and I have gotten a new computer since and I tried to install their software and it won't install correctly, etc. Everything has to be so complicated sometimes. I understand what your saying about self balancing and I read where one guy put dampers in all of his returns, which seems to me a bit much, but if you have plenty of PD available I guess you could just damper every opening you have, but to me you've designed the system wrong doing all of that with the little bit of knowledge I know. The reason I was concerned because the second bedroom is actually the closet to the plenum and I purposely tried to put a few more feet of distance between it and the plenum, but it was still a little bit noisy, tolerable but you know what I am saying as compared to one 30 feet away, you wonder is there any return air going on extreme. Again, please be patient, if I have to send them one at a time until you are tired of getting them tell me and I will stop. Thanks again.


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