# New furnace question????



## jamjr74 (Jan 25, 2012)

I am replacing my 22 year old armstrong 75,000 btu gas air furnace. I also have A/C but am hoping to replace that next season since I do not have the money this season. I am choosing between 95.5-96% efficiency. My home is small and only around 1300 sq ft. I have had 2 estimates who recommend the following:

1. 80,000 btu York TG9S- single stage

or


2. Goodman (gcvm96))- 60,000 btu variable speed

Any input on the brands would be appreciated. Also is there a big difference in the single stage or variable speed since my home is small??? Thank you


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## beenthere (Oct 11, 2008)

1300 sq ft. Probably only need a 40,000 BTU furnace. Unless you have lot and lots of windows, and no insulation in the walls or ceilings.

Goodman makes a 45,000 BTU model.


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## jamjr74 (Jan 25, 2012)

beenthere said:


> 1300 sq ft. Probably only need a 40,000 BTU furnace. Unless you have lot and lots of windows, and no insulation in the walls or ceilings.
> 
> Goodman makes a 45,000 BTU model.


Is single stage or 2 stage better?


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## beenthere (Oct 11, 2008)

If you can find a 2 stage in that small of a size. it will provide better comfort.


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## Jackofall1 (Dec 5, 2010)

Goodman definately has a 2 stage 

http://www.acwholesalers.com/Goodman_gas_furnaces_lp_natural_gas_furnace_p/11137.htm

This is a high efficiency unit.

And I agree fully with beenthere, 45K is much closer to what you would need.

Mark


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## REP (Jul 24, 2011)

Do not,,,, I repeat DO NOT buy any furnace without them showing you a proper manuel "J" and a manuel "D" .
Fuel is just too expensive to guess what size equipment you need.


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## jamjr74 (Jan 25, 2012)

Deciding between 2 contractors

1. 80,000 btu York single stage

2. 60,000 btu goodman 2 stage


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## hvac5646 (May 1, 2011)

some houses are so small a load calc is useless...this one is very close.


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## beenthere (Oct 11, 2008)

neither. they are both over sizing the furnace. And it will cost you more to heat your house then it should.


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## jamjr74 (Jan 25, 2012)

beenthere said:


> neither. they are both over sizing the furnace. And it will cost you more to heat your house then it should.


Why is that? I've had 4 estimates and all recommended 60-80k btu!


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## beenthere (Oct 11, 2008)

They are all guessing.

Do your own load calc, and find out what size you really need. It will pay back with both savings, and greater comfort.

I have 2400 sq ft homes heating fine with 70,000 BTU furnace. Even when its below 0 outside, maintaining thermostat set temps of 72.


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## dosy777 (Feb 6, 2012)

jamjr74 said:


> Why is that? I've had 4 estimates and all recommended 60-80k BTU!


You should do a load calc, but then the problem is the load calc may say that you need 66,000 btu's of Heat....they don't make a 66,000 BTU furnace. So you can get close but not right on. Thats were a two stage or even better is a modulating furnace will come into play.Every house is different, different windows,doors, sky lights, and insulation value.A mod furnace can "make up " for an over sized guess on btu's.It works on the same theory as my on demand water heater, if i have 5 faucets open it goes full blast, but if i only open 1, it barley uses any gas at all. The mods can do the same thing, using as much or as little as needed.​


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## beenthere (Oct 11, 2008)

Mod furnaces start up at 70% of max firing rate. this is to heat up the heat exchanger quickly to prevent condensate in the primary heat exchanger. 

An over sized mod won't provide as comfortable a heat as it should when it is over sized for the house or duct system.

Nothing wrong with using a 60,000 BTU input, 57,000 BTU output furnace on a home with a 48,00 BTU heat loss.

How ever, using a 80,000 BTU Mod on a home with a 36,000 BTU heat loss defeats the purpose of a Mod. Since it would be at 30,400 BTUs output at its min firing rate.


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## Jackofall1 (Dec 5, 2010)

hvac5646 said:


> some houses are so small a load calc is useless...this one is very close.


Now thats some nonsense, a load calc works for all applications in regards to knowing what is required for both heating and cooling. 

Large or small a load calc is always a good idea. 

The old ways of X btu's/hr x sq ft really doesn't account for insulation, windows, sun exposure, and wind exposure, it should be mandated, not just suggested.

The OP should really find a contractor who knows how and uses todays available heat loss / gain programs to properly size the equipment.

Mark


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## hvac5646 (May 1, 2011)

Jackofall1 said:


> Now thats some nonsense, a load calc works for all applications in regards to knowing what is required for both heating and cooling.
> 
> Large or small a load calc is always a good idea.
> 
> ...


Ain't no nonsense i...if you have been doing this a long time then there are certain types of construction that identical from home to home.
Smaller homes usually are the ones you can do this with. A 1000sqft ranch w/basement...very common here. After doing several load calc that came out almost exactly the sam e each time convinced me that the short form is all that is needed. So we make sure with a short calc that assumes an 8 ft cieling. Comes out to the same as the long form.

Not saying you don't need a load calc everytime. But there are exceptions.

I see some of the most knowledgable guys getting it right just from the size and construction description in a post.

Beenthere did it here. And I and Uncle have both seen Baldlooney (sp? I dont go to the other place much my self)do it at the other place.


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## jamjr74 (Jan 25, 2012)

My hvac guy said that since my home is 1200-1300 sq ft I need approx. 48,000 buts to heat my home. He recommends a 2 stage 96% efficient furnace 60,000 btu. He said the 60,000 but was the smallest btu in the 2 stage for the brand he uses. This is more in line with the general consensus on this thread.


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## craigshd (Feb 11, 2012)

*furnace replacement*

goodman is the best to buy less repairs cost is better and has less eletronic controls to go bad also a reputable hvac contractor should also size this for you with an estimate.


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## beenthere (Oct 11, 2008)

jamjr74 said:


> My hvac guy said that since my home is 1200-1300 sq ft I need approx. 48,000 buts to heat my home. He recommends a 2 stage 96% efficient furnace 60,000 btu. He said the 60,000 but was the smallest btu in the 2 stage for the brand he uses. This is more in line with the general consensus on this thread.



Probably is the smallest 2 stage for all manufacturers.

Still doubt it need 48,000 BTUs. And if he does a load calc now, he'll fudge it to say that you need a 60,000.

A 2 stage 60,000 95% will output 37,050 BTUs. Probably all your house needs. So if you get the 60,000 2 stage, it will only need to go to second stage during recovery.


How well are the walls insulated, the ceiling/attic, what kind of windows?


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## jamjr74 (Jan 25, 2012)

beenthere said:


> Probably is the smallest 2 stage for all manufacturers.
> 
> Still doubt it need 48,000 BTUs. And if he does a load calc now, he'll fudge it to say that you need a 60,000.
> 
> ...


Insulation is ok and windows are new 6 years ago. I'm adding I shalt ion to attic this month. House does seem drafty at times though.


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## jamjr74 (Jan 25, 2012)

jamjr74 said:


> Insulation is ok and windows are new 6 years ago. I'm adding I shalt ion to attic this month. House does seem drafty at times though.


Hate typing on phone, lol!!! Adding insulation I meant!


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## plummen (Jan 10, 2010)

beenthere said:


> 1300 sq ft. Probably only need a 40,000 BTU furnace. Unless you have lot and lots of windows, and no insulation in the walls or ceilings.
> 
> Goodman makes a 45,000 BTU model.


Exactly


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## plummen (Jan 10, 2010)

hvac5646 said:


> Ain't no nonsense i...if you have been doing this a long time then there are certain types of construction that identical from home to home.
> Smaller homes usually are the ones you can do this with. A 1000sqft ranch w/basement...very common here. After doing several load calc that came out almost exactly the sam e each time convinced me that the short form is all that is needed. So we make sure with a short calc that assumes an 8 ft cieling. Comes out to the same as the long form.
> 
> Not saying you don't need a load calc everytime. But there are exceptions.
> ...


:thumbsup:


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## beenthere (Oct 11, 2008)

jamjr74 said:


> Insulation is ok and windows are new 6 years ago. I'm adding I shalt ion to attic this month. House does seem drafty at times though.


Seal the house a little better, and you be even more comfortable. You don't need a big furnace.


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## jamjr74 (Jan 25, 2012)

beenthere said:


> Seal the house a little better, and you be even more comfortable. You don't need a big furnace.


Thanks for your help! I live in MA which is a colder climate as well. Currently adding some additional insulation and doing some sealing.


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## REP (Jul 24, 2011)

You are absolutely killing me.
We are all (almost all ) telling you how to get the best outcome for your house and all you want to do is ignore us.
SO YOUR HOUSE NEEDS 48,000 BTU S .why DOES IT NEED THAT.
It seems yopur "guy" is yet another contractor that can't do it the right way.Its almost like your job isn't worth it to him to put the time into your quote that your money deserves.
What the hell is the manuel "J" numbers.What,what????
If he is going to take a short cut in quoteing your job,what makes you think he won't take short cuts in installing your job????
He'll probably take short cuts in using flex for the distrabution (duct) system by using hard pipe cfm charts instead of flex charts in sizing.
Which brings me to the manuel "D" .No one even mentioning that.Another easy job that too hard to do for a proper quote.
Its one thing for a contractor to be lazy but you seem to want to let him be lazy.What is wrong with you? Your money is worth something.Make the bidders do an honest bid for your money.


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## jamjr74 (Jan 25, 2012)

REP said:


> You are absolutely killing me.
> We are all (almost all ) telling you how to get the best outcome for your house and all you want to do is ignore us.
> SO YOUR HOUSE NEEDS 48,000 BTU S .why DOES IT NEED THAT.
> It seems yopur "guy" is yet another contractor that can't do it the right way.Its almost like your job isn't worth it to him to put the time into your quote that your money deserves.
> ...



Dude relax! I didn't know I would be scolded for asking questions! I am taking the forums advice which is why I am asking the questions! I am trying to make the best informed decision I can but it is difficult with 10 different "experts" telling me 10 different things! I agree that 80,000 btu is way to big for my home and I can tell this just by doing my own research online. I was unfamiliar with the heat loss chart prior to my joining this forum but now I know.


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## ben's plumbing (Oct 6, 2011)

why not continue with armstrong they make 50,000 btu 95% single or dual stage ..Iagree with beenthere don't over size unit...


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## joepierson (Oct 26, 2011)

jamjr74 said:


> Dude relax! I didn't know I would be scolded for asking questions! I am taking the forums advice which is why I am asking the questions! I am trying to make the best informed decision I can but it is difficult with 10 different "experts" telling me 10 different things! I agree that 80,000 btu is way to big for my home and I can tell this just by doing my own research online.


The reason why the contractors seem to be oversizing is more of a practical matter, those calculations don't account for bad duct work (leaky ducts), which could result in 40% heat loss of your furnace. Now during installation they may fix the ducts, but over time the ducts will start leaking, and if you have a barely adequate 40K furnace it will no longer heat your house and you will bad mouth the installer. That it what they don't want.

There will be very little energy saving between a 60K and 40K furnace heating a 1200 square foot house that needs only 40k of BTU, and many studies show almost no difference at all. 

All I saying is it really doesn't matter all that much, I have seen 120K units in 1000 square foot houses.


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## plummen (Jan 10, 2010)

bungalow_steve said:


> The reason why the contractors seem to be oversizing is more of a practical matter, those calculations don't account for bad duct work (leaky ducts), which could result in 40% heat loss of your furnace. Now during installation they may fix the ducts, but over time the ducts will start leaking, and if you have a barely adequate 40K furnace it will no longer heat your house and you will bad mouth the installer. That it what they don't want.
> 
> There will be very little energy saving between a 60K and 40K furnace heating a 1200 square foot house that needs only 40k of BTU, and many studies show almost no difference at all.
> 
> All I saying is it really doesn't matter all that much, I have seen 120K units in 1000 square foot houses.


My standard furnace back in the day for most smaller houses around south omaha used to be a 100,000 80% ,but in my defense most of those houses had no insulation in the walls or ceilings.
Junk windows and doors with 1/4" gaps around them :laughing:


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## joepierson (Oct 26, 2011)

plummen said:


> My standard furnace back in the day for most smaller houses around south omaha used to be a 100,000 80% ,but in my defense most of those houses had no insulation in the walls or ceilings.
> Junk windows and doors with 1/4" gaps around them :laughing:


I bet most of those older houses still have never been upgraded, and even if they have they keep shifting so gaps reappear


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## beenthere (Oct 11, 2008)

bungalow_steve said:


> The reason why the contractors seem to be oversizing is more of a practical matter, those calculations don't account for bad duct work (leaky ducts), which could result in 40% heat loss of your furnace. Now during installation they may fix the ducts, but over time the ducts will start leaking, and if you have a barely adequate 40K furnace it will no longer heat your house and you will bad mouth the installer. That it what they don't want.
> 
> There will be very little energy saving between a 60K and 40K furnace heating a 1200 square foot house that needs only 40k of BTU, and many studies show almost no difference at all.
> 
> All I saying is it really doesn't matter all that much, I have seen 120K units in 1000 square foot houses.


All those study's, that had over sized furnaces, were on duct systems that were sized to the furnace. An over sized furnace, on a duct system that is only good enough for the correct size urnace, they use a lot more gas/oil.

The ducts can be sealed. an the money saved eaisly pays or resealing again years down the road. With money left over.

Resealing the home every several years also pays back with a big dividend. 

Using "the house and duct work will just leak again later" as a reason for justifying an over sized furnace, only promotes greater needless fuel usage.


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## jamjr74 (Jan 25, 2012)

UPDATE... I finally had an estimate from someone who used the heat load calc. He said I need 64,692 btu to heat house. I had been quoted 60,000 and 80,000 btu furnaces from 5 different companies. If this is correct then I need to go with the 80,000 correct?


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## plummen (Jan 10, 2010)

Yeah sounds like an 80,000 is your best bet


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## REP (Jul 24, 2011)

jamjr74 said:


> UPDATE... I finally had an estimate from someone who used the heat load calc. He said I need 64,692 btu to heat house. I had been quoted 60,000 and 80,000 btu furnaces from 5 different companies. If this is correct then I need to go with the 80,000 correct?


If this is true then a 95% 70,000 furnace would be better.A two stage for the fall and spring heating demand would be better then again.
I must point out that this quote only shows a half effort on the contractor's part as there was no mention of a manual "D" with a design showing a return in every room.I must point out too that a manual"D" showing the differance between hard pipe and flex pipe will be VASTLY differant so you should know what the contractor's intentions are.


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## beenthere (Oct 11, 2008)

Ask to see the load calc. 49 BTUs per sq ft sounds like a lot.


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