Replacing a forced air furnace....


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Old 11-12-05, 04:48 PM
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Replacing a forced air furnace....

Hi all. First time postee.

Iam going to replace my current Lennox Airflo GHR5-135M-1
putting out 135,000/108,000 with a newer system. Not sure which brand but I've been looking at Trane, Bryant and Rudd 80% AFUE, 115,000, 2 stage systems.
Haven't been able to find a date on the furnace but the manuel was printed in 1956. So Iam guessing its ancient.

Anyways..
I live in N. New Mexico at 6000 ft. I would say it has moderate winters. House is 2300 sq.ft. Metal frame windows, single pane. Hope to replace all windows within 5 yrs. At the moment Iam replacing the duct work with insulated duck work.

I hoping to install it myself. It will be going into the same closet. Its a downflow.

I guess I want to know if I'll be able to use all the old/new duct work that is already there with the new system. Will it be just a matter of hooking up the new furnace with the old heat exchanger? (The long box under the house that distrutes the hot air)

Just read the thermo question. Do I need to run a new thermo stat for a 2 stage system? Mine is single stage. I think.

Any recommendations with which system and size.

Hope you can help.
Heath
 
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Old 11-12-05, 06:53 PM
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You need to find some real tech data. You have to know that the replacement furnace will have the proper clearance in your closet, for one thing. At the bottom of the furnace where the duct is is not the heat exchanger. That is the plenum. I guess you are in either a basement less house and/or double wide trailer?

How were you able to "size" the furnace yourself, yet not know some of the other stuff you need to know, is my question? Shouldn't you be going to furnace dealers and running all this by them? IF you can buy the furnace yourself, to be able to do the job yourself, you would think they would be helpful as long as they are making the sale.
 

Last edited by mattison; 11-13-05 at 07:06 AM.
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Old 11-12-05, 07:52 PM
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good luck getting a heating Co. to sell you a furnace. that ain't gonna happen. the co. would be responsible for that furnace if it was installed wrong and killed someone.
 
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Old 11-13-05, 08:56 AM
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Thanks for the respones.
Iam in a house with a basement/crawelspace.
As for sizing it I took a educated guess. And at this moment its only for getting a idea on pricing. Next week my gas co. is coming out for a heat audit and I will have a few heating com. come out for some estimates.

So, I guess its not a problem using the old/new plenum and duct work.

Also, anybody know of a good website with prices, tech sheets and a wide selection?

Thanks
H
 
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Old 11-13-05, 09:55 AM
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Originally Posted by HAH
Thanks for the respones.
Iam in a house with a basement/crawelspace.
As for sizing it I took a educated guess. And at this moment its only for getting a idea on pricing. Next week my gas co. is coming out for a heat audit and I will have a few heating com. come out for some estimates.

So, I guess its not a problem using the old/new plenum and duct work.

Also, anybody know of a good website with prices, tech sheets and a wide selection?

Thanks
H
What key words have you typed into Google, so far? Anything like "gas furnace specifications", "sizing a gas furnace", "best gas furnaces", "most efficient gas furnaces", "furnace installation information" (or knowledge, instructions), etc.
 
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Old 11-13-05, 04:03 PM
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Yeah, I've checked some specs out. Somewhat.

I guess what I want to know is,
Is it just a matter of pulling the old one out and sticking the new one in? What will be my biggest problem? Gas and elec. line fine. Closet is large enough. Fresh air intake good, already have a exhaust.

Thanks
H
 
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Old 11-14-05, 04:51 PM
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Originally Posted by HAH
Yeah, I've checked some specs out. Somewhat.

I guess what I want to know is,
Is it just a matter of pulling the old one out and sticking the new one in? What will be my biggest problem? Gas and elec. line fine. Closet is large enough. Fresh air intake good, already have a exhaust.

Thanks
H
I've never put in a furnace myself (who would sell me one?), but have been around when they have been installed/replaced and I don't think there is any one particular big obstacle. Sort of like changing out a water heater .You may have to have sheetmetal adapted to the floor plenum, and there could be a height difference with the furnace where you would have to adapt for your exhast piping. Also, regarding the exhaust piping(the flue), the furnace you get may have some working principles that require say a triple wall flue due to fresh air intake or something and the worst case scenario would be that you have to redo your complete flue. I can't think of anything else.

Where are you getting this furnace from anyway...where you can't ask questions of the person you are getting it from? Buying it through a friend of a friend of the guy who works at a furnace supply store or something, where you don't dare ask a lot of questions?

If you are on natural gas, you have to have a furnace set up for natural gas. And if you have LP, you have to have a furnace set up for LP. Very important as the gas pressures are different.
 
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Old 11-17-05, 08:04 PM
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Thanks for the reply.

Now there has been a change of plans. So, no new furnace till off-season. But, I can see its going to be a problem buying a furnace without them installing it.

Later
Heath
 
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Old 11-18-05, 07:04 PM
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Biggest reason why it's hard to get you own furnace is WARRANITY.. If you put it in yourself, The warranity is GONE.

Who is going to support you if you do have major problems.?

Lot of the big names like Trane, Rheem, or Carrier will NOT sell thier product to a DIY homowner, they want to protect thier product, and also Lawsuits.. Lot of them now days..

Also, Seems like a LOT of heat for your area..

I have 60,000 for our home here in Minnesota.

Make sure you have a Manual J done on the home.
 
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Old 11-19-05, 09:11 AM
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When I called around to get est. whenever I asked if they are going to do a Manual J on my house, it seemed like they had no idea what I was talking about.
So, for this year I think Iam going to finish replacing all the duct work with insulated duct work and then get the furnace "tuned up"

The house is cinder block, no insulation on exterior walls. We have a old flat roof and then a newer steeped roof on the house. The flat roof is insulated. The big project will be to "fur out" all exterior walls and insulate and replace windows. That should be fun.

Later
 
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Old 11-20-05, 07:19 AM
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Where are the duct work?

Are you sizing the ductwork right???


As for the Manual J, I am suprise the dealer don't know what it is... :-(

If you want, I think you would be spending the best $50 for home using this program..
http://hvaccomputer.com/talkref.asp

download it when you are ready to get the new equipment.

Right now, you are dong the right thing.. Get the house sealed up! ;-)

Otherwise, if you sized the equipement to the home now, and then seal up the home, the equipemtn will be oversized!.... Oversized meant discomfort.
 
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Old 11-20-05, 07:55 AM
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The duct work is all under the house in the crawelspace/basement.
I hope Iam sizing it right. I just followed what is already in place. 8" to 6" and keeping the "T's" and branch outs at roughly the same spots. So far Iam happy with it. Alot less leaks in the duct work then what there was before. In that regard I should save a bit. Using R4.2 insulated duct work.
Still have 4 rooms to do. Blahhh

Later
 
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Old 11-20-05, 07:59 AM
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Does the house already have A/C?
 
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Old 11-20-05, 08:05 AM
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Yeah. Has a seperate swamp cooler on top of the house.
Which has only one register into the living room. That will be another project to run a few ducts into the bedrooms at the least. I have heard of conflicting arguments on refrig air in the southwest compared to a swamp cooler.
 
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Old 11-20-05, 09:04 AM
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Swamp coolers are not found around here in Minesota.

So i couldn't say.. From my own personal Opnion, Get rid of them.. I think they are big breading ground for germs and what not.. Again, that my own opinon since I have not been around these.
 
 

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