Flipping a downdraft furnace?


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Old 11-07-09, 06:35 AM
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Flipping a downdraft furnace?

I'm having overhead ductwork installed to replace my under-slab ducts, and I'm just wondering if there's any sense in seeing about converting my downdraft furnace to updraft mode (it is the convertible type, 80% efficiency rating). Would the cost to do that make it more sensible to just replace the furnace at this point? I have to replace the A-coil anyhow. Thanks for the input, guys.
 
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Old 11-07-09, 06:37 PM
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We need more info.. Make and model # of the furnace?


some you can't change, and other you can.
 
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Old 11-07-09, 09:55 PM
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Thanks, Jay -
The unit is an Aire-Flo AF80 (made by Lennox), which was installable horizontally, upflow, or downflow. I'm guessing it can be converted, but don't know if it would be economically worthwhile. I appreciate your help - thanks again!

-Bert
 
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Old 11-08-09, 08:48 AM
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How old is it?

Honestly, being you are in the norther part of the states with cold winter, I would update it to a 90% furnace.
 
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Old 11-08-09, 09:16 AM
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Well, I'm not planning on staying in this house for a whole lot longer, but it's probably wiser to just replace everything and start clean. Thanks for your input, Jay.
 
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Old 11-09-09, 12:13 PM
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followup question

I don't think I'll be in the house long enough to see payback on a 90% model installation, but I have a question about the BTU requirement. Given that the house is poorly insulated, brick exterior, and about 1000 sf, does a 100,000 BTU furnace sound too large or about right? Also, should I demand a manual J from the contractors? Thanks!
 
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Old 11-09-09, 09:04 PM
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I still say 90% is the way to go. You get a few credit here and there. Fed. Tex Credit, Local utility, gas utility, and from the brand themselves.

I would ask for the dealer to do a Manual-J on your home. 100k still seem awful big. 80k at the most.
 
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Old 11-10-09, 03:12 PM
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Thanks again, Jay. It's becoming a nightmare with this project. Had two estimates so far - both from guys with good reputations. The first wanted to sell me a 100K 80% Rheem furnace and the bid for the job came in at $6300 with the attic ductwork. When I asked about that possibly being too big a unit, he said because the house is so drafty he wanted to get more heat into it more quickly. Now, that just sounds wrong to me, based on what I've read. He also said that the tax credits only apply for 95% afue units, and they start at over $4000.

The second guy hasn't submitted his price yet, but thinks I should mount the unit in the attic (which, again, sounds like not such a great idea in this area). At least he didn't think 100K was a good idea for this house. He said it would be more efficient up there, and the installation cost would be about the same as keeping it where it is.

The first guy said he didn't think my existing furnace could be flipped (even though it's designed for all three installations). The second said he thinks it could, if that's the way I want to go. If I'm not going to upgrade my 80% 75K unit to a high efficiency model, there doesn't seem to be much sense in replacing like with like, huh?

The info I'm getting is so disparate, I don't know who to believe at this point. If you have any other non-biased words of wisdom, I'd really appreciate it. Thanks!
 
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Old 11-10-09, 03:37 PM
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I'm supposing you have your furnace in a closet on the main floor of your house?


Personally, I'd keep the furnace there rather than putting it in your attic.

Furnaces in attics and crawl spaces tend to get poorer maintenance because it's hard to work on the equipment.
 
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Old 11-10-09, 05:17 PM
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Yeah, the existing furnace is in the back corner of the kitchen, and I walled it and the water heater in. I kind of felt the same about the attic installation. Thanks for the input. I hope you guys can enlighten me about the choices and which way might be best to go at this point.
 
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Old 11-10-09, 05:22 PM
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Originally Posted by SeattlePioneer View Post
Furnaces in attics and crawl spaces tend to get poorer maintenance because it's hard to work on the equipment.
Tell me. I have to go up through a ceiling, and fit between lights, wires and pipes, to get at one - that I don't think anyone has looked at in years, because of it's location. It amazes me it still even works. Last summer a/c condensate water was spilling though the ceiling from that unit and I had to remedy that.
 
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Old 11-10-09, 05:37 PM
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Maybe more efficient in attic(per the one HVAC guy) because they can go to a cheaper open combustion furnace that will draw outside air into the attic, and not pull cold combustion air through your already drafty house.

So your existing Lennox 80 unit already is a downflow? Why can't that be used downflow in the attic, if say it is raised up in the air to allow the plenum/ducts to come out the bottom? Or is there a height problem, or something I'm missing, as to why that is impractical. I am not an installer - but there might be something to what I am bringing up.

Why is it that you are making the change?
 
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Old 11-10-09, 05:47 PM
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Attic

If you do decide to go with an attic installation, stick with an 80% model. Condensing furnaces (90% & above) can be major headaches in an uncondioned attic. I've seen more than one secondary heat exchanger which froze & split.
 
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Old 11-10-09, 05:51 PM
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Sorry to hear about your woes with the attic installation. That's exactly the kind of stuff I'd rather avoid, if possible. The reason I'm making the change is because my old ductwork is buried under the slab and in pretty bad shape. I heard about a company that has some kind of spray they can run through the ducts to restore them, but haven't been able to determine if it's legit or not. Sounds too good to be true. So, the only option is to run attic ductwork.
 
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Old 11-10-09, 06:09 PM
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Ducts in slab

I've heard of sealing in-slab ducts but have never seen it done nor know of anyone who has had it done.
 
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Old 11-10-09, 06:43 PM
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Originally Posted by Grady View Post
If you do decide to go with an attic installation, stick with an 80% model. Condensing furnaces (90% & above) can be major headaches in an uncondioned attic. I've seen more than one secondary heat exchanger which froze & split.
I didn't look to see where he is from. Yeah...that be true alright. And the entire condensate system could freeze...lines, traps, maybe a pump....everything.

And I have seen or heard of areas of the country be hit by hard freezes, say even once every 20 years or so, with temps you could never even imagine.

The attic I have to deal with is actually an enclosed conditioned one, so it does not get super cold up there.
 
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Old 11-10-09, 09:03 PM
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Ummm. Well, the existing deteriorated ductwork makes a reasonable case for relocating the furnace.

Where IS the furnace located? What surrounds it?

De4pending on where it is, it might be worthwhile investigating a contractor who can repair it and find out what it might cost and get references to decide if you trust their methods and competence.

I'm not familiar with that procedure, but investigating it sounds like it might be worthwhile considering.
 
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Old 11-11-09, 03:33 PM
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Originally Posted by flukeslapper View Post
Yeah, the existing furnace is in the back corner of the kitchen, and I walled it and the water heater in. I kind of felt the same about the attic installation. Thanks for the input. I hope you guys can enlighten me about the choices and which way might be best to go at this point.
The furnace doesn't need repair, just flipping to updraft mode. It's the ducts that are the problem. I wouldn't mind replacing the furnace if I had to, but it wouldn't make much sense to replace it with another 80% model when this one works fine.
 
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Old 11-11-09, 03:52 PM
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If you still have or can get the installation manual, I agree that flipping it would probably be your least expensive route. As I recall there are some furnaces which once converted to downflow there's no going back.
 
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Old 11-28-09, 11:59 AM
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Here's a follow-up, for anyone interested. I confirmed today that the ductwork is beyond repair. Ran a vacuum into one of the ducts and went straight through the metal into the soil. So, at least I know where I stand with that. Now, I still have to figure out whether to flip or replace the existing furnace, and whether the attic installation makes any sense as an option. I think it might be an easier installation for the contractor, as space is tight where the furnace is now. I'm still a bit skeptical of furnaces in the attic in freezing winters, though. If you guys have any other thoughts, I'm all ears!
 
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Old 11-28-09, 03:36 PM
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I don't think you mentioned how old the existing furnace is but I would not feel comfortable flipping a furnace that had been in use for several years.

While this could change in the coming years a high efficiency furnace has never been a selling point that garnered more money when selling a house. Probably 75% of all home buyers don't care in the least about the furnace as long as it heats the house. After they buy the house they may care but not before. A new furnace will mean more to a buyer than any efficiency rating. On the flip side, installing a high efficiency furnace will give you lower fuel bills for the remainder of the time you live in the house.
 
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Old 11-28-09, 05:58 PM
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Attic Installation

Now that you have confirmation of the ducts being shot, I think I'd suggest an attic installed 80% furnace. You are north of me & I've seen frozen 90%er's many times.
 
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Old 11-28-09, 09:13 PM
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Thanks again for the info, guys. I'm a bit paranoid about an attic installation, because it just seems to multiply the number of chances for something to go wrong, like leaks, vibration issues, etc. I've read both good and bad on the attic installs, and I'm not sure it's the right move at this point. I figure the system will be more protected from the heat and cold extremes if it's kept in the house, even though it would be nice to have it further from the living space. I agree with you that it's wiser replacing the furnace and getting that over with. Just not sure about the attic installation. They're asking over $8500 for the furnace and ductwork, which seems pretty steep. No manual J or specifics were given on number of ducts to be installed. I'm thinking I should get a few more estimates, so that I can get even more confused.
 
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Old 11-28-09, 10:32 PM
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I would consider the age of the furnace. I see a 2005 manual online, so this furnace was recently in production.
The 3rd and 4th digits of the serial number can be an indication of the year.

http://www.aireflo-hvac.com/products/pdfs/AF80_1006.pdf
 
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Old 11-29-09, 06:20 AM
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The furnace was installed in 2000. Sadly, I was going to have the attic ductwork done at the same time, but couldn't swing it.
 
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Old 12-12-09, 01:03 PM
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Another update, and more questions... Finally had a contractor who took the time to really examine my situation and be thorough. He recommended either a Carrier Infinity 96 or a Trane XR95 or XV95, 60K BTU models. He was willing to flip the old furnace but said that it would only save me $1300, after factoring in the 1500 tax credit for the new furnace. Questions:
1. If I'm not keeping the house for another 5 years or more, does it make sense to go with the 95% AFUE models?
2. Would a 90% cost less (no tax credit to offset the up-front cost) and maybe be a wiser choice?
3. Should I lean toward the two-stage / variable blower features, or are they more repair-prone?

Thanks so much for your input, guys - really appreciate it!
 
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Old 12-12-09, 01:38 PM
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Originally Posted by flukeslapper View Post
1. If I'm not keeping the house for another 5 years or more, does it make sense to go with the 95% AFUE models?
I would, gas is not going to get any cheaper.

2. Would a 90% cost less (no tax credit to offset the up-front cost) and maybe be a wiser choice?
Maybe not enough to even bother.

3. Should I lean toward the two-stage / variable blower features, or are they more repair-prone?
I have it and LOVE it.. I won't anything but that. The house has a better comfort.. If you do get it, be sure you get a two stage t-stat foro better comfort control.

As long the ductwork is sized to able to handel the air flow, VS is not going to be more prone than a standard system.

But to have a peace of mind, I'd get the 10 years parts/labor warranity. they can be transfered to the next home owne.

I'm happy with my Trane. Carrier Infinity will be another great furnace if it's matched up with the Infinty t-stat.
 
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Old 12-12-09, 03:49 PM
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Thanks, Jay. Well, it looks like the difference in price between the XR95 (single stage) and the XV95 is over $1300, which brings the total cost a bit too high, and the contractor actually said that the XV95 might not offer much advantage in my particular situation. (surprising, coming from a salesman). So, it looks like it's the single stage version for me this time around. I'm taking your advice and sticking with the 95% AFUE, even if I may never see the payback on it. After being with a really BAD system for too long, I'm ready for a good one. Thanks again for all your help!
 
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Old 12-13-09, 08:40 AM
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Couldn't find a way to edit the last post... The actual cost difference between the single-stage and two-stage was about $1050, not $1300. The contractor said he had to estimate 12 man hours labor to flip the existing 80% furnace, which seems high, compared with 8 hours to install the new one (especially since the 95% models will require the venting and drain pipe modifications). So, the price difference between keeping the old furnace and going with the new 95% one is $2850. I know that I won't be here long enough to recoup the cost difference, and the tax credit is a crap-shoot. After sleeping on it, I'm back on the fence!
 
 

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