Furnace efficiency

Hi. Getting bids for a new gas furnace in the house (don't need AC). We got a couple bids, and they all gave them for the 80% efficient furnaces, not the 90%+ efficient ones. They said that we wouldn't recoup the cost of the more efficient one through utility savings <over the lifetime of the unit>, and that the 80% efficient one has very few moving parts, and thus has less need for repair and maintenance, whereas the high efficiency ones (some claim >97%) are far more complicated, and thus more susceptible to breakages/misalignments/etc. Furnace brands were Bryant and Trane.
Can anybody speak to any of these issues, or share about their decision in a similar situation? Also, the local gas company offers a $200 rebate and a $350 tax credit to get a >90% efficient unit.
Thanks, h
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Halvey wrote:

I would go for the 95% one. They are solid engineering now and I believe have the lowest lifetime cost.
You did not say where you are, but have you considered A/C at the same time?
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Joseph E. Meehan

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Willamette Valley, Oregon. AC is not an issue, *very* rare around here. Our days peak at about 90 degrees F, with an occasional day (1 or 2 per summer) of ~100 degrees F. Low humidity. It cools down to about 55deg at night, and the house stays cool during the day. So, no, AC not needed.
Joseph Meehan wrote:

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X-No-Archive: Yes
What you're talking about is a "condensing furnace". It has an extra stage in the heating process. I read somewhere that even if the unit is well made, it can still be a problem, because a lot of HVAC techs don't know how to work on these units and they might screw it up.
The cold air from intake goes through a first heat exchanger that exchanges heat with furnace vent which condenses the water out of combustion waste. The pre-warmed air enters a second heat exchanger which exchanges heat with the combustion.
The first stage heat exchanger takes an advantage of latent heat of water. Not surprisingly, this process makes liquid water which needs to be drained out just like air conditioning drain.
Halvey wrote:

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Condensing furnaces cool the exhaust gas to the point where the steam condenses to liquid water.
Requires a drain -- to drain off the water. Which is often corrosive by this point.
Needs also venting and air intake through PVC tubes, instead of through the steel flue pipe you presently have. It's doable, I know... I've helped install a bunch of them.
The rebate sounds like a good clincher to encourage to go with the 90 plus unit.
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This is Turtle.
If you live in Oregon the 90%+ AFUE will pay for it'self if the installer don't kill you on the installation cost.
If you live in the Southern states where you don't use much heat. The 90%+ AFUE will usely not pay for it'self.
TURTLE
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90+ will pay back how quickly depends on what you pay, what are your costs to heat. The 96.7 % Carrier -Bryant is limited to one 38000 btu model of their line up the smallest one of course, kind of a bait BS deal . The higher btu models are apx 94.5% There is a formula I forgot it , but the savings of a 82 vs 94.5 are greater than 12.5% , more like 14% . If you have a significant heating season go for the highest % efficiency and get the 10yr warranty, as gas goes up your payback time will go down. The trend is up. The VS DC motors will give additional electric savings you should consider, yes when they break they cost more to fix, so get the 10 yr warranty . Also VS DC can give better comfort by running on a lower speed continuosly and with AC can run a dehumidistat with aproximatly double the moisture removal. Get a load calc done first , you may be oversized.
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The 90+% efficient furnaces are condensing units as noted in another post. Which means a pump and a way to get rid of the resulting water. However, another big difference is that the 90+% combustion air comes from the outside and then is subsequently discharged to the outside, both through 4 in. PVC piping. Built into the cost savings is the cost of using air that you have already paid to heat (from within the house) for combustion purposes (80% unit)? More uneven heat, more drafts as the air being sent up the chimney has to be replaced by outside air. You could do the arithmetic relative to the cost and considering the escalating cost of gas your payback time frame may be shorter than you think. Check into your Utility company, they often offer significant rebates for the more efficient furnaces with the variable speed motors. I got a $450 rebate which was almost half the cost difference between the two furnaces--and then I would estimate that I saved approx $150 this winter in gas costs. MLD

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Four inch? Huh? i've seen two inch and three inch....
But it does need a drain.
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Installers prefer to install what they know, and most installers don't know very much. Thy make mony by installing the same thing over and over, even if it is outdated---the customer usually doesn't know any better and they can do it with their eyes closed.
If they tell you not to get a condensing furnace, don't get a condensing furnace from them. Find someone who knows condensing furnaces. They are prefectly reliable now---they used to have problems when they first came out 15+ years ago.
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I no longer even install 80% units. The 90%+ are much more reliable than the units of only 4 years ago, and installed correctly, they will last as long as any. If the installing company isnt wanting to sell you one, that means they are not familiar with them, and dont realize that they are doing you no favors with the 80%.
If you dont need AC, you must be in a more northern clime, where you WILL be using your furnace more. The 90% unit can indeed pay for itself...
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I have been installing Carrier High Efficiency furnaces for about 6 years now, and i keep going back to previouse clients, not to repair or replace, but to ask about the savings, and keeping a mental note for myself for future customers. And the response is overwhelming, THEY SAVE MONEY, BIG TIME. As for the company that won't get into 90%+, he's right, they probly don't like the extra work involved in running new vent, fixing HWT Venting, Running drain lines and setting up the control board to work properly with existing equipment, or even running new stat wire and T-stat to properly control the new equipment, so they stick to what is EASY. Sad , these new furnaces are awsome. But do get the 10 year warrenty as there are some small and expensive parts that like anything else out there, can go bad. I just bought a house, and one of the selling features was that it had new furnace, A/C , and HWT. The first thing i did when i moved in, was throw out the 2 year old lenox 80%, and drop in a Carrier MVP High efficiency Furnace, It is 1/2 as loud, 14%+- more efficient, and as a bonus Carrier/Bryant carry a nice warranty as well as parts being easy and cheap to find, unlike Lenox who have a tendency to make their own parts, and are very difficult to work on. Hope this helps....
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