Need help selecting new furnace

Old 04-03-24, 11:43 AM
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Need help selecting new furnace

I am having intermittent starting issues with my furnace that PJmax has diagnosed as a bad controller on a seperate thread. Thank you again Pjmax for all of your time and effort in directing my testing to do the diagnosis.

The furnace is 29 year old so I'm guessing at this point, that it probably makes sense to replace the furnace rather than spend a couple hundred to buy a new controller (I'd replace it myself). I was initially hoping it just needed a $40 part and I could hold on a couple more years before replacing the furnace but I want to do what makes sense. The current furnace is a Trane XE80 Model TUD140C960B1 140,000 BTU. There is a sticker inside the cabinet that says it is actually an American Standard.

I've done a little Googling trying to educate myself a little on the various brands and features to know what to have installed, but I'm getting some contradictory information from different articles which just creates more confusion. The general feeling that I'm getting (which may or may not be correct) from the few comparison articles that I have read is that Trane and Carrier are the best brands to choose from? Coincidentally, I googled HVAC companies in my immediate area and the largest company appears to install exclusively Carrier and the next largest installs only Trane. If I call them out for an estimate both companies will be giving me a sales pitch on why their brand is better than the other and I'll just end up totally confused. So I was hoping to get advice from you experts who deal with the various brands everyday so I can either make an informed decision ahead of time as to which brand I should go with, or at least know what features to look for and what questions to ask.

I will also need a new A/C coil installed with the furnace. The outside A/C compressor is an American Standard unit which was replaced maybe 15 years ago (so also potentially nearing end of life) but I was hoping to not replace that yet unless absolutely necessary for compatibility?

So some general questions:
1) What is the most reliable brand?
2) I'm located near Pittsburgh. Should I upgrade to a 90+% efficiency unit? Does the higher initial cost for the higher efficiency unit really pay for itself in decreased utility bills, or is it basically a wash over the life of the unit? I should probably mention that we spend the majority of our time in the family room and adjacent open kitchen. I have a ventless gas log unit in the family room which I pretty much use as the primary heat for that area and leave the thermostat set around 62-64 for the rest of the house (maybe that's why the furnace lasted 29 years). The house is 2 story 2,900 sq ft.. The second story of the house gets little use.
3) Seer rating. What should I be looking for on the A/C side?
4) Warranty? I've seen some references that Trane provides a better warranty?
5) Heat exchager. Are there specific things I should be lookg for. I've seen there may be different designs? Are they all construced of stainless steel?
6) Condenser Coil. I've read some are copper, aluminun and maybe stainless steel? One article said that aluminum is more efficient initially but copper has longer longevity?
7) I have allergies so would like to utilize an allergen filter. I put one on our current furnace a couple months ago and it started short cycling. There was a 4" filter on the furnace some years ago and it worked fine, maybe the short cycling was the first sign of things going bad. I assumed the short cycling was caused by insufficient air flow thru the allergen filter, so I removed the allergen filter and the short cycling stopped, but a couple weeks ago we were getting random flame out conditions (furnace blowing cold in the morning) and hard starting which PJmax diagnosed as a faulty controller. I should also mention we have always had very poot air flow from the air vents on the second floor. It can be fairly warm up there in the summer. I'm guessing the cold air returns maybe don't work as well as they should either because when the furnace runs there is a strong draft under the door leading to the basement. The house was built in 1995 (we purchased in 1999) so I assume the original installer just did a very poor job with the ductwork design/install. 75% of the basement is finished with drywall ceilings so ductwork in that area is not accessible. The area with the furnace and exhaust are not finished.
8) Price. Seeing that I got 29 years from an American Standard, I'm assuming that I don't necessarily need to purchase the very top of the line model to get good reliability?

I'm sure there are many more questions that I should be asking of the HVAC companies that I talk to, so I appreaciate any and all feedback. Just like there are Chevy guys and Ford guys etc, I assume among the HVAC experts there is also not 100% agreement on the top brands. So please enlighten me on what you see as the pros and cons of the various brands so I can at least make an informed decision in selecting a new unit.

Thank you!!!!
Old 04-04-24, 04:09 PM
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Call three installers. Have them come and offer estimates.
Ask them why they use that brand,

You need a new gas furnace.
You will be replacing the condenser and evaporator coil.
You'll get a package price on all three.

There are many good brands. I have access to all of them.
I opted for Goodman. Their replacement parts are priced realistically.
I did not opt for a "high" efficiency system as not only do they cost more up front... the repairs are more costly. I opted for higher efficiency but not max.

Keep in mind that power and gas companies offer systems installed, rebates and on payment plans.
I had called my gas provider to come and see what I needed. They were a month out.
I did it myself..... no rebate.
bigjake59 voted this post useful.
Old 04-04-24, 08:32 PM
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Good to know. Thank you.
Old 04-05-24, 04:45 AM
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PJmax, can you share the model number of the furnace you opted for? I am a believer in the so-called 80/20 rule, not a big fan of "Hi-efficiency" myself, so would be good to know. Thank you.
Old 05-17-24, 07:18 AM
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OK so I've recieved a few quotes to replace my furnace and AC. My furnace is an 80% Trane 140,000, Ac has a 3.5 13 Seer Compressor and a 5 ton coil. None of the guys that came to give me a quote could understand why I had a 5 ton coil with a 3.5 ton Compresssor.

First and second floor add up to about 2500 sq ft. basement ((75% finished) is 1500 sq ft. Ceilings are 90% 8 ft, 2 rooms have 10 ft ceilings.

Sticking with an 80% furnace, the concensus seemed to be that I need 110,000 BTU and a 3.5 Ton A/C

Company A ( a very large company with high overhead and a salsman getting a commission) gave me 3 options:
Carrier: 58SB0B 110M 21-30 110,000 BTU Single Stage 18 Speed Motor and 16 Seer 3.5 Ton AC Total Price $14,498
Payne: PG80MSAA60 110C 110,000 BTU Single Stage 18 Speed Motor and 16 Seer 3.5 Ton AC Total Price $12,672
Lennox (actually Concord) 80G1UH 110 CE 20 110,000 BTU Single Stage, Constant Torque Motor and 15.2 Seer 3.5 Ton AC Total Price $12,754

Company B with about 10 employees and a saleman making a comission semed more inclined to stick with a simiair size gurnace to what was original to the house
Payne: PG 80VTLB66135D 2 Stage 135,000 multo speed ECM motor and 14 Seer 3.5 Ton AC Total Cost $9,130

Company C is a independent contractor with a single installation crew and a couple service guys who has been in business about 25 years and does all installs himself and came and did the estiamte himself so has very little overhead.
Lennox: ML80UH110 110,000 BTU Single Phase Furnace and 3.5 Ton 14 Seer AC (ML14XC 1042) Total Price $5,900
I can upgrade to a 2 stage variable speed furnace for an additional $1,475.
I can upgrade to a 16 Seer AC fo $1,285.

It seems to be an obvious choice to go with Company C.
A little research says that going to a 16 Seer vs 14 Seer saves about 13% in energy costs. Looking at my TOTAL electric bills the past 2 years for June, July and August (our AC season in Pittsburgh) My total monthly bills are about $150 (actually less). So if my entire electric bill for those 3 months was just for the AC at 13% savings my annualy savings would be $58 which means I would NEVER recoup the price of upgrading to a 16 Seer AC.

The issue that really has me confused is whether I should stick with just a Single phase furnace (as I have now), upgrade to the 2 Stage/Variable Speed furnace or there also seems to be an option of a Single Phase furnace with a Variable Speed motor. The issue is that apparently the original installer did a very poor job on the ductwork and the air flow from the 2nd floor vents is very minimal. It is probably 10 degrees hotter on the second floor on hot summer days. Fortunaltely our master bedroom is on the first floor and we don't use the second floor much. Because of the minimal air flow on the 2nd floor, I'm not clear if it would be better to have the single phase blower motor at high speed for shorter periods or the variable speed motor blowing at a lower speed for a longer period? (my basic understanding of how they would operate differently). My gut feeling is if the current single phase is blowking very little air on the 2nd floor, then it seems like a variable spped motor blowing at a lower speed would send basically no air to the 2nd floor? Energy wise, my gas bills during the winter average about $225.

Another issue that I have is my wife likes the bedroom very cold during the winter so as a result the master bedrrom and bathroom have very little air circulation and the bathroom humidity might be 60% (even with running the exhaust fan for an hour after showers) while humidity in the rest of the house may be 30%, so on cold winter days we get an enormous amount of condensation on the bathroom windows running down onto the wood window sills. The best solution I've found for this is to run the furnace on FAN mode for a couple hours before going to bed to circulate the air though the house and signigicantly lower the humidity in the bathroom. (there isn't alot of space to just put a dehumidifier in the bathroom) . I've read that some(?) variable speed blower motors run constantly to circulate the air through the house, which would seem to ne a solution to the humidity build up in the bathroom, but other than during the cold winter days where condensation is a probblem, it seems having the fan run continuously would be a waste of energy and I assume if the motor was running constantly that would shorten the life span of the motor? I asked the Comany C guy if having the blower run constantly during the night was something I could turn on and off. He said he had to research that more.

It seems the ideal option would be a programmable thermostat that would run JUST the fan during the night to reduce the humidty level in the bathroom but I'm not aware of programmable thermostats that can be set to run ONLY the fan wothout the heat?

I'd appreciate any feed back and suggestions. Thank you!

Last edited by bigjake59; 05-17-24 at 07:34 AM.
Old 06-07-24, 03:49 PM
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1. You need a absolutely huge house to need such a large furnace. To size properly, you should have an accurate manual j load calc done. Most homes will heat on 40 to 70 000 btu.
2. 80% furnaces make zero sense in real-winter climates unless venting/condensate drainage without freezing condensate lines are not practical for the application.

Condensing/90%+ furnaces are not very much more than 80% and they are far better due to supporting sealed combustion and having no open flames - less noise - taking cleaner air for combustion directly from outside.
My opinion is you should also forget getting a single stage furnace, 2-stage is far better for comfort and noise levels thanks to longer heating cycles with less intense heat and doesn't cost much more for same blower motor type and brand.

I regard 80% single stage furnaces to be obsolete considering the better options out there.

Your humidity/condensation issue is caused by a lack of ventilation -> installation of and proper use bathroom and kitchen exhaust fans directly vented outside would solve it.
Old 06-15-24, 10:49 AM
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2 stage furnaces and AC units are not about saving money - they are about comfort. Bear in mind 2 stage systems tend to be upper tier with higher SEER, though (you won't find a 2 stage 13 SEER system). For any given SEER rating, you won't save one penny by going to 2 stage system but it will improve comfort immensely (I would never go back to a single stage system in my home). Also, systems with a higher SEER/SEER2 will cost slightly less to run but it won't be the same as the difference in SEER.

There is no one "most reliable" brand - they are all pretty much the same. A good installation is what make a reliable system and, similarly, a poor installation will result in an unreliable system. Get the most efficient, 2 stage system you can afford and try to get a sense of who will do the best installation.

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