Opinion on Trane XL15i AC with XT80 Furnace

[outbacker]

I've been quoted a Trane XT80 single speed furnace to go with an XL15i AC unit (non-HP). The coil that is quoted appears to be the variable that makes this the only XL15i combination that qualifies for the $1500 tax credit. Here are the part numbers:

4TTX5024A1000A -XL-15i
4TXAB031BC3 -Trane coil
TUD1B080A9H3 -XT80 furnace

This is a 2-ton unit and I'm confident that it is sized correctly. It is for a single 500 sq. ft. upstairs bonus room with 1 outside wall, 2 "attic walls", roof approx 1 ft. above ceiling, 2 windows, and a loft opening to downstairs.

Most info I've seen indicates that a variable-speed furnace is recommended with the XL15i, such as the HV80 (for 80%) or HV95 (for 95%). I want to take advantage of the tax credit and I'm not sure I need a variable speed system for my relatively small room. With the tax credit, I'm getting the XT80 for free. I confirmed that the quoted system does qualify for the tax credit (even though it's an 80% system). It's 13.2 EER and 16 SEER.

Does anyone see any problems with, or have any concerns/comments about the combination that I've been quoted?

Thank you, in advance, for any guidance or info.

[phbsales]

The variable speed furnace will work a lot better with Trane / Am. Std's Comfort-R ® setting which is designed for better humidity control and overall better comfort in the space you are heating and cooling.

I would give the variable speed product more consideration. :D

[motoguy128]

2 Tons seems a little big for 500 square feet unless you're in a very humid climate with a leaky poorly insulated space. An 80k BTU furnace is WAYYY too big. A 45k BTU furnace is probably evan a little large.

Although the only qulifying sizes are 2 Ton units with the 2.5 Ton coils. What worries me is the latent capacity won't be ideal.

A better match would be a 60k BTU XV80 VS furnace with a 1.5 Ton XL15i. It meets the tax credit limits and should cost less overall to operate sicne it will dehumidify better.... expecially with a IAQ thermostst that can lower the fan speed to aide dehumidification. Try ARI number 1418718.

[motoguy128]

I also found some XR14 1.5 TON outdoor units with non VS furnaces that meet the ratings with some 40k BTU furnaces. but I'm not sure what type of indoor coils they are. Maybe the PRO's can help here.

Also keep in mind, you will need smaller less expensive ductwork with a 1.5 Ton and 40k or 60k furnace. A 80k furnace needs almost 1200 CFM on high stage heat. While a 40k furnace should only needs around 600 CFM on high stage. That's ductwork that's 1/2 the size with half as many vents.

An oversized system with undersized ductwork will be very noisy, have high electricity costs, and can shorten equipment life.


a 60k XV80 might only be 20% more expansive than a 80k XT80... maybe even the same cost when you factor in smaller ductwork.... if your installer cares about sizing ductwork correctly. If they don't... send them packing.

[outbacker]

Thank you, motoguy.

Did you mean ARI# 1418781 (instead of 1418718)? I do see that it qualifies and is a 1.5 ton.

We're replacing a 2-ton builder model Carrier split system that has a shorted compressor. The only reason I'm replacing the 8 year old furnace is because it's free after the tax credit. The original indoor coil is also rusting and is the likely source of a small refrigerant leak.

I also should have mentioned that I live in NC in an 8 year old home and the winter climate is fairly mild. I'm leary to go with a 1.5-ton since the Carrier 2-ton did a pretty good job, although it did cycle quite frequently and there were also some very hot days where it could not keep up, though (thermostat set on 80 but AC could not get it below 83, for example). I would *think* that a 1.5 ton would have a harder time keeping up but I may be mistaken. With the 2 "attic walls", this room is tough to cool in the middle of summer. No problems with heating it.

[motoguy128]

Ooops.. typo yes ...18 not 81. The builder grade unit with a outdoor unit and corroded indoor coil might not have been producing 2 tons of cooling anyway. actually the rusted coil indoors might have been what killed the compressor.

Make sure this new system is installed right and the condensate drains properly!!! An indoor coil shouldn't rust out in 8 years. I wonder if it had too little airflow. Possibly undersied duct and/or a dirty air filter. Low airflow might cause freezing on the coil and condensation on the casing.


Have the contractor do load calculations and guarntee the system performance. It's alway possible to go to swithc to a 2 ton unit using the same indoor coil. On the hotest afternoon 95F+ the system may likely run continously, but you should have low humidity and be able to maintain 80F. If not, look for air leaks to seal or consider adding some insulation or venting to the roof if possible. You might want to look at a radiant barrier behind the siding and below the roof to reflect some of the heat.


Aslo check the insulaton under the floor. You might be getting a lot of heat form the garage below.

[BaldLoonie]

Both seem too big for 500 sq ft bonus room. Friend lived in such a place over daughter's 3 car garage. Cooled with a 1 ton, heated on 5kw (17,000 BTU). This is area that is 95 in the summer and 0 or a bit below in the winter. Somebody better run an accurate load calc. Do not oversize!!! Around here, a stand alone 1500 sq ft house would have the equipment you are proposing for a much milder winter!

[steve f]

I also should have mentioned that I live in NC in an 8 year old home and the winter climate is fairly mild. I'm leary to go with a 1.5-ton since the Carrier 2-ton did a pretty good job, although it did cycle quite frequently and there were also some very hot days where it could not keep up, though (thermostat set on 80 but AC could not get it below 83, for example). .

Something is not right with your current system. I live just northwest of Atlanta GA, our top floor is 1650 s.f. and we have a 2.5 ton Trane that does a good job of cooling. I lived in a house many years ago that had a finished attic about the same size as what you're talking about, and a window air conditioner cooled it better than what you're reporting.

[outbacker]

After the responses here and a little more research, I started questioning the 2-ton XL15i AC and XT80 combinatrion I was quoted. My contractor readily agreed to do a load calculation. The calculation showed that a 1.5-ton unit will work for us, with about 20% safety factor. So, he quoted a 1.5-ton XL15i AC with an XV80 furnace. It's the same price as the 2-ton XL15i with the XT80 (after a $200 Trane rebate). I feel much better about this combination and I'm having it installed this week.

We're getting the combination that you located, motoguy, ARI# 1418781. I did not mention this combination to my contractor, he proposed it. Thank you very much for your responses.

With the $1500 tax credit, I'm getting the furnace for free and I think the final price is fantastic.

I wanted to thank everyone that responded and prompted me to question my original quote. Your participation in this forum provides a great service to homeowners. I now know more about HVAC than I ever thought I would, and I learned it over a span of about 3 weeks.

Thank you!!!!

[beenthere]

Are you getting a smaller furnace also.

I can't see needing a big furnace for that area either.
Specially since its open to the lower floor. Heat rises. So the first floor system will provide a majority of the heating needs.

[outbacker]

We're getting a 60k XV80. I believe it is 60k for stage 2 and 41k for stage 1. You're right about us not needing much heating capacity upstairs. I'm thinking that the furnace will rarely run at stage 2.

Thank you for asking about this.

[beenthere]

Your welcome.

Unless you set the temp back and then recover, I doubt it will ever use second stage.

Wish they made a 2 stage 40,000 input furnace.