Not quoting a 90%+ Gas Furnace on new system

[sg789]

I'm getting quotes on replacement for my upstairs system (walk up attic)
Current is a 1996 - Trane XE100/XE78 2.5-Ton

I got the quote back on a Trane and Goodman systems. I was a little surprised when they were only 80% units. Here's what he said:

I did not quote any 90% efficient furnaces because they produce water when they heat, and there is a possibility the drain line could freeze and cause water damage to the ceiling below.

Hadn't heard that one? I understand the water vapor but I would think the water pan would catch any spill over. We normaly don't have many weeks of below 32 in central NC either.

Units Quoted:

Goodman GME80704BX - 80% - 2 stage
CHPF2430B6 - GSC13
(will field install a TXV)
Trane TUD1B060A9361A (XT80)
2TTR3030A1000A (XR13)


I'm thinking of having him quote the 14 or 15 Seer units along with a 90% efficient units.

[larobj63]

There was just another thread in here on this very same subject.

I am of the opinion that if it is installed correctly, a condensing furncae will live very happily in an unconditioned attic. What I mean by installed correctly - measures must be taken to avoid freeze-up issues.

Push them on it, or shop around, IMO.

[gary_g]

We normaly don't have many weeks of below 32 in central NC either.

The heat pump should provide the majority of the heating requirement for your winters. I would indeed look into a 14 or 15 SEER with 12 EER and 9 HSPF ratings. Maybe the 90+ efficient furnace is overkill for your climate if the heat pump is primary heat and the furnace is auxillary heat. Is there a big $$ difference in purchase price between the 80% and 90+%?

Good luck.

[larobj63]

The heat pump should provide the majority of the heating requirement for your winters. I would indeed look into a 14 or 15 SEER with 12 EER and 9 HSPF ratings. Maybe the 90+ efficient furnace is overkill for your climate if the heat pump is primary heat and the furnace is auxillary heat. Is there a big $$ difference in purchase price between the 80% and 90+%?

Good luck.

Good point. But that model number is not a heat pump. (In fact, it's an R-22 cooling only unit, bad idea.)

If a heat pump were used - the gas usage might be so little that the extra cost and effort for the condensing furnace might not be warrented. The HP would be doing the vast majority of the work.

Look at the XR15i - it has good performance in heating. Depending on your rates - it is likely that the heat pump will be cheaper to operate - but that is a leap of faith without knowing your gas and electric costs. Is this LP or Natural Gas?

NG is usually so cheap its hard to beat, but a high efficiency HP can come out ahead. Plus, then you can have the 80% backup furnace knowing you'll hardly ever use it. Heck, maybe electric resistance back-up makes sense here...

[gary_g]

Good point. But that model number is not a heat pump. (In fact, it's an R-22 cooling only unit, bad idea.)

I missed that - thank you.

The GSC13 is an R22 a/c condenser, the GSH13 is the R22 heat pump.

[larobj63]

I missed that - thank you.

The GSC13 is an R22 a/c condenser, the GSH13 is the R22 heat pump.

Right - and the Trane HP model is a TWX, the TTR's are cooling olny.

I think he should look into the 4TWX50030 (XL15i HP) mated with the TUD1B060A9361A.

[sg789]

Thanks for the advice. I'll search for the other thread .... got it.
http://hvac-talk.com/vbb/showthread.php?t=183744

Gas has moved around but it's been cheaper as a rule in NC.
I'd have to run more power from the basement to the Attic to switch to a heat pump; not worth the cost.

I was under the impression you needed new copper lines for 401 so I'm staying with R22 (if the lines are good). The run from the outside unit to the evaporator is around 50 feet (basement, two floors, attic). I'd have to tear up drywall run new lines or go up the outside of the brick (ugly).
Not to mention the cost of that copper.

I'll thinking of going to at least the 14 seer unit; not sure how much benefit there is on the 15i over the 14i 16 is 401 only and the 19 is too much.