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03-13-2005, 05:52 PM #1Regular Guest
- Join Date
- Mar 2005
I'm building a new house outside Chicago, and I'm considering having the builder install a heatpump (recommended to me by a trusted person). Most of the contractors in my area either don't suggest using this here, or don't believe its a good idea period.
The house is about 2700 SqFt on two floors and has been calculated out to require 99K BTU heating load, and 48K BTU for cooling. (R15 walls, r38 attic, Low-E glass everywhere, 2000 SqFt on English basement unfinished)
My idea is to install a Trane XL16i heatpump at 4 tons, paired with a Trane XV90 5 ton furnace. In theory, this will allow for heating scalability from 48K BTU through 112K BTU at three stage levels.
It seems to me that since the house is built so tight, that a heatpump should suffice during the milder months of march - june, and september - mid december saving natural gas usage for a significant portion of the year.
The operational intention is to lock the heatpump out at about 38 - 43F outside, and then use gas exclusively below this point. My t-stat of choice at this moment is the Honeywell Vision Pro + humidity supporting three stage heating.
My concerns are:
How do you control 4 potential heat stages to use only three??
What indoor coil would be used with this configuration??
Is using a heatpump in northern Illinois a good idea??
Do any of you have other brand suggestions?? (IE..Carrier, Lennox, American Standard, Other)
Any other comments??
03-13-2005, 07:58 PM #2
4th stage would have to be controlled by the furnace timer. The Vision Pro would control 2 stages of the heat pump, the 3rd stage would fire the furnace. On the XV90, there's an adjustment on how fast you want it to switch to high. Set it at 15 minutes.
With the price of gas these days, I'd go for dual fuel. I doubt there is any payback for the 16i though. Friend of mine is building an extremely tight new house. She asked about the 16 and even buying at 1/2 price (she's an dealer) I can't see that paying back. With the 14 SEER on the variable speed 90, she can get 15 SEER and mid 8s on the HSPF for so much less bucks.
Today's stuff is unreliable, buy an extended warranty on whatever you do.
That sounds like a lot of cooling for such a well insulated house. Are they sure on that load? That much glass?
I have a heat pump and XV80. I use all 3 stages controlled by the stat though the Vision Pro won't do it.
03-13-2005, 09:47 PM #3Regular Guest
- Join Date
- Mar 2005
The eastern wall of this house has massive amounts of windows and each floor has 9' ceilings. This is probably why the cooling load is so high.
I was thinking to use the 16 to keep humidity down becuase it can get pretty bad around here in peak summer months, otherwise I would agree with you that it may not yeild its value in cost savings.
I have a 14i now in my current place and it seems like the humidity in late July and August can be pretty bad, while the house stays cool.
Do you suggest a different t-stat??
03-14-2005, 06:16 AM #4
Not sure of any 4 stage stats.
How about single stage unit with a whole house dehumdifier? There are many cases where the stat is satisfied but humidity high. No matter what you have for equipment, you won't be able to dehumdify unless you overcool the space.
Our utility has a moisture expert and he doesn't seem very impressed with 2 stage units as moisture controllers. He pushes the big dehumdifiers such as the Aprilaire or Thermastor models.
I've looked at the sensible to total ratio of some of these 2 speed units. On low, they aren't good moisture-suckers. Haven't looked at the 16i, I'll do that today if I have the time.