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boswest1
10-21-2008, 11:40 AM
I own a small 2 story home that is heated by a forced hot air fueled by natural gas (6 year old system). It is a one zoned system. I have a two story addition going in (garage w/MBR over it and a family room behind it that connects to the kitchen). I have a proposal from a heating contractor (that my GC agrees with) that I'm not sure about. He wants to add a new furnace to the system to heat the new section with 2 zones, up and down in the new section and leave the old system alone creating 3 zones. Would it not make more sense to have 2 zones with the old system doing the first floor and the new doing the second (where all the bedrooms are)? The way it is proposed would seem to force me to have my old system running most of the time as it would be heating the 2 floors of my original home. The only savings during the day would be in the MBR as it would be a zone unto itself, and the only savings at night would be in the family room as it would also be a zone but with bleed over from the original system.
m kilgore
10-21-2008, 01:07 PM
Your old system may not have enough capacity to heat and cool the new family room.

I would do what the contractor said and zone the new space with a new properly sized unit.

This is all just a guess as I have no idea what the layout is or the capacities needed for each zone.
beenthere
10-21-2008, 01:14 PM
Using the old furnace for the first floor including the new first floor addition, may make it oversized.
boswest1
10-21-2008, 01:34 PM
The new space on the first floor is less than the existing space on the 2nd floor so the concern might be too much capcacity?

It just seems to me that it would be an odd zoning to have it laid out 1400 2 story sq feet of zone, 600 sq ft of 1st floor as another zone, and 500 sq ft of 2nd floor as the 3rd zone. Balancing them out would seem impossible.
boswest1
10-21-2008, 04:56 PM
BTW, the proposed new system for the 1100 sq. ft. 2 story addition is a Goodman GMH95045. Any opinions on Goodman's and the capacity of that system.
beenthere
10-21-2008, 05:06 PM
Without seeing the prints, can't say anything about the size for sure. But probably is as close as you will get.

More then one house has that zoning set up.
boswest1
10-21-2008, 05:25 PM
How about mixing a new 2 stage with an old single stage? Is that okay as well? How about Goodman's, as a brand are they okay?
beenthere
10-21-2008, 05:39 PM
Nothing wrong with a 2 stage in teh addition and a single stage in the existing.
Goodmans fine.