I have a 13 year old house which has 3 floors and 5 HVAC systems.
Two 107,000 BTU furnaces for the 3rd floor located in the attic.
Two 107,000 BTU furnaces for the 2nd floor located in the basement.
One 100,000 BTU furnace for the lower floor also in the basement.
I want to replace the 2 in the attic with one multi-stage, probably a 2-speed, and zone it, as I already have two separate sets of ductwork.

I want to do the same in the basement, only in the basement, I want to include the 3rd furnace, and get a 3-speed multi-stage to handle all 3 "zones" that presently have their own dedicated single speed HVAC's.

Question 1.
Is this feasible?

Question 2.
Assuming answer to 1 is yes,
Do residential multi-stages come in high enough BTU capacity to replace 314,000 btu's worth of furnaces?
If no, do they come in sizes to replace 214,000 btu's?

Question 3.
Assuming the answers to 1 and 2 are yes,
Will doing this reduce total gas usage, as that is the objective.

Question 4.
Assuming the answers to 1, 2, and 3 are yes,
Can I use the (total of 5) A/C compressors in the 2 resulting multi-stages, or do I need corresponding multi-stage compressors?

Ira Eisenstein
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