Residential furnace selection 2

[dvd]

I am working on a zoned heating and cooling system for my 90 year old, steam-heated home. I have calculated the upstairs cooling load at 32500 Btuh sensible and 42000 Btuh total and heating load at 51000 Btuh.

I am interested in US manufacturers who have a high-efficiency (90%+) furnace with a 60,000 Btuh heating capacity and cooling fan flow for 3 1/2 or 4 tons. Everything I have seen for a 60,000 Btuh furnace has a maximum of 3 tons cooling fan capacity. Your comments and recommendations would be greatly appreciated.

 

[Blackstick]

That is correct. Typically for residential units you select the furnace based not on its heating capacity but on the air delivery for cooling and the size cooling coil that matches the cooling load. This will result in a furnace heating capacity that can be two or three times the heat load. Unless you have a modulating gas burner or staged electric heating coil you will have to live with the furnace cycling more than normal due to it being oversized. Remember, you are using a furnace unit to cool with and the process to heat is much easier (simpler) than to cool. Delta T to heat is usually much greater than delta T to cool.

 

[Waunakee]

I would consider the Carrier lo/hi fire; natural gas fired hi efficiency furnace with a two stage Air Cooled Condensing Unit. You may wish to go with a 4 ton ACCU and a 4.5 ton evap coil. That way you can match a lo heat model with a hi A/C model, still maintain efficiency, and you will have one hell of a proud/satisfied customer - I guarantee it! Be sure to provide good filtration for 1800 cfm on the main return, then seperate to dual returns, one to each side of the furnace to maintain proper air flow, don't forget OA.
Questions?
kjp11@charter.net
Kevin

 

[dvd]

Thanks for the information.

 

[mt31]

For a high quality split home comfort system, I would recommend that you look into the LENNOX line of systems. They have a 94% eff. natural gas fired furnace that you can match with a 15 SEER hsx15 CONDSER AND A ASPEN EVAP COIL AND PULL 16 SEER. The furnace is a two stage variable speed unit. nice!!