how big of a furnace for 800sq. ft?

[scdrnr]

I`ve got estimates to install 90plus furnaces ranging from 40,000btu to 75,000btu. Who`s right? I really trust the guy wanting to instal an Armstrong 45,oobtu. My house is 800 sq. ft. with raised ceiling (exposed beam) and near Milwaukee, Wisconsin. My old furnace is an oil burner with a .75 nozzle on a becket burner.

[Hube]

A lot depends on your house construction, such as insulation, windows, location, etc.
If too large a unit, you will have short (not economical) cycles
although a slightly undersized unit is better than an oversized one, it can prove to be very hard on various parts, etc..

The only way to really know would be to do a HEAT LOSS (Manual J) and find out what your home really requires, and what is best suited for your area (temperature differential)...
Then you will know for sure what BTU input/output is required.
A good reliable HVAC contractor will calculate this usually for free. It's best to get 2 or 3 estimates, then you'll know. Good luck Hube

[imeduc]

Get 3 bids for the job make sure they run a heat loss on the home

ED

My mistakes dont define me they inform me.