We've received recommendations from HVAC dealers to replace our current 125,000 BTU 80% efficient furnace with a 90% efficient furnace, but they are recommending units with different BTU's from 100,000 to 110,000 to 120,000. How do I know which furnace will work the most efficiently in my home?
2007-03-20 07:41:30 · 3 answers · asked by rmd 1 in Home & Garden ➔ Maintenance & Repairs
A furnace with a higher efficiency does not need the same large capacity as your old furnace. You probably can get away with a 110K BTU furnace, especially if you are in a mild area - not New England. The best way to determine your BTU requirement is to have a heat loss calculation done on your home. Heat loss calcs are a program - you plug in room sizes, ceiling heights, how many windows, doors, how much insulation, type of construction, and it will tell you exactly how much heat your house will lose per hour. That is why they call it heat LOSS calculations. You then need to install a furnace large enough to replace the heat you lose. Most plumbing and heating supply stores will do the heat loss calc for you if you buy the furnace from them. If you are going to invest in a new furnace, check out how well insulated the house is. A poorly insulated house sends heating dollars flying out the roof and walls.
2007-03-20 13:41:09 · answer #1 · answered by Dave 5 · 0⤊ 0⤋
An 80% furnace at 125 k input is actually 100k output.
110k input at 90% is 99k output.
I'm trying to understand why you are replacing a fairly new heater with 80% ratings with a 90%. Are you sure the rating of the existing furnace is not lower? How old is the existing heater? Can you provide me model and serial for verification of AFUE %?
E-mail if you need further clarification
Good luck!
Newt
2007-03-20 21:32:13 · answer #2 · answered by Newtgadget www.T-C-Pro.com 2 · 0⤊ 0⤋
BTU's are the measurement of the heat output from the furnace, the efficiency rating is the amount of energy used to create the same amount of heat. Why not keep the same size? They are trying to downsize the furnace to keep the cost of the installation down.
Did the original keep the home warm, or did you still get cold? I would keep the same size myself, and I did when I had mine replaced.
2007-03-20 14:49:12 · answer #3 · answered by Fordman 7 · 0⤊ 1⤋