# Your Old Furnace At 92%...

Posted by Dodgeman on April 13th, 2002 10:35 AM
In reply to Older furnace replacement by R.C. on April 12th, 2002 09:17 PM [Go to top of thread]

Would put out approximately 110,000 BTU. If you go with a new furnace rated at 100,000 BTU at high efficiency, say 96%, your new output would be in the order of 96,000 BTU. That is about a 13% reduction in output.
Now if your old furnace seemed to have more capacity than needed, then the new 100,000 should be ok. But if in very cold weather, your old furnace ran a high percentage of the time, then I would question if you could go to the 100,000 BTU. It may be marginal.
I would think that the 75,000BTU would be too small. Its output would be 72,000BTU at 96% which would be about a 35% reduction in output compared to your old.
What does the furnace installer say? He should be able to take a fresh look at your house and do the calculations for sizing the furnace.
Good Luck,
Dodgeman
(now back to spreading crabgrass preventer)