||01-11-2013 04:41 AM
Originally Posted by JJboy
CFM = _________________ =
Temp rise x 1.08
Trane service guide says to get bthu output from furnace nameplate and multiply by the furnace efficiency (ex: 0.80) but I saw in another manual that doesn't need to multiply by the furnace efficiency. Wich one is correct?
If the furnace has a BTU output listed, you don't multiply the output by efficiency. If it only has a BTU input listed, you multiply the input by efficiency.
EG: 64,000BTU output, don't multiply.
80,000 BTU input, multiply, 80,000 X .8 equals 64,000
On a nat gas furnace, you should clock the meter to make sure it firing at its rated input. On LP, you should check the manifold pressure to make sure its firing at rated capacity.