Could one estimate their heat load by clocking the meter and adjusting the
gas valve on the furnace?
I turn down the gas valve reducing flame size until the furnace runs
continuously on a design temp day, then clock the meter to determine the
input btu's. Multiply the input btu by the AFUE factor should provide the
ie: existing furnace input btu 100k, output 80k
Turn flame down and read meter clocked at 60k (furnace running continuously
and maintaining temp)
Effective heat loss would be 60k * .8 = 48k
Would this not be more accurate than a mathematical model assuming the
in/out relationship of the existing furnace is still 80%.