Tom,

1) What is your temperature rise? Should be 40 to 60 degrees. If you
increase air flow, your gas efficiency will go up a little as you
remove more heat from the heat exchanger. Your flue temperature will
go down slightly, increasing combustion efficiency slightly. The
electric efficiency will go down a little as you will use more
electricity to move a little more heat. With a lower temperature rise,
your supply air temperature will go down, which may reduce your
comfort. Now your furnace supply air will feel like that from a heat
pump.

2) How did you measure the air flow? What instruments did you use?


There are tradeoffs to everything you do.

Stretch