changing blower speed

JR_7

I would like to lower the blower speed (MH to M) on my Heil NTGM100 propane furnace. Am I going to "mess-up" something efficency wise, etc., by doing this? Thanks.

Techman

JR

1-check the "temp rise" across the heat exchanger,lower fan speed results in a higher temp rise, too high of a temp will kill your heat exchanger 2-check that the blower speed for AC is proper,some units are wired for only one speed for both heat and AC.Too low of a fan speed will ruin the compressor and your day !

Empire_2

On the side of the furnace

Appears a temp rise,..Usually 40 to 80 Aprox. You have a heil or ICP unit and as long as you remain in the Temperature rise parameters, you are OK. Air flow becomes an issue of flow to furthest registers and if you are happy with what you get to the furthest runs..Go for it.

Mike T.

JR_7

OK. Just to be sure then- Temp rise is the difference between a reading at the closest(to furnace) heat register and return register. My Rating plate shows 40-70. OK?

Empire_2

JR

Take the return air reading at the R/A duct just before it enters the furnace and the S/A about 1 to 2' above the heat exchanger.

Mike T.