Oversize furnace, interested to use smaller orifice for Lennox furnace

dean_h

My house is just under 2,800 sqft, and it has Lennox 80MGF4/5-140A gas furnace. The furnace is way oversize. During the coldest winding day of 2F in NJ[ no the winter of 2014], it fired 11 minutes out of 19 minutes interval of the thermostat call for heat. The worst day is around 40F, it only fired about 5 minutes for every 25 interval. I checked out one of neighbor's furnace. It is same Lennox line, but it is only 100K btu unit with 5 burners. The neighbor say her furnace can keep the house toasty during coldest day.

My furnace has 7xsize 44 orifices. I am thinking changing them to size 48 orifices, and set the blower to lowest speed to maintain the rise on the temperature. Is that possible?

Thank in advance.

Dean.

j a_2

What does the manufacture say?

John Mills_5

I'm sure they will say don't do it!

captainco

I guess if you don't mind higher bills, rotting out the heat exchanger and the flue, it is okay.