Thank you.
I would like to ask where the return air at the furnace is I find a 3 or 4 inch flex tube at the top of the furnace. is that it I am use to a regular box that you install a filter in.

I hope that you can help. I just moved in to a modular home with an intertherm mgh 077a furnace. It is propane fuled and I had 150 gal of fuel delivered on dec 23 keep the therm at 60 but i have used all of the 150 gal of fuel. it is jan 27. temp at the nearest vent is 80 deg. The filters were filth...