I do not do residential work so could use some help here.Have a upflow oil fired furnace, ductwork comes out the top elbows down to floor runs under house.Want to replace with a oil fired counterflow furnance.
Question: already have new 3 ton coil and condenser,does coil have to be on the supply side of furnance or can it be in the return.
Has open return, putting in ducted return above ceiling.