Installation of surburban furnace in a GMC

[thomas g. warner]

Anyone that has exchanged the original furnace with a surburban will see the
situation I am in.

The old Solaire furnace uses 3 inch heat ducts and a 3 inch cold air return.
The surburban calls for a minimum of 36 square inches of hot air runs to
properly and safely use it. All of the GMC registers have fittings for 3
inch runs. How did everyone install the 4 inch ducts and adapt them to the
registers? How many ho9t air runs did you install?

 

[gary miller]

Tom--
I kept the oem 3" ducts and used the flanges from the removed Solair to connect
them to the new furnace. Five ducts gives pretty close to the 36 sqin. Anyway,
It works just fine.
Gary
North Bend, Oregon Coast

> Anyone that has exchanged the original furnace with a surburban will see the
> situation I am in.
>
> The old Solaire furnace uses 3 inch heat ducts and a 3 inch cold air return.
> The surburban calls for a minimum of 36 square inches of hot air runs to
> properly and safely use it. All of the GMC registers have fittings for 3
> inch runs. How did everyone install the 4 inch ducts and adapt them to the
> registers? How many ho9t air runs did you install?

 

[gary miller]

Emery
I converted one of the original returns (the one in the rear of the coach) to a
supply and in my floorplan, the small (worthless) bathroom duct also feeds a full
size floor register. Thus, five full sized supplies for about 36 sqin. The
return is gigantic--pulls air from louver door in front of furnace as well as
from behind kitchen countertop.
Gary
North Bend, Oregon Coast

>
> I kept the oem 3" ducts and used the flanges from the removed Solair to
> connect
> them to the new furnace. Five ducts gives pretty close to the 36 sqin.
> Anyway,
> It works just fine.
> Gary >>
>
> Gary - are some of your five ducts return air? If so you've probably got 3
> heat runs for a total of approximately 21.4 square inches. In addition you
> might have the small hose going to the bathroom area which probably isn't
> much more than 3 or 4 square inches. I don't have a Suburban, but if the
> instructions call for 36 sq. in. then it would probably run a lot more
> efficiently if you added ducts or enlarged the existing heat runs and return
> runs. Its probably OK to have less square inches on the return lines as cool
> air will have less volume than hot air.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM