Furnace Replacement Plan Check Needed

[SteveHogan]

Due to blower failure on my 53 year old Rheem 3204-80 furnace, I may be facing an unplanned furnace replacement.

I live in Orange County California in a 1200 square foot house built in 1954 with added attic insulation.  The furnace is in a closet at the end of the hallway in an appropriate location for a cold air return/intake, BUT .. the house builder cut a hole in the floor of the closet to draw in 100 % fresh air from the (dusty) crawlspace under the house and installed a manual blower switch on the outside of the furnace in order to user the furnace blower during the summer to draw cool air up from under the house and blow it thru the register vents.  (There is no central AC).  We do not use the furnace to do this job.

If I am forced to put in a new furnace due to high cost of repairing or replacing the blower, I plan to remove the old furnace, block off the hole in the floor either completely or partially  (do I need to add some fresh air??) and frame up a raised plywoood platform/floor that would act as the new return air intake plenum. That way the furnace would draw in air from inside the house (location is at the end of the main hallway -- pretty much perfect location even for Central AC), instead of from under the house.  This should improve efficiency by a huge amount since the furnace will have to heat 60 degree F inside air instead of 45 degree F outside air. 

I would cut off the bottom of the existing closet door, and where the bottom of the closet door was I would install an furnace filter frame grill into the new opening created by the raised platform.  Instead of a standard, full-height furnace closet door at the end of the hall, there would be instead a framed-in return air grill (with filter) at the bottom and a half-door at the top to allow access to the furnace.

Presently the lower combustion air openings are below the level of the proposed new raised platform, but they can easily be raised.  The combustion air is supplied from the attic, thru the space between the studs.

I believe that there is plenty of room to move the furnace higher and still add an AC evaporator eventually.  No money now for that, but I believe that the new return air  routing would be required to make central air work efficiently and correctly.

Can someone please do a sanity check on my proposed course of action?

Thanks --

 

[dkpd1581]

A replacement motor capacitor and wheel should be less than $250...the real question is whether or not you  heat exchanger is cracked if it is in fact that old.

Installing a furnace in the closet should not be a problem.  If you are installing a 90%+ furnace as a replacement, they will use 3" PVC for combustion air inlet so that will be no problem.

If you are going with an 80% furnace I would simply follow the installation manual's suggestion.  I would cut a grill into the door that exceeds the CFM of the blower and the inducer's needs, set the unit on a return plenum box or legs and mount the filter right there underneath the unit