heat pump: coil placement with gas furnace

[jcm55]

Looking for some advice on placement of a heat pump coil with an existing gas furnace:

Option 1: Standard placement above upflow furnace, gas burner runs during heat pump defrost cycle. Problem: high pressure at compressor, possible early failure

Option 2: Standard placement above upflow furnace, gas burner does *not* run during defrost cycle (blower only). Problem: cold air from registers during defrost

Option 3: Evap coil placement in cold air return plenum, before furnace. Problem: air flow can blow coil condensation through furnace, leading to corrosion of internal components.

[t527ed]

option 4: coil on top of furnace where it belongs with tempering control to allow gas furnace to run during defrost.............:cool:


fuel gas code does not allow coil to be before gas furnace unless manufacturer has approval to do so.

[beenthere]

Coil on top, burners run during defrost.
Unless your furnace is over fired, it won't cause high pressure back at the compressor.

[tinmantu]

Based on his post on another board recently, he wants to do it himself and has no clue of what a fossil fuel kit is...I told him on that board to hire a pro.

[beenthere]

After he cost himself a few extra thousand bucks, he''l learn its not as easy as just reading instructions.

Wait till he gets to deciding if he wants TT defrost, or Ondemand