Ex. heat pump unit, now with standard gas furnace

[Rich Sumen]

I ran across a house today with an exterior AC unit that had on the label "Listed section of a heat pump" on the label. So when I went inside I expected to see a heat pump type of heating / cooling system. What I found was a new high efficiency, standard gas furnace. My questions are:
Is this common and OK to leave the old "Exterior section of a AC / Heat pump" unit and put a new standard gas furnace in.
Will it operate OK? (as an AC unit only)

Byrant Serial 2991E48544 Model 691ANX030000ABAA

Thanks / Richard

[Robert Alfred Moller]

They are using the furnaces blower motor . A heat pump is a reverse acting Air Conditioner.
Was a new evaporator coil also installed in the new furnace. Also it must be a multispeed motor as the furnace runs at a slower speed.

[Jim Luttrall]

Is this common and OK to leave the old "Exterior section of a AC / Heat pump" unit and put a new standard gas furnace in.
Will it operate OK? (as an AC unit only)

Byrant Serial 2991E48544 Model 691ANX030000ABAA

Thanks / Richard

Yes, research "dual fuel".

[Vern Heiler]

Rich,

Are you sure the indoor coil is not a heat pump coil? Some of the systems I see are dual fuel and use gas furnace as secondary heat.

If it is dual fuel system it is important that the thermostat is capable of dual fuel and that it is programed correctly. If the thermostat is wrong type or not programed correctly the compressor can run in heat mode at the same time the furnace is supplying heat and can damage the indoor coil due to high pressures.

[Rich Sumen]

The furnace when run in "heat mode" came on right away, with only gas.
The exterior "unit / fan" did not come on, so it could not produce heat.

[Rich Sumen]

Yes, I do know how a heat pump works but one question is....
If an old "Outside Unit" of a heat pump system was kept. (As this is)
and now connected to a new, standard gas furnace, using the outside
unit for AC only, would it be OK?
It did have a "standard gas / AC" type therm.

[Vern Heiler]

Yes, I do know how a heat pump works but one question is....
If an old "Outside Unit" of a heat pump system was kept. (As this is)
and now connected to a new, standard gas furnace, using the outside
unit for AC only, would it be OK?
It did have a "standard gas / AC" type therm.

Yes, it will work just fine that way.

[Rich Sumen]

Thanks Vern

[Steven Saville]

Shouldn't be a problem at all. Would work the same as any AC / gas furnace combination. From what you are saying, the heat pump is just never going to switch to heating mode as the reversing valve is not being operated.

I replaced my standard gas furnace and A/C with a high efficiency heat pump and high efficiency furnace so I could switch between heat pump or gas heat depending on gas prices. At the time I installed the system natural gas was around $1.35 a therm.
Now that it is around 0.75 a therm, I just leave the thermostat on "Emergency" heat mode which uses the gas furnace exclusively. As mentioned, the system needs to be wired and programmed properly so that the heat pump is never operating when the gas furnace is operating.

[Rich Sumen]

I didnt think it would be a problem, but just checking to be sure.
Very rare that I see this.
Thanks

[James Duffin]

Shouldn't be a problem at all. Would work the same as any AC / gas furnace combination. From what you are saying, the heat pump is just never going to switch to heating mode as the reversing valve is not being operated.

I replaced my standard gas furnace and A/C with a high efficiency heat pump and high efficiency furnace so I could switch between heat pump or gas heat depending on gas prices. At the time I installed the system natural gas was around $1.35 a therm.
Now that it is around 0.75 a therm, I just leave the thermostat on "Emergency" heat mode which uses the gas furnace exclusively. As mentioned, the system needs to be wired and programmed properly so that the heat pump is never operating when the gas furnace is operating.

I have my dual fuel heat pump setup the same way but I have a propane (no natural within 10 miles) hi-eff furnace that I installed with the heat pump so I could use the gas heat with my 5k generator if the power goes out. Propane is about $3.25 a therm so I use the heat pump down to 20 degrees. The COP drops to 2:1 But it is still cheaper to use than propane. I have the gas furnace locked out at the thermostat.