I have a standard southern California tract home that was built in 2010. It has a Carrier gas-fired furnace, Carrier 5-ton A/C, and a smart thermostat.
I'm slowly upgrading the major systems and replacing gas with electric wherever feasible.
However, since the gas furnace is already there, is it possible and/or feasible to upgrade the A/C to a Heat Pump by replacing only the outside unit, leaving the gas furnace in place as the air handler and as the secondary/emergency heat?
The system as it exists now:
- Carrier 58STX110 gas-fired forced air furnace
- Carrier 24ABB360W320 A/C compressor (R410a)
- Unbranded evap coil ASFM6026A (X-reference lookup tells me Allstyle Coil Co)
- Ecobee thermostat
My reasons for wanting to upgrade the A/C to a heat pump:
- Gas heat as primary is stupid and wasteful in this climate
- The current A/C compressor is going on 13 years old
- Current A/C compressor is an 11 SEER - newer one should be a fair bit more energy-efficient all year, not just the 2 month heating season
- I have gobs of extra solar during the winter that I'd rather use on-site than sell to to the PoCo for a fraction of its worth
My reasons to try to retain the gas furnace as backup heat:
- Aside from the compressor being cool-only, the rest of the system is in fine working order - might as well create less waste and save material costs
- All the indoor HVAC equipment is in the attic of a narrow 2-story. Reusing instead of replacing should also save labor
- Only 120V/15A electric available in the attic (and it would be very difficult/destructive to route additional wire up there, so 240V strip heat for Em. heat would be costly/impractical)
- Blower motor was recently replaced with an Evergreen IM ECM blower.
- Ecobee thermostat has the ability to control multistage heat/cool
So... is this idea realistic? I'm going to have to involve a contractor anyway because of the refrigerant, but I don't want to be sold a full tip-to-tail system if I can realistically only swap out the parts that need to be swapped.