Adding a heat pump alongside a natural gas furnace

I recently replaced our 30-year old air conditioner with an air-source heat pump.

It mostly went smoothly, except that I noticed it could only run for six or seven minutes at a time, and it made loud hissing and gurgling sounds as it was about to shutdown. This is known as “short-cycling.” The HVAC company sent out a technician who measured the coolant pressures as the heat pump was operating, and he determined that the pressures were far too high. He had to remove a substantial amount of coolant to bring the pressures into the proper range. He noted that since we have a very short run of copper tubing between our heat pump and HVAC system, even the coolant that came pre-charged in the heat pump may have been excessive. Since he adjusted the pressure, the heat pump has been working well.

Since I kept our high-efficiency natural gas furnace as well, that required me to decide a temperature threshold for switching between the dual fuel options (natural gas and electricity). See for more on that.

Michael LeMay
Michael LeMay
Senior Staff Research Scientist

Views expressed are my own and do not necessarily represent those of my employer. #IamIntel