Two opposite complaints bring people to this page: a heat pump that turns on and off every few minutes, and one that never seems to stop. The first is usually a problem. The second is often normal. Here is how to tell.
Long run times are normal for heat pumps
A heat pump delivers heat more gently than a gas furnace. The air coming out of the vents feels warm rather than hot, and the system runs for longer stretches to put the same heat into the house. Variable speed and inverter heat pumps are designed to run almost continuously at low speed. On a cold Sacramento morning, a heat pump running for an hour or more is not a malfunction.
It becomes a problem when the house loses ground while it runs, when the air feels cool for long periods, or when the electric bill jumps without explanation.
Short cycling: on, off, on, off
Short cycling means the system starts, runs for a few minutes, stops, and starts again shortly after. It wastes energy, wears the compressor with every start, and never gets the house truly comfortable. The causes, most common first:
- An oversized system. It satisfies the thermostat quickly and shuts off. Very common in Sacramento tract homes where the original equipment was larger than the house needed. See what size AC or heat pump you need.
- A clogged filter or restricted airflow. In heating mode, restricted airflow makes the indoor coil run too hot and a high pressure safety can shut the compressor off. In cooling, it can ice the coil. Change the filter first.
- A thermostat in the wrong spot. Near a supply vent, in direct sun, or near a heat source, it reads warm and shuts the system off early.
- Thermostat settings. Some thermostats have a cycle rate or swing setting that is set too tight for a heat pump.
- Low refrigerant. Pressures fall outside the safe range and a low pressure switch cuts the compressor, then it resets and tries again. Refrigerant is not consumed, so low charge means a leak.
- A failing control board, pressure switch or sensor that drops out intermittently.
Running constantly and not keeping up
If the heat pump runs nonstop and the house still will not reach the setpoint, look at:
- Leaking duct work in the attic. Heated air lost into the attic before it reaches the rooms. Very common here. See duct sealing versus replacement.
- A dirty outdoor coil or one packed with debris.
- Frost that is not clearing because defrost is not working.
- Low refrigerant.
- A stuck reversing valve that leaves the system partly in the wrong mode.
- An undersized system, usually after an addition or converted garage.
Backup heat running all the time
Most heat pumps have electric backup heat strips for very cold weather and defrost. In Sacramento’s mild winters, they should come on only occasionally. If your thermostat shows auxiliary or emergency heat running constantly, the heat pump itself is not carrying the load, and your electric bill will show it. That needs a technician.
What you can check
- Replace the filter.
- Open all supply registers and clear the return grille.
- Clear leaves and debris around the outdoor unit.
- Check the thermostat is not in direct sun or near a vent.
- Note how long each cycle lasts. That detail speeds up the diagnosis a lot.
What we do
We measure the temperature split, check static pressure and airflow, verify the refrigerant charge, test the defrost controls and look at the thermostat setup. Our diagnostic is a flat $69 and it is credited toward the repair. The furnace version of this problem is covered in furnace short cycling and a furnace that keeps running. See also heat pump not heating and our heat pump services page.
Frequently asked questions
Is it normal for a heat pump to run all the time?
Longer run times are normal, especially for variable speed models and on cold mornings. It is not normal if the house keeps losing temperature, the air stays cool, or the backup heat runs constantly.
Why is my heat pump turning on and off every few minutes?
The most common causes are an oversized system, a clogged filter or restricted airflow, a thermostat in a poor location, low refrigerant, or a failing control or safety switch.
Does short cycling damage a heat pump?
Yes. Every start puts wear on the compressor, the most expensive part of the system, and short cycling also wastes energy and leaves the house less comfortable.
Why is my heat pump running constantly but not warming the house?
Leaking attic ducts, a dirty outdoor coil, frost that is not clearing, low refrigerant or a stuck reversing valve are the usual causes.
Should my heat pump use backup heat a lot in Sacramento?
No. With mild winters, backup heat should run only occasionally. If it runs all the time, the heat pump itself is not carrying the load and needs to be checked.
How much does it cost to fix a short cycling heat pump?
Our diagnostic is $69 and credited toward the repair. A filter or thermostat setting costs little. A refrigerant leak or control board costs more, and we quote before starting.