A breaker trips to protect the wiring from drawing more current than it should. With a heat pump, which breaker trips, and when, tells you a lot about the cause. Reset it once. If it trips again, leave it off and call, because repeatedly resetting a breaker that is protecting against a fault is a fire risk and hard on the compressor.
Which breaker tripped?
A typical heat pump has two breakers:
- The outdoor unit breaker, feeding the compressor and outdoor fan
- The air handler breaker, feeding the indoor blower, controls and, usually, the electric backup heat strips. On many systems the heat strips are on a large double pole breaker, sometimes two.
Air handler breaker tripping in winter: think heat strips
Electric heat strips draw far more current than anything else in the system. They come on during defrost and whenever the heat pump needs help. Common causes of trips:
- A shorted or failing heat strip element
- A failed sequencer or relay that brings all the strips on at once instead of in stages
- Low airflow from a clogged filter or failing blower, which overheats the strips
- Loose or overheated connections at the strip terminals or breaker
- A breaker that has weakened after years of heavy load
If backup heat is running more than it should, the heat pump itself may not be carrying the load. See heat pump using too much electricity.
Outdoor unit breaker tripping
This follows the same pattern as an air conditioner:
- A failing run capacitor, the most common cause. The compressor draws very high current trying to start.
- A dirty outdoor coil, raising pressure and current, most often in summer
- A failing outdoor fan motor
- A compressor that is failing or seizing
- Damaged wiring, including rodent damage
- Ice buildup in winter that stalls the fan. See heat pump freezing up.
Our article on an AC tripping the breaker goes deeper on the outdoor side.
Timing clues
- Trips the moment it starts: capacitor, compressor, or a direct short
- Trips after running a while: heat buildup from a dirty coil, a struggling motor or overloaded heat strips
- Trips only in heating mode, air handler breaker: heat strips or their sequencer
- Trips during defrost: heat strips coming on during defrost
What you can safely check
- Replace the filter. Low airflow overheats heat strips.
- Clear ice, leaves or debris from around the outdoor unit.
- Make sure the thermostat is not on emergency heat.
Do not open the electrical panels. Capacitors can hold a dangerous charge even with the power off, and heat strip circuits carry high current.
Why it matters
Every trip and reset is a hard start on the compressor, the most expensive part to replace. See compressor replacement cost. On the heat strip side, overheated connections are a fire risk. Neither is worth resetting through.
What we do
We measure current draw on the compressor, fan and each heat strip, test the capacitor and sequencer, inspect connections and the breaker, and check airflow. Our diagnostic is a flat $69 and it is credited toward the repair. See heat pump not turning on, heat pump light codes, and our heat pump services page.
Frequently asked questions
Why does my heat pump keep tripping the breaker?
On the air handler breaker, usually the electric heat strips, their sequencer or low airflow. On the outdoor breaker, usually a failing capacitor, a dirty coil, a fan motor or the compressor.
Why does my heat pump trip the breaker only in winter?
The electric backup heat strips run in winter, especially during defrost. A shorted strip, a failed sequencer or low airflow can trip the breaker.
How many times can I reset a heat pump breaker?
Once. If it trips again, leave it off and call. Repeated resets are a fire risk and can damage the compressor.
Can a dirty filter make my heat pump trip the breaker?
Yes. Low airflow overheats the heat strips in winter and raises pressure and current in cooling.
Is it dangerous if my heat pump keeps tripping the breaker?
The breaker is doing its job, but the underlying fault can be an overheated connection or a failing component. Have it checked rather than resetting it.
Does a heat pump have more than one breaker?
Usually yes, one for the outdoor unit and one or more for the air handler and its heat strips.