How to Reset a Heat Pump: Power, Lockouts and Waits

By Ray Bennett · Updated 2 October 2026 · 4 min read · Checked against the makers’ own manuals

How to Reset a Heat Pump: Power, Lockouts and Waits

Short answer

A heat pump is reset by cycling its power, at the breaker and the outdoor disconnect, not with a button. Before you do, rule out the waits that look like faults: the thermostat's five minute delay, a short cycle timer, and defrost. Many controls retry by themselves: Carrier after 15 minutes for a pressure trip, and after 4 hours from a lockout. If the same code comes back, stop resetting.

A heat pump that has stopped is often not broken. It may be waiting on a timer, defrosting, or sitting in a lockout that clears itself. When it does need a reset, that is usually done by cutting its power, not with a button on the unit.

This page brings together what the makers’ own instructions say, as quoted on this site’s brand pages: which stops are normal waits, how a reset is done, and when to stop resetting.

Before you start

What to carry: a torch and a pen. Fifteen minutes, longer if you choose to wait.

Gas or electric? Electric. The outdoor unit runs on 240 volts from its breaker and a disconnect box on the wall beside it.

Note any code first. A light or a display on the outdoor unit names the fault, and some controls lose it when the power goes off: the blinking yellow light.

Before you cycle the power. 240 volts outside. Use the breaker and the disconnect. Leave the inside of the unit to a technician.

After a long shutdown in the cold. Bosch recommends powering the outdoor unit with the thermostat off for at least 12 hours before the compressor runs, so the crankcase heater can warm it.

The same fault again. A reset that fails twice is hiding a fault. Stop and call a technician.

The waits that are not faults

Four stops that clear themselves. Rule them out before any reset.

Check 1Free, fifteen minutes

Rule out the normal waits

The thermostat’s delay. Many thermostats hold the compressor off for about five minutes after a change: the five minute wait.

A short cycle timer. Controls hold the compressor off for a while after it stops. On the White-Rodgers 49S25 the display shows C3 or P3 while it waits: the 49S25 codes.

Defrost. In winter the unit stops heating for a few minutes to melt ice off the outdoor coil, often with steam: frost and defrost.

Too cold outside. Bosch’s IDS stops the heat pump below -4°F and hands over to the backup heat: aux heat explained.

How to reset it

The reset is the power: the breaker in the panel and the disconnect beside the unit. Many controls also clear themselves with time.

Check 2Free, ten minutes

Cycle the power

The breaker and the disconnect. Switch the outdoor unit off at its breaker, or pull the disconnect beside it, then back on.

Copeland’s Comfort Alert. Copeland says to cycle the power to the module off and on. The last code flashes for 60 seconds, then clears.

Carrier’s lockouts. Carrier says a 4 hour lockout clears after 4 hours or when the 24 volt power is recycled: Carrier’s codes.

Bosch’s H5. Bosch marks it as needing a hard restart, the power off and on: the Bosch codes.

A ductless mini split. Most have no reset button, and MrCool gives 15 minutes off at the breaker for several of its codes: what a mini split reset really is.

The retries it does by itself

Check 3Free, 15 minutes to 4 hours

Let it retry

Carrier’s 15 minute retries. For pressure and thermal trips, Carrier says the control stops the compressor and tries again after 15 minutes if the demand is still there.

Carrier’s 4 hour lockouts. After repeated trips, the unit locks out for 4 hours. Carrier says a lockout means the same fault happened several times in a row.

Comfort Alert. Copeland says the code turns off by itself if conditions return to normal.

When to stop resetting

Check 4A service call

Know when to call

The same code returns. After one reset, watch it. A returning code means a technician.

The breaker trips again. Something is drawing too much current: why the outside unit is not running.

Keeping warm meanwhile. Google says emergency heat is for when the heat pump is not working or not keeping the home warm. Switch it on by hand while you wait for the technician, and back to Heat afterwards, because it is expensive to run.

It stays off with no code. The heat pump pages walk through the rest: why a heat pump is not heating.

Questions people ask

Is there a reset button on a heat pump?

Usually not. A heat pump is reset by switching its power off and on at the breaker or the outdoor disconnect.

How long should I leave the power off?

For a mini split, MrCool gives 15 minutes for several of its codes. For a Carrier lockout, recycling the 24 volt power clears it. Then give the unit a few minutes before judging it.

Will my heat pump reset itself?

Often. Carrier’s control retries after 15 minutes for pressure and thermal trips, and a 4 hour lockout clears by itself after 4 hours.

Why did my heat pump stop in winter with steam coming off it?

That is defrost. It melts ice off the outdoor coil and starts heating again by itself in a few minutes.

Why won’t it start straight after I change the thermostat?

Many thermostats hold the compressor off for about five minutes, and many controls add a short cycle timer. Wait it out.

Can I use emergency heat while it is locked out?

Yes, if your system has it. Google says emergency heat is for when the heat pump is not keeping the home warm. It costs more to run, so switch back to Heat once it is fixed.

How many times should I reset it?

Once. If the same code or trip comes back, the fault is still there and needs a technician.

Sources: The makers' own instructions, as cited on this site's brand pages: Carrier 24-25-9SM, Copeland Comfort Alert, Bosch IDS 2.0, White-Rodgers 49S25 and MrCool