Why Does My Heat Pump Keep Tripping the Breaker? (UK Causes and What to Do)
Why Does My Heat Pump Keep Tripping the Breaker? (UK Causes and What to Do)
Why Does My Heat Pump Keep Tripping the Breaker? (UK Causes and What to Do)
Why Does My Heat Pump Keep Tripping the Breaker? (UK Causes and What to Do)
Why Does My Heat Pump Keep Tripping the Breaker? (UK Causes and What to Do)
UK Heat pump Help Technical Team
Independent Heat Pump Engineer
Quick answer: A heat pump that keeps tripping the breaker is reporting an electrical problem somewhere between the consumer unit and the compressor. The usual causes are water getting into electrical parts, a heating element leaking to earth, the wrong type of RCD for an inverter-driven unit, a fault inside the outdoor unit, or an overloaded circuit. Reset it once at most. If it trips again, leave it off and get a qualified electrician involved. Repeated resetting can turn a small fault into a dangerous one.
It tends to happen on a cold morning. The heating comes on, the house goes quiet, and the heat pump is dead. You flick the breaker back, it runs for ten minutes, and then it clunks off again.
It’s worrying, and it’s easy to assume the heat pump itself has died. Often it hasn’t. The breaker is doing its job and stopping something unsafe from carrying on. The hard part is working out what that something is, and that’s what this guide is for.
First, work out what has actually tripped
Not every heat pump stop is a tripped breaker, and the difference matters. Check these in order:
An RCD or RCBO in the consumer unit. These have a test button and trip when they detect current leaking to earth. This is the most common one on heat pump circuits.
An MCB (miniature circuit breaker). This trips on overload or a short circuit rather than leakage.
A separate isolator or small consumer unit near the outdoor unit. Many installations have one on the wall by the heat pump.
The main switch at the consumer unit. If this has gone, the whole house is drawing too much, not just the heat pump.
If nothing in the electrics has moved and the heat pump simply stops and restarts by itself, that’s the controller, not a trip. Our guide on why your heat pump keeps turning off explains how to tell normal cycling from a real problem.
If the controller comes back up showing a fault code, photograph it before you reset anything. Our guide to common heat pump fault codes explains what the main categories mean. A trip that cuts power outright won’t always leave a code, so don’t worry if there isn’t one.
Is it safe to reset it?
Once, yes. If the breaker holds and the heat pump runs normally, make a note of the date, the weather and what the system was doing, then keep an eye on it.
If it trips again, whether instantly or twenty minutes later, stop. Leave the breaker off, switch off the heat pump’s own isolator, and call a qualified electrician. Please don’t remove covers or poke around inside the unit. Electrical faults, refrigerant work and anything inside the outdoor casing are jobs for people with the right training and test equipment.
Some signs mean you shouldn’t wait for an appointment slot:
A burning smell or scorch marks around the isolator or consumer unit
Buzzing, crackling or sparking
A breaker or isolator that feels hot to the touch
Standing water around electrical connections
Keep away from the equipment, switch things off only if you can do so without touching anything wet, and call an electrician urgently. If you see smoke or flames, leave the building and call 999.
What usually causes a heat pump to trip the breaker
Water where it shouldn’t be
If your heat pump only trips in rain, snow or during a frosty spell, moisture is high on the list. Outdoor isolators, cable glands and connection points can let water in over time, particularly if they were poorly sealed or have been knocked about since installation. Condensation can build up inside electrical enclosures too.
Heat pumps produce a lot of water in cold weather. That water should drain away from the base of the unit, not pool around it or freeze. If you want to understand what’s normal, our guide on heat pump condensate drainage covers it, and our article on where an outdoor unit should go explains why the position affects drainage and exposure. Water and ice around the unit isn’t automatically a fault. Water getting into electrical parts always is.
The wrong type of RCD, or one shared with other circuits
This one catches a lot of people out, and it usually shows up soon after installation. Inverter-driven heat pumps produce leakage currents that are more complicated than those of an ordinary appliance. Some RCD types can’t read those currents reliably. The result is nuisance tripping, sometimes when the heat pump starts up or shuts down, with nothing actually wrong with the heat pump.
The Heat Pump Association, with NICEIC and NAPIT endorsement, publishes guidance on RCD selection for heat pump installations. It says the manufacturer’s instructions should specify the type, that older Type AC devices aren’t suitable, and that Type A devices can cause unwanted tripping on these installations. It also points out that a heat pump sharing an RCD with other circuits can complicate things.
If your heat pump was installed recently and the tripping started on day one, ask your installer which RCD type the manufacturer specifies and what’s actually fitted. That’s a quick question and a very reasonable one.
A heating element leaking to earth
The immersion heater in the hot water cylinder is a classic culprit. Elements can develop insulation faults over time, and the breaker may only trip when the immersion comes on, for example during a hot water boost. Some units also have small heaters of their own for the base or compressor.
If the trip tends to happen when hot water is being heated, mention that to your electrician. It gives them a very useful place to start.
A fault inside the outdoor unit
Compressor windings, fan motors and control boards can all develop insulation faults. These tend to trip the breaker quickly, sometimes the moment the unit tries to start, and they don’t improve on their own. An electrician can test the insulation resistance of the circuit and help narrow it down. If the fault turns out to be inside the unit, the manufacturer or an approved heat pump engineer needs to take it from there.
An overloaded or mismatched circuit
An MCB that trips under load can point to a breaker that’s too small for the unit, loose connections generating heat, or a circuit that’s carrying more than it should. It’s less common with modern inverter models because they start softly, but it can still happen with older fixed-speed units or a heat pump sharing a supply with other heavy loads.
Please don’t ask someone to fit a bigger breaker to make the problem go away. The breaker protects the cable. A larger one on cable that can’t take it creates a fire risk, and it won’t fix an RCD that’s tripping on leakage in the first place.
A tired breaker
Breakers and RCDs wear out. An old RCD can become oversensitive and trip at a lower level than it should. Pressing the test button on your RCDs every few months is good housekeeping. If an RCD doesn’t trip when you press it, or the same one keeps tripping with no obvious cause, ask an electrician to check it.
Wiring problems from the installation or later work
Damaged cable, poor terminations, a shared neutral or something altered after commissioning can all cause trips. These tend to show up in the first weeks or months of a new system. If that sounds like your situation, our article on heat pump problems after installation and who’s actually responsible explains how to stop being passed between installer, manufacturer and electrician.
What the pattern tells you
The pattern is a clue, not a diagnosis, but it helps an electrician a lot:
When it trips | What it often points towards |
|---|---|
Straight away every time you reset it | A hard fault: wiring, a failed component or a failed breaker |
Only in rain, frost or snow | Water ingress at the isolator, glands or connections |
When the compressor starts | RCD type mismatch, inrush on an older unit, or a compressor or wiring fault |
When the hot water heats | The immersion heater or its wiring |
During or just after defrost | Water, ice or a heater leaking under cold, damp conditions |
Randomly, hours apart | A marginal fault, an ageing RCD or leakage building up on a shared circuit |
After new equipment was added | Overall load or a shared RCD that now has too much leakage on it |
What to write down before you call anyone
You’ll save time and money if you can answer these:
Which device tripped, and where is it (consumer unit, separate unit by the heat pump, main switch)?
How soon after resetting did it trip again?
What was the heat pump doing: heating, hot water, defrosting, just starting?
What was the weather like?
Was anything new added recently, such as an EV charger, a new circuit or other work on the house?
What fault code, if any, did the controller show? A photo helps.
When was the heat pump installed, and has it tripped before?
A photo of the breaker labels and the heat pump’s data plate.
Who should you call?
If the system is new, start with your installer. Tripping at or soon after commissioning is their problem to solve, and your warranty may depend on the right people doing the work. Check your warranty terms before anyone else opens the unit.
If it’s an older system, a qualified electrician is the right first call. It helps if they’ve worked on inverter-driven heat pumps. A general electrician can swap a faulty breaker, but they may not know to question the RCD type.
If the electrician finds nothing wrong with the supply and points at the unit, the manufacturer or a heat pump engineer is next.
What we can help with, and what we can’t
Our Fix My Heat Pump service is remote, and we can’t test circuits or work on live electrics over a video call. Nobody should try.
What we can do is go through the tripping pattern, fault codes, settings and operating history with you. That lets us work out whether the evidence points at the heat pump, the hot water side or the house wiring, and give your electrician or installer a clear brief so they aren’t starting from scratch. We’re independent, so there’s no incentive to sell you a repair.
How to reduce the risk this winter
Most trips that appear in the first cold snap were building for a while. A pre-winter check is the cheapest way to catch them. Our winter maintenance checklist walks you through what to check while the weather is still mild.
A few extra things worth doing:
Keep the area around the outdoor unit clear and make sure defrost water has somewhere to go.
Press the test button on your RCDs every few months.
Don’t ignore the first trip. A one-off that never repeats is fine. A second one is a pattern.
Tell your installer or electrician if you add anything big to the electrics.
Frequently asked questions
Can I just keep resetting the breaker?
No. One reset to see if it was a one-off is reasonable. Repeated resetting means you’re pushing power into a circuit that’s telling you something is wrong, and it makes it harder for an engineer to find the fault.
Is it normal for a heat pump to trip in cold or wet weather?
No. Frost, ice and meltwater around the unit are normal in winter. Tripping isn’t. Cold or wet weather often just exposes a weakness that was already there, such as moisture getting into a connection.
Will a bigger breaker fix it?
Almost never, and it can be dangerous. An MCB protects the cable from overload, and an RCD trips on leakage, not on load. Fitting something larger doesn’t fix the leakage and may leave the wiring unprotected.
Can tripping damage my heat pump?
Frequent hard stops aren’t good for any equipment, but the bigger risk is the underlying fault going unfixed. A leakage fault that’s been left to get worse is more expensive to sort than one caught early.
Heat pump keeps tripping and you’re not sure why?
Send us the details and we’ll help work out where the problem is likely to sit before you pay for the wrong job.
Quick answer: A heat pump that keeps tripping the breaker is reporting an electrical problem somewhere between the consumer unit and the compressor. The usual causes are water getting into electrical parts, a heating element leaking to earth, the wrong type of RCD for an inverter-driven unit, a fault inside the outdoor unit, or an overloaded circuit. Reset it once at most. If it trips again, leave it off and get a qualified electrician involved. Repeated resetting can turn a small fault into a dangerous one.
It tends to happen on a cold morning. The heating comes on, the house goes quiet, and the heat pump is dead. You flick the breaker back, it runs for ten minutes, and then it clunks off again.
It’s worrying, and it’s easy to assume the heat pump itself has died. Often it hasn’t. The breaker is doing its job and stopping something unsafe from carrying on. The hard part is working out what that something is, and that’s what this guide is for.
First, work out what has actually tripped
Not every heat pump stop is a tripped breaker, and the difference matters. Check these in order:
An RCD or RCBO in the consumer unit. These have a test button and trip when they detect current leaking to earth. This is the most common one on heat pump circuits.
An MCB (miniature circuit breaker). This trips on overload or a short circuit rather than leakage.
A separate isolator or small consumer unit near the outdoor unit. Many installations have one on the wall by the heat pump.
The main switch at the consumer unit. If this has gone, the whole house is drawing too much, not just the heat pump.
If nothing in the electrics has moved and the heat pump simply stops and restarts by itself, that’s the controller, not a trip. Our guide on why your heat pump keeps turning off explains how to tell normal cycling from a real problem.
If the controller comes back up showing a fault code, photograph it before you reset anything. Our guide to common heat pump fault codes explains what the main categories mean. A trip that cuts power outright won’t always leave a code, so don’t worry if there isn’t one.
Is it safe to reset it?
Once, yes. If the breaker holds and the heat pump runs normally, make a note of the date, the weather and what the system was doing, then keep an eye on it.
If it trips again, whether instantly or twenty minutes later, stop. Leave the breaker off, switch off the heat pump’s own isolator, and call a qualified electrician. Please don’t remove covers or poke around inside the unit. Electrical faults, refrigerant work and anything inside the outdoor casing are jobs for people with the right training and test equipment.
Some signs mean you shouldn’t wait for an appointment slot:
A burning smell or scorch marks around the isolator or consumer unit
Buzzing, crackling or sparking
A breaker or isolator that feels hot to the touch
Standing water around electrical connections
Keep away from the equipment, switch things off only if you can do so without touching anything wet, and call an electrician urgently. If you see smoke or flames, leave the building and call 999.
What usually causes a heat pump to trip the breaker
Water where it shouldn’t be
If your heat pump only trips in rain, snow or during a frosty spell, moisture is high on the list. Outdoor isolators, cable glands and connection points can let water in over time, particularly if they were poorly sealed or have been knocked about since installation. Condensation can build up inside electrical enclosures too.
Heat pumps produce a lot of water in cold weather. That water should drain away from the base of the unit, not pool around it or freeze. If you want to understand what’s normal, our guide on heat pump condensate drainage covers it, and our article on where an outdoor unit should go explains why the position affects drainage and exposure. Water and ice around the unit isn’t automatically a fault. Water getting into electrical parts always is.
The wrong type of RCD, or one shared with other circuits
This one catches a lot of people out, and it usually shows up soon after installation. Inverter-driven heat pumps produce leakage currents that are more complicated than those of an ordinary appliance. Some RCD types can’t read those currents reliably. The result is nuisance tripping, sometimes when the heat pump starts up or shuts down, with nothing actually wrong with the heat pump.
The Heat Pump Association, with NICEIC and NAPIT endorsement, publishes guidance on RCD selection for heat pump installations. It says the manufacturer’s instructions should specify the type, that older Type AC devices aren’t suitable, and that Type A devices can cause unwanted tripping on these installations. It also points out that a heat pump sharing an RCD with other circuits can complicate things.
If your heat pump was installed recently and the tripping started on day one, ask your installer which RCD type the manufacturer specifies and what’s actually fitted. That’s a quick question and a very reasonable one.
A heating element leaking to earth
The immersion heater in the hot water cylinder is a classic culprit. Elements can develop insulation faults over time, and the breaker may only trip when the immersion comes on, for example during a hot water boost. Some units also have small heaters of their own for the base or compressor.
If the trip tends to happen when hot water is being heated, mention that to your electrician. It gives them a very useful place to start.
A fault inside the outdoor unit
Compressor windings, fan motors and control boards can all develop insulation faults. These tend to trip the breaker quickly, sometimes the moment the unit tries to start, and they don’t improve on their own. An electrician can test the insulation resistance of the circuit and help narrow it down. If the fault turns out to be inside the unit, the manufacturer or an approved heat pump engineer needs to take it from there.
An overloaded or mismatched circuit
An MCB that trips under load can point to a breaker that’s too small for the unit, loose connections generating heat, or a circuit that’s carrying more than it should. It’s less common with modern inverter models because they start softly, but it can still happen with older fixed-speed units or a heat pump sharing a supply with other heavy loads.
Please don’t ask someone to fit a bigger breaker to make the problem go away. The breaker protects the cable. A larger one on cable that can’t take it creates a fire risk, and it won’t fix an RCD that’s tripping on leakage in the first place.
A tired breaker
Breakers and RCDs wear out. An old RCD can become oversensitive and trip at a lower level than it should. Pressing the test button on your RCDs every few months is good housekeeping. If an RCD doesn’t trip when you press it, or the same one keeps tripping with no obvious cause, ask an electrician to check it.
Wiring problems from the installation or later work
Damaged cable, poor terminations, a shared neutral or something altered after commissioning can all cause trips. These tend to show up in the first weeks or months of a new system. If that sounds like your situation, our article on heat pump problems after installation and who’s actually responsible explains how to stop being passed between installer, manufacturer and electrician.
What the pattern tells you
The pattern is a clue, not a diagnosis, but it helps an electrician a lot:
When it trips | What it often points towards |
|---|---|
Straight away every time you reset it | A hard fault: wiring, a failed component or a failed breaker |
Only in rain, frost or snow | Water ingress at the isolator, glands or connections |
When the compressor starts | RCD type mismatch, inrush on an older unit, or a compressor or wiring fault |
When the hot water heats | The immersion heater or its wiring |
During or just after defrost | Water, ice or a heater leaking under cold, damp conditions |
Randomly, hours apart | A marginal fault, an ageing RCD or leakage building up on a shared circuit |
After new equipment was added | Overall load or a shared RCD that now has too much leakage on it |
What to write down before you call anyone
You’ll save time and money if you can answer these:
Which device tripped, and where is it (consumer unit, separate unit by the heat pump, main switch)?
How soon after resetting did it trip again?
What was the heat pump doing: heating, hot water, defrosting, just starting?
What was the weather like?
Was anything new added recently, such as an EV charger, a new circuit or other work on the house?
What fault code, if any, did the controller show? A photo helps.
When was the heat pump installed, and has it tripped before?
A photo of the breaker labels and the heat pump’s data plate.
Who should you call?
If the system is new, start with your installer. Tripping at or soon after commissioning is their problem to solve, and your warranty may depend on the right people doing the work. Check your warranty terms before anyone else opens the unit.
If it’s an older system, a qualified electrician is the right first call. It helps if they’ve worked on inverter-driven heat pumps. A general electrician can swap a faulty breaker, but they may not know to question the RCD type.
If the electrician finds nothing wrong with the supply and points at the unit, the manufacturer or a heat pump engineer is next.
What we can help with, and what we can’t
Our Fix My Heat Pump service is remote, and we can’t test circuits or work on live electrics over a video call. Nobody should try.
What we can do is go through the tripping pattern, fault codes, settings and operating history with you. That lets us work out whether the evidence points at the heat pump, the hot water side or the house wiring, and give your electrician or installer a clear brief so they aren’t starting from scratch. We’re independent, so there’s no incentive to sell you a repair.
How to reduce the risk this winter
Most trips that appear in the first cold snap were building for a while. A pre-winter check is the cheapest way to catch them. Our winter maintenance checklist walks you through what to check while the weather is still mild.
A few extra things worth doing:
Keep the area around the outdoor unit clear and make sure defrost water has somewhere to go.
Press the test button on your RCDs every few months.
Don’t ignore the first trip. A one-off that never repeats is fine. A second one is a pattern.
Tell your installer or electrician if you add anything big to the electrics.
Frequently asked questions
Can I just keep resetting the breaker?
No. One reset to see if it was a one-off is reasonable. Repeated resetting means you’re pushing power into a circuit that’s telling you something is wrong, and it makes it harder for an engineer to find the fault.
Is it normal for a heat pump to trip in cold or wet weather?
No. Frost, ice and meltwater around the unit are normal in winter. Tripping isn’t. Cold or wet weather often just exposes a weakness that was already there, such as moisture getting into a connection.
Will a bigger breaker fix it?
Almost never, and it can be dangerous. An MCB protects the cable from overload, and an RCD trips on leakage, not on load. Fitting something larger doesn’t fix the leakage and may leave the wiring unprotected.
Can tripping damage my heat pump?
Frequent hard stops aren’t good for any equipment, but the bigger risk is the underlying fault going unfixed. A leakage fault that’s been left to get worse is more expensive to sort than one caught early.
Heat pump keeps tripping and you’re not sure why?
Send us the details and we’ll help work out where the problem is likely to sit before you pay for the wrong job.
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Whether you need help with an existing heat pump, a pre-installation review, cooling advice, servicing or a room-by-room heat loss survey, send us a few details and we'll point you in the right direction.
Whether you need help with an existing heat pump, a pre-installation review, cooling advice, servicing or a room-by-room heat loss survey, send us a few details and we'll point you in the right direction.
Whether you need help with an existing heat pump, a pre-installation review, cooling advice, servicing or a room-by-room heat loss survey, send us a few details and we'll point you in the right direction.
