Heat Pump Tripping? Electrical vs Heating Fault Explained
Heat Pump Tripping the RCD or Breaker? Electrical vs Heating Fault Explained
Heat pump tripping is one of the most common sources of confusion for homeowners, because the symptom looks identical whether the cause is electrical or mechanical — the power just cuts out. This guide focuses on what we know well: the electrical protection side. For anything specific to the heat pump's own operation, we'll point you in the right direction rather than guess.
Why heat pumps need Type B RCD protection
Heat pumps are frequency-controlled equipment — they use inverter-driven compressors to vary their output rather than simply switching on and off. Under BS 7671 Regulation 531.3.3, this type of equipment can produce residual currents under fault conditions that a standard Type A RCD isn't designed to reliably detect. A Type B RCD is required specifically because it can detect these smooth DC and complex waveform fault currents, not just the simpler waveforms a Type A device handles.
This is worth checking first if a heat pump has started tripping and previously didn't: confirm the correct RCD type was fitted for the installation in the first place. A Type A RCD on a heat pump circuit can be a source of both nuisance tripping and, in some fault conditions, a genuine protection gap — see our guide on Type B RCDs for the full explanation of why this matters for frequency-controlled equipment generally.
Electrical fault or heating system fault? A quick triage
| Sign | Points toward |
|---|---|
| Trips instantly the moment it's switched on or plugged in | Electrical fault — likely earth leakage inside the unit's wiring or a component failure |
| Also trips other circuits sharing the same RCD | Electrical fault — the RCD is protecting more than just the heat pump, worth confirming what else is on that circuit |
| The breaker or RCD won't reset and hold, even with the heat pump disconnected | Electrical fault — the protective device itself may have failed, independent of the heat pump |
| Only trips during a specific part of the heating cycle (e.g. defrost, hot water mode) | Heating system-specific — likely something to do with how the unit itself is operating, not the electrical supply |
| Shows an error code on the unit's own display when it happens | Heating system-specific — the manufacturer's error code is the right starting point, not general electrical troubleshooting |
| Runs fine electrically but isn't heating properly | Heating system-specific — this is a performance issue, not a tripping/electrical one |
This is a general pattern to help you decide who to call first, not a diagnosis. Some situations genuinely have overlap — for example, a heating-system fault can sometimes present as a hard electrical trip. If you're not sure after working through this, starting with an electrician is usually the safer first call, since they can also confirm whether the electrical side is genuinely fine before you pay for a heating engineer visit.
If it looks electrical
Don't assume tripping automatically means the heat pump is broken — in many cases it's the protective device, its type, or the wider circuit that needs attention, not the appliance. This is exactly the same principle covered in our EV charger tripping guide, which goes into more general detail on how RCD/RCBO faults present and what "sticky" or unresponsive protective devices usually indicate.
Type B RCDs, RCBOs and SPDs for heat pump circuits, in stock with trade pricing.
View heat pump protection units →If it looks heating system-specific
If the tripping pattern points to something happening within the heat pump's own operation — a specific cycle, an error code, or a performance issue rather than a clean electrical trip — this is genuinely outside what an electrical protection guide can responsibly diagnose. Contact your heat pump's installer or manufacturer directly; they'll have access to the unit's specific fault codes and service history, which matters far more here than general electrical knowledge.
Frequently Asked Questions
Why does my heat pump need a different RCD to the rest of my house?
Heat pumps use inverter-driven, frequency-controlled compressors, which can produce fault current waveforms that a standard Type A RCD isn't designed to reliably detect. BS 7671 Regulation 531.3.3 requires Type B protection for this type of equipment specifically, rather than the Type A devices commonly used elsewhere in a domestic installation.
Should I call an electrician or a heating engineer if my heat pump trips?
If the trip happens instantly on power-up, affects other circuits, or the protective device won't reset even with the heat pump disconnected, start with an electrician. If it only happens during a specific part of the heating cycle or shows an error code on the unit's display, a heating engineer or the manufacturer is the better first call. If you're unsure, an electrician can usually rule the electrical side in or out fairly quickly.
Can the wrong RCD type cause a heat pump to trip unnecessarily?
Yes. A Type A RCD fitted to a circuit that should have Type B protection can be a source of nuisance tripping on frequency-controlled equipment like heat pumps, since it isn't designed to correctly interpret the fault current waveforms this type of equipment can produce.
Do heat pumps need surge protection as well as the correct RCD?
Surge protection is generally recommended for heat pump installations, similar to other significant fixed appliances, to protect the unit's control electronics from voltage spikes. See our guide on heat pump electrical protection requirements for the full picture.
Further reading:
Heat pump electrical protection requirements
Heat pump protection units explained
What is a Type B RCD?
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This guide covers general electrical protection principles only and does not diagnose heat pump-specific mechanical or performance faults. Any electrical testing, RCD/RCBO replacement, or circuit work must be carried out by a qualified, registered electrician. For issues with the heat pump's own operation, contact your installer or the manufacturer directly.
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