RCD tripping every time the boiler tries to start
If the trip switch only ever goes when the boiler is attempting to fire, and not at other times, that timing is the clue. It points strongly to an electrical fault inside the appliance rather than a wider household wiring problem.
The engineering behind an RCD tripping at boiler start-up
A pump or fan motor with a developing earth fault draws enough leakage current at the moment it starts to trip a sensitive RCD, even though it may run apparently normally for the rest of the day. Moisture ingress into an electrical connector, often following a leak elsewhere in the appliance, produces the same symptom intermittently depending on humidity and temperature. This is treated as an electrical safety issue and the appliance should not be repeatedly restarted against a tripping RCD.
An RCD tripping at boiler start-up — the facts that change the job
- Timing that matches boiler start exactly points at the appliance itself
- A developing earth fault in the pump or fan draws sudden leakage current
- Moisture in a connector produces the same symptom intermittently
- Do not keep resetting the RCD against a repeatedly tripping appliance
- This is an electrical safety fault, not a plumbing or gas issue
Who should undertake the work
- Gas appliance work must be completed by a suitably qualified Gas Safe engineer
- Oil appliance work should be completed by a suitably qualified OFTEC technician
- Jamie Crawford Heating states both Gas Safe and OFTEC registration
Questions we get asked
- Is this a gas or electrical engineer's job?
- It sits in electrical fault-finding territory, though the same engineer who services the boiler can usually diagnose it.
- Should I isolate the boiler until it is checked?
- Yes — repeatedly forcing a tripping circuit to reset is not a safe long-term workaround.
Where we deal with this
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Services that cover this
Get an RCD tripping at boiler start-up looked at properly
Put simply: Consistent timing between the trip and boiler start-up points firmly at an internal electrical fault needing proper diagnosis.
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