Boiler Tripped RCD

[jwadd215]

Hi all,

UK: The RCD on the circuit my boiler is on has tripped, I have a water supply issue in my area today and switched on my hot tap for a moment or so and there was low pressure, could the low level of water in a modern boiler (Logic) cause the RCD on the consumer unit to trip?

I'm unsure if it's a fault elsewhere as earlier on before the water supply issue everthing else on the circuit was working as normal, sockets etc, and the circuit has not tripped since I have swicthed the boiler off at the spur whilst waiting for the water supply to be restored.

Thanks,
James.

 

[mainline]

Hi all,

UK: The RCD on the circuit my boiler is on has tripped, I have a water supply issue in my area today and switched on my hot tap for a moment or so and there was low pressure, could the low level of water in a modern boiler (Logic) cause the RCD on the consumer unit to trip?

I'm unsure if it's a fault elsewhere as earlier on before the water supply issue everthing else on the circuit was working as normal, sockets etc, and the circuit has not tripped since I have swicthed the boiler off at the spur whilst waiting for the water supply to be restored.

Thanks,
James.

It's possible for any type of boiler when fired up to cause an RCD to trip, but a modern combi type boiler shouldn't for no water alone as there should be sensors for overheating or water flow etc.

Common things would be a water pump, igniter, or fan.

 

[EricMark]

There are some things with older boilers which could cause an RCD to trip with no fault. But in the main the modern boiler is designed to have an RCD, so will not have any spark igniters likely to cause it to trip.

So we have to test, we can to an extent use trial and error, but if that fails, then we need to test, we have three tools, the insulation tester, I would use 250 volt setting, the clamp-on ammeter, needs to read in increments of 1 mA or better, and the RCD tester.

Remember the insulation tester uses DC, and likely there are items in the boiler which will not be active once switched off, so neutral to earth is often the way forward, if not tripped the clamp-on ammeter is better, as it will show capacitive and induction linking, and show how close to the wind you are sailing.

The RCD tester on ramp can do the same, the permitted leakage is 30% so for a 30 mA RCD that's 9 mA, so it should trip at between 6 and 30 mA, clearly if tripping at 6 mA, although within limits, one can expect problems, in the main we see around 20–26 mA with a ramp test. This is why I prefer to use the clamp-on.

The standard test with an RCD and many circuits, is turning off all MCB's and turn them on one at a time. If one MCB causes it to trip, try it on its own, but since load with raise the neutral voltage above earth, and an MCB does not normally switch the neutral it is not a fail-safe test.