Trippin’

[ebee]

Yes I once had one that tripped RCD on turn off but never on turn on. ins res tested ok. swapped switch and problem vanished. consensus was one pole was delaying at switch off

 

[ericmark]

Sometimes RCDs do just trip when a switch is turned on or off. I don't think we really know why.

I also would like to know why, I had two RCD's feeding two Wylex fuse boxes with MCB's replacing the fuses, one RCD would trip, and on resetting it, the other would trip, also some times it would not reset unless all MCB's turned off, but would not trip when they were turned on again.

I did from time to time try and find a fault, and would get out the insulation tester, but no fault found, and it would seem to trip maybe 4 times in 2 weeks, then go for two years before next trip.

I think caused by spikes, either on the supply or due to switching some thing, there was no SPD fitted, and the RCD's were old, no type AC, A, F, B etc marked on them, and I think no electronics inside, I got them from work in the 90's second hand, so god knows how old. Still have a spare in a box, maybe I should break it open and see how it works?

New house all RCBO's so no longer an issue, but it seems odd,

I have an boiler on a separate circuit.

… and RCD trips. MCB is fine.

I can see how a separate circuit with a RCBO, but to have a RCD feeding only the boiler seems odd? I have seen this with a shower, but not a boiler, the word boiler is likely wrong, we often call things boilers when in fact they only heat the water, if they boiled it we would say it is faulty, but this means we have many items we loosely call boilers, I call my oil fired water heater a boiler, but the two real boilers in daily use I call kettles, but really are one cup boilers.

So can you explain exactly what you have, new RCD's are designed not to be affected by spikes, but old ones it seems are.

 

[Dinny991]

Sorry - I wasn’t clear. When I said separate circuit I meant not ring - just a single spur feeding the boiler from an MCB at the CU. RCD is protecting a few circuits, but only trips, on occasion, when the switch to the boiler is turned on. Nothing else trips the RCD.

 

[Dinny991]

Changed switch about a week ago - no tripping yet, but early stages still. One thing I forgot to mention was the old switch had a light indicator when it was on. Not sure if this also could be causing the problem, so I replaced it with one with no LCD.

 

[Dinny991]

So it’s been about a month ago and since I changed the switch it’s not tripped. It’s very likely to have tripped by now, I reckon, and so I think that it must be the switch. The old once had a neon light and the new one doesn’t. So I’m not sure if this has any relevance - ie could it be the neon that is leaking current?? Or the switch? Either way I don’t really care as it’s working now. Thanks so much for all your help. Saved a hell of a lot of time trying to get this solved otherwise. Thanks again.

 

[EFLImpudence]

So it’s been about a month ago and since I changed the switch it’s not tripped. It’s very likely to have tripped by now, I reckon, and so I think that it must be the switch.

Ok.

The old once had a neon light and the new one doesn’t. So I’m not sure if this has any relevance - ie could it be the neon that is leaking current??

It shouldn't. It would need to leak to earth, don't forget.

Or the switch? Either way I don’t really care as it’s working now. Thanks so much for all your help. Saved a hell of a lot of time trying to get this solved otherwise. Thanks again.

 

[JohnD]

If it is an immersion heater tripping the RCD, the cost of having it tested might be about the same as getting a new one fitted. They might last around 20 years with light use, less if daily.

Paying for a test, and then for a replacement, would be the most costly option.

Check all the screws are tight, on the heater, the switch, and the MCB.

This is easy and cheap. If the switch is old, or discoloured, or SP, fit a new DP one with "neon" (LED these days)


Edit
Oh, I see it's fixed now.