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Plumber's reason for RCD tripping.

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Plumber changes boiler and RCD main switch starts tripping at various times when its firing up or soon after. (I was there doing other work).

I test ring (that its connected to) and get +299Mohms on all tests. RCD doesn't trip at x0.5 and trips at x1 and x5, all fine.
I've suggested to them that the boiler must be faulty.

Customer has since messaged me saying plumber says its tripping as consumer unit needs changing as it's and older consumer unit and RCD is not compatible with the boiler.

I've since finished my works and asked customer if it's still tripping.

"No but they had to put an older model of pump in... Something about the ERP pump and earth leakage. Apparently only certain breakers cause it to trip, most are fine but our current one isn't. (I hope that makes sense as I have no idea what it means)"

The plumber has his own spark who
he called for advice while I was there. I was sure it is a get out excuse and they have 'saved face ' with that excuse and at the same time putting the old non faulty pump back on.

I'm getting a board change out of it but for my own peace of mind, is there something special about a new pump or is it simply faulty with +30ma leakage.

I didn't do a ramp test with loads connected but at x0.5 with loads connected it did not trip (I know loads should be disconnected but I tested from a local socket).

Thank you

Every day is a school day, so happy to be

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Sounds like the plumber is talking BS to me

That is my thoughts but then I start doubting myself as he has a spark to get advice from.

I can't/won't push the point with the customer as the plumber is related to them.

Also I can see me changing the board and then plumber comes back with a new pump, identical to the last faulty new pump, claiming it is the same pump and low and behold I've changed the board and voila the new board doesn't trip!
I'd be asking for confirmation from the pump manufacturers about the exact details regarding the alleged 'non compatibility'

Are trying to say that this pump is not compatible with a BS4293 RCD, but is compatible with a BS61008. If they are both 30mA, they are both designed to trip under the same circumstances. It sounds like absolute rubbish to me.

If you don't need the work, I'd consider getting paid up from your non related completed works and walking away.
This is a very common situation,where you have to weigh up the importance of either electrical science - or politics.
If there is any chance of it being a safety issue,then it is a easy choice,if not,it is always going to be a personal call.

The only hiccup i could anticipate,is if in the future,any other "professional" gets involved,you can find yourself being lumped in with the plumber,as his opinion was not challenged :)
I recall here, but can't remember the details, with someone posting about a CH pump tripping either RCD or MCB.

The remedy was using the manufactures supply lead. Anybody remember?

PS: that CU does look like the customer could do themselves a favour and replace it.
Thanks for the replies. I've been paid up for the recent work. I'll be quoting for a new board but will be adding something regarding the nuisance tripping from the boiler (if the old 'new' pump is replaced back in). I'm assuming they will get a new new faultless pump and carry on with their fabricated pump scientology!
solution... put plumber's head in toilet bowl. flush toilet. the bog brush can then be inspected to ascertain which has the highest IQ.. the wet-pants or the toilet.

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