rcd trip

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Wislum

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I have recently fitted a reefer socket arrangement in a clients premises(3P+E 60309 type). Installation checked out fine until new machine was plugged in. All was well while using machine but when machine was switched off it tripped the rcd. At a loss at present as to reason for trip. Rest of installation ok only this machine causes the trip

 
The machine is a high frequency weldeing maching operating at 27.5Mhz and drawing around 25 amps peak

 
Something loose? Check connections all the way back I would as a start..............what about other circuits? Neutral to earth fault elsewhere?

 
Rest of installation is ok only occurred since fitting a 3p+E as opposed to 3P+N+E. site is industrial rcd is 80 amp 30mA rcd. Faulty circuit is fed from a sub board protected by a 32A mcb sub board has 80Amp main switch fed fom main board

 
I thought about that but the machine only trips the rcd when the machine is switched off not when running

 
The last 3 phase welder i wired stated in the instructions it had to run through a RCD.

I have had the same problem of the RCD tripping when turning off a water feature pump. I changed the pump & RCD. I also fitted a double pole switch , spoke to loads of people about it including the retailer but not the Chinese manufacturer.I never did resolve it and came to the conclusion (in my head) it was back EMF as the pump was still turning when it was being powered down. It was not a big deal as it was an RCD locally, just for the pond although i never got another call from that client. I asked about it on the IET forum and a few other people had had the problem, one with fluorescent lights. Never got a definitive answer though.

 
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may be the welder dumping to E what is left in it, if you get my drift.

where exactly is it being turned off? at the welder itself or via a wall mounted isolator?

 
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