Welder tripping main RCD ... solutions

[Symptoms]

I've acquired for my home workshop (in my ex-garage attached) an old Oxford Olympic 185amp oil cooled arc-welder which is tripping the main RCD next to my consumer units ... there is no fault on the welder as I have used it elsewhere.

My home set-up:
in the cellar
100 amp main fuse then meter
to
5 way DP Service Con Box (this has some spare ways)
to
Wylex WEM 80/2 RCD (80amp 100mA trip)
to
a pair of Wylex NN616 consumer units (these are linked to create sufficient ways - big house!)

then from a 30A MCB (Wylex NB30) in the consumer unit via 4.0mm T&E (radial) to a Wylex 3 Way Metal Consumer Unit (rewireable fuses) in the garage

one lighting circuit
one ring main for sockets
one radial terminating at a 32 Amp 3 Pin Wall Socket.

This set-up has worked perfectly.

It's into this industrial socket that the welder is plugged and when the arc is struck the main RCD in the cellar trips. Now clearly the RCD is doing what it's meant to do but I want to use the welder.

Maybe I could create a dedicated 'welder circuit' by installing a 1 way consumer unit (rewireable) in the cellar from a couple of spare ways in the service box and run new cable to the industrial socket in the garage. This would by-pass the main RCD so avoiding it tripping. Is this feasable under the new regs or do I have to include a RCD (which will trip thus rendering the welder redundant)?

So are there any suggestions ...

 

[ban-all-sheds]

When you used it elsewhere, was there an RCD?

Is the 80A RCD you have before the 2 CUs the only one?

If you need two boards because it's a big house, is an 80A device sufficient?

Are welders prone to tripping RCDs, or might there be a genuine fault with yours that ought to be fixed, not worked around?

Anyway - you can do what you suggest, as long as the cables aren't concealed, as 32A sockets don't have to have RCD protection, but how are you going to isolate the supply to make it safe to do this?

If you're in England or Wales it's all notifiable.

 

[RF Lighting]

There must be something pretty fundamentally wrong if you are tripping a 100mA RCD.

a 30mA then maybe, but 100mA don't trip for the fun of it.

I'd definately suspect the welder first of all, and suggest you maybe have your installation checked out.

Fitting a non RCD supply to avoid having the fault repaired is just madness.

If you car seatbelt didn't clip into the holder properly would you have the belt removed or would you get it fixed so it can continue to do it's job and protect you in the event of a crash (or electrical fault)?

 

[Symptoms]

sheds & RF - the tackle was used at our main workshop as recently as last week with no probs and has had it's annual inspections. We've got 3-phase there with 32 Amp 3 Pin Wall sockets off a phase & neutral - the distribution board has fuselinks so no RCDs.

At home the 80A RCD is before the 2 CUs and is the only one; each CU has it's own 100A mainswitch (810N) and the usual range of MCBs. The home set-up was installed 25 years ago and has regular inspections, the most recent PIR was this Summer.

I've checked a couple of weldings forums and this isn't an unknown problem with the welder's inductive surge current causing the tripping.

 

[ceraunic_level]

Sorry I don't know the answer to your question, but what sort of current will that welder pull.

 

[Symptoms]

I had another go with the welding tackle yesterday and on the 50volt (for general welding setting) at 60amps and 75 amps the RCD didn't trip; when I ramped-up the amps to 95, 120, 150 170, 185 settings it did trip. On the 80 volts (for light gauge welding & special electrodes) it was fine at 35amp, 50amp and 60amp settings but tripped on 70, 80, 90, 100, 110, 120, 150.

The rating plate is marked as:
220-240-415v (can be used 3-phase if needed but never has)
max duty cycle 5.5kva