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Electrical noise created by 3ph machine

Steve Phillips

Hello all

Life long sparky... semi-retired now, but working at a local workshop

The company had a local (rather shoddy) electrical company come in and re-supply a 3ph, 35A per phase painting/spray machine.    It was fed before and created flickering in the office fluorescent lights.

But, it still does it.  The fluorescent lights in the offices on the mezzanine nearby flicker when the machine pulls a high load.

It's fed from a sub DB that has a 125A, 25mm 3ph SWA supply (This run is considerable from the incomer - probably somewhere like 70M+.   

Machine MCB is 32A

They used 6mm 5 core SY cable (I would have gone 10mm) over a 25M run.  But they laid it on top of (not in) a 4" galv trunking with T&E inside.  Entirely possible the lighting feeds run within this trunking.

I may unstitch the cable and move it away from the trunking, but I am not entirely convinced that is the issue.

Any ideas on what to try?  

Personally, I would rewire the machine directly back to the incoming mains cupboard, but that is no easy task.

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  • 0

    OK.  I have done some investigating.

    Lighting is wired in some pretty shoddy 1.5mm and fused at 20A.  I would assume that is a throwback to the days when they had sodium lights?  Don't think I have ever seen a lighting circuit protected by 20A.

    The company had someone come in and check all the wiring and said all was fine.  But it isn't.  DB lists are wrong for starters.

    Question.  As a qualified, 55 yrs old lifelong sparky but who is no longer registered with the Niceic (because I no longer install - quit 2 years back), am I OK trying to sort out this issue?

    I was told by this highly suspect electrical company that as it's a industrial site, it doesn't need to be signed off.  Not sure that is correct.

    But, I do know that we don't want them back, and I would do the job properly.  Just wondered what the regs were these days, seeing as they change every 15 minutes.

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  • 0

    OK.  I have done some investigating.

    Lighting is wired in some pretty shoddy 1.5mm and fused at 20A.  I would assume that is a throwback to the days when they had sodium lights?  Don't think I have ever seen a lighting circuit protected by 20A.

    The company had someone come in and check all the wiring and said all was fine.  But it isn't.  DB lists are wrong for starters.

    Question.  As a qualified, 55 yrs old lifelong sparky but who is no longer registered with the Niceic (because I no longer install - quit 2 years back), am I OK trying to sort out this issue?

    I was told by this highly suspect electrical company that as it's a industrial site, it doesn't need to be signed off.  Not sure that is correct.

    But, I do know that we don't want them back, and I would do the job properly.  Just wondered what the regs were these days, seeing as they change every 15 minutes.

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