Lighting circuit fault

[Cmbayrshire]

This is a weird fault I can't quite figure out. I'm sure I'll get it eventually. Sometimes you need to step back and start again to get it.
I recently tested a new lighting circuit that constantly has a low voltage running through it. Disconnecting everything at the joint box it only seems to happen through the three core and earths.
For example, I disconnected one three core from the joint and removed the switch, insulation tested it between all cores showed clear.I connected the brown core back into live and left the rest disconnected and had between 5 and 15v on them.
I wouldn't have noticed this as it all showed clear on the original test but I fitted led gu10 lamps into some spots and they glow faintly with the problem.
could this be a cable problem even after it tests clear at 500v?

 

[Sharpend]

Not a cable fault. Probably back feed.

 

[stuartcourt]

what have you got between neutral and earth

 

[Cmbayrshire]

All clear between n & e

 

[Sharpend]

Is that no volts reading? Or clear when meggered?

 

[Cmbayrshire]

Totally clear meggered n to e. testing between n and e with the cable disconnected and power running through one core only I get the problem voltage.All t and e legs to lights and switches from the joint are fine. Just on the three cores. Strange.

 

[stuartcourt]

sounds like to me you have a power running through your lights and then not returning on neutral but going back into your circuit with reduced volts taken by the lamps

 

[Brightspark2]

Induced voltage...youll need to fit a snubber into the curcuit to stop the LEDs glowing...

On the 3 core what cores are used for what?...

 

[Cmbayrshire]

Think that's very plausible.Will check that out on Monday. Cheers.

 

[stuartcourt]

no prob if you meant me

 

[SYKRAPS]

Avoid CEF snubber lamps as they do NOT work...............defo induced voltage IMO, any LED's or electronics still connected whilst testing?

 

[Cmbayrshire]

Induced voltage...youll need to fit a snubber into the curcuit to stop the LEDs glowing...

On the 3 core what cores are used for what?...

mostly 2ways. One I was concentrating on was for 2 switch wires.Spots on one , wall light on the other. Figured if I solved one lone cable I would solve them all.
Whats a snubber, new to me.

 

[Cmbayrshire]

Nothing in while testing. All lamps out.Just standard light fittings throughout so no electronics. What can be causing induced voltage?

 

[SYKRAPS]

Nothing in while testing. All lamps out.Just standard light fittings throughout so no electronics. What can be causing induced voltage?

This is the question you should be asking yourself tbh, what are your thoughts?

You testing with MS and all mcb's and rcd's off?

Any rcbo's?

 

[telectrix]

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