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Topic Title: RCD trips with light switch.....
Topic Summary: .....but lights not on RCD
Created On: 05 March 2013 12:57 PM
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 05 March 2013 12:57 PM
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Avatar for JZN.
JZN

Posts: 562
Joined: 16 November 2006

Called to a rental property. Tenants say that occasionally when they operate the living room light switch, the RCD opens and all sockets go off, but lights still work.

House rewired 8 years ago. Looks neat and in good condition. TNS earth system, split load crabtree board with lights by main switch and then an RCD covering shower and three socket circuits. All terminations in right places and tight. RCD trip times OK and ramp test trips it at 25mA.

They were a bit vague on how often this happens but about every few weeks. Certainly not daily and I could not get it to happen when i was there.

There is one blank gap between the lighing breakers and the RCD so EM coupling should not be an issue.

I did an IR test on all circuits and found no problems.

Anyone got any ideas for me?

Back to work now. Will check in later.

Thanks a lot
John
 05 March 2013 01:04 PM
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AJJewsbury

Posts: 11548
Joined: 13 August 2003

No immediate answers, but a few extra questions:

- does the RCD trip when the lights are switched off, or on (or both).

- did you insulation test between the various circuits (e.g. sockets N - lights N), rather than the usual between conductors of the same circuit.

- Does the light have any "active" components in it (transformer, electronics etc)?

- Andy.
 05 March 2013 01:09 PM
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Vortex

Posts: 16
Joined: 14 September 2010

I have had this before after installing a bathroom 2D light fitting - with ballast. Every time the light was switched on (or off - can't remember) the RCD on the sockets tripped (16th edition property so no RCD to lights)

It was a long time ago and I can't remember the details but we either replaced the fitting and it solved it or it was due to a high Ze (TT). Or it was a combination of the 2.

What kind of lights are in the living room?
 05 March 2013 04:49 PM
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Avatar for JZN.
JZN

Posts: 562
Joined: 16 November 2006

Thanks for the replies.

It's just a pendant light fitting in all rooms except the bathroom which is 2D but they have not said the problem occurs with use of this light.

I have not IR tested as suggested, just on individual circuits.

John
 05 March 2013 04:57 PM
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AJJewsbury

Posts: 11548
Joined: 13 August 2003

It's just a pendant light fitting

What sort of lamps? GLS? CFL?

My gut feel is some sort of connection between the circuits or something co-incidental (when they use the light switch they stand on a bit of floor they don't otherwise tread on and one of the floorboard nails is within a hair's breadth of a conductor - that sort of thing).

- Andy.
 05 March 2013 06:26 PM
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24Hour

Posts: 189
Joined: 06 April 2006

Ive had this before, all insualtion tests fine etc etc, my problem was with the fitting, the capacitor in the fitting was faulty, it was a tncs though, funny though never had this fault before and havent since, ballast in fitting was the primary culpret but insulation tested fine, cant remember why i changed capactor but as soon as i did it stopped.

-------------------------
Yes i do do 24/7 everyday of the FLAMIN year.
 05 March 2013 10:36 PM
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antric2

Posts: 1067
Joined: 20 October 2006

Start back at the board and dont just check tightness of terminal screws but tug each cable especially neutral.
Also, has any decorating been done recently.
If so switches may have been removed and refitted back to the boxes that may have top and bottom lugs left in and maybe just touching terminal screw of switch,
Go around each light switch turned on and give them a tap and see if tripping occurs.

Are the lights wired as in and out of the switches ie;are live and neutral fed from switch to switch.

Is there any security lights or a bathroom fan that may be seized fed off light circuit.

Good luck on your mission and may the thoughts be with you!!
Regards
Antric
 06 March 2013 05:17 PM
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Avatar for michaelbrett.
michaelbrett

Posts: 935
Joined: 28 December 2005

Last time I had something like this, it was a defective item on another circuit that was absolutely dead-short Line-Earth. No interconnection between the two circuits. Both on individual RCBOs.

Never did figure out why it tripped another RCBO.

After repair both circuits were ok. Both RCBOs tripped ok on test.

So, check the other circuits.

Hope this helps.

Regards

Mike
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