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Topic Title: RCBO Tripping
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Created On: 23 July 2013 02:55 PM
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 23 July 2013 02:55 PM
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jonathanjames

Posts: 2
Joined: 23 July 2013

Hello everyone,

I have wired an RCBO into the CU to feed x4 LED bathroom downlights and a bathroom extractor fan off the same circuit.

Any ideas why it is tripping?

It is a split load CU and not only does it trip the RCBO on the MCB side it also takes out the RCD in the board?

Any help would be greatly appreciated as the missus is coming home soon!
 23 July 2013 03:10 PM
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AJJewsbury

Posts: 11587
Joined: 13 August 2003

Sounds like you've got the N in the wrong N bar - by the sounds of it the bathrooms lights N have been connected to the RCCB's N bar rather than the unprotected one (although other faults could give similar symptoms, I'd check that first).
- Andy.
 23 July 2013 03:22 PM
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John Peckham

Posts: 7523
Joined: 23 April 2005

Jonathan

Welcome to the forum.

Assuming you have wired it in to the board correctly as Andy has suggested above it could be the RCBO is doing it's job in that it is detecting a fault to earth. Either line or neutral on the circuit has a low insulation resistance to earth.

-------------------------
John Peckham

http://www.astutetechnicalservices.co.uk/
 23 July 2013 03:41 PM
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jonathanjames

Posts: 2
Joined: 23 July 2013

Thanks for the quick reply guys, i will check it out when i get home.

Jonathan
 24 July 2013 11:27 AM
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AJJewsbury

Posts: 11587
Joined: 13 August 2003

Just to clarify my earlier reply - the N from the circuit protected by the RCBO connects to the RCBO's N out terminal (alongside L), the RCBO's fly-lead N then connects to the unprotected N bar (the one supplied direct from the main switch, not through the RCCB).

The symptoms you describe - both the RCBO and RCCB tripping - suggest that the bathroom lights etc circuit has had its N connected to the RCCB rather than the RCBO.

Otherwise, there would be a suggestion of a some cross-connection between the bathroom lights circuit and some other circuit protected by the RCCB - a borrowed N for instance, or something nastier such as a nail through two cables.

Or you have a couple of unrelated faults and it's just chance that both devices are tripping at the same time.

- Andy.
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