rcbo tripping

[keithbr13]

know there are other questions on here abt shared neutral but they dont seem to answer my question. i have recently added sockets to an upstairs ring in a terraced house.the kitchen ring has an rcbo, i fitted the same to the other ring but as soon as you switch on the other rcbo trips. will the shared neutral be between the ring circuits or could it be on any of the other circuits, i.e. lights, cooker, waterheater. If so whats the best way to find it?

 

[m4tty]

Sorry mate i cant answer you question but will be watching this thread with interest. Welcome to the forum matey anyways

 

[batty]

Did you do an insulation test on cables?

 

[Revved Up Sparky]

know there are other questions on here abt shared neutral but they dont seem to answer my question. i have recently added sockets to an upstairs ring in a terraced house.the kitchen ring has an rcbo, i fitted the same to the other ring but as soon as you switch on the other rcbo trips. will the shared neutral be between the ring circuits or could it be on any of the other circuits, i.e. lights, cooker, waterheater. If so whats the best way to find it?

The first thing I would do is unplug all the loads on that upstairs ring and megger the neutrals to earth to make sure you have'nt got a N-E fault. I've had situations like this and found the little earth bar that connects the two earth terminals on the back of one of the new sockets has pressed against a ring neutral and made a little indentation on it and that has been enough to create a fault !.

To check for shared neutrals I would probably unplug all loads from both ring mains, isolate both ring mains then disconnect the outgoing neutrals for the upstairs ring from the neutral bar on the consumer unit and connect them to the earth bar. Then I would get a plug with a short piece of flex connected to it ending in three connectors (L,N&E), plug it in to all the sockets on the other ring main and test between the N & E on the connectors with an ohmmeter. If you get a zero ohms reading between N & E then you know that you have a shared neutral. Then pull the neutrals out of the earth bar and see if the reading goes open circuit then that will prove it.

 

[Evans Electric]

MMmmmmm. ....... interesting .. there must be a link between the two circuits I would think, for that to happen.

Welcome by the way. :Welcome:

 

[SPECIAL LOCATION]

know there are other questions on here abt shared neutral but they dont seem to answer my question. i have recently added sockets to an upstairs ring in a terraced house.

the kitchen ring has an rcbo,

i fitted the same to the other ring but as soon as you switch on the other rcbo trips.

will the shared neutral be between the ring circuits or could it be on any of the other circuits, i.e. lights, cooker, waterheater. If so whats the best way to find it?

I just need to get my head around the circuit arrangement here Keith?

Are you saying:

Existing Kitchen ring supplied via RCBO has been working OK no trips.

Whilst modifying the upstairs ring you have now fitted an RCBO onto the upstairs ring as well.

When you switch on the upstairs ring the Kitchen RCBO trips

but the upstairs RCBO stays on?

We are we definitely talking of RCBO's not RCD's?

Or have I got me pants on back to-front again at the moment? :Blushing

Few other thoughts and questions re extending the upstairs ring..

Did you actually add new sockets by continuing the ring circuit or are they branched as spurs off the ring?

I presume you tested the existing ring before you extended it?

i.e.

what were the r1, r2, rn end to end readings?

what were the insulation resistance test readings?

A straight neutral to neutral joint between the two circuits would have prevented the Kitchen RCBO from setting ON in the first place IMHO. :|

If the kitchen RCBO only trips when the upstairs is energised that would imply power flowing from the upstairs is making its way back via the downstairs.

e.g. A load connected with Live from upstairs and Neutral from downstairs.

Are the downstairs floors solid, such that the downstairs ring is wired up the downstairs walls through the upstairs floorspace then back down the downstairs walls to the next socket?

Could the wrong cables have been cut and broken into when extending the ring? e.g. 1 upstairs cable and 1 downstairs cable?

:|

cant think of any more at the moment! :|

:coffee

welcome to the forum

 

[Evans Electric]

I think you've covered it there Specs, and I thought you wore your pants on your head ??

 

[keithbr13]

Thanks for the feed back, I will try an answer all the questions, kitchen circuit allready fed from an rcbo, the other circuitwith the new rcbo, i have added sockets to by breaking into the ring which covers both bedrooms, landing and front room the back rooom has two sockets which appear to be spurs off this ring fed from upstairs. when the kitchen rcbo is energised and i try to energise the other it trips the kitchen but stays on and if I reverse it the kitchen stays on. I have pluged in a socket tester to every socket and they all indicate correct wiring. The insulation results after completeion are all 500 meg, but trying to check Ze makes the rcbo trip.

 

[Revved Up Sparky]

Thanks for the feed back, I will try an answer all the questions, kitchen circuit allready fed from an rcbo, the other circuitwith the new rcbo, i have added sockets to by breaking into the ring which covers both bedrooms, landing and front room the back rooom has two sockets which appear to be spurs off this ring fed from upstairs. when the kitchen rcbo is energised and i try to energise the other it trips the kitchen but stays on and if I reverse it the kitchen stays on. I have pluged in a socket tester to every socket and they all indicate correct wiring. The insulation results after completeion are all 500 meg, but trying to check Ze makes the rcbo trip.

What about the borrowed neutral theory ? the socket tester would not be able to pick that problem up. Have you also double checked the outgoing ring legs on each RCBO to make sure you have'nt mixed them up ? If the RCBO's are next to each other then it might be an easy mistake to have a live or neutral ring leg in each RCBO instead of together. This could create such symptoms. We've all done that at some point in our careers- well I have anyway lol.

 

[keithbr13]

I did nt disconnect the kitchen rcbo it was fitted some time ago,

 

[Tooold]

I'v come across existing ring mains crossed at the cu, its worth a ring con test just to eliminate it.

 

[keithbr13]

Thanks for all your help, went back today checked every skt on the ring and found nothing wrong. retested circuit all readings good, refitted the rcbo and it worked fine, sure got me beat !