6 amp rcbo fault

[Dews84]

6 amp rcbo moeller was installed in 2009 no work been done in the property since the new consumer unit installed 2009 whoch is a Split load fuse box with unprotected rcd side and protected rcd side. Unprotected side rcbos have been used for the sockets and lights. The 6amp rcbo had tripped and would not reset, the switch was sloppy as t say it was a internal mechanical fault with the rcbo. I therefore piggy backed the line conductors to the rcd side 6amp mcb which controlled the other light circuit which worked perfectly until the next day when I picked up a new rcbo 6amp from the shop. Installed the rcbo as per usual reconnected the line conductors (and the e lead t e bar as previous rcbo didn't have.) all worked fine all lights no tripping etc, so I press the test button on the rcbo and it works but wen I go to reset it won't and a small flash can b seen behind the rcbo on the live busbar. (The other rcbo for the sockets test button works and resets fine) if I switch off the main incoming fuse/breaker then reset the rcbo and then allow the system to come live again by the main fuse all is fine. Any suggestions ?? As I'm pretty stumped with this one. The lights on the rcbo consist of typical ceiling roses and spot lights in the bathroom, the rcbo side of the consumer unit is old colour wiring and the rcd side is new. Please no silly or smarmy answers I have all my papers and I am an electrician

 

[truckster]

Is the busbar correctly inserted in the bottom of the RCBO, the small flash suggests not.

 

[Dews84]

Yes I double checked this too as been a common fault with flashing as well as it is a Wylex rcbo not a moeller now, but was told that it was compatable and does fit snug .Any more suggestions?

 

[GLENNSPARK]

is the C/U a metalclad? Is the line conductor tucked behind the busbar....nicked maybe and shorting onto the busbar...and hence to earth?

 

[GLENNSPARK]

are you sure ALL connections are tight n secure....line?..neutral?......if all fails at the c/u then test circuit...IR here...

 

[GLENNSPARK]

do not IR through the RCBO...

 

[Dews84]

The insulation resistance and continuity of the circuit has been done and is satisfactory. The c/u isn't metalclad but the line does go behind the busbar bar but is not touching or 'nicked', and isnt earthing.I also wouldnt ir an rcbo thanks for suggestions tho anymore would be appreciated. All connections are tight.

 

[GLENNSPARK]

is there a blown lamp anyware on the circuit that this RCBO feeds...perhaps one that you`v missed as youv gon round....could be shorting...

 

[sedgy34]

SERIOUSLY!!! have you got correct connections cause i know the crabtree rcbos they changed the L and N round.

 

[GLENNSPARK]

Ramp it n all...

 

[GLENNSPARK]

SERIOUSLY!!! have you got correct connections cause i know the crabtree rcbos they changed the L and N round.

wylex n all...

 

[Dews84]

I'll have a look u could be right on this one, but I still don't see why it would allow me to reset it if this was the case Or am I wrong

 

[Dews84]

Connections are definitely correct

 

[Dews84]

And I was saying right on the lamp been blown somewhere

 

[sedgy34]

yeh could be a lamp then somewhere

 

[sedgy34]

errr just a thought did you "trim" down the leads on the rcbo.

 

[Dews84]

Surely tho if it was a lamp shorting tho it wouldn't allow me to reset ??

 

[GLENNSPARK]

swop the circuit onto another RCBO...if its clear...then its the RCBO thats faulty...if not...start thinking about something on the circuit...

 

[sedgy34]

errr just a thought did you "trim" down the leads on the rcbo.

bloody hell, im replying to my self lol as above if you have cut the lead wires it will cause this problem had it before

 

[Dews84]

Rcbo is new. Previous was faulty.and as I say the circuit worked fine in a normal 6 amp mcb with rcd protection and tested and reset fine. It is only wen I test the rcbo that it will not reset without first switching off the main supply then resetting the rcbo and switching the system bk live then it's fine. But I know this is not the normal operation for rcbo hence y I'm confused I have also taken out he e lead to make sure it wasn't this cause the indifference

 

[GLENNSPARK]

like i said...try this circuit on another RCBO..one of the others that you know are good....if it holds : then faulty RCBO...if it lets go/wont reset : start thinking circuit/connected load/s....dont rule owt out here...RCBOs can be faulty straight out of the box...i`v had it before..

 

[sedgy34]

easy question here!!!! HAVE YOU CUT THE E & N WIRES DOWN ON THE RCBO???

 

[GLENNSPARK]

Rcbo is new. Previous was faulty.and as I say the circuit worked fine in a normal 6 amp mcb with rcd protection and tested and reset fine. It is only wen I test the rcbo that it will not reset without first switching off the main supply then resetting the rcbo and switching the system bk live then it's fine. But I know this is not the normal operation for rcbo hence y I'm confused I have also taken out he e lead to make sure it wasn't this cause the indifference

RCBOs will work without the functional earth connected to the earth bar...

 

[Dews84]

No I haven't cut the lead wires down and never have unless they are causing an obstruction as there is no need. I have found there is one lamp out but after checking connections etc and replacing the luminaire it works. But I still have the same issue with the test button. I have also used anothe rcbo in the consumer unit and it does it wen under the light load. Therefore suggesting there is a problem with the circuit. But after ir and continuity an checking all light connections at the switch and fittings I'm still stumped as to the issue. If it was a short I would expect it to not let me reset at all yet it does. Only wen testing the rcd function of the rcbo.

 

[Engineer54]

easy question here!!!! HAVE YOU CUT THE E & N WIRES DOWN ON THE RCBO???

That will have absolutely no effect whatsoever on the operation of the RCBO!! Be it the neutral fly lead or the functional earth lead!!

 

[sedgy34]

That will have absolutely no effect whatsoever on the operation of the RCBO!! Be it the neutral fly lead or the functional earth lead!!

Surprising comments if you havnt had this problem before how would one know, I appreciate you are mr wisdom on here but new rcbos what I mentioned

 

[Engineer54]

Correct i've never had a problem with cutting fly leads to RCBOs, because there isn't a problem cutting these leads. They are definitely Not resistance set bias leads.

All the leads on RCBO's in our DB's will be trimmed to size as and where required, and were talking literary hundreds of the things (MG/SCHNEIDER). Contact the manufactures if you need confirmation and get it from the horses mouth so to speak.

What you have experienced, is in all probability pure coincidence, we have all been caught out by that, in one form or another!! ...lol!!

 

[sedgy34]

not convinced

 

[Engineer54]

not convinced

As i stated, don't rely on what i'm saying on a forum, contact the manufacturers, if you are not convinced!!

 

[Engineer54]

Why manufactures don't like these neutral flying leads trimmed/cut to size, is because you are then cutting the factory fitted ferrule off. Fine multi-stranded conductors don't make very good connections trapped under screws, unless you replace with an on site fitted crimped ferrule.... Which should ALWAYS fitted when these fly leads are trimmed to size...