tripping rcd

[isitintheregs]

Hi All. I was called out today to a tripped RCD in a domestic split board that not would reset unless the main switch was off. All mcbs off, all phase conductors removed in case of stuck mcb but still no rcd reset unless main swith was off. Any ideas, householder was not prepared for more extensive exploration at Sunday rates. Going back to-morrow.

 

[bigbaddave]

is this both RCD'S? If not i had this once and was a faulty RCD. As soon as voltage was applied it was tripping. Swapped it over and it was ok

 

[Brightspark2]

Its a neutral to earth fault then??...:mickey:

 

[KAS1]

N fault, but I'm not telling you which 1 you'll have to find it yourself lol

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Beat me to it lol

 

[ayjay]

split board that would reset unless main switch was off.

Read more: http://www.electriciansforums.net/e...l-forum/70374-tripping-rcd.html#ixzz2HtPgUx4e​

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[Octopus]

Hi All. I was called out today to a tripped RCD in a domestic split board that would reset unless main switch was off. All mcbs off, all phase conductors removed in case of stuck mcb but still no rcd reset. Any ideas, householder was not prepared for more extensive exploration at Sunday rates. Going back to-morrow.

No power over night??

 

[isitintheregs]

It can only be a neutral to earth fault but how can there be a fault at the rcd if no circuits are energised? The lighting circuits are not on an rcd so no sockets till tomorrow Murdoch.

 

[HandySparks]

It can only be a neutral to earth fault but how can there be a fault at the rcd if no circuits are energised?

Your MCBs will generally be single pole, so all your neutrals (and CPCs) will still be connected. It doesn't take much voltage to push 30mA through a N to E or a N to N short.

What's the earthing system?

 

[Octopus]

It can only be a neutral to earth fault but how can there be a fault at the rcd if no circuits are energised? The lighting circuits are not on an rcd so no sockets till tomorrow Murdoch.

So its a high integrity board then or is a 16th edition "type"?

 

[guest119]

This is the sort of question you would normally get from a householder.

Boydy

 

[isitintheregs]

So its a high integrity board then or is a 16th edition "type"?

A high integrity board would have all the circuits on at least two rcds, this is the older split board with half the circuits on an rcd, the other half not.

It's a TN-S installation.

 

[Deleted member 9648]

As already stated it will be a N-E fault.......I'm somewhat flabberghasted that as an arms member this isnt something you have come across before.

 

[Octopus]

A high integrity board would have all the circuits on at least two rcds, this is the older split board with half the circuits on an rcd, the other half not.

It's a TN-S installation.

Just checking, your OP wasn't clear.

 

[isitintheregs]

As already stated it will be a N-E fault.......I'm somewhat flabberghasted that as an arms member this isnt something you have come across before.

I'm probably more flabbergasted than you! I inspected the installation today expecting to find the N-E fault we would all expect. All circuits IR tested, no faults. 8 Meg ohms L-E on one ring final circuit but that was all.
The rcd behaved and tested as one would expect when everything was back together. My original question still remains but I will re-phrase it.
Why does an rcd trip when there is no current passing through it?

 

[moose]

It seems the House Holder has removed a faulty bit of equipment like an Iron, or something, or you have corrected the fault when putting the Neutrals back in the correct RCD places maybe, or did i miss the point LMAO its l8 for my old eyes.

 

[Robert Turnbull]

It will trip on continuity of N+E

Say you turned the mcb off and cut the cable the rcd would trip.

Sounds like it was most likely something plugged in.

 

[isitintheregs]

It seems the House Holder has removed a faulty bit of equipment like an Iron, or something, or you have corrected the fault when putting the Neutrals back in the correct RCD places maybe, or did i miss the point LMAO its l8 for my old eyes.

No and no! I removed all loads prior to testing and tried every appliance or portable equipment available in the house when finished. All circuits were removed one at a time and replace as found. The installation was fine up to the point the rcd tripped and would not reset even with all line conductors removed, and it is fine again now.

 

[guest119]

Wet joint box somewhere?
8 megs aint good, especially if it is only l-e and not on n-e.
In an occupied and dry house IR should be better.
Have you tested end to end yet?

Boydy

 

[Robert Turnbull]

Taking out line conductors won't stop a rcd tripping.

 

[Deleted member 9648]

No and no! I removed all loads prior to testing and tried every appliance or portable equipment available in the house when finished. All circuits were removed one at a time and replace as found. The installation was fine up to the point the rcd tripped and would not reset even with all line conductors removed, and it is fine again now.

The neutral and earths are still connected though arent they....it stops tripping when you turn off the main switch because you are then isolating the neutral.