Hello there guys n girls, can anyone offer any help with what i've come across this evening. My mate asked me to take a look at his lights,as they trip both his protectice devices. He has two separate lighting circuits in his CU (domestic) both are protected by RCBO's. I've narrowed the faulty light point down to his attic landing light. Its a one way light. I'm guessing theres a borrowed neutral somewhere along the line, because its causing both circuits to trip out. But i'm stuck on the actual cause for the light to trip in the first place. I didn't have time to perform and tests (continuity and IR) but i will in the morning. Anyone have any obvious explainations. All replies will be much appreciated. Thanks.
Dodgey lighting circuit
- Thread starter danijah
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if both are tripping, most likely borrowed neutral. and most likely on the light that trips RCBO's when its switched on
thats what he said....
PaulSC
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Sorry Andy, what I meant was when the CU was first installed and commissioned, the borrowed neutral would have been immediately obvious to whoever installed it. He hasn't stated if its a new install, unless I'm misreading something.
Agree, most likely borrowed neutral however i had an interesting fault a while back.
Retro fitted a new C/unit fitted with Rcbo's, tested and left. About 2 months later the customer phoned with the same fault, turning on the landing light caused both the upstairs & downstairs Rcbo's to trip. The staircase had a 2 gang-2 way switch at both top & bottom one switch controlling a landing light and the other the hall light. The strappers had always been crossed between them. The couple living in the house always kept to the same regime by switching off downstairs and on upstairs from the bottom and when going to bed turning off the upstairs, like this the correct cables were always being used. 2 months later though they operated the switches in a different order and brought a different strapper into use which joined the 2 circuits and caused the Rcbo's to trip.
Retro fitted a new C/unit fitted with Rcbo's, tested and left. About 2 months later the customer phoned with the same fault, turning on the landing light caused both the upstairs & downstairs Rcbo's to trip. The staircase had a 2 gang-2 way switch at both top & bottom one switch controlling a landing light and the other the hall light. The strappers had always been crossed between them. The couple living in the house always kept to the same regime by switching off downstairs and on upstairs from the bottom and when going to bed turning off the upstairs, like this the correct cables were always being used. 2 months later though they operated the switches in a different order and brought a different strapper into use which joined the 2 circuits and caused the Rcbo's to trip.
Theorysparky
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had this fault recently (well very similar)
tenant changed a lamp and rcd wouldnt reset ,,,both sides kept tripping intermittently
turned out to be the replacement lamp !!!! shorting to earth
so borrowed neutral is not where you should be looking
tenant changed a lamp and rcd wouldnt reset ,,,both sides kept tripping intermittently
turned out to be the replacement lamp !!!! shorting to earth
so borrowed neutral is not where you should be looking
That would not trip an rcd, maybe a mcb, unless they had a new type of light bulb with an earth connection
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