rcd tripping on landing light!!

[sparkyork]

hi all, first of all ive just got in from work, had they day from hell and im shattered! did a consumer unit change, test and a couple of minors works all on same job, as well as having to repair a pipe that was not supposed to be wear i was clipping (fecking plumbers!) they never heard of zones!

anyway all was well new board running nicely for a few hours, i did get a low ish reading on N-E on upstairs lighting of about 8 Mohms, but didnt think it would cause rcd to be a prob as ive always had much lower readings on rcd faults due to insulation resistance.

rcd only trips when the landing ceiling rose is switched ( i think ), there was an old energy saving lamp in it that i noticed was just flickering which seemed odd, like it was backfeeding off something?? any way took the bulb out reset rcd and tried the switch again, "trip" off it goes, disconnect lampholder just leaving rose and i can operate switches and its ok (so presuming strappers have gotta be ok, as i tested these when Ins Testing anyway)

didnt have a spare lampholder in van so couldnt try a new one, im off back there tomorrow afternoon, anyone got any ideas for a tired fellow spark!?

ps both rcd's are going, which also dont seem to be a compliance with the 17th either!!! sure it sounds like some sort of strappers problem occuring when a load is been switched but im confised.com

 

[mpfisher@hotmai]

sounds like borrowed neutral problem upstairs lights have upstairs neutral. And i'll guess the feed is taken from the 2g 2way on the downstairs circuit.

Mark

 

[sparkyork]

cheers mark i was thinking on the same lines me self spesh as its all ok at the minute but as soon as any load is applied to that rose it all goes. why did they have to wire it like this!!

but why would it do it with a lampholder wired in and not trip when it was out?? the lampholder wiring is above 500M ohms

 

[mpfisher@hotmai]

Just to give you something to do in the morning and keep you outta the pub

Mark

cheers mark i was thinking on the same lines me self spesh as its all ok at the minute but as soon as any load is applied to that rose it all goes. why did they have to wire it like this!!

but why would it do it with a lampholder wired in and not trip when it was out?? the lampholder wiring is above 500M ohms

Sparky its tripping out because 1x lighting circuit is connected to both RCDs

You need to take a neutral to the landing light from the downstairs circuit and take out the neutral that is there now

,Mark

 

[sparkyork]

yeah now ive had chance to relax it all makes sense now!! im gonna have to reconnect the upstairs neautrals tho cos there looping off to something esle as well.

 

[EasyFox]

This is going to be a common problem.
Quickest way to check, bang all the lights onto one rcd.

 

[rumrunner]

cheers mark i was thinking on the same lines me self spesh as its all ok at the minute but as soon as any load is applied to that rose it all goes. why did they have to wire it like this!!

but why would it do it with a lampholder wired in and not trip when it was out?? the lampholder wiring is above 500M ohms

I understand the borrowed neutral thing ,but cant get my head around why it trips with the lamp removed,

 

[EasyFox]

Rum it doesnt trip with the lamp removed (unless I've had one beer to many) no load.

 

[rumrunner]

Rum it doesnt trip with the lamp removed (unless I've had one beer to many) no load.

what hes saying is with the lamp holder connected it trips and disconnected it doesnt .i presume that he removed the lamp first ,still cant get my head around it maybee i need another beer

cheers mark i was thinking on the same lines me self spesh as its all ok at the minute but as soon as any load is applied to that rose it all goes. why did they have to wire it like this!!

but why would it do it with a lampholder wired in and not trip when it was out?? the lampholder wiring is above 500M ohms

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[sparkyork]

ill confirm this wierd occurance tomorrow and post here!!

with an energy saving bulb fitted it was flickering slightyl and trippiing both rcds when switch was switched. i took bulb out and its still did it!! disconnected lampholder and everythings ok. i really dont get it either but thats how ive been able to leave the house tongiht so they can have some lights on!!

i will check again tommorrow, i even wondered of maybe the screws holding the rose up might be nicking the neutral above or something, but like easy and everyone else says as well as logic, it should only do it under load?????

 

[PAUL M]

i have come across the same thing a couple of months ago when first started using the 17th boards,i did a thread called beware the borrowed neutral,its quite a common problem in older properties.as easy said try putting all the lights on one rcd ,if it dont trip then you just got to persuade your customer to let you run a new neutral.have fun.

 

[montybaber]

The RCD will trip when it detects an imbalance between the phase and neutral on that circuit, the imbalance occurs when the switch live is energised on the landing light circuit 1 when the neutral belongs to circuit 2 it wont trip without lampholder due to you effectively taking the borrowed neutral out of circuit.

Thats how I see it anyhow...prob wrong

 

[rumrunner]

The RCD will trip when it detects an imbalance between the phase and neutral on that circuit, the imbalance occurs when the switch live is energised on the landing light circuit 1 when the neutral belongs to circuit 2 it wont trip without lampholder due to you effectively taking the borrowed neutral out of circuit.

Thats how I see it anyhow...prob wrong

you are correct in what you say above,but....
Its tripping out with the lamp removed,and it doesnt trip with the pendant removed ,dangler insulation resistance is above 1/2 a meg ,whats the difference between taking out the lamp and removing the pendant?
very strange

 

[sparkyork]

right ive got me morning job done and im off to go put another neutral in at this job, willl confirm this wierd thing that its doing, i also dont get what the differemce is with pendant removed not tripping rcd, theres no load going across it?

the customer was aware that often certain problems come up when changing boards and it should be cool. not gonna be easy getting neutral up tho, board is under staircase!!

defo a shoddy way of wiring things, the loop in loop out at the rose is live from upstairs lighting and sw/live is live from downstairs lighting, proper poo poo!! shock city!

 

[montybaber]

you are correct in what you say above,but....
Its tripping out with the lamp removed,and it doesnt trip with the pendant removed ,dangler insulation resistance is above 1/2 a meg ,whats the difference between taking out the lamp and removing the pendant?
very strange

Sorry must've read it wrong... your right thats wierd