RCD tripping after moving MCB

[hotspothannon]

Hi all...advice needed.
I have just replaced a MCB on my girlfriends board...as it was faulty and tripping intermittently. Whilst doing that I decided to 'tidy' up the board as it's a bit of a mishmash with labels and such. Whilst labeling....I went through the whole house finding what MCB fed what, now I found a 16amp MCB labelled 'immersion heater'. This took my interest as I knew she had this ripped out when she brought the house 10 years ago. I finally found this one breaker fed one single socket in her kitchen. This breaker was on lighting side of the consumer unit ie 'no RCD' protection. Behind the said single socket there is a pair of twin n earth, one connected to the supply on the socket, one left in the back - which is dead. I can only assume someone broke into the immersion heater supply and made this single socket part of the radial circuit.
I decided to just move the MCB over to the RCD protected side of the bus bar.... And that was that...labeled it up...everything great. Great until she came to use it. Normally all she had plugged in it was a 'air freshener'.... And this was OK. However we seen since you plug anything else in then as soon as it's switched on - the RCD trips. This is with any appliance, except ones without an earth...ie air freshener, phone charger etc.
Now here's my question.....would it be OK just to put the MCB back to the 'non RCD protected' side....where it worked perfectly well for 10 years? I have tried to find the route of the cable but it is in the kitchen behind a tiled wall right next to the door frame. I can't even make out if the cable goes up or down. Downstairs she has solid wood flooring ( so that ain't coming up) ....upstairs I have had the carpet up where all the old immersion heater was, and all the old wiring, however the feed to the single socket is not there.
I'm thinking there is a N-E fault somewhere...but it's like where????
Any advice would be appreciated

 

[Darkwood]

Welcome to the forum

There seems to be alot of assumptions here, clearly you seem to have a fault so why would you ever contemplate putting back on an rcd unprotected circuit and putting someones safety at risk? (not comfortable reading from someone who should know better)
What test results do you have, these will tell you whether there's any obvious faults causing the rcd to trip.

 

[telectrix]

your problem is probably the neutral. this also needs moving to the RCD side. ii.e. you have 2 N bars. 1 for the RCD and 1 for the non-RCD. if it still trips, you have a fault and need to call out an electrician. if you are to the south and/or west of manchester, i'm available.

 

[Leesparkykent]

IR n-e=?

 

[Darkwood]

your problem is the neutral. this also needs moving to the RCD side. ii.e. you have 2 N bars. 1 for the RCD and 1 for the non-RCD.

Good call, I made the assumption with his qualifications that he wouldn't make a basic error as such but it seems he won't be experienced with domestic split boards so you might have done the preverbial nail on head.

 

[Octopus]

Got any test kit?

 

[malcolmsanford]

Worry about things like RCD's tripping ............label it as a suitably identifed socket......such as air freshner only and bung it back on the MCB......jobs a good un............

Or as Tel said more than likely the neutral is in the wrong neutral bar. Make sure the neutral is also transfered over. If you have and it still trips, then testing is in order.

 

[hotspothannon]

Hi.thanks all.
I work in a factory so your right I only have general experience on domestic installation. I have a megger at work which I will bring home and test next week...but that's as far as it goes for test equipment ( other than my fluke).
I did think I will need to swap my natural phase over to the RCD side...so that will be my first step. I will also measure ir between all conductors and post if I have a problem. I take it I can measure ir with the double pole off and the MCB still on? Or should I measure with the conductors removed from the MCB n neutral bar?

 

[hotspothannon]

Hi thanks for the replies. I was thinking I would have to move the natural over to the RCD block...so that will be my first port of call.
I work in a factory so I have little domestic experience and I have no test kit other than my fluke and a megger ( both at work :-\) so I will bring my megger home next week and test ir L-N, L-E, N-E.
Can I test ir on the circuit in question with just the main double pole switch off and RCD... So the MCB still on? Or should I remove the conductors from the MCB and neutral bar - then test?

 

[telectrix]

if the N is in the wrong bar, then the load will draw L from the RCD but N from the other, thus creating an imbalance in the rcd. it will only trip whem a load is applied.

 

[hotspothannon]

Yes makes perfect sense...thank-you.... Feel dumb for not doing it in the first place
As for IR test....I take it I'm OK leaving the conductors in, as long as the RCD is off...and MCB off.....purely to protect the RCD from damage off the megger?
Sorry for the two replies above...new to the forums and not waiting for approval Haha.
Great site too

 

[Darkwood]

Always disconnect the final circuits from rcd's before commencing any Insulation Resistance testing, damage may occur otherwise , usually a sticker is placed somewhere near or on the rcd expressing this but not always depending on how lazy the previous sparky was.

 

[SIIVION]

Your socket was probably an old supply to a central heating programmer. You say the other cable is dead, please check it with your tester, put a connector on then tape it up, nice and neat, peace of mind.
Also, as you have limited experience just turn everything off at the main switch when testing at the board. Again, peace of mind.

 

[Octopus]

I can't believe you aren't familiar with RCD's and RCBO's !

 

[hotspothannon]

I have tested the other T&E in the back of the socket.... I did that when I did the labelling and replaced the MCB.... It's dead. The last spark has put a crimp on each conductor....I wanted to remove it all together...but the back box is literally trapped in by the tiles...and right next to the door frame which is the way the cables go.
As for testing...experienced or lack of...I always turn off at the main switch.....something drilled into us at work ( lots of red tape to work on anything live....including PPE that would make working impossible - leather gloves + rubber gloves + plus face hood)
As for RCD's...we don't come across them at work....if we do an installation requiring a socket... We install a double with built in RCD