Installed a new C/U now have fault

[Grapejuice18]

New here so sorry if posted in wrong place,
I have installed a new consumer unit as the title says it’s a split load rcd board, anyway to the point one of the rings seems to now have a neutral fault which is taking out one side of the board I have checked all obvious things, touched no appliances since installing only moved the existing wiring to the new board location etc. The thing that I can’t get my head round is I have continuity end to end but on both legs of the ring I have a short between live and neutral, all I can think of now is to IRT the circuit and see maybe this could be down the the install being 30 years old and degraded T&E over time? Maybe the inner cores are now touching? Seems funny tho because the old c/u was old but was still rcd protected so surely that would of seen the fault? And surely both legs wouldn’t have sustained damaged when I’ve moved the cables?
can give me details if required thanks in advance

 

[JBW175]

I’m guessing you charge for full EICR prior to advising a board change? I’ll do a pre survey of standard things like main earth, bonding, condition of accessories (age) advise customer that should any faults be found whilst testing then additional cost involved. Also you test it after completing consumer unite has been changed and this particular issue would have been picked up if done properly.

Not at all, and when I am conducting an EICR, it’s not a 40 minute drive by, full of LIMS and dodgy recommended remedial works used as a cash generator. It’s a thorough inspection that I charge accordingly for.

Now if you read my post properly, you’ll see i stated that a full range of tests needs to be completed prior to energising the board, IE, on completion of the board change and not just bang test it.

 

[JBW175]

@westward10, sorry just seen your post. Must have posted as I was typing my reply.

 

[buzzlightyear]

we can all throw the hats in the ring its down the the op to go and fault find .
learn once never again it will go down to experience, and we have all be there .

 

[Dartlec]

New here so sorry if posted in wrong place,
I have installed a new consumer unit as the title says it’s a split load rcd board, anyway to the point one of the rings seems to now have a neutral fault which is taking out one side of the board I have checked all obvious things, touched no appliances since installing only moved the existing wiring to the new board location etc. The thing that I can’t get my head round is I have continuity end to end but on both legs of the ring I have a short between live and neutral, all I can think of now is to IRT the circuit and see maybe this could be down the the install being 30 years old and degraded T&E over time? Maybe the inner cores are now touching? Seems funny tho because the old c/u was old but was still rcd protected so surely that would of seen the fault? And surely both legs wouldn’t have sustained damaged when I’ve moved the cables?
can give me details if required thanks in advance

Was it a 30mA RCD previously? It's possible that it was faulty and not picking up the fault.

As already mentioned, splitting the ring and testing is the only way to track down the fault. Then you can isolate it down to a particular length of cable or perhaps a fitting or two rather than taking everything apart looking for what might be something simple.

 

[FatAlan]

Think the general consensus is to test the existing installation prior to ripping the old board out to identify any faults that will leave you in a sticky spot with the new board....just when you’re looking to head home for a few we’ll earned beers ?

 

[Grant1987]

we can all throw the hats in the ring its down the the op to go and fault find .
learn once never again it will go down to experience, and we have all be there .

Yes that’s it the guy posting is obviously struggling with the fault and needs to learn how to fault find. In future I would advise anyone with limited experience to do the job during day time hours because it becomes more difficult when the dark nights kick in early

 

[Grant1987]

Not necessarily once you’re confident in fault finding can be easily rectified with limited time needed. All a learning curve though

 

[HappyHippyDad]

Yes that’s it the guy posting is obviously struggling with the fault and needs to learn how to fault find. In future I would advise anyone with limited experience to do the job during day time hours because it becomes more difficult when the dark nights kick in early

I'm not one of the crew that thinks an EICR is needed before a board change. I think that is way over the top. However, to just change a board without any kind of pre-visit check is just asking for trouble and isn't very professional.

You simply do a 15 minute pre-work check during your initial visit. During this visit you would do a global N-E IR test which would highlight a fault bad enough to trip an RCD (i.e < 0.01Mohms). You then give the customer a quote which includes the fault finding which generally you would do before hand.

The OP sounds new to this and I'm sure this will be a good lesson for him (i.e to check N-E before changing a board). Good luck in finding the fault chap. Stay calm and ask again on here if you get really stuck.

 

[MJPD29]

Interesting, any chance there's a borrowed neutral somewhere? What were IR readings on ring circuit?

 

[HappyHippyDad]

Not necessarily once you’re confident in fault finding can be easily rectified with limited time needed. All a learning curve though

If you had said can 'usually' be rectified with limited time, I would agree, but sometimes a fault can be really difficult to track down. I generally say to the customer I find faults within 2-3 hours (on average), just to give them a rough idea. I always add it could be shorter or longer. Sometimes it can be 10 minutes. Once it was 2 days!

 

[streamer]

The thing that I can’t get my head round is I have continuity end to end but on both legs of the ring I have a short between live and neutral,

It stands to reason that if you have continuity end to end that the same fault is going to show up on both legs unless you split the ring at a mid point. Also it could well be that your live to neutral 'fault' on the ring circuit is an appliance still plugged in or a spur switched on. Some are hard to find but remember things like TV splitters in the attic, spurs behind/above cooker hoods etc. So the fault causing the RCD to trip may well not be on the ring circuit.

 

[Grant1987]

If you had said can 'usually' be rectified with limited time, I would agree, but sometimes a fault can be really difficult to track down. I generally say to the customer I find faults within 2-3 hours (on average), just to give them a rough idea. I always add it could be shorter or longer. Sometimes it can be 10 minutes. Once it was 2 days!

Yes good point, we have all had a mere on certain jobs and a quick fix on others. Rough with the smooth I always say. Anyhow hope the guy finds the fault and isn’t stressing just got to stay calm and think of it logically

 

[davidanthony41]

New here so sorry if posted in wrong place,
I have installed a new consumer unit as the title says it’s a split load rcd board, anyway to the point one of the rings seems to now have a neutral fault which is taking out one side of the board I have checked all obvious things, touched no appliances since installing only moved the existing wiring to the new board location etc. The thing that I can’t get my head round is I have continuity end to end but on both legs of the ring I have a short between live and neutral, all I can think of now is to IRT the circuit and see maybe this could be down the the install being 30 years old and degraded T&E over time? Maybe the inner cores are now touching? Seems funny tho because the old c/u was old but was still rcd protected so surely that would of seen the fault? And surely both legs wouldn’t have sustained damaged when I’ve moved the cables?
can give me details if required thanks in advance

You might have mixed the neutrals up .there are two neutral bars one for each rcd

 

[Pete999]

Not a Borrowed N is it?

 

[SJD]

It would be nice if the OP could perhaps give us an update?