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

 

[telectrix]

short as in 0 ohms, or loww IR? diss allloads then split ring to narrow down.

 

[buzzlightyear]

did you not do a EICR before hand .

 

[pc1966]

30 years is nothing for decent PVC wire that has not been abused (thermally or physically).

As above, did you do an IR test before all the circuits were re-connected and put in to use?

L-N or L-E faults are pretty obvious no matter what the old CU was, but N-E could have been there for years and without an RCD nobody would have notice.

 

[SJD]

As Tel says, more precise measurements, rather than a "short" which is somewhat vague and not very helpful.

For example, if a fraction of an Ohm N to E, then it is often easy to track down where in the wiring this is.

Also, do you have measurements for all the other circuits on this RCD that is tripping? E.g. a N to E short on a circuit that didn't used to have RCD protection, on this RCD, now causing the socket circuit to trip when under load.

I'm sort of assuming you do have an MFT and did make some measurements?

 

[buzzlightyear]

I have a short between live and neutral,

and where do you think it is ,so the rcd tripping ,sounds to me the sockets .

 

[Grant1987]

did you not do a EICR before hand .

Don’t need to do an EICR beforehand, what difference would that make? When upgrading the consumer unit you have to do an install certificate anyway, Going back to the OP you need to use your tester to find the fault now, Split the ring at board then guess mid point one side should be clear with high readings the other 0 by swnds of it. Chase the fault is pretty much really easy when you understand the logic

 

[JBW175]

The reason we do an EICR before hand, or at the very least a site survey with some testing as the minimum, (as recommended I’m the best practice guide), is to find and iron out any problems prior to fitting a new board.

You should also be carrying out a full range of tests before energising the board and not just doing the bang test to bring it into service.

 

[pc1966]

Re-reading the OP's post it does sound like that act of moving the cables over has triggered a fault.

However, before it was all live I would have expected the usual test to have shown this up (IR, ring continuity, R2 or R1+R2 for lights, etc, etc).

Irrespective of how they got here, the next step for the OP is to do fault-finding to identify what the issue is. So take the final circuits out and IR test them (loads off/unplugged) and when the offending circuit is identified, then do the usual process to locate the fault (e.g. split half-way and see if it is a fault in the 1st or 2nd half, rinse and repeat...)

 

[Farmelectrics]

an eicr would have detected this fault before you changed the consumer unit.

 

[Grant1987]

The reason we do an EICR before hand, or at the very least a site survey with some testing as the minimum, (as recommended I’m the best practice guide), is to find and iron out any problems prior to fitting a new board.

You should also be carrying out a full range of tests before energising the board and not just doing the bang test to bring it into service.

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.

 

[Grant1987]

an eicr would have detected this fault before you changed the consumer unit.

This fault would have been picked up after board change. Carrying out the correct testing schedule. Simple stuff this don’t need to be charging for an EICR and then charging for board change, change the board rectify any faults and all sorted.

 

[Wilko]

Hi - I’m assuming that one RCD is now tripping? Are the circuits in the new board on the correct N bar? If you post a pic it can often be seen if there’s a simple wiring error of that sort.

 

[westward10]

Can we get back to the OPs issue and not another debate over doing an EICR first.

 

[Grant1987]

Can we get back to the OPs issue and not another debate over doing an EICR first.

Sorry @westward10 one of my bug bears this one don’t like double charging but anyhow hope the OP knows how to use a tester ?

 

[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 ?