I have a bit of a head scratcher yesterday and am hoping somebody can offer sone pearls of wisdom. So I was asked to change two sockets in a study from plastic to chrome. Tester in the socket 243v. Turn off mcb 33v still present. Turn off rcd 1 6v. Turn off rcd 2 0v. The board is a dual split Hager. Tested Ze 0.11 Pfc 1.56 Gas bonding in place (tried disconnecting but no difference). Water is nit present but I think it might be plastic. I can't do rcd test due to the voltage present and zs >2.99 on all circuits. That was as far as I got as I only quoted for an hours work.
What are you seeing this 33v on? An MFT? Did you get 33v on all other sockets on the same circuit? Sounds like poor earth
33v measured with my megger MFT. My martindale was also making a funny sound and indicating an error not even identified on the legend. Zs on ground sockets and newly installed kitchen ring,cooker circuit >299. Buy Ze at origin was good. I'm wondering if it could by a dodgy RCD.
You will have to tell them that you've found a problem and it's going to cost to fix it!!!!!!otherwise turn off power and say that it's not safe to use!!!
possibly ghost voltage from energised cables, solution is to test with a substantial load such as old Drummond lamp, however this may present problems with rcd tripping, alternately dead cont. testing all the way which will be time consuming and disruptive. ask them if they are prepared to pay extra to investigate what you have found, also write on the invoice a brief account of the situation to cover your backside.
Cross connected Neutral is a possibility, although you would expect RCD issues if this is the case. This doesn't explain why i'm not getting a Zs reading though. I am booked to go back next week and investigate. The customer is a reasonable guy and just wants it made safe. I'm just looking for possible reasons to fix it as quick as possible.
That was my initial thought. 16mm main earth looks good. MET ok. TNS system and Ze 0.10 so no obvious supply problems. The problem is on every circuit on RCD#1.
Any possibility that there is a loose/bad connection with ref to the main neutral in bar on RCD1 side?
Nothing evident. I tightened all the Neutrals in the board but nothing appeared to be loose. No reports of any flickering either.
Crikey that really is a tough fault to find - good luck Hersham and it will be interesting to see what the actual fault is in the end.
Is the voltage present on the rcd1 side neutral bar in the consumer unit? You say you cannot test the rcd but could you test it at db position with all outgoings disconnected . I presume you are testing the rcd at socket position which shows the 33v and probably negates trip test?
I had a gut feeeling it could have something to do with a breaker or RCD. I will bring some spares with me and try replacing them. Another curious thing was my MFT when plugged in to the isolated circuit was occoasionally jumping from 33v, 17v 0v in what appeared to be a regular pattern, maybe 3 or 4 seconds between each.
Isolate each circuit in turn (MCB off, N & CPC out of each bar) and test and find which the offending circuits are. With no main water bond, I'd guess temporarily disconnecting supplementary bonding may stop the fault as well...
As above.... Sometimes quicker to start from scratch than to keep guessing. Go back to basic testing procedures...as if it was a new install. unplug everything..and test from the board.....all conductors removed. Remove and check rcd, mcb's.....connections....etc...crossed neutrals... You need to confirm a hard earth everywhere. RS
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