Earth Fault / Voltage on Earth?

[danrich123]

Hi,
I've been called to a job today where the customer had recieved a bad shock touching some metalwork.

I've been and checked it out and found a couple of faults, but am stumped on one. I found the live had shorted to the backbox, and blown up the socket. They had got another "electrician" out who replaced the socket but had left it with the live and earth terminals the wrong way round. This was the reason he got a bad shock when he touched his caravan which was plugged into mains.

I've rectified these faults, but am getting some funny readings when i now test the socket. When I try a Zs test on the socket it wont let me perform the test, it says >50v, it also says V1 and 3 phase rotation is ok. This is a puzzle as its a single phase. I've checked the voltages which are ok between live and neutral / live and cpc. Neutral and Earth though produces 17v. I tested the other sockets in the kitchen which gave me good reading, and this socket was on the same circuit. I could'nt get access to test the CU as it was buried.

What should I be looking for when I go back. Any tips as I'm abit unsure what might be causing this fault.
Cheers

 

[RF Lighting]

Sounds like a missing earth.

Possibly a joint has blown out as a result of the previous fault.

 

[Spark123]

Strange thing re the phase rotation, in my eyes either L1,L2,L3 is OK as is L1,L3,L2.
I'll second the problem being an open circuit earth somewhere, you need access to the main board and conduct a Ze test. What is the supply type?

 

[danrich123]

I did get to the supply, which was fine (tns ze 0.22) just couldnt get to the cu. i checked whether the neutral and earth were connected in any way, couldnt find any. if the earth is open ciruit how would i get 240 between l and e.

the l1l2l3 is a puzzle as the supply is single phase nt 3 phase. if i just perform a continuity check to see if the cpc on the socket is connected to cpc of a good socket, that should show me if its open circuit?

 

[RF Lighting]

Hopefully.

You might be able to leak 230V down the CPC in a really small quantity enough to show an a meter, but not enough to perform a loop test.

It definately sounds like a joint has gone high resistance. These faults are great for throwing up really bizarre readings!