Socket testing.

[CortinaV8]

Could someone please enlighten me as to the correct way to test a socket and what voltages i should be looking for ideally, I am pretty confident I know what I am doing but am getting some curious results.

With the power on.

L-N - 230ish volts
L-E - 0
N-E - 230volts

With the MCB switched off.

L-N - 60ish volts
L-E - 0
N-E - 230volts

The socket in question is a spur off a JB on the ringmain.

Not what I was actually expecting.

Purpose of the testing, curiosity when replacing a socket, electrics seem to work fine in general.

 

[jj4091]

If what you say in the post is correct then you have a problem. You should read a voltage live to neutral & live to earth but not neutral to earth. I would suggest you call out an electrician, particularly if you get the same results on other circuits.

 

[The Dentist]

I would suspect a L-N reverse here, you will need to check out the polarity at your CU first, if that is OK then you need to investigate the circuits, best check em all now you have found one dodgy one

you should be getting
L-N 230v
L-E 230v
N-E 0v

 

[CortinaV8]

My CU is a Split load Mk Senty.

I had a look in there a while back, its all connected correctly at that end.

Will have a look at the other sockets on the circuit later on tonight, if a socket is reversed, it must have been like that for at LEAST 15 years.

 

[Taylortwocities]

Looking will not hack it, testing with the correct test equipment will.

I recently got called out to a rental property because the John Lewis engineer would not install a washing machine because the polarity on the socket was reversed.
When i got there I found that whoever had put in the consumer unit had got the live and neutral supply tails switched over. The installation label said it had been there for 25 years.

All that time, and I expect that quite a bit of electrical work had been done. At no point had anybody tested any of the work that they had done.

I'm not saying that we live in a perfect world but this is one of the reasons that Part P was introduced..

 

[Spark123]

What type of supply is it?
Does sound like there is an issue upstream of the CU to have a supply present with the MCB switched off.
In the interest of safety I'd recommend you phone an electrician.

 

[CortinaV8]

The Service Head has a PME sticker, supply is from my neighbours property, it runs at high level around the back of my house, must have been overhead supply at some point, it is not now.

I do not have an earth at the service head, but do have an earth spike, gas and water are also bonded.

 

[Ghughes]

deleted post

 

[Spark123]

Need to confirm the tails entering the CU are correct polarity, not really a job I'd call DIY

 

[OilLecky]

Test some other sockets. Are any more incorrectly connected? If so go back to the Consumer Unit and start there. You were doubtful enough to ask the question in the first place but now that you have been told you have to be confident as to what to expect. If not get an Electrician in. If you only have the one socket on a spur that has incorrect polarity then check the wiring in that socket, in the junction box and in the point where it is spurred from. There is a cross-connection somewhere. DO NOT LEAVE IT LIKE THIS!

 

[Spark123]

Considering there is 240v when the MCB is off suggests to me a fault upstream from the MCB.

 

[CortinaV8]

Tested two more from each ring, up and down, going to test a light or two after tea, but I imagine its going to be the same. Looks like a reverse polarity fault at the CU as all the lives and neutrals are where they should be.

If its the incomers that are reversed the guy who installed it wants stringing up!

 

[ban-all-sheds]

With the power on.

L-N - 230ish volts
L-E - 0
N-E - 230volts

Which is what you'd expect for a L/N reversal

With the MCB switched off.

L-N - 60ish volts
L-E - 0
N-E - 230volts

If the reversal is at, or upstream of the MCB this would make sense - the MCB is switching the conductor going to the socket Lives, but it's the Neutral. So the one going to the socket Neutrals, which is actually the Live doesn't get switched off, which is why you still see 230V "N-E".

The 60V is probably just induced - I bet if you measure it with an analogue meter, or with a lamp connected between L&N it would disappear.

Purpose of the testing, curiosity when replacing a socket, electrics seem to work fine in general.

They will seem to work just fine with a L/N reversal, until something goes wrong, or it bites you when you thought it was off..

I do not have an earth at the service head, but do have an earth spike, gas and water are also bonded.

So it's not PME then.

Do you have an RCD protecting all of the circuits?

Tested two more from each ring, up and down, going to test a light or two after tea, but I imagine its going to be the same. Looks like a reverse polarity fault at the CU as all the lives and neutrals are where they should be.

Do you mean that you've found the same fault-indicating voltages at other sockets and other circuits, but all the colours are in the right places?

If its the incomers that are reversed the guy who installed it wants stringing up!

Could have happened at a meter change....

 

[CortinaV8]

I have checked the wires at a few sockets and all seem as they should, to be honest I've seen most of the junction boxes and backs of the sockets in the course of decorating etc and not found any obvious faults.

Inside the CU all seems ok, if not a bit messy, the board is an MK Sentry Dual RCD board.

Had the CU installed prior to finding out about Part-P by an electrician, however I was given no paperwork for it , I was at work when the job was completed so have no idea what went on, he replaced the meter tails as they must not have been long enough to reach the new board, he also fitted the earth spike.

I have a guy coming round on sunday to take a look,

 

[ban-all-sheds]

I have checked the wires at a few sockets and all seem as they should, to be honest I've seen most of the junction boxes and backs of the sockets in the course of decorating etc and not found any obvious faults.

Have you found the same L/N reversal at any other sockets?

Had the CU installed prior to finding out about Part-P by an electrician, however I was given no paperwork for it

Mmm. A good sign that is not.

he replaced the meter tails as they must not have been long enough to reach the new board

Ah.

he also fitted the earth spike.

A TN-C-S system into a TT he turned. A good sign this is also not.

I have a guy coming round on sunday to take a look,

Let us know what he finds, please?