Neutral fault on ring (12 volts)?

[davemc]

Got a call from a friend who's just changed his old c/u for a new one. He said everything seemed fine when he swithched it all on until he plugged his socket tester in and it said he had a neutral fault. He said the neutral bar was live until he took the two neutrals from the ring out of the neutral bar and then when he tested between live and neutral he gets 11-13volts. Didn't give me any more information than that.

Any ideas?

 

[Marvo]

Missing incoming neutral perhaps? This is the kind of fault that will give him a shock if he's not careful. Is there an RCD supplying the socket circuits??

 

[davemc]

yeah, he said its a new board.

said i'll go round and have a look tomorrow. don't know if i'll be able to help with my limited experience, but its worth a shot. He's isolated the circuit.


if it were a missing incoming neutral, would it not affect the other circuits?

 

[Marvo]

If the neutral bar was live at any time then there's no main neutral connected to the bar.

 

[SirKit Breaker]

If all is well with the circuit disconnected then i would do the following. disconnect the circuit fully, check r1/rn/r2, then R1 + RN, then R1 +R2, this will show up any problems with the circuit if done as per the BRB or GN3. Sorry if your experience is limited, but these checks should have been done prior to energising the circuit after the alteration. I don't have the time to explain in detail the test procedures. and you will need an instrument with a range to 2 decimal places, a normal mutlimeter isnt accurate enough.

Cheers........Howard

 

[telectrix]

it seems to me that the fault is one your mate has introduced himself. first test for correct voltage and polarity, then look for something stupid. as you say you have limited knowledge, be careful and safe and don't try and exceed your knowledge.

 

[Marvo]

If all else fails you can always go the old fashioned route and get an electrician in for an hour. This might not be a bad idea if you buddy has replaced the CU and doesn't have the skills to work out a neutral fault.

 

[tony mc]

Davemc I would have it looked at by someone who is competant and able to do the job I don't know the extent of your experiance so appologys if you are competant. If you don't possess the correct test equipment to carry out the vast amount of tests you might be missing a serious faults.

Sorry Marvo I did't type quick enough

 

[bugsy]

Is it a split load board and has he connected the neutral link?

 

[telectrix]

some CUs, e.g. square D, come with no manufacturers links fitted so as you can configure the board in various ways. could be he's missed or crossed a link when making the board up. as previosly said, if in doubt, call in a qualified sparks with the necessary test gear.

 

[topquark]

The fact that you have such a small voltage difference sounds like a dimmer or small volt drop accessory connected from another circuit. Has he only replace the CU or has he been rewiring something as well?

 

[davemc]

Thanks for the advice everyone. I'll nip round later and see what's happening. If it's not something immediately obvious then I'll give one my other mates a ring (a fully qualified spark) and they'll have to sort it between them.

Thanks again everyone, if/when it gets sorted I'll let you know what it was for future reference just incase it can help someone else

 

[davemc]

The fact that you have such a small voltage difference sounds like a dimmer or small volt drop accessory connected from another circuit. Has he only replace the CU or has he been rewiring something as well?

no, nothing new added, just the new c/u

 

[leeeel]

Have you checked if it is a loose neutral, I have had this myself on a job and the fault was a loose neutral in the cut out.

 

[telectrix]

Have you checked if it is a loose neutral, I have had this myself on a job and the fault was a loose neutral in the cut out.

for which, of course you called DNO and they came out and tightened it 6 weeks later. LOL.