150V between neutal and earth

[BobSmith652]

I'll start from the beginning. I got in the shower a week ago, and the water came on, but did not get hot. I noticed that the neon in the isolator came on, but when I turned on the shower, it went out. After opening up the shower, I found water coming out of the heater element can, so decided to get a new shower. I thought it must be shorting out inside with the leak, although the RCD and shower breaker in the fuse box did not go off.

I fitted the new shower today, and it also will not come on. The neon in the isolator switch goes out when I turn it on, as with the last one.

I measured 250V between live and ground, and I also have 150V between neutral and ground. I also have 28V between live and neutral. When I measure the voltage between neutral and ground, the power neon comes on on the shower.

I have 2 showers, so I swapped the circuit breakers over in the fuse box. I get the same happening, so I know it is not a faulty breaker, and the other shower works fine.

Has anyone any ideas what is going on? I have not changed any electrics for at least 6 months (swapped a dimmer in the lounge), so I don't see why something should have changed.

 

[Adam_151]

50p says the neutral has burnt up in the shower isolator switch

 

[BobSmith652]

50p says the neutral has burnt up in the shower isolator switch

That was quick!

Everything looks fine in the switch. I can't smell any burnt out smell in there.

Do you mean visible burning, or could the burnout be in the run of cable between the switch and the shower?

 

[RF Lighting]

If everything looks ok in the switch i.e. no burnt insulation on the wires, and all the copper is bright and shiny then it may be the switch that has burnt out.

Test for voltage at the switch on the connections marked supply, and then repeat the tests on the load connections.

This will tell you if the switch has failed or if the problem is further down the line.

 

[BobSmith652]

I just did an RCD test - I was sure I was touching just the earth when I got a massive spark and bang. The earth is very close to the live supply terminal, and I must have been too close to that with the probe.

I will have another look tomorrow when I have calmed down... Unless I need to test/replace the trip switch or RCCB before going any further?

 

[BobSmith652]

With all wires in, I get 0V on the neutral on the supply side, and 150V on the neutral on the load side.

I disconnected the load side, just to make sure that the wires are on the right sides. I have 0V on the live that was on the supply side, but the neon doesn't come on when I turn on the isolator.

Is this right? Does the neon normally only light up if there is something wired into the load side?

Anyway, I get 150V in the empty neutral terminal, so the live on the supply side is really the supply, and the neon lights up as I measure the 150V on the neutral.

Does this mean it is just a new pull switch?

 

[flameport]

I just did an RCD test - I was sure I was touching just the earth when I got a massive spark and bang.

Please stop what you are doing, and call an electrician before you kill yourself.

 

[BobSmith652]

Thank you for your concern, but I have seen "professional" sparkies do a funny little dance while working on lights at work.

 

[riveralt]

Thank you for your concern, but I have seen "professional" sparkies do a funny little dance while working on lights at work.

The point that is being reflected is that you are testing live using the 'bang' approach which is both foolish and dangerous.
If you believe you have a problem with the circuit then do the testing properly by following the correct 'dead test' procedures first.
That should give you an indication of where the problem might be.
Though given your previous experience I hesitate to suggest to go near the consumer unit to conduct this test and it might be wise to call in an electrician as suggested by flameport.

 

[Monkeh]

Thank you for your concern, but I have seen "professional" sparkies do a funny little dance while working on lights at work.

So because they're not doing their job safely, it's okay for you not to?

 

[conny]

One 'Flash/Bang means you were lucky. Luck runs out! Get a spark in, for your familys sake if not your own!

 

[ban-all-sheds]

I just did an RCD test

How, and with what?

 

[BobSmith652]

Thank you for your concern, but I have seen "professional" sparkies do a funny little dance while working on lights at work.

The point that is being reflected is that you are testing live using the 'bang' approach which is both foolish and dangerous.
If you believe you have a problem with the circuit then do the testing properly by following the correct 'dead test' procedures first.
That should give you an indication of where the problem might be.
Though given your previous experience I hesitate to suggest to go near the consumer unit to conduct this test and it might be wise to call in an electrician as suggested by flameport.

I have only ever worked on wiring with the fuse from the consumer unit in my pocket before. The "bang" was not a planned part of the testing procedure, I can assure you. And I am sure none of the people jumping on this thread have ever had a multimeter probe slip. If you read further up, you will see that I needed to have the power on to find if the 150V was on one side or the other of the switch.

As no-one has answered my question, I will be buying a new switch tomorrow.

 

[bernardgreen]

As no-one has answered my question, I will be buying a new switch tomorrow.

There was the answer that the neutral was not being closed in the switch which, from your description is the most likely fault. That assumes ther are no junction boxes on the cable route in which the neutral connection has failed.

A regards meter probes slipping, It has happened many time to me but my probes for use on live mains ciruits have only a millimeter of exposed metal contact area so a slip is not going to bridge between two conductors.

 

[riveralt]

I have only ever worked on wiring with the fuse from the consumer unit in my pocket before. The "bang" was not a planned part of the testing procedure, I can assure you. And I am sure none of the people jumping on this thread have ever had a multimeter probe slip. If you read further up, you will see that I needed to have the power on to find if the 150V was on one side or the other of the switch.

Why are you fixated with 150v - do a dead continuity test on each part of the circuit at the very least to find out if you have a complete circuit - or whether there is a jb with a loose (netural) somewhere.
I would also say do an insulation resistance test but doubt whether your multimeter has this facility.

As no-one has answered my question, I will be buying a new switch tomorrow.

At the very least do a continuity test on the old one to establish whether its broke or not first.
With the switch on place the probe between supply L and load L then supply N and load N - you should get a low resistance ohm reading for each test. If you do then with the switch off test again - you should get zero continuity. If the results are as described your problem is not with the switch.