56v on neutral

[Jolead]

Evening

I've not posted for a while and have had to set up a new account as I can't find my old one.

Moving on I have a wiring conundrum.

Customer called said heating had died no lights on programmer. At the property the customer also asked if I could change the honeywell wiring centre (with pcb) as it was in pieces whilst there. Stupidly I did not check neutral to earth etc before starting apart from if there was a live to backplate with death stick. So changed programmer and just put in a honeywell junction box with no pcb. Turned spur on and boom - breaker goes out.

After much effort of checking disconnecting etc I couldn't get the breaker to stay on. Fuse board was breaking on mcb and had two rcds. In the end I had a new fused spur wired into brand new programmer only (literally nothing else) this time when I put the spur on the breaker broke again. I then checked the programmer on a fly lead from bedroom sockets and it worked perfectly.

I Advised customer that a new wire from the board and fused spur is needed (retired spark- he agreed) meantime I wired heating back together and run off a fly lead from bedroom sockets and three pin plug fused to 3amp. Three port moved to hot water only to mid to heating only perfectly boiler pump all working..

Customer runs new cable and tests with socket tester which said fine then puts in fused spur. I go back to today. Remove fly lead and put into spur. Turn spur on and exactly the same problem. I wire back to fly lead/plug and all works fine again

Has anyone got any ideas. Thanks in advance

 

[SJB060685]

Was it breaking an RCD or MCB? How did you arrive at 57 volts on the neutral?

 

[Jolead]

Was it breaking an RCD or MCB? How did you arrive at 57 volts on the neutral?

Mcb. And neutral to earth 57v

 

[SJB060685]

I'm not an electrician so I'm not sure I'm thinking along the right lines. Where you getting this neutral voltage at the fused spur?. @Murdoch can you explain the possibilities for the above problem?

 

[Jolead]

Yes at the spur

 

[SJB060685]

So you have 57 volts between neutral and earth on incoming to spur and as soon as you flick the switch the mcb trips? And that was the same with a new fused spur and just a programmer?

 

[Murdoch]

Sounds like a problem at the spur to me.

 

[Aquarius]

If it works ok without the spur, then I’d say it’s the spur as per @Murdoch

 

[SJB060685]

He replaced the spur with a new unit (although not proved faulty as well) and still the same. Could this be a broken neutral problem somewhere? Was an initial thought of mine but like I said I'm not an electrician

 

[Aquarius]

What about wiring from the spur? could it be ghost voltage if using a Fluke?

 

[Murdoch]

A broken neutral would be at 230v or zero normally.

somebody with competence and test kit needs to get involved

 

[Jolead]

Guys just thought I would update thread.

Went back today with my electrician.

Basically a socket tester only checks the path of a neutral. So the fact the socket tester indicates it was ok didn't mean it was not the problem.

He actually wired in a lamp that worked fine. However when he wired the heating in it broke the mcb.

It's a neutral fault somewhere in the house that needs to be rectified which he is going back to do.

Hard lesson here I think is the basic electric tests I should have carried out on the spur rather than presuming it was the heating wiring in the first place.