How to find where cable fault is?

[Agile]

A lady that I know has converted two upstairs bedroons into self contained with electric showers and WC and basins for letting.

She has a partial basement with three CUs and the 6mm T&E shower cables disappear into the underfloor in the basement.

There is no indication of where the cables for the two upstairs showers go and the ground floor covering is laminate.

The supply to the rear bedroom has failed although it is leaving the CU in the basement.

How would a typical electrician try to identify where the shower supply cable has failed without a massive intrusion into the ground floor and wall ? The total cable length is about 5m vertically and 8m horizontally.

 

[sparkwright]

Most typical failures in shower supplies at the shower isolation switch, typically a pull cord in the bathroom, or a wall switch just outside the bathroom somewhere.

These switches have a tendency to burn out.

It could also be a bad connection somewhere.

No need point in pulling up floors and destroying walls until the obvious things have been checked.

Do you have a two probe voltage tester?

 

[CBW]

I think they usually bell wires out?

 

[Murdochcat]

Failures like this can happen happen many years after construction

Let the spark do their investigation and see what they find

Why do you think the cable has failed?

 

[ajstoneservices]

A cable resistance test can give you an indication.

 

[Harry Bloomfield]

How would a typical electrician try to identify where the shower supply cable has failed without a massive intrusion into the ground floor and wall ? The total cable length is about 5m vertically and 8m horizontally.

Various methods to try...

BT would use a gadget which sent a pulse down the line, then measure the time for the reflections to return - time = length to fault.

A signal generator, clipped to a failed wire, then a tuned amp connected to a coil, would allow the cable to be traced to the break.

Likewise, make the cable live, and assuming not buried too deep, or screened by metal, a sensitive voltstick might be able to follow it to the break.

 

[RandomGrinch]

Do you have a two probe voltage tester?

I should hope so, given the HP3585A Spectrum Analyser and the Tektronix 2246 Scope, pictured in his thumbnail!

 

[oldbutnotdead]

What @sparkwright said. I've met a few where the neutral connection has been loose in the terminal in the isolator.

 

[Agile]

I was wondering how an average electrician would expect to find the problem.

There is a break in the live somewhere.

And no isolator in or near the shower.

 

[securespark]

Maybe there is a junction box somewhere?

I have seen crazy ass things like switches lying loose under floors and in loft spaces, etc.....

 

[Agile]

There could well be but totally out of sight under floors or behind walls.

 

[Harry Bloomfield]

I was wondering how an average electrician would expect to find the problem.

There is a break in the live somewhere.

There is a similar thread on here, somewhere, where the OP has had 'electricians and plumbers' out to quote for repairing. Rather than looking to find the fault, they have simply quoted to scrap the whole system and install all new, from scratch.

An actual break in a cable is rare, almost unheard of in a larger cable, especially a stranded core, so I would be concentrating on the terminations.

 

[RandomGrinch]

An actual break in a cable is rare, almost unheard of in a larger cable

Unless there is evidence of rodent activity!
But I doubt they would get through the whole of a shower cable!

 

[Agile]

I have access to the terminations and they are both fine.

Both solid 6mm conductors.

But I do not know if there are any joints hidden somewhere.

 

[EFLImpudence]

6mm² T&E does not have solid L & N conductors' nor does 4mm².