weird fault

[ian]

Hi guys hope you can help me resolve this weird fault.

Was called to a fault earlier, a bloke had removed a socket and one of live conductor broke as it entered the box, anyway sorted that, but while I was repairing the fault the downstairs light MCB (5 amp 3871) tripped. I thought a lamp had blown and tripped the MCB, but a couple of minutes after resetting the MCB it tripped again, and it trips every couple of minutes, part of the circuit is old VIR and some T&E.

I haven't had time to do any proper tests yet but given the condition of the VIR I would imagine that the I.R's are going to be poor. Anyway the question is, is it just coincidence that the light MCB started tripping while I was repairing the fault at the socket, or could the faults be linked (cant see how) Also it's the first fault I have come across that takes a couple of minutes to trip the MCB, so not sure why this should happen.

Any help would be appreciated.

By the way TNC-S system.

Thanks
Ian

 

[WarrenG]

Hi guys hope you can help me resolve this weird fault.

Was called to a fault earlier, a bloke had removed a socket and one of live conductor broke as it entered the box, anyway sorted that, but while I was repairing the fault the downstairs light MCB (5 amp 3871) tripped. I thought a lamp had blown and tripped the MCB, but a couple of minutes after resetting the MCB it tripped again, and it trips every couple of minutes, part of the circuit is old VIR and some T&E.

I haven't had time to do any proper tests yet but given the condition of the VIR I would imagine that the I.R's are going to be poor. Anyway the question is, is it just coincidence that the light MCB started tripping while I was repairing the fault at the socket, or could the faults be linked (cant see how) Also it's the first fault I have come across that takes a couple of minutes to trip the MCB, so not sure why this should happen.

Any help would be appreciated.

By the way TNC-S system.

Thanks
Ian

Tripping after a few minutes sounds like classic overload, but it also sounds like there is a bit more to it than that.

How many lights are being feed on the lighting circuit?

Are you sure the lighting feed and the socket are not connected in anyway? If its an old installation who knows whats been done?

The very fact that the bloke was removing the socket in the first place and had to call you in, is a bit worrying - I'd tread carefully!

I would do a continuity and IR test.

Warren

 

[wattsup]

Knock all circuits off except the light in question, does it still trip?

Put clamp meter on line at dis board, whats it read

 

[ian]

Thanks for your replies guys.

The old guy removed the sockets because the switch had broken on it.

There are only 7 pendants on the circuit and the intruder alarm, which is never used. The lights are mostly wired in VIR, TRS and one is wired in T&E. Not sure if it’s connected with any other circuit yet (haven’t been back to test, luckily they are aware for the weekend)

I will try all the obvious things on Monday, IR, continuity, splitting circuits etc. Even if the two circuits are connected, can’t understand it’s tripping after the original fault on the socket has been repaired.

I think it’s going to be difficult to explain to this customer, the house needs a rewire (which it does) when all I was asked to do was repair a simple fault.

Thanks again.
Ian

 

[Tapouchoke]

Mate I get this all the time it is dealing with Joe public

I would explain that the house needs a rewire to comply with the electricity at work act 1989 and if it doesn’t comply with this your supplier will isolate your supply until its safe
Just because it works don’t mean its safe

Oh and most of all and get ya invoice in for your time

 

[wattsup]

<<I would explain that the house needs a rewire to comply with the electricity at work act 1989 >>>
Mm, then I guess 90% of houses in the UK are without power -

 

[Tapouchoke]

HUMMMM how would you explain the rewire to the customer that wont spend a brass farthing on works baring in mind the installation is in vir cable and it is 2008
comments good and bad appreciated

Cheers

Tapout

 

[jeremy]

I tested a property built in 1946 all original wiring, but recent (1970s) switches and pendants sockets. All ins res tests and Zs was fine. It's the 1960/70s cable and the 1970/80/90s wiring that scares me!