Cicuit Breaker switched and now the whole circuit's down

[matpj]

I wired in a new light switch today - and unknown to me at the time, the screw that attches the switch to the metal back-box had chewed into one of the wires.

when I turned on that part of the lighting circuit afterwards, the breaker did its job and also the main consumer-unit breaker went down.

after switching them all back on again - the light circuit I was working on does not have any power.
the breaker is up (in the on position)

Any ideas from anyone?
could I have blown something in that circuit breaker? - or could it be something more sinister?

 

[Spark123]

It is possible the circuit breaker has thrown its hat in. Switch off the main switch on the CU. Remove the cover. Careful not to touch any metal within the CU, switch back on. With a multimeter set to volts AC range (240v+), measure between the suspect MCB out and the neutral rail. If you do not get a reading of around 240v then the MCB is faulty. Switch main switch off again before putting cover back on.

 

[matpj]

thanks for the response.
I took the cover off the CU and removed the breaker for the circuit that is having problems.

the breaker was fine. the switch worked - I checked the resistance and threw the switch.
all fine.

replaced everything and hey presto, the circuit worked. cant work it out.

HOWEVER, if I turn off the main breaker, I cant then turn it on again. so I turn off all individual circuits and am then able to turn on the main breaker.

I then turn each individual one on and they all stay on.

 

[securespark]

Have you an MEM board?

 

[matpj]

hi, what is a MEM board?

 

[nabby68]

MEM is a brand of consumer unit full name is MEMERA