Keeps Tripping

[carl9254]

installed a PIR Outside light today, took supply from landing light to a junction box, live down to switch and back upto junction box as swith live, then switch live, neutral and earth out to light. The light did its test and seemed fine and the downstairs lights swithed on too. So went away happy, few hours later got a phone call back, the MCB had tripped, the guy came back to his house while dark, the outside light worked but as soon as he went in and switched landing light on it tripped the MCB and it wont reset, you just see a blue spark everytime you try to reset????

HELP???

 

[carl9254]

Fixed this yesterday. Took switch off and tried resetting mcb and it reset, put another switch on and fine, bit strange but guess they are faulty sometimes

 

[beanzntoast]

That is a strange one how a faulty switch can trip an MCB when theres only live's going to it,Never heard of that 1 before.you learn something new everyday

 

[amp]

Carl i would go back and check the cables in the light switch you may have crushed the live with the plate screw and now have an exposed live conductor where it was crushed this can be very easily missed. This will blow an mcb especially ir there is no RCD

 

[nrbspark]

I agree you should look for a damaged live in the switch, this was probably enhanced by the plastering work you carried out with the moisture in the plaster causing the short from permanent live in switch to the back box.

Hope this helps.