Light circuit fault

llywelyn111 · Oct 28, 2012

A sparky that I know very well and is a good sparky (went to college with him) just rang me up. He has a fault on a lighting in a log cabin. He says he's IR'd the circuit that blows the MCB and RCD and is totally clear. He said a two gang dimmer, one of them doesn't dim now. So I said it must of being the dimmer failing causing a short. He changed the dimmer MCB back on Customer made him a coffee. 15 mins later MCB and RCD trips again. Same dimmer blow again and now won't dim again.

400watt dimmer with x4 50watt GU10 on that dimmer.

Told him to IR it again and it's totally clear (lamps taken out).

Told him to leave the light on with the blown dimmer so it would just work like a normal switch. Still blows after about 15-45 mins.

so it's got to be that switch live and neutral T&E (feeds taken to switch, no access above due to vaulted roof) from that dimmer that has been damaged somehow. Anything else I could get him to check? or come across something like this before.

fylthespider · Oct 28, 2012

put normal switch on and try again. if still blows, isolate out-going side of switch and try again, at least u find which side causing problems. could be heat from lamps cooking trapped cable or rodent damage?
ive had water in t&e cables and when it gets hot the IR drops. dont know why but it does.
i hate halogen spots.
best of luck.

llywelyn111 · Oct 28, 2012

It's a new log cabin, so can't be rodent damage. He says it still trips only with them four lights connected in a temp 1 gang switch. So it must be a trapped cable or coving pinned and damaged the cable. He'll have fun replacing the cable haha

fylthespider · Oct 28, 2012

just the thing for sunny sunday afternoon eh?
i'd be looking at the connections to the lamp holders first and then a good pub second (you know, one with no mobile signal).