Mini Circuit breaker randomly switching off

[abusimbel]

Hello and any help would be much appreciated! Basically the circuit breaker (MCB) that is on the household lights is randomly switching off. We have never had a problem before like this. The breaker may stay on for days, hours or only seconds with all the lights on only to spark and break without any lights on. Lights on or off it doesn't seem to change why the breaker is switching off. It seems to me if there was an electrical short somewhere we wouldn't be able to switch it on at all. I've also replaced the circuit breaker with a new one and it continues to flip.

I've attached a photo of the breakers and circled the lighting circuit. It is a B6.

Any thoughts are much appreciated. Thanks!

Untitled

• abusimbel
• 10 May 2009
• 1

 

[bongos]

If you have a high resistance L/N fault then you may find you have random trips like this.

If you can get to the lighting circuit junction boxes & ceiling roses then check all the connections are tight. But it's more likely that there is some damaged cable somewhere causing a breakdown in the insulation which is causing this short.

Any history of mice in the attic - they like to gnaw on cables. Also from looking at your fusebox it suggests that the rest of your house wiring may be old. It could simply be that the insulation in the cables has started to break down because of the age.

It might be time to call out an electrician who will be able to test the circuit and find the fault. unfortunately these kind of intermittent faults can be a real pain to sort out.

 

[abusimbel]

Yeah I probably need to get an electrician out. So, even if the circuit is fine for anywhere from days to minutes, with lights running normally, it could still be a short?

Thanks much.

 

[plugwash]

I would guess an intermittent short, e.g. two wires that have lost thier insulation (or a wire that's lost it's insulation and a terminal or an earthed enclosure) that sometimes touch depending on the movement of the house.

 

[securespark]

rodent or impact damage to cable OR outside lighting or wiring either damaged or water-logged.

 

[ColJack]

virtual pint says it's a cable crossing a heating pipe or vice-versa?

hot pipes expanding or someone walking over the top pushes it against the pipe and "pop!!!"...

 

[abusimbel]

Found it. At some point when the previous owner replaced a switch they screwed it directly into a inner wall stud (with wood screws) with no housing. Very very foolish. The screw eventually made contact with one of the wires. Maybe using the switch over the past couple of years pushed the screw into contact. Who knows. The screw had melted in half from the contact. The wood was blackened from the arcing. definite fire and shock hazard. At any rate it will be fixed and I am checking all of the switches in the house to make sure they have housings. Thanks much for all the advice.

 

[bernardgreen]

At some point when the previous owner replaced a switch they screwed it directly into a inner wall stud (with wood screws) with no housing. Very very foolish.

I am not surprised.......These DIY people What will they think of next......