Cooker circuit issues!

harryharman · Oct 17, 2012

Evening all, had a nightmare day with a stupid cooker circuit. I've just joined a new firm and they sent me to a job they have done recently- kitchen refurb. Cooker circuit (40A) mcb keeps tripping every now and then, no structure to tripping. 6mm T&E coming from board extended in kitchen supplying electric cooker & electric hob. I have tested circuit, continuity, IR, zs all fine, I even changed breaker to a new one just in case it was faulty. Cooker was working when i left job at 1 oclock, phone call at 5 this evening from client, she got in from work and it has tripped again- hadnt even used the oven it was off when she got in. Oven engineer came out and checked elements, lamps etc as well this morning and he said all ok. I really dont know what else to suggest as I really cant see what the hell is making it trip?! Any suggestions what so ever as is driving me crazy and doesnt look good in front of new boss if cant fix it!

Many thanks

Harry

Guest55 · Oct 17, 2012

mcb trips when oven off , then look again at the cable & switch.
especially the bit where you suggest its been extended ( cable ? )

KFH · Oct 17, 2012

Something is causing it to trip and you have tested / done the obvious, now you will have to consider the not so obvious. Mice, cable trapped somewhere and people walking/doors closing/temp differences causing a contact, nail through cable temp differences causing it to touch, other equipment attached to circuit and not documented. Intermittent problems are a pain to solve. I would clamp the supply with the cooker off to see if there is any load anywhere perhaps leave it on max hold for while tracing the cable route looking for potential problems. Then I would get someone to stamp around along the route while I look at the MCB. Other than that I have no ideas.

Good luck

I wish I could type faster. The connection for the extension looks a good place to start as suggested.

Maestro · Oct 17, 2012

maybe its a build up of earth leakage that's why it fine when you left, did you leave it on when you lef the houset set the time ect on the cooker

Deservices · Oct 17, 2012

If they have fitted a new kichen they could of damaged the original wire maybe.

Octopus · Oct 17, 2012

Maestro said:
maybe its a build up of earth leakage that's why it fine when you left, did you leave it on when you lef the houset set the time ect on the cooker

Why would earth leakage trip the MCB?

kduck · Oct 17, 2012

I had this a few years ago, all test's where ok. Could not work it out, turned out to be the earth sleeve on the cooker socket was just too short. As the socket was pushed back the sleeve moved showing bare copper just across the live connection. It was totally random tripping.