New oven blew - then discovered loose wiring on the cooker switch.

Fairly over the Hill

Hi All,

I installed a new oven last week and all worked fine until yesterday. While using the grill, the breaker tripped. When I reset it, the oven is totally dead.

Today I discovered that the live and neutral were loose in the cooker switch. I can't see anything else wrong so I am just wondering if this might have caused it. I can see how this might trip the breaker, but killing the oven seems odd.

The oven in on a 32A breaker. The oven itself is 3.6 kW but there is a hob on the same circuit so it probably needs a bigger breaker for that reason.

I am a bit worried that the wiring fault in the house might have just cost me a brand new oven. It 's a NEFF and wasn't cheap!

Any advice would be appreciated.

kirk.

Oven and hob should be ok on breaker as diversity is applied to them

Wouldn't expect loose wiring to trip MCB, they'll have to be retightened anyhow

Fairly over the Hill

Thanks Kirk. So I guess it must just be a fault in the oven itself that caused the issue?

meercat

Agree with Kirk. It’s unlikely that a loose connection in cooker switch would cause the mcb to trip.

kirk.

https://www.boards.ie/discussion/comment/120247827#Comment_120247827

Dunno but it's not unknown for new cookers to be faulty

I've seen them trip mcbs out of the box , not saying that's what happened

kirk.

https://www.boards.ie/discussion/comment/120248590#Comment_120248590

Loose screwed connection could cause a series arc fault

Shouldn't be a hazard in an enclosure such as a cooker back box

Are they mandated on any circuits now ?

horseman34

https://www.boards.ie/discussion/2058284510/new-oven-blew-then-discovered-loose-wiring-on-the-cooker-switch

are you sure its a mcb? can you show some pics?

meercat

https://www.boards.ie/discussion/2058284510/new-oven-blew-then-discovered-loose-wiring-on-the-cooker-switch

Just check that the trip switch is reset properly

pull it down firmly all the way and push it back up

10-10-20

Also, if the loose cables were the cause you should be seeing signs of overheating or arcing within the switch connection. Were there any such signs?

kirk.

https://www.boards.ie/discussion/comment/120251669#Comment_120251669

It wouldn't trip an MCB but he should check for damage

adrian92

Just a thought. It seems unlikely a fault with your oven and hob.

The loose wiring on the switch may have caused a short circuit (due to internal heating in the switch) that caused the MCB to trip (possibly an open circuit later , so nothing works)

I would suggest replace the switch (and, of course, ensure that all cables are tightened)

I do do not think it a good idea, from what you have described to use the existing wall switch - the thermal affects are likely to have irreparably damaged it

kirk.

https://www.boards.ie/discussion/comment/120260002#Comment_120260002

Don't think I've ever seen that happen

Fairly over the Hill

https://www.boards.ie/discussion/comment/120250328#Comment_120250328

Thanks horseman - it's the 32A on the right...

Fairly over the Hill

https://www.boards.ie/discussion/comment/120250620#Comment_120250620

Hi meercat - yes it's definitely reset. the hob is on the same circuit and that's working fine...

Fairly over the Hill

https://www.boards.ie/discussion/comment/120251669#Comment_120251669

Hi 10-10-20 - not, there were no signs of arcing at switch. I hadn't thought of that so good point, it's probably not the cause of the problem.

meercat

https://www.boards.ie/discussion/comment/120264010#Comment_120264010

Where are the oven and hob connected to

is there a joint box connection for the 3 cables

id look there (and the connection into the oven)

kirk.

It's common enough to have issues at the switch

So I would hazard a guess 2 issues ,. could be something to do with the install as above , hard to say

Fairly over the Hill

https://www.boards.ie/discussion/comment/120264373#Comment_120264373

Hi Meercat,

The hob and oven are both wired into the main cable coming from the fuseboard at a junction box which is down on the floor under the kitchen cabinet which houses the oven. The hob still works fine so I assume that that wall switch is ok.

Thanks for all your comments so far - it's a big help. I have rang the shop and they are sending someone out from Neff in case it was just a fault in the oven that caused the whole thing. If that is the case, the loose wiring might be just a coincidence but I have tightened all that up now anyway.

My main worry was (and still is) that wiring a 3.6kW oven into a 32A fuse might not have provided sufficient protection to the appliance which might invalidate the warranty.

kirk.

Probably whatever the manual says as regards fusing

I always wired them separate with a 6sq and 2.5 from board

Single oven can then be wired off a 13a spur or a double pole switch and 16amp MCB with RCD protection

Electric hob on a separate cooker isolator

Fairly over the Hill

https://www.boards.ie/discussion/comment/120265964#Comment_120265964

Yea - I can see that separate wiring would be best but I am kind stuck with the wiring I have unless I go chasing walls for a separate feed for the oven, which is not easy. In a previous house, the oven was just plugged into a socket but that's not an option with a 3.6kw oven (at almost 16A on its own). The manual just says 'fused appropriately' and does not go into specifics. Which is why I am hoping that both the oven and hob wired into the 32A is an option. But if it's a no-no, then I'll have to get the professionals in.

Thanks for your time on this.

kirk.

Wouldn't worry about it 90% are done that way on the 32 amp

Not sure if that 3.6 kw is max load or total connected load either , maybe they vary I dunno

monseiur

So you just replaced an old oven with a new one and the old hob is still working away. Did you decide to replace the oven due it occasionally tripping breaker or had it reached the end of it's 'natural' life ?? If the latter, it's hardly unlikely that the loose wires in socket would have caused your new oven to die. My guess is that the new oven was faulty, double check that all wiring is in order before rep from Neff arrives ....in case he goes looking for a scapegoat 😉 You should get a replacement without issue.

Fairly over the Hill

Thanks everyone for all your help on this.

It turns out that there was a dent in the back of the oven and the casing touched the circuit board which tripped the circuit.

The guy from Neff said it could have been caused during installation or during transport so he is giving us the benefit of the doubt and we are just waiting on a replacement at the moment.

Have to hand it to Neff doe customer service....