Cooker keeps tripping off circuit.

[VickyBH]

I have recently purchased a property that has a freestanding electric hob and double oven all in one unit. The place had been empty for 7 month and I tested the hob in the last viewing and it was working.

Yesterday I switched on the hob for the first time after moved in, it took out the circuit breaker and RCD after about 5 min of use. Since then, it’s tripping off the circuit as soon as it’s switch on.

Is there a way to establish that the fault is definitely from the cooker not in the circuit? The hob/oven has its own 32A MCB and is hot wired with a 6mm cable. The cable is connected back to a wall switch that also has 1 wall socket. (see photo).


I’m reluctant to get another cooker because we will be renovating the whole place in few month time. I’ve got couple of spare Pattress box and sockets, and wondering if I could connect them to the cable that’s’ connecting to the current hob/oven, and use plug-in twin induction hob for the time being?

 

[chivers67]

Is The MCB tripping or RCD or both now?

If it's the MCB I wouldn't keep resetting it there's clearly an issue somewhere, have you anything Electrical Test wise?

 

[daviesm1976]

You could disconnect the cooker take the cooker out and use a simple multimeter to check the resistance of the elements.

Davis savery on YouTube did a video where he checked and replaced the elements on his cooker.

 

[crystal ball]

If it has been stood for a while some elements are prone to getting damp ingress, or it may be a fault that manifests when its hot

 

[VickyBH]

Thx for the reply.

Both MCB and RCD tripped now and the very first time too. No electrical test has been done recently but there was a new addition of kitchen circuit in 2011.

I haven't used the oven so not sure if checking resistance on oven element means anything? I have a air fryer and a microwave already so if cooker circuit can supply power to plug in a portable twin induction hob I should be sorted for next few month until renovation take place?

 

[daviesm1976]

"Is there a way to establish that the fault is definitely from the cooker not in the circuit."

Might be that the hob element resistance is too low, causing too high a current to flow or that there is too low a resistance between earth and live on the appliance.

An electrician will have proper equipment for testing the appliance or circuit

Obviously you can just try your different appliances if you already have them

 

[sircerebus666]

Thx for the reply.

Both MCB and RCD tripped now and the very first time too. No electrical test has been done recently but there was a new addition of kitchen circuit in 2011.

I haven't used the oven so not sure if checking resistance on oven element means anything? I have a air fryer and a microwave already so if cooker circuit can supply power to plug in a portable twin induction hob I should be sorted for next few month until renovation take place?

If you are not confident fault finding or don't own a multimeter then you are best off just disconnecting the cooker and using your other appliances

You check the resistance of the elements because that's the commonest fault on a cooker , the elements failing and shorting out , and is a simple , quick and cheap fix

 

[johnny2007]

Had the same problem a few years ago and it was the earth cable that was loose in the wall connection.
Once tightened the screw, the same cooker worked without problems until we changed it.

 

[VickyBH]

Last night I was going to pull out the cooker I thought I should I should check if the oven is working at all as I've only tried the hob previously and perhaps it's just the hob that's faulty.

I turned off all other circuits on CU leaving just cooker MCB and the RCD live, as soon I turned on cooker switch in the kitchen (the one in the photo), a loud POP sound came from behind the switch and the MCB and RCD went. I didn't even have a chance to touch oven switches or any switches on the cooker. Could the cooker switch be faulty? I haven't got a slotted screwdriver to open up the switch plate but will do so tomorrow.

 

[securespark]

Yes. It sounds (literally) like there is a fault there.

Open up the switch (make sure power is safely isolated) and see if there is an obvious problem. If not, disconnect the oven completely from the switch and power up. If the oven is faulty the switches will stay in the ON position.

 

[VickyBH]

Opened up the cooker isolation switch, L/N/E connection are all solid. The led/neon light don’t work anymore so I removed the cable.

I then pulled the cooker out to disconnect the hardwired cable, only to see that the connection block is pretty fried up.


In an attempt to unscrew and disconnect the for further testing, the plastic casing around each terminal screw just cracked. The screws are now stuck and I can’t remove the cable. I’m thinking to cut the cable from bottom at once but sheathing looks quite thick. Would a utility knife be ok to cut through it?

 

[VickyBH]

Here’s the photo a cracked terminal.



I’ve now managed to cut the cable free from attaching the cooker and the circuit doesn’t trip anymore!

According the the spec, the hob is 5.8Kw max and oven is 2.3kw max, bringing the total to 8.1kw, I think 10mm T&E should’ve been used instead 6mm. I am guessing this is why the cable was fried?

 

[johnny2007]

Replace the cable and the wall connector

 

[JohnD]

I am guessing this is why the cable was fried?

No, it's much more likely because the cable was not tightly secured in the terminal. From your pic this appears to be the connector on the cooker, so you will need to order a spare part. Ask someone like
https://www.espares.co.uk/search/ma154pt1985/cooker-and-hob-terminal-blocks/belling?SearchTerm=belling fse
Tell them your make and model and send a photo.
Otherwise approach the makers.

If the cable itself was grossly overloaded, it would have overheated along its entire length, but, because of the way cookers work, it is pretty certain not to be.

You have not shown us any reason to distrust the wall connector or the cable.

After you've cut off the heat-damaged part of the cable (which I'll wager is only a few inches adjacent to the terminal) and fitted a new terminal block, tighten the screws until they feel tight. In a week's time, tighten them again. I bet they will screw down a bit more because copper, being a soft metal, squashes down under the pressure of the screw.

Tighten them again after a couple more weeks. That should do it.

This is a problem with large, stranded cables but not, AFAIK, with the more common single core found in the smaller cables normally used for sockets and lighting circuits in UK. Shower switches are quite prone to it.

 

[JohnD]

also buy some side-cutters to cut the cable.