Oven tripping the electrics

vacheron

 Doonhamer said:

Doesn't really explain it tripping the RCD though. Just having a 6mm cable rather than a 10mm won't trip anything.

I also think the cable rating is also distracting from the main issue, that ‘something” is tripping.

We still don’t know for certain if this is an RCD, MCB or RCBO, nor the rating if it’s either of the latter as we don’t have a pic of the consumer unit. 

As Doonhamer says, an underrated cable will not trip any of the above unless the MCB or RCBO is also underrated (for the load, not the cable).

If the MCB or RCBO is rated for the load the only way that the cable could cause tripping would be if it was getting so hot that it was literally melting the PVC between the cables and allowing them to touch each other, (or something else that is earthed)! 

Grandad2b

Catbenetar said:

If anyone is still following I do have an update.

We had an electrician out who said the wiring is too small to accommodate a 10kw oven. The installer really ought to have spotted this at the time it was put in. 

Our options are to either try and get another oven (though most are around 10 so this will be a struggle) or have a new cable run from the oven to the fuse box. 

Nightmare!

With all due respect to your landlord's electrician this sounds like total rubbish* to me. 
I have to admit it's been a long time since I was completely au fait with the Regs so there have been some changes I don't know about but the current carrying capacity of copper cable is determined by the laws of physics which haven't changed.

When I was a working electrician there was a thing called diversity which is what allows your sockets for example to be wired in 2.5mm^2 cable even though it can only carry (from memory) 23A.
For a cooker circuit the load was calculated as 10A + 100% of the largest ring or oven + 70% of the next largest + 30% of the rest. If there's a socket outlet at the cooker switch add 5A (I may have the percentages wrong - if so I'm sure someone will be along to correct me before the electrons are dry). Unless the cable is buried in insulation it's highly unlikely to be too small for the current you're drawing.
It's possible that this diversity formula has been changed in which case perhaps a 10mm cable may now be required.

The usual reason a 10mm cable was required was not because of current but volt drop.

However, as someone else has mentioned, this is not the cause of your tripping problem and replacing the cooker cable is unlikely to sort it.


* I was going to use a more anatomical term but it's a family forum...

Doonhamer

vacheron said:

 Doonhamer said:

Doesn't really explain it tripping the RCD though. Just having a 6mm cable rather than a 10mm won't trip anything.

I also think the cable rating is also distracting from the main issue, that ‘something” is tripping.

We still don’t know for certain if this is an RCD, MCB or RCBO, nor the rating if it’s either of the latter as we don’t have a pic of the consumer unit. 

As Doonhamer says, an underrated cable will not trip any of the above unless the MCB or RCBO is also underrated (for the load, not the cable).

If the MCB or RCBO is rated for the load the only way that this could cause tripping would be if the cable was getting so hot that it is literally melting the PVC between the cables and allowing them to touch each other, (or something else that is earthed)! 

My reading of this is that an RCD is tripping because it's taking out bedroom and kitchen sockets and lights, so likely a split load consumer unit. Also it trips when the oven is not fully on, in fact is sound like it trips when the oven is even off. The only time it doesnt trip is when the cooker wall switch is off. So it's nothing to do with the size of the cable. The cable from the fuse box to the wall switch must be OK, so the fault is between the wall switch and the cooker

"It trips everything on the circuit which are the lights and all sockets in the kitchen and my bedroom. Rest of house remains active."

"Sometimes only the fridge will be on when it trips. Stuff is plugged in but not running."

"Yes switching off at the wall is the only way to get the power back on. At present we can't turn it back on at all as it trips every time."

vacheron

Yes, this is why I though (first reply to this thread) that it could be cumulative earth leakage with the new big oven nudging the quiescent leakage close to 30mA, then it only takes a fridge compressor to switch on to nudge it over and trip the earth leakage circuit. 

As most leakage comes from the input filters and front end power supply circuitry. It is often still present even if the devices are not being used but are still plugged in. 

I mentioned it because I’ve had this problem personally as did a friend who also had new ovens / hobs installed. 

Catbenetar

vacheron said:

Yes, this is why I though (first reply to this thread) that it could be cumulative earth leakage with the new big oven nudging the quiescent leakage close to 30mA, then it only takes a fridge compressor to switch on to nudge it over and trip the earth leakage circuit. 

As most leakage comes from the input filters and front end power supply circuitry. It is often still present even if the devices are not being used but are still plugged in. 

I mentioned it because I’ve had this problem personally as did a friend who also had new ovens / hobs installed. 

Please can I ask what the fix would be for this if this is the cause? The whole circuit has been tested more than once and no other faults detected. It’s is only ever and has only ever been the cooker that causes any issue. 

Last night I had fridge on, microwave, air fryer and boiler all at the same time. No issues. 

The electrician changed the cable from the cooker to the switch so that we will still be able to use the hob and so far this has been ok. 

Catbenetar

I’ll upload some pictures tomorrow as I feel this will really help with getting to the route of the problem. 

I really really appreciate all the input from you all. 

Catbenetar

Grandad2b said:

Catbenetar said:

If anyone is still following I do have an update.

We had an electrician out who said the wiring is too small to accommodate a 10kw oven. The installer really ought to have spotted this at the time it was put in. 

Our options are to either try and get another oven (though most are around 10 so this will be a struggle) or have a new cable run from the oven to the fuse box. 

Nightmare!

With all due respect to your landlord's electrician this sounds like total rubbish* to me. 
I have to admit it's been a long time since I was completely au fait with the Regs so there have been some changes I don't know about but the current carrying capacity of copper cable is determined by the laws of physics which haven't changed.

When I was a working electrician there was a thing called diversity which is what allows your sockets for example to be wired in 2.5mm^2 cable even though it can only carry (from memory) 23A.
For a cooker circuit the load was calculated as 10A + 100% of the largest ring or oven + 70% of the next largest + 30% of the rest. If there's a socket outlet at the cooker switch add 5A (I may have the percentages wrong - if so I'm sure someone will be along to correct me before the electrons are dry). Unless the cable is buried in insulation it's highly unlikely to be too small for the current you're drawing.
It's possible that this diversity formula has been changed in which case perhaps a 10mm cable may now be required.

The usual reason a 10mm cable was required was not because of current but volt drop.

However, as someone else has mentioned, this is not the cause of your tripping problem and replacing the cooker cable is unlikely to sort it.


* I was going to use a more anatomical term but it's a family forum...

The general opinion is that it is something else causing the tripping. I just don’t understand why it is only tripping when the cooker is in use. I can have absolutely everything else on at once and there will be no issues. 

It doesn’t help that I have very little understanding of how electrics work 😂 
I’m just someone who replaced a faulty oven and has seemingly now opened a can of worms. 

Though the more this thread goes on, the more I wonder if the old oven was even the issue? 

Catbenetar

Can I clarify something? If the oven is running on the 6mm cable and this is not big enough, would it just trip out or would there be some damage to the cable which would cause the trip as many have suggested? 

Doonhamer

Nothing would trip, the supply cable may overheat though if it's supplying more current than it's rated for depending how it's installed. But this would likely only be if you had the oven and all the hobs on full at the same time. Each hob will have a power rating from say 1.5kw to 2.5kw depending on size, and maybe 2.5kw for the oven making up to the 10kw. So if you have the oven on and 2 or 3 hobs full power it would be <7kw and should be ok on 6mm. Only with 4 hobs and the oven on full would it take 10kw, but of course the electrician rightly has to work to the max rating of the appliance.

Bostonerimus1

Let's hope the circuits are clearly labelled.