Kettle / Cooker Socket Question

[Iggifer]

So I was at my friends today, she previously had an issue with her cooker switch socket combo - somebody got the kettle wet and then boiled it. This tripped, I believe the MCB but as I was talking her through it on the phone it may have been the RCD.


She says to me today 'I can't have the cooker switched on and the socket because it trips' she didn't know whether it was the MCB or the RCD so I did minor investigation - she boiled the kettle with the cooker off, boiled fine. I reboiled with the cooker on, all good. Ran the toaster in the socket with the cooker on - all good.

I said, seems to be ok. I went and sat down and 2 minutes later heard the RCD pop, asked what she'd done and she'd just reseated the kettle on it's base.

Without touching the kettle I reset the RCD and it stayed up.

Question is, appliance or socket? I am 99% certain it's the appliance but odd that it had managed to boil twice with no issue.

Worth getting the megger on the kettle? Or shall I just stick with my current recommendation of throwing the kettle in the bin?

 

[EFLImpudence]

You seem to have figured it out already.

If other appliances do not cause a trip then it would appear to be the kettle.
You could try more things in the socket to be sure.

I wouldn't bother testing the kettle base as it's an intermittent fault.
It will dry out in a while and probably be alright.

 

[Iggifer]

Yea I was thinking there's some residual water in there somewhere.

Shame it's a kettle as I think even an MK cooker / outlet combi is cheaper than a half decent kettle

 

[EFLImpudence]

If that's what it is it'll dry out.

 

[Iggifer]

Yea the initial trip was about a month ago, so either it got REALLY wet or she is just rubbish at filling the kettle.....

 

[ericmark]

Three possible causes.
1) The spike caused when switching the kettle is taking out RCD.
2) The kettle is faulty.
3) The kettle load is causing a volt drop on the neutral line which in turn is allowing some other item with a neutral - earth fault to trip RCD.

So step one test the kettle see what readings are. If readings are OK then look for other fault.

Spikes are hard to find so only real option is to change RCD for something like the X-Pole which should be able to handle spikes better but much cheaper to renew kettle so even if the RCD is at fault at around £6 for kettle in Tesco I would just renew kettle.

But the neutral - earth fault is a hard one to find. Many items only switch the line so the faulty item may be switched off. I would use my PAT tester and insulation tester but without them I am a little uneasy at saying how to test as have no idea of your ability.

But you say friend so likely easy way is swapping kettles for a day and see if problem swaps from house to house or not.

The problem is with no load the neutral and earth are at the same voltage so any connection between neutral and earth will cause no current to flow. So RCD will not trip. However once one starts to use current the voltage on the neutral will rise slightly in respect to earth so depending on how much leakage between neutral and earth will control at what current draw enough will flow to trip the RCD. Since a kettle draws about the maximum for a 13A plug if anything is going to trip it the kettle is most likely. You could try a fan heater or some other high load device and see if you get same results.

Going around unplugging items may help find the cause. Switching cooker off at isolator and same with immersion heater etc.

It does not even need to be on the same circuit. The MCB in the consumer unit only switches off line it does not switch neutral and so will not remove any neutral - earth fault.

 

[vibrobullit407]

Is there a socket circuit protected by a different RCD that you could try the kettle in to see if it trips that one out?

 

[Iggifer]

Yea there is, will give it a go, it's a really bizarrely configured Eaton board with the main switch in the middle and the two RCD's at either end. Not how I'd configure a split load but there must have been some reasoning behind it

 

[Iggifer]

Bit of an update on this one. Been round today. Seems to be a combination of earth leakage causing the RCD to trip.

Came round with no tools as wasn't expecting to be looking into anything.

As mentioned, it's a combined mk cooker + 13a outlet plate

Cooker + Toaster (with other appliances on, on the same RCD) = trip
Cooker + Kettle (and other appliances) = trip
Cooker = No trip
Kettle/toaster = No trip
Disconnected cooker entirely = no trip
Disconnected CPC to cooker + lots of appliances = no trip

I suspect the highest earth leakage is coming from the cooker, but less than the RCD is tripping at, add a couple of appliances into the mix and it's tripping.

It's an Eaton split load board, and I do have a 32a RCBO I could on to separate the cooker from the RCD.

First im going to ramp test the RCD, cos if it's tripping at a really low point it might just be worth replacing that. I had a good visual check over the cooker wiring and there's no visible damage/scorching.

Having said that, you can trip the RCD by banging the cooker (doesn't work everytime).

Never dealt with this cooker before, it's a leisure Zenith 100. Anybody had any dealings with this before? Any tips on what to check

 

[17thman]

so you are disconnecting cpc's and energising circuits and appliances? Have you tested insulation resistance on any circuits yet? you turned up with no tools and decided to conduct electrical random testing? banging cookers looking for faults with no cpcs connected?

 

[Iggifer]

No I wasn't the one banging the cooker I was shown look 'this trips it'

And obviously when I disconnected the CPC I made sure that people stayed away from the cooker. There was definitely no touching of the cooker by anyone when the CPC was disconnected. It was energised for a maximum of one minute.

IR testing will be tomorrow when I come with tools / tester. Would have brought them today but I thought the problem had resolved itself

 

[riveralt]

IR testing will be tomorrow when I come with tools / tester. Would have brought them today but I thought the problem had resolved itself

Hope your business insurance is up to date.

 

[17thman]

Disconnected CPC to cooker + lots of appliances = no trip

 

[Iggifer]

Disconnected CPC to cooker + lots of appliances = no trip

Sorry, by this I meant I just disconnect the cpc to the cooker. Not lots of appliances.