New cooker tripping RCD

[maffoo]

Firstly, I am not an electrician so please go easy on me and if I have omitted anything please ask.

We've had a new cooker and induction hob installed from Ikea. Here's some information on the setup :-

• New consumer unit, 100A 30mA RCD feeds 8 MCB's
• First MCB in line from the RCD is a 40A MCB for the cooker
• New cable from the above MCB to cooker switch (10mm)
• New cable from cooker isolator switch to cooker terminals behind cooker (10mm)
• Induction hob wired in to cooker terminals (2.5mm)
• 13A fused spur wired in to cooker terminals which feeds the cooker (hard wired cable from cooker)

The RCD is intermittently tripping and it "appears" to be the cooker/hob causing this. Here is some information about the various situations after some troubleshooting :-

• Cooker and hob work fine, appear to have no issues
• The RCD has never tripped whilst the cooker or hob have been in use, even at the same time
• The RCD has never tripped whilst the cooker switch has been turned off
• The RCD has tripped only once when turning on, but mostly when turning off
• The RCD trips hours after the cooker/hob has stopped being used, but isolator switch remains turned on
• On one occasion I couldn't get the isolator switch to turn on without the RCD tripping. After switching off the fused spur to the cooker (leaving only the hob) the power could be turned on. As soon as the fused spur to the cooker was turned on, the RCD tripped again

So after troubleshooting the above, I assumed it was the cooker causing the issue so phoned Ikea and they sent a replacement. However, this is physically damaged so also needs to be returned. In the meantime I have read up on earth leakage and got myself an earth leakage meter as there are a lot of recommendations that maybe the leakage is nearing 30mA throughout the house and it may be the hob/cooker are causing this to go over the threshold.

I've not had time to test everything throughout the house yet but I've measured the hob earth leakage and it's 5mA. Considering the whole house is limited to 30mA, this seems a bit high to me. What is the "normal" leakage for an appliance like this? I will test the cooker shortly too and I suspect that this could be "high" as since the cooker has not been connected at all, the RCD hasn't tripped with only the hob connected.

Any comments appreciated.

 

[telectrix]

Stoke is on my patch if you want expert (no crap from respected members allowed ) advice.

 

[telectrix]

Thanks, that's what I was looking for - an actual suggestion

So, get rid of the 100A RCD for 100A main switch and replace the MCB's with RCBO's?

that's an ideal solution, albeit expensive. what make is the board?

 

[Toneyz]

Thanks, that's what I was looking for - an actual suggestion

So, get rid of the 100A RCD for 100A main switch and replace the MCB's with RCBO's?

I would get the electrician to do this F.O.C. any electrical certificate been issued?

 

[maffoo]

that's an ideal solution, albeit expensive. what make is the board?

I'm at work now so don't have the info on that. Maybe get him to change it to a split load, so 2 x 80A RCD's?

 

[maffoo]

I would get the electrician to do this F.O.C. any electrical certificate been issued?

Yes, but not sure what's on it.

 

[telectrix]

if you go for a dual RCD board, you'll lose 4 ways. RCBOs are the way forward.

 

[Octopus]

Yes, I have paperwork. Again, what regulations does it not comply with?

If you believe the RCD tripping issue lies with the consumer unit installation quality then that's fine. Otherwise, I'm being led down the wrong path and still have a potentially faulty hob/cooker. When you guys have tested hobs/cookers/appliances etc. previously, what would expect the earth leakage to be? Is an item considered faulty if it's above a certain mA?

Best you review the results and let us know what the IR readings are

There is no way you can say its "fine"

No - impossible to state - unless of course its leaking over 22mA

and may I add with a MFT you can't test the RCD either

 

[maffoo]

if you go for a dual RCD board, you'll lose 4 ways. RCBOs are the way forward.

Is it possible/within regs to have 1x RCBO protecting just the cooker circuit and an RCD protecting the other circuits?

 

[Toneyz]

I'm at work now so don't have the info on that. Maybe get him to change it to a split load, so 2 x 80A RCD's?

I don't think that you have the room from what your previous posts have said.

 

[Octopus]

Is it possible/within regs to have 1x RCBO protecting just the cooker circuit and an RCD protecting the other circuits?

You've already stated that there is a space restriction.

Best you get the spark back who did the install to do some more tests and then advise you on how best to make the installation comply with the regs.

Personally I'm very doubtful a spark was involved ... but you could try and convince me

 

[Wilko]

Hi - it's possible to get RCD tripping with a combination of things and it's possible your cooker is the "last straw". I have seen a manufacturer advising to only connect their cooker via a dedicated RCD/RCBO...

 

[maffoo]

I don't think that you have the room from what your previous posts have said.

Unfortunately, I'm not in front of it now. I "may" have 1 way free on the unit. Thinking about it, I think that I have 1x 2P RCD and 7x MCB's.

 

[Octopus]

So you've got a new fuseboard plus at least 1 circuit - so not only should you have an EIC (electrical installation certificate) plus a Building Control Part P compliance certificate.

Here's hoping

 

[HappyHippyDad]

Is it possible/within regs to have 1x RCBO protecting just the cooker circuit and an RCD protecting the other circuits?

Not really Maffoo. No electrician is going to fit it this way for a main consumer unit. Also, it would be pretty irresponsible of any electrician to give you step by step instructions on how to do it properly as (no offence intended) it sounds like you may try and do it yourself and even though you may be able to get it working there is lot more too it than that.
My advice is to get an electrician to change the current configuration of the board to all RCBO's. If you wanted an RCD protecting some circuits and some RCBO's protecting others then it is doubtful your current board has the capability to do that as it will probably only have one neutral bar in it.

 

[Octopus]

So you've got a new fuseboard plus at least 1 circuit - so not only should you have an EIC (electrical installation certificate) plus a Building Control Part P compliance certificate.

Here's hoping

So @maffoo ............ a "dislike" - what for ......... pointing out the paperwork and compliance certificates you should have

Rather odd feedback IMHO