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.

 

[DPG]

I think he's gone now.

 

[Dave OCD]

We seem to have a few lately who know better than a bunch of professionals with hundreds of years experience between them. A genuine offer of top quality help seems to scare most away with the awful fear of having to actually pay someone, or so it seems.

 

[GMES]

We've got 100 of years experience with @telectrix alone.

 

[telectrix]

We've got 100 of years experience with @telectrix alone.

is that before or after evolving from an ape?

 

[Dave OCD]

That's a bit harsh, maybe 150 between Tel and Pete though.

 

[GMES]

is that before or after evolving from an ape?

My comment was payback for the couple of ape jokes you've been subtly dropping over the last couple of days.
I'm always watching, even if you can't see me.

 

[Harry_P]

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.

Thank you and all of you for the information, which complied with the "be nice" rules

Just to be clear, I have no intention of messing with the consumer unit myself. Never have and never will - which is why I'm still alive at 40 Whilst I'm confident with most DIY projects, this is something I will leave to the professionals. This has come about out of my natural curiosity and the need to investigate.

It now seems likely that I've had the cooker replaced for no apparent reason

Sounds like it could be an issue with the cooker isolator and could be a loose connection or faulty contacts within the switch. As you already know now,replacing the cooker first was a mistake

 

[Toneyz]

Sounds like it could be an issue with the cooker isolator and could be a loose connection or faulty contacts within the switch. As you already know now,replacing the cooker first was a mistake

I think he was having a new IKEA cooker anyway.

 

[Devonchris]

It now seems likely that I've had the cooker replaced for no apparent reason

 

[Peter Buckby]

Might sound daft,,,but we had trouble once with brand new cooker elements,,the manufacturers suggested that we put them in a oven and heat them up,because of dampness that they sometimes get,,

 

[dave274]

Who goes out and buys an earth leakage tester rather than call an electrician? also he uses too many correct terms and knows too much to not be involved much more than he's letting on.

 

[DPG]

I'm with 274.

 

[chrisdungan]

1 RCD there's your problem.
New cooker? the elements will have absorbed moisture = high leakage which combined with the combined leakages of the other circuits is 100%guaranteed to trip the solo RCD.
Solution fit at least another RCD. fit narrow MCBs to make room for extra narrow RCD, not ideal but there you go

 

[Toneyz]

Solution fit at least another RCD. fit narrow MCBs to make room for extra narrow RCD, not ideal but there you go

Please explain! I've not got a clue what you are on about the OP has limited space the C.U is fitted with an RCD as the main switch (not compliant). If there are no faults to be found on the installation then more than likely it is communitive leakage currents, therefore, change the RCD to a main switch and fit RCBO's.

 

[oracle]

Surely instead of all or nothing approach, why not a mix of MCB's and RCBO's as appropriate? But the sum total of leakage is a concern