Cooker DP switch tripping RCD

[Fidget7]

Hi guys,

First post on here, though I've been reading the forum for years. I'm looking for a bit of advice with a frustrating problem.

Recently had a new kitchen fitted, including an induction hob and electric single oven.

I deliberately selected a 3kw induction hob and a 2.5kw single oven so that they could both run on the existing 45A cooker ring.

I've got a flat plate 'black nickel' 45A DP cooker isolation switch with led's mounted above, with the appliances correctly wired into a cooker connection unit below the worktop.

We always switch the cooker wall plate switch off at night. I know there's probably no need but for peace of mind we do.

Problem is that every so often (about one in 20 times) when switching the cooker wall plate on the next day, it trips the rcd in the consumer unit.

It's frustrating and I cannot find the cause. All wiring is sound. Connections are sound. Consumer unit is fairly new (about 3 years), just can't see what's tripping it. I wonder if its because the Mrs sometimes turns the oven knob on before flicking the cooker power switch?

Could it just be the switch, i.e slight leakage neutral to earth as the switch is thrown?

Anyone had this? It's not big deal, just a pain in the backside having to go and reset the consumer unit when it happens!

Grateful for any advice.

 

[RF Lighting]

Sounds like a bit of a poor contact when the switch is closing. You could try a different switch for a bit and see if the problem disappears.

 

[Fidget7]

Sounds like a bit of a poor contact when the switch is closing. You could try a different switch for a bit and see if the problem disappears.

Thanks - good idea. I didn't think of that.
I've still got the old white plastic switch in the shed, may chuck that on (wont look as nice!) for a while and see if it happens with that.

Trial and error I guess, always worth a go!

 

[Taylortwocities]

Is it really the RCD that is tripping, or an MCB?

 

[JohnW2]

Sounds like a bit of a poor contact when the switch is closing. You could try a different switch for a bit and see if the problem disappears.

I often hear such suggestions, but have you any idea how that could cause sn RCD to operate (particularly when, as is presumably the case here, little or no current is being switched)? I personally really can't think of a mechanism that could cause this to happen.

Kind Regards, John

 

[Fidget7]

Is it really the RCD that is tripping, or an MCB?

Yes, apologies for getting it wrong, it is indeed the MCB that trips, not an RCD.

Effectively the consumer unit has a section covered by the MCB and when the cooker trips, so too does everything else in this section.

 

[333rocky333]

If the whole section goes off then as you said earlier it is an RCD

 

[JohnW2]

Yes, apologies for getting it wrong, it is indeed the MCB that trips, not an RCD. Effectively the consumer unit has a section covered by the MCB and when the cooker trips, so too does everything else in this section.

If the whole section goes off then as you said earlier it is an RCD

This is obviously getting a bit confusing but, frankly, regardless of whether it is an MCB or RCD, I can't really think of a mechanism whereby operating a switch (even one with faulty contacts, unless they were resulting in a fault to earth) which was interupting little or no current could cause the device to trip.

Fidget7 ... this thing which is tripping, does it have a 'test button' on it?

Kind Regards, John

 

[Fidget7]

If the whole section goes off then as you said earlier it is an RCD

Okay, I confused myself!

The section covered by RCD (not MCB) all trips when the switch cooker trips!

A switch issue or a fault elsewhere? Or...as was suggested to me by a friend... A very sensitive consumer unit?

It seems to me that the answer might be just to leave the switch on all of the time although the Mrs is paranoid one of the kids might switch the hob on (even with the safety features of induction)

 

[Fidget7]

Yes, apologies for getting it wrong, it is indeed the MCB that trips, not an RCD. Effectively the consumer unit has a section covered by the MCB and when the cooker trips, so too does everything else in this section.

If the whole section goes off then as you said earlier it is an RCD

This is obviously getting a bit confusing but, frankly, regardless of whether it is an MCB or RCD, I can't really think of a mechanism whereby operating a switch (even one with faulty contacts, unless they were resulting in a fault to earth) which was interupting little or no current could cause the device to trip.

Fidget7 ... this thing which is tripping, does it have a 'test button' on it?

Kind Regards, John

Yes indeed, there is a test button..

 

[JohnW2]

Okay, I confused myself! The section covered by RCD (not MCB) all trips when the switch cooker trips!

Thanks for clarifying.

A switch issue or a fault elsewhere? Or...as was suggested to me by a friend... A very sensitive consumer unit?

Hard to tell. Although, as I've been saying, it's hard to think of a mechanism for the switch being to blame (unless operation of the switch mechanism is somehow resulting in a temporary short to earth), nor should an RCD (no matter how 'sensitive') trip as a result of a healthy switch being operated.

It seems to me that the answer might be just to leave the switch on all of the time although the Mrs is paranoid one of the kids might switch the hob on (even with the safety features of induction)

I wouldn't really advise that, not only because of the kids, but also because it's just possible that something (which could get worse) may be going on in that switch. Swapping temporarily back to the old, plastic, switch, as you sugegsted, ought to give some sort of answer.

Kidn Regards, John

 

[Fidget7]

Thanks for your thoughts on this John. I think that I may well swap back to the old switch for a couple of weeks and see what happens. If its not tripping with the old switch then its plain where the fault lies. If it carries on, then further investigation required

Thanks again.

 

[JohnW2]

Thanks for your thoughts on this John. I think that I may well swap back to the old switch for a couple of weeks and see what happens. If its not tripping with the old switch then its plain where the fault lies. If it carries on, then further investigation required. Thanks again.

That sounds like a reasonable plan. Make sure you do the switch swapping safely.

Kind Regards, John

 

[333rocky333]

I assume theres electronic bits in these ovens, I sometimes wonder if its because double pole switches and devices, again i assume, are built to switch L and N supposedly at the same time and that occasionally the N makes later than the L.
Somehow causing the rcds to trip but dont ask me why.

In the same way as why some rcds wont switch on under load

 

[JohnW2]

I assume theres electronic bits in these ovens, I sometimes wonder if its because double pole switches and devices, again i assume, are built to switch L and N supposedly at the same time and that occasionally the N makes later than the L. ...

I think you'll find that a good few DP switches are designed so that L and N do not switch simultaneously but, whatever ....

Somehow causing the rcds to trip but dont ask me why.

Quite- and don't ask me why, either - because, as I've already said, I can't really think of a 'why'. Let's face it, even a SP switch (i.e the N never being switched) should not result in an RCD trip, so I don't see why a DP one with a slight difference in L and N switching timing should!

Kind Regards, John