New Miele Oven causing main RCD to trip. :(

newbieneedshelp · 5 Nov 2009

Hi guys, Im after some advice and tbh Im at the end of my tether with this now. Im supposedly hosting a fireworks bash on Saturday night and thought it would be a great opportunity to also 'show off' our new kitchen/diner extension to our friends.

Its been finished a week and last night I thought I'd better try the oven out before I decide to shove 20 jacket potatoes on there on Saturday night!

Its a Miele pyrolytic oven which I bought from an authorised Miele dealer - it was installed in their show room and apparently has the full 2 year cover from Miele - I just need to register it.

The problem is - everytime I turn the oven on - within 2 mins (so not straight away), the 30a RCD in the main consumer unit trips and all the lights/sockets in the kitchen die.

I called my builder and am still awaiting a reply so Im asking for advice here.

Is it likely to be a faulty oven or is it likely the RCD rating would need 'upping'?

The oven was the only thing on at the time, appliance wise. The oven reported it had got the temperature upto 33 deg and then everything went off. I then tried boiling two big saucepans of water on the induction hob - no issue. Went to the oven - turned it to a 170 deg programme and within 2 mins it shut everything off again.

Im just hoping its not a major issue with the kitchen wiring and can be resolved easily and ideally, quickly.

As Im still awaiting a call back from the builder I'd really appreciate some advice.

Thank you,

Lee

holmslaw · 5 Nov 2009

JohnD · 5 Nov 2009

yes, good idea to call Miele.

But, in the meantime:

if the oven has not been used for a while, there is a possibility it is damp inside.

Just to check, the thing that trips is an RCD, with a "Test" button on it?

When the RCD trips, do any circuits go off except the kitchen? this is important. If you have got more than one RCD, and some circuits are on a different one, UNPLUG every other appliance on a circuit that goes dead (especially fridge, washing machine, dishwasher, kettle and computer, outdoor lights, outdoor sockets, fountain, aquarium etc, because "watery" appliance, and PCs, usually have a bit of earth leakage) and try to warm the oven up again. If it is a bit damp, heating it up will dry it out. The other problem with heating elements is that they tend to develop leakage with age, but that does not seem to be the case with you. Use a timer and see exactly how many minutes it takes - if it is always the same, it may be a fault in the cooker.

The problem you might have is that the oven has a small earth leakage (say, 10mA) and you have small leakages from other things, (totalling, say, about 20mA) and so the RCD will trip when they are all in use at the same time, but the Miele people might reasonably say that their oven is not making much leakage, so it isn't their fault.

mikhailfaradayski · 5 Nov 2009

Having took a moment to read what you typed, it does sound as though its the oven is faulty.
It may well be the thermostat as Holmslaw suggests, best to contact Miele. Either directly or via the shop that you bought it from.

newbieneedshelp · 5 Nov 2009

Thanks very much guys. Im suspecting issue with an oven directly and I guess I could ask and pay for the electrician to confirm this? I'll register the warranty details tonight and then get Miele called out.

BTW - the oven has never been used before, it was in a showroom display. Its also been sitting in place in our new kitchen for approx four weeks before being connected so I dont think damp is an issue and its an RCD specifically for the new kitchen that is going each time (located in the main unit under the stairs; the new fuse board in the kitchen deosnt trip anything out) - the rest of the house is unaffected at least but THANKS again.

Lee

bernardgreen · 5 Nov 2009

When the unit was on display do you know if it was connected, for example did any of the displays light up ?

If so then the internal wiring may have been altered to prevent any of the elements operating in the display area. If that internal wiring was not put back correctly then the fault you appear to have could be the result.

Not very likely but it has been known for ex-display items to be delivered with elements disconnected.

newbieneedshelp · 5 Nov 2009

bernardgreen said:
When the unit was on display do you know if it was connected, for example did any of the displays light up ?

If so then the internal wiring may have been altered to prevent any of the elements operating in the display area. If that internal wiring was not put back correctly then the fault you appear to have could be the result.

Not very likely but it has been known for ex-display items to be delivered with elements disconnected.

Thanks for the reply. The oven was certainly getting hot before tripping the RCD. As far as I can remember - it wasnt plugged in in the show room in anyway but I may be wrong.

riveralt · 5 Nov 2009

Hi there, I assume that the oven is on its own or part of the cooker circuit.
I take it that the MCB didn't trip at the same time as the RCD.

I say this because some Miele pyrolytic ovens are rated at 3.6kw which exceeds the 13amp rating of a standard plug and so should be on its own circuit and protected by appropriately sized cables and MCB.

You should find this information on the electrical installation certificate you will have been issued on completion of the new kitchen.

newbieneedshelp · 5 Nov 2009

riveralt said:
Hi there, I assume that the oven is on its own or part of the cooker circuit.
I take it that the MCB didn't trip at the same time as the RCD.

I say this because some Miele pyrolytic ovens are rated at 3.6kw which exceeds the 13amp rating of a standard plug and so should be on its own circuit and protected by appropriately sized cables and MCB.

You should find this information on the electrical installation certificate you will have been issued on completion of the new kitchen.

More great info - thanks.

Not sure what the 'MCB' is but nothing else tripped - the only thing that trips is the RCD in the main consumer unit that looks like it deals with the kitchen. The smaller fuse board that has all the kitchen items fused (which sits in a kitchen cupboard) doesnt trip anything when the oven 'dies'.

We have a Miele steam oven also installed (but not currently connected due to me loosing the three pin power lead (one thing after another....) and the kitchen fuse board has a fuse labelled 'ovens'. Induction hob is seperate, as are boiler, underfloor heating, internal lights, external lights (patio area) etc etc - they all have a seperate fuse in the new kitchen fuseboard - god, I hope as a total amateur Im making some sense!

Looking at the Domestic Electrical Installation certificate it states (regarding the oven supply) .....

F, A, A, 2 (no. of points served), 2.5 (live mm), 1.5(cpc mm), .4(max disconnect time), 60898 (bs), B (type no.) 20 (rating A), 6 (capacity kA), 30(operating current mA), 1.84 (max zs)..... .63 max measured earth fault, 34 (rcd operating times at 1 - ms), 11 (rcd operating times at 5)

IIRC the actual oven model is a Miele H 4681 BP KAT 60 cm pyrolytic oven

and the Miele info for this oven states:
voltage - 220 - 240
Rated load - 3.6
Fuse rating - 16

Thanks again,

Lee

riveralt · 5 Nov 2009

The figures given from the Electrical Installation certificate appear fine.
Assuming that the other items on the EIC such as continuity and insulation resistance are also correct and no one has altered the circuit since the EIC was issued then the circuit wiring appears okay.

Analysing RCD problems on site is difficult enough, doing it on the phone or internet near impossible.

I will assume that you followed the advice of JohnD regarding unplugging anything else on the circuit and measuring the time taken for the oven to trip.

A Portable Appliance Test on the oven may identify the earth leakage problem but since the oven is under warranty I would get Meile out - though be prepared for them to blame the circuit rather than the machine.

For your information the MCB (minature circuit breaker) protects the circuit from overcurrent problems caused by undersized cables against the load. Thus protecting equipment and hopefully preventing fire Whereas the RCD (Residual Current Device) constantly checks the difference in currents between the two live cables (line and neutral) and is there to hopefully prevent you or someone else receiving an electric shock.

newbieneedshelp · 6 Nov 2009

Thanks for the very informative reply.

When you say take anything else off the circuit - I assumed that as it had its own fuse (the marked 'ovens' in the fuseboard) that it meant it didnt actually have anything else on there - I thought this would mean there was a circiut put in specifically for these (remembering the 2nd oven, a steam oven, isnt yet connected)??

The electrician is coming back this afternoon to check over the appliance and any possible relating issue so thats great - its unlikely to be running for Saturday but I least I can get it confirmed by him and then go to Miele with a solid case in saying its the oven at fault.

Im not sure how good Miele appliance support/repair are but I always expect the worst from companies agter they have had your money

Thanks again for the help guys, all the best,

Lee

bernardgreen · 6 Nov 2009

The shop you bought it from is the place that has provide you with items for purpose so if it is defective your first contact is them who should refund the purchase price or replace the item with one that is fit for purpose.

Miele were very helpful to a neighbour who had difficulties getting an appliance satisfactorily installed when the kitchen fitter did not have the necessary to do the job properly.

JohnD · 6 Nov 2009

newbieneedshelp said:
When you say take anything else off the circuit - I assumed that as it had its own fuse (the marked 'ovens' in the fuseboard) that it meant it didnt actually have anything else on there

That is partly true, and it is good if you have a dedicated oven circuit with no other appliances on it, but if it is the RCD that is tripping, therre may be (usually are) several circuits running off one RCD. You need to remove all the other loads from that RCD by unplugging them. Switching of at the wall or the MCB is not good enough, except in the case of fixed applianced with a dual-pole switch.

newbieneedshelp · 10 Nov 2009

Really weird one this.

The electrician came back but didnt have his multi meter in the van (it was a Saturday, passing visit as a favour to my builder!) so cpuldnt look specifically at the oven issue.

(I have a feeling my builder had actually forgot to mention the oven issue to him....)

He swapped a fuse in the kitchen board to rectify a lighting issue - a 6a to a 10a as on three occasions the fuse has tripped due to me powering on all the lights (14 x 50w mains, undercabinet led, plinth leds and an led 9 metre strip around the skylight) but since he has been in to do that - the oven has worked fine!

I dont understand it as they are indelendant circuits and have nothing to do with each other. Im guessing it will now become an internittant problem possible but all I know is it killed the RCD a total of three times - every time it was asked to heat up to 175 degrees or similar and last night I set it to 180 degrees and it cooked the fish, fishfingers and chips perfectly for the 25 minutes needed! No issue whatsoever!

Im keeping my fingers crossed its cured itself

but I do have the two year Miele warranty to fall back on if need be.

Thanks again for all the advice,

Lee

Aragorn84 · 10 Nov 2009

700w of lighting....

You could light half my street with that!

Also fitting a 10A fuse probably doesnt comply with the regulations, as the switchgear and fittings are only rated to 6a.

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New Miele Oven causing main RCD to trip. :(

holmslaw

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