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#216518 - 12/27/15 07:31 PM I REALLY hate RCDs
annemarie1 Offline
Member

Registered: 03/16/15
Posts: 44
Loc: england
My mum was just getting ready to cook the roast veg for Christmas dinner she switched on the oven and the RCD tripped its the second time its happened I was able to re set it after I switched off a filtered plugstrip on the same circuit I know its all down to leakage but could the plugstrip be affected by switching on the oven? The RCD is 32 amp rated and 30mA trip current

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#216520 - 12/27/15 08:44 PM Re: I REALLY hate RCDs [Re: annemarie1]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8530
Loc: SI,New Zealand
Hang on a second there.
I thought that ovens were supposed to be on their own dedicated circuit, fed direct from the Consumer unit?
What I mean is, why is there a plug-strip connected to a 32 amp circuit in the first place?

While I'm not totally conversant with the Wiring Regulations in the UK, but I would have thought that an RCD was not necessary on something like an oven, owing to it being a stationary appliance.

Over here in NZ, we don't put ovens or refrigerators on an RCD, mainly due to the heating and cooling of the appliance causing nuisance tripping due to possible moisture build up and this in turn lowers the internal insulation resistance and causes the RCD to trip.
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#216536 - 12/28/15 05:45 AM Re: I REALLY hate RCDs [Re: annemarie1]
AdrianW Offline
Member

Registered: 05/23/11
Posts: 10
Loc: Nottingham, UK
Large, free standing electric cookers (Ranges) do need to be on a separate 32A radial circuit.

Annemarie1s' mums 'oven' could be just a single built-in oven (no cook top). These often have a rating of around 2.4kW @ 230V and come fitted with a 13A plug. They are intended to be plugged into the general kitchen ring final just like anything else.

Alternatively, it could be a 'full size' cooker connected to a dedicated 32A radial using a 'cooker control unit'. These often incorporate a 13A aux socket (in days of old, that could well have been the only 13A socket in the kitchen) so the plug strip could be plugged into that...

A third alternative is that the house has only the one RCD and that is the main switch. Not really upto code anymore but thousands of installs like that (including mine).

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#216537 - 12/28/15 06:08 AM Re: I REALLY hate RCDs [Re: annemarie1]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2331
Loc: Vienna, Austria
In areas with a TT supply it's been common practice to slap everything on a whole-house RCD for ages and the most common nuisance tripping issue was lightning (transients) by far. These days OVE requires at least two RCDs for domestic buildings but I still see new homes with one RCD for everything. Our flat was last renovated quite some time ago so we only have one RCD and TBH I can't remember the last time it tripped.

Was the power strip by any chance a surge protector strip? These usually have varistors wired from line and neutral to earth and when they blow due to a surge they trip the RCD.

Neutral earth faults in fixed wiring are where it gets interesting...

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#216545 - 12/28/15 11:06 AM Re: I REALLY hate RCDs [Re: annemarie1]
annemarie1 Offline
Member

Registered: 03/16/15
Posts: 44
Loc: england
Hi just to clear a few things up yes the oven is rated at 2.2Kw and came fitted with a 13 amp plug which plugs into a socket shared with the gas hob ignition circuit. Another socket is for the freezer and then 2 doubles in the lounge for the electric fire some lights and a filtered surge protected power strip for the house phone and interweb thingy. The trip occurs when just the fan and internal oven light come on but before any heaters are switched on

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#216546 - 12/28/15 11:07 AM Re: I REALLY hate RCDs [Re: annemarie1]
annemarie1 Offline
Member

Registered: 03/16/15
Posts: 44
Loc: england
Oh should of said the strips fine its still working OK. Holly never smelt any nasty burning smells and she's got a real sensitive nose

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#216549 - 12/28/15 02:01 PM Re: I REALLY hate RCDs [Re: annemarie1]
Texas_Ranger Offline
Member

Registered: 12/17/01
Posts: 2331
Loc: Vienna, Austria
Interesting... could be that the surge protector strip has a constant fault current of 10 mA or so and power filter caps in the oven or something like that add enough current to trip the RCD. It'd be interesting to plug that power strip into an appliance tester or clamp an amp meter to its earth wire to see how much leakage it has. Remember, 30 mA RCDs are supposed to trip anywhere between 15 and 30 mA!

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#216551 - 12/28/15 03:01 PM Re: I REALLY hate RCDs [Re: annemarie1]
annemarie1 Offline
Member

Registered: 03/16/15
Posts: 44
Loc: england
That could be it I will try to borrow a clamp meter and see how much the strip is passing to earth I suppose if one of the MOVs is getting a bit tired it mite be leaking more than it should and as you say if any caps in the oven are passing current it isn't difficult to exceed 10 mA

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#216568 - 12/29/15 04:26 AM Re: I REALLY hate RCDs [Re: annemarie1]
Trumpy Offline

Member

Registered: 07/05/02
Posts: 8530
Loc: SI,New Zealand
Originally Posted By: annemarie1
Hi just to clear a few things up yes the oven is rated at 2.2Kw and came fitted with a 13 amp plug which plugs into a socket shared with the gas hob ignition circuit. Another socket is for the freezer and then 2 doubles in the lounge for the electric fire some lights and a filtered surge protected power strip for the house phone and interweb thingy. The trip occurs when just the fan and internal oven light come on but before any heaters are switched on

2.2kW you say?
Do UK Ovens no longer have a higher rated Grill element at the top rated at about 6-7kW?
_________________________
Let's face it, these days if you're not young, you're old - Red Green grin

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#216569 - 12/29/15 07:41 AM Re: I REALLY hate RCDs [Re: annemarie1]
annemarie1 Offline
Member

Registered: 03/16/15
Posts: 44
Loc: england
Hi I don't think any grill is that powerful as far as I know even the largest cookers were only about8 Kw total though normal one were about7.2 Kw that's 30 amps at 240 volts which is standard cooker circuit size. I think there's a general trend away from cookers as one unit and instead they are oven and hob separated usually gas hob and electric oven

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