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Rockingit

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Just got back from a call-out, simple case of cooker taking the RCD out. A twin oven, seems in good working order so after a bit of a faff managed to get a clamp over the cpc at the switch (no idea where the house rod is!) and sure enough the bottom oven is leaking about 10mA when firing. So, after a bit of poking about decided it's most probably just tipping the balance on cumulative leakage from all over - only a 16th board and one RCD, with 2 x fully equipped home offices. Explained the schoolboy physics to them and all is well, told them to buy a new oven (just not worth the mending time) but both top and main running quite happily when I left.

Wasn't going to get into field stripping the oven to IR elements etc (has digital controls etc) as just not practical but if we reverse the maths based on 500v then it might have made around 50Meg, so theoretically would pass anyway. But I just can't shift this slight unease that I should have ripped it out?
 
...if we reverse the maths based on 500v then it might have made around 50Meg, so theoretically would pass anyway. But I just can't shift this slight unease that I should have ripped it out?

If there was 10mA leakage at 230v then the IR would be 0.023 Meg by calculation. The IR would probably be considerably lower at 500v.
 
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If there was 10mA leakage at 230v then the IR would be 2.3 Meg by calculation. The IR would probably be considerably lower at 500v.

Ah. Forgot the zero's division! That's what happens after working a 36hr day.

Would also explain that niggly feeling something was maybe close to the wind. I'm going back to do some other stuff for them anyway (always nice to pick up other jobs whilst you're there) so I'll make sure they do get that oven swapped.
 
0.23Megs might be borderline okay, what's the minimum IR requirement for appliances in the UK regs? The insulation might also improve when it heats up....that said it might also get worse though.
 
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Maximum protective conductor current, for a stationary, Class 1, appliance is 3.5mA. This may be doubled in certain circumstances, where the appliance has no control device other than a cut-out, a thermostat without an OFF position or an energy regulator without an OFF position, or all control devices have an OFF position with a contact separation of at least 3mm and disconnection in each pole.
Maximum protective conductor current, for a Class 1, heating appliance is 0.75mA or 0.75mA/kW, whichever is the greater, with a maximum of 5mA.
Certain heating and cooking appliances may initially unable to meet the maximum protective conductor current requirement, such as where metal sheathed, mineral insulated elements are used. It may be necessary in such cases to to switch the appliance ON for a period of time to drive off any absorbed moisture before conducting the test.
 
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its how do you fixit.. do you look for damaged parts???

You don't. You go to Currys. Or rather, they do.

By the time you've spent 3 or 4 hrs messing about and ordered in a new element, it would have been better for the client to have bought a new one. Not better for a sparky with gaps in the diary, admittedly.
 
Why can't you put the cooker on it's own RCBO? It will eliminate it from the rest of the rcd protective circuits.

No need to buy a new cooker just yet, gives the client a bit of funding time.

:thumbsup
 
Slightly lost on this one for the calculations.

For a 10mA current at 230V resistance should be 230/0.01=23kohms?
Maximum leakage for a class I heating appliance is 5mA or IR of 0.3Mohms.

You had 10mA so it is over but may well drop after running if the element is damp, so long as the IR problem is the element and not overheated wiring.
If the cooker is rarely used and the hob is often used a lot of damp about. Once you have run it for a bit should be OK as seems to be the case here, however definitely on its way out.

I may have been tempted to remove the control knob for the bottom oven and said just use the top oven! (whilst they arrange for a new cooker)
 
Is it a cooker or just a twin builtin oven?

If it's a cooker with solid hotplates, one's got a hairline crack in it.

If it's just ovens it could be the light glass cracked or missing.
 

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