Earth leakage woes pt 2

Sorry, 11.6 mA, though that would be stupid!

which part of BS EN IEC 60335-2?

e.g. I can find parts about washing machines, insect killers, sewing machines, etc etc ... nvm, looks like part 36, I've got it

for cord and plug connected appliances

for other appliances

Thanks! My understanding is that 9mA design leakage is the maximum for a 30mA RCD/RCBO. So how do you protect a cooker circuit adequately to reduce electrocution risk?

I couldn't find a copy of EN61009 floating around easily, but according to this flotsam from CEF:

Where Idn = earth leakage current rating. Therefore for a 30mA device the RCBO can acceptably trip out if it sees any current between 15 and 30mA. Generally Proteus RCBOs will operate between 20 and 25mA, however due to manufacturing tolerance and the nature of the sensitive magnetic sensing core this trip current can extend outside these designed limits to values as low as 17mA and as high as 28mA, still however within British Standard specification for performance."

So for your setup any 30mA RCBO on the dedicated cooker circuit should suffice.

I believe it's common to test RCDs/RCBOs for 0.5x Idn (shouldn't trip) as well as 1x/2x/5x, even if I think not all of them are required.

Theo

What do you mean by drying out?

Is there way you can move this onto it's own RCD or RCBO?

I had a similar problem recently and it may be a coincidence but I replaced a temperature controller that was U/S or simply through using it.

At one point I disconnected the earth to measure leakage directly. I also got a cheap megger but the problem mysteriously went away.

Not really without replacing the rather old consumer unit. Or perhaps by connecting a daisy-chained new box, but I have already got one of those for computers and freezers!

That makes good sense in practice, but ISTR reading some regulation, or advice derived from the regs, that said a circuit should not be designed with a leakage more than 30 percent of the nominal RCD trip current. IE 9mA for a

What I really want to know is, if I ring the manufacturer and say it is faulty, will they:

1. Say it is in spec;
2. Say that 7.6 mA is too high and offer to repair it;

or 3. (Most likely) refuse to discuss specs, send someone to look at it, and

Anyone any idea what the practical solution is, short of changing the consumer unit to one I can get RCBOs for?

How old is it? They probably regard elements as "wear items" ...

It's nothing to do with the elements. This is with none operational. It is one month old. If an element was leaking this much to earth unpowered it would probably fail dramatically switched on.

How do you know? If they're only switching the live to the elements there could still be neutral to earth leakage.

I suppose one way to test that would be to only wire the live and earth to the cooker and see if the RCD trips. Then wire only the neutral and earth to the cooker and see if it trips.

(don't touch the cooker while doing this, just in case anything unexpectedly becomes live when there's no neutral)

You could also try removing each element one by one to see if you can isolate the problem.

Theo

It's probably the filtering of the switch-mode regulator driving the electronics. Capacitors from live and neutral to ground.

Seeing it's only a month old I'd rather the seller of the cooker did that! The big difficulty I have is whether they would agree that 7.6mA earth leakage is a fault.

I agree, but my question is whether this is acceptable for cooker.

It seems that it probably isn't a fault, based on the mA/kW mentioned upthread.

Another thing you could do is run it with the earth disconnected to see if you can dry out the elements in order to reduce the leakage.

But, unless you can speak to the technical department they probably won't discuss specs on the phone, they'll just send somebody round to investigate.

However that person may decide it's a fault with your wiring (outdated CU, too many leakage sources sharing an RCD, needs a separate RCBO) rather than a fault with the cooker.

I think the bottom line is you either: a) try to resolve the fault yourself, eg by drying out the elements b) look at how to wire it on a separate RCBO (spare way in the CU, new CU, second slave CU, etc)

Theo

You're over-thinking this. The average buyer has no electrical knowledge and would just think that the oven was faulty. You should simply play dumb and tell the supplier that you think it's faulty because it keeps tripping the RCD (and ask "is there a fire or shock risk because of this?"). All this soshul meeja chatter is just causing delay and not solving the problem. The time to investigate further is if/when a replacement causes the RCD to trip.

How are you measuring this, and has the reading been confirmed as correct? Be aware that clamp type meters are not particularly accurate, and even when you do get a reading, there can be other influences that make that reading inaccurate. On a TNCS system, turning off the power to your house, then taking off the earth bonding can result in a spark - earth leakage from an adjacent property. I've seen this a few times when changing bonding cables. It was a bit of an experience when I first saw it, I thought the installation must have been live still, but on checking, it was all turned off.

Thanks! That's exactly the conclusion I had reached (except it's not the heating elements for reasons aforesaid - though it may well be the inverters for the induction hob) and I would be quite willing to pay an electrician to change the CU if I could find one round here who actually wants any work. It is not an attractive task, as the CPC wires in particular have been stretched ridiculously short, and might require putting all the cables in a connection box before the new CU if there is no slack on the cables. It is not totally beyond my skills, but doing it in a reasonable day's work may well be!

Done it twice, once with a clamp meter that claims 1uA resolution and once with a mA meter in series with the circuit earth. They agreed within 0.1mA, strikingly enough!

Agree about the earth bonding, and I would be disinclined to do the experiment of disconnecting it. Although there are only five houses on one pole transformer, that does not exclude neutral fault with one of them! There is a problem with another circuit leaking neutral to external earth rather than CPC, but this is not a problem with the cooker.