???
Not suggesting that
Merely that leakage current as measured at the CU tails is going up by c8mA when the kettle is used because the kettle is directly responsible for that leakage current, and it's not because the load is increasing.
- Thread starter meerkatmag
- Start date
Not suggesting that
Merely that leakage current as measured at the CU tails is going up by c8mA when the kettle is used because the kettle is directly responsible for that leakage current, and it's not because the load is increasing.
meerkatmag
DIY
Yeah checked my daughters (new) hairdryer. 5ma at the plug, 5ma extra at the cu. So does seem to tally. If a single device can create 5ma leakage or even 8ma for the kettle then surely my readings of 15ma leakage current at base level is fairly normal? Turning my computers on seem to cause a spike of around 10 to 15ma so causes trip. Does this all sound normal then? Is it just to be expected? Can't be every device in my house is faulty so these amounts must be normal????
Not suggesting that
Merely that leakage current as measured at the CU tails is going up by c8mA when the kettle is used because the kettle is directly responsible for that leakage current, and it's not because the load is increasing.
I like the sound of earth neutral fault, something concrete to investigate. I guess I need an electrician to do better tests.
Every "electronic" device that involves switching power supplies, or even 'mechanical' switches, is fitted these days with a filter to prevent electromagnetic interference. It's a requirement of the ElectroMagnetic Compatibility standards that devices must comply with to earn the dreaded CEUK or equivalent mark, to be legitimately put on the market.
The filter includes capacitors across the mains, and from each supply wire to ground. This results in a small current to earth, which may be a few (or more!) mA.
Just one big ring and a kitchen ring, in a big house, with multiple devices, chargers, appliances, all relying on one or two rcd's, I would say could be a problem itself, not necessarily the wiring.
An electrician could easily check the fixed installation with a high voltage Insulation Resistance tester to prove the wiring wasn't contributing to the mA leakage. But you could do a crude check at the meter tails, by literally pulling out all plugs, switching off spurs etc etc, to see if there is a residual current.
Out of interest, is this hairdryer a class 1 or class 2 item? Class 2 would have a 'square within a square' symbol somewhere on it, and possibly (though not definitely) a plastic earth pin on its plug.
meerkatmag
DIY
Got the square within a square symbol, see attached. So class 2? And yes plastic earth. So how could there be earth leakage? I'm confused by that. Is my clamp meter wrong?
Attachments
meerkatmag
DIY
I'd love to get each floor separated into separate rings with rcds integrated into each breaker. Maybe that would be the solution. It's going to be really expensive job though.
I did find once some very old wiring with cloth insulation in a ceiling light fitting. That was replaced but it's not impossible there would still be some in other places.
I'll try to do the check you suggest checking for residual current.
I have a very similar clamp meter to yours, probably the same one re-branded. Whilst it has its uses, I'm not convinced of its accuracy at mA resolution. I suspect it falsely reads a certain amount of leakage, roughly proportional to the amount of current flowing through the clamped conductors, even where there is no actual leakage to earth. For this reason, I seldom use it for fault-finding in this way.
If I were asked to fault-find this problem, I'd start with an insulation resistance test, then perhaps RCD ramp tests under different loads, then look at the possibility of a faulty RCD.
how are you checking this earth leakage? as in what conductors are you clamping.
most neutral to cpc faults cause instant trip of any (RCD) Residual Current Device ,however a double insulated device cant put current down a cpc.
is there any outside equipment may have got wet ?
most neutral to cpc faults cause instant trip of any (RCD) Residual Current Device ,however a double insulated device cant put current down a cpc.
is there any outside equipment may have got wet ?
You could consider splitting the ring finals using rcbos
I feel I may well be missing something here (Or just not read the thread thoroughly), but... Isn't it simply that there is too much earth leakage and the single RCD trips? Or even if it's a dual RCD, it may well be too much? A 30mA RCD trips at anywhere between 19mA and 23mA usually.
If it's an RCBO board then I'd be thinking more a N-E fault.
What Consumer Unit do you have @meerkatmag . Single RCD, Dual RCD, RCBO's? A picture would be great.
If it's an RCBO board then I'd be thinking more a N-E fault.
What Consumer Unit do you have @meerkatmag . Single RCD, Dual RCD, RCBO's? A picture would be great.
Right at the start @HappyHippyDad the OP said there was 2 RCDs… so a dual RCD board.
Money is on just too much “normal” Earth leakage across several circuits.
Everything tests fine, but cumulative leakage knocks it over.
It could be possible that continual trips have weakened the rcd…. So a 30mA rcd that would normally trip at 19 to 23 like you say, may be as little as 10mA if faulty.
RCD tester with ramp test would confirm.
Money is on just too much “normal” Earth leakage across several circuits.
Everything tests fine, but cumulative leakage knocks it over.
It could be possible that continual trips have weakened the rcd…. So a 30mA rcd that would normally trip at 19 to 23 like you say, may be as little as 10mA if faulty.
RCD tester with ramp test would confirm.
meerkatmag
DIY
Hi thanks for all the help by the way!
It's a dual RCD CU by Harok. We had this fitted about 10 years ago but the house wiring wasn't changed at the time. Wiring in house is old Red/Black easily 20 or more years old.
The RCD started tripping randomly right after the CU was fitted 10 years ago and has got gradually worse over the last 10 years. Possibly because we have modernised the house and fitted more electronics. The kids have grown up and now have computers etc. The problem was improved greatly by moving as many devices from the house Ring to the Kitchen ring. Spreading the load more evenly between the two. I moved the washing machine/dryer and freezer to the kitchen ring and that made a huge reduction in random trips.
Since then it mostly only trips when you plug in a high power device, especially multiple devices using a 4 gang all at once. So the idea that it's just too many devices on a large ring and/or an old weakened RCD does sound likely.
I've been doing more tests this morning and as far as I can tell everything seems to be reasonably normal. I've been using the hairdryer to test earth leakage. As I know this device doesn't have an earth it literally can't leak. I think my earth clamp is inaccurate as previously stated. The higher the overall current going through the wires the more leakage it shows. I've tried using the meter just on the earth cable from the CU and this seems more consistent.
With this setup I get about 2 to 3 ma leakage from the hairdryer. About 10 to 15ma of base level leakage with average house load all on (that's across both RCDs). Interestingly if I turn everything off (breakers/RCDs/Main) I still get about 2ma of current in the earth cable. Is that normal? As I turn the breakers on - the current actually drops in the earth cable, before devices start turning on and it returns to higher amounts. Is that the capacitors draining to earth after losing power maybe?
Are these two ring finals protected by the same RCD?
A picture of your consumer unit might help.
A picture of your consumer unit might help.
meerkatmag
DIY
each ring is on a different RCD. Pic Attached
Attachments
Meerkatmag
You ask some questions in your posts that I'm afraid we don't always respond to.
You might be interested to look at the paper below on RCD selection and testing. A bit technical, but gives some idea of 'normal' leakage values and what should be the aim in design.
Also shows some waveforms, drawing attention to the complexity of this subject, and why a more basic tester would not give "true rms" accurate results.
Only if you're interested, i'm not trying to make a point, other than I suppose that to make sense of measurements in this domain, one probably needs accurate calibrated specialist test equipment!
You ask some questions in your posts that I'm afraid we don't always respond to.
You might be interested to look at the paper below on RCD selection and testing. A bit technical, but gives some idea of 'normal' leakage values and what should be the aim in design.
Also shows some waveforms, drawing attention to the complexity of this subject, and why a more basic tester would not give "true rms" accurate results.
Only if you're interested, i'm not trying to make a point, other than I suppose that to make sense of measurements in this domain, one probably needs accurate calibrated specialist test equipment!
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