Here's a bit of an old chestnut - but with a responsibility angle.
My girlfriend lives in a Housing Authority house. Those nice people have done a bit of updating, including the consumer unit.
Now, when she puts the washer on, the CU frequently trips. The housing authority say, it's her appliance(s). She says it didn't happen before.
I was thinking of measuring the current in the appliance earth cables
- suspecting capacitors included in radio interference suppression components ???
I was also thinking of changing the RCD from 30mA to 100mA. I think that is legal and would likely stop it ???
By the way, I think that a 30mA trip could just about prevent a lethal shock, wheras 100mA would not. [I don't really fancy the "responsibility" of changing a "safety" component in a rented house.] But (at least to me), a 30mA RCD seems to offer NO protection against:
right hand on live.
left hand on neutral. i.e. current through the heart, not shoes to earth when wearing seriously insulating shoes (eg rubber soled trainers).
Well if there wasn't an RCD then it could not have happened;!"..
DO NOT do this you'd be leaving yourself open to all sort of liabilities.
An 30 ma RCD should work fine in domestic environments even with dishwashers and the like on the go .. Theres one on our gaff thats fine and in some others we have all ticking just so.
Its quite possible that they might have an obscure earth to neutral wiring fault or indeed her machine could be playing up it needs someone who knows what their doing and regretfully a lot of sparks don't understand quite how RCD's work and nuisance trip.
But just don't change it yourself grumble and complain is the best bet..
If you find no trips with a large other load on the RCD protected circuits then its not likely to be a wiring fault. If it only plays up when her washer on then its likely it has a faulty heating element...
I'm NOT going to - it was just a passing thought as a "brute force" way to stop this. I agree I definately don't want the liability of changing a safety related component on a house I don't even own.
I will do some checking though on earth current on a few appliances.
The wasing machine would apear to be the culprit from what you have told us. Not sure how you intend measuring leakage current though.
You may well see the leakage safely by unplugging it and measuring the resistence on a multimeter between the earth and live and/or neutral pins of the plug, If the reading is less than in than 1 Megohm, then you can try to isolate suspect components of the machine.
I would try the following main motor (carbon debris on brush carrier tracking to metal frame) pump (close to moisture) heater element (same reason)
The programmer usually only switches single pole (live) the heater's neutral will still be connected and the RCB isn't fussy if the leak is N-E so it will still trip. Don't you agree?
Which can be true, but it does not disprove there being a fault that was undetected before.
Not that easy to make direct measurements. A high sensitivity clamp meter would probably be your best bet.
No, this would not be legal. The 17th edition wiring regs require 30mA RCD protection. It may stop it.
This is generally true. 100mA trip devices are more for equipment and installation protection rather than personal shock protection. See:
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[I don't really fancy the "responsibility" of changing a "safety"
Indeed.
Agreed, there are a bunch of scenarios where the RCD will offer no additional protection. However there are also plenty where it can make a significant difference.
For details on RCDs and how to trace these types of trips see:
I was sort of assuming the leakage - if the heater element - got worse as it heated up. If not, I'd expect it to be fairly constant and therefore not cause an intermittent fault. But like all these things it's only a guess.
Likely to be a wahsing machine fault, with most likely culprits being heating element & carbon dust on the motor. Probably worth leak testing all the appliances with a multimeter on high R range. Unplug and check R from L&N to E, and look for any with less than stellar insulation resistance.
Mucking about with the CU isnt the best plan. RCDs reduce a lot of shocks, but as you say not all.
Very true. We moved in and didn't use the oven for over a year. When the guy came to check my new wiring, he found excessive earth leakage on the circuit. He connected anyway, ran the oven for a bit and then it was fine.
Our previous house had a TN-S earthing arrangement, neutral was usually floating about a couple of volts above earth. I could guarantee to trip the RCD by shorting N-E, even with the circuit fuse removed from the consumer unit, so no current flowing there.
We've got a TN-C-S system in this house so the same problem doesn't arise.
Interesting problem; so this post respectfully offers a side comment. Sounds like the RCD maybe 'too sensitive'?
Here (In this part of Canada) RCD type breakers are coming into use; especially for new installations under revised codes.
However for quite a while now individual (duplex) outlets equipped with RCDs have been recommended and also fitted extensively to existing installations. We have several locations where we have added them. We have two more that will be added shortly to this house which was wired 38 years ago in accordance with the then codes that didn't even mention RCD/GFIs!
Here the RCD type outlets are called GFI (Ground Fault Interruption) outlets, the 'ground' something of a misnomer since they operate on the unbalance of currents in the neutral and live wires; similar AFIK to how an RCD operates. But the idea seems to be that, like RCDs, it protects for currents to ground through a human body and this is what would cause the unbalance and rapidly trip the circuit.
GFI (RCD outlets) can be wired to 'protect' just themselves or; themselves and all other outlets 'down stream' of them on our radial type domestic wiring. (Ring mains not used!).
These GFI are either recommended or now mandatory for any outlets in damp/outdoor locations etc. Garden tools, garages, our bathroom etc. However; and this is the point of this comment, they are NOT RECOMMENDED for any appliance that has an electric motor (with possible exception of lightweight counter appliances such as a food mixer, blender etc.) . They are not to be used for fridges, freezers etc. because a) Possible unbalance currents as the motors start up can trip the GFI/RCD. b) Also a not working fridge/freezer can cause food spoilage. Fridge motors probably smaller and lower HP than a washer?
So respectfully suggest that it may be the unbalance due to a motor starting that may be causing the RCD breaker to trip? Not sure if that's a potential fault or leakage or the ground and neutral at the washer in contact with each other?????? Is it kosher to try reversing live and neutral at the washer? Maybe not cos the switch will, should be, be in the live wire????
Anyway the point is that it seems to be 'well known' over here (North America) to not use GFIs on any motor equipped appliance circuits.
For what this is worth all the best for this season. Cheers.
They can be too sensitive in two ways... one being a faulty unit that trips below its anticipated tripping current, or one that trips when it should do, but your appliance / circuit has more than expected leakage.
"duplex" is what we would call a "double socket" I take it?
Yup, here RCDs have been mandated for any circuit which is likely to be used to power equipment outside for some time. Recent changes to the regulations require their use on additional circuit types as well - such that RCD protection will become common for almost all circuits)
Yup - the same as our RCDs
Indeed - that is one of the occasions we use RCDs. They are also used where it is necessary to protect a circuit and the earth fault loop impedance (i.e. the round trip resistance from supply line to earth) is too large to reliably trip the circuit protective device. This scenario is commonly seen where there is no earth/ground provided by the power company, and a local earth spike is used instead.
You can get sockets like this here - although they usually don't have the capacity to protect additional sockets (they would obviously be incompatible with ring circuits). These can be retrofitted to older installs to provide a safe socket to power garden equipment etc. More commonly, the RCD is fitted at the consumer unit (fuse board/box) on modern installs.
Our regs have not allowed sockets in bathrooms at all until recently. They still preclude them in small rooms since there are minimum distances between baths etc and a socket if fitted.
Motors are not usually cited as typically causing problems with RCDs here - although when a RCD is already loaded very closely to its tripping current, any power surge (as may be caused by motors starting) can push them over the edge.
With regard to Fridges/Freezers (and anything else you don't want tripping like the central heating, or your tropical fish tank etc)), it advisable to place these on dedicated circuits without RCD protection (or with their own dedicated RCDs). (we have devices called RCBOs which are circuit breakers and RCDs combined into a single unit - quite handy for fitting to circuits like this)
Indeed, you should not reverse the L/N connections for the reason you highlight. The common RCD trip mechanisms in washers tends to be either internal leaks that are allowing the electrics to become damp, or a heating element that is close to its end of life - the mineral insulation can become damp and conductive and hence result in enough leakage to cause a problem. Regular usage however can mask the fault by keeping it dry enough to not trip.
What trip rating are your GFIs usually specified at? (30mA is typical for our RCDs that are intended to protect against shock).
I also have a feeling that the standards to which RCDs are designed also requires a certain amount of harmonic noise interference rejection to mitigate problems caused by switch on/off surges.
And to you also! (only six hours to christmas this side of the globe!) ;-)
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