Electrical advice: Washing machine tripping RCD

[charles]

but very rarely if it's unplugged

[Bob Eager]

Well, he also said: "The strange thing is that I've left the washing machine unplugged and yet the RCD still tripped a couple more times"

I think so too! There is something very marginal, and the WM may have a minor leak (e.g. heating element).

[The Natural Philosopher]

almost any load that puts a momentary pulse on the mains will add to leakage current via RFI caps that are effectively between live and earth.

If you have a neutral/earth short the trip will be acting more like a current trip anyway. Anything wiill tip it over the edge.

[tony sayer]

In article [e-mail], [e-mail] scribeth thus

Some appliances around the house have a bit of earth leakage thats when the Live line supply is going back to the neutral at the substation end via a path other then the neutral supply.

The principal of the RCD is to monitor the current IN on the live incomer and then OUT on the neutral no matter what the overall actual current is, its the balance between them, current flowing in MUST be the same as that going OUT on the neutral line any that's not the same i.e. leaking to Earth and NOT returning via the Neutral line it will if it exceeds the trips rated tripping level then the trip will just go on a trip;!

So in your instance there is likely to be a bit of equipment thats got some leakage, it might be say around 20 milliamps now thats below a 30 milliamp RCD so all's well.

Now add in something else thats got some leakage say its a bit of gear like a washing machine thats got say 15 milliamps "ma" for short! Then you can see that added 20 and 15 makes 35 which is now in excess of the trips rated current - not good!..

Some PC gear can and does have a small amount of leakage many PC's all on the same circuit can cause tripping. However in a domestic situation Cooker hotplates, Immersion heaters, heating elements in washing machines, same in dishwashers, motors in washers anywhere where water can get into the electric's will cause leakage.

One other real PITA with trips is the Earth Neutral short this doesn't immeaditly cause a trip its the same principal live in must equal neutral out here the neutral is connected to earth so some current is leaking away Via earth instead of the neutral.

If nothing is switched on then the trip will remain OK but if something is switched on and it DOES NOT have to have any leakage at all in it at all, it can be earth free if the current now rises so that more than the nominal 30 ma is going away via the earth short then out will go the trip.

This can be a sod to find and cause a lot of confusion needs someone with a multimeter to test for that there should be infinite resistance between earth and BOTH the live and Neutral conductors in the wiring.

HTH...

[kalicoorguk]

Update:

Well, this is proving an odd one!

I have had no more RCD trips whilst the washing machine is unplugged, so maybe just coincidence before that the cct tripped without it plugged in.

I took the advice to remove the motor and blow out any carbon dust. Actually, there wasn't really any dust there and all looked in good order with the brushes. I plugged the WM back in, with the motor disconnected and there was no RCD trip.

I then tried it with the newly cleaned motor reconnected and still no trip RCD. Hooray! Except that was a little premature.

I ran the machine with the back off and all tickety-boo. But when I pushed it back under the worktop and put some washing in, it ran for only a few minutes before tripping the RCD. Drats!

So this time, a full test with a different cct/RCD and still it trips the RCD, so I think that rules out the RCD.

I've dismantled the whole front and got the control panel off. Checked the PCB over and no sign of burning or anything like that.

When it's all connected, I got these strange resistance readings:-

Switched off gives:- E-N = 500KOhms (all approx) E-L = 700 KOhms

Switched on gives:- E-L = 800 KOhms E-N = 980 KOhms

Switch back off gives (strange this):- E-L = 1.5 MOhms E-N = 1.5 MOhms

Testing across the mains filter that is at the back of the machine, immediately connected to the incoming cable, gives:- E-L = 330 M Ohms E-N = short (0-ish Ohms)

If I disconnect the front control panel then plugging in the WM doesn't trip the RCD. But if I reconnect everything back up, then it trips immediately.

I'm afraid I don't know enough about those filter things, but is that E-N short correct? Could it be the filter that's duff?

The control panel has a big sealed switch for the main control know, so I've no idea what the contacts are like inside. Moreover, I don't know if it's possible to buy another panel (economically at least) or if it's just time for a new washing machine.

Thanks again gents for all your expertise. Hoping someone might know a next step to try.

[Roger Hayter]

I am assuming these are all readings taken with the machine unplugged and with a low voltage multimeter rather than a high voltage insulation tester, and taken across the mains input, may as well be at the plug pins

The first three sets are fairly consistent, and show significant leakage, though only in the sense that the leakage is likely to be much higher when hot and at 240V. It might just be the electronics showing a slight leakage to earth and of no significance though.

The fourth readings at the mains filter are not consistent and should not be different from the others as the mains lead has negligible resistance for this purpose. Either there is an intermittent earth to neutral short circuit here or you made a mistake. Most likely the latter, as E-N short would probably trip the RCD regardless of the machine being on or the front panel being connected. So I shall assume the fourth set are wrong. By all means repeat them, as an E-N fault would be highly significant. But would not explain the control panel connection being relevant. And would be evident in the first three sets of readings.

Your observation with the control panel may mean the latter is at fault or may mean the control panel wiring completes some connections, especially of neutrals, in other parts of the machine.

So not much further forward.

If you can isolate both ends of the heater element then check leakage from either end to earth. If there is any, this is probably the cause of the fault. If you can temporarily disconnect the heater and tape the connectors to it safely enough to turn the machine on with the control panel connected this would establsh whether the element is at fault. This could be repeated with other parts, disconnecting both live and neutral, and if none prevent the fault then it probably is in the control panel. The only way to test the innards of the control panel is by standard electronic fault finding methods.

[tony sayer]

That shouldn't be like that Earth to Neutral short if the machine is disconnected from the mains unplugged..

Try that again and report back with the machine unplugged.

If there is an E to N short than these the cause of the problem its one of those barsteward leaks that won't trigger till you get some current flowing.

The usual cause of tripping is a Live to earth short in the water heating element had this more than the once!..

But this filter, can you pull all the leads of it then run those ohms checks again, make a careful note of which wire goes where or take a pic of it!.

[The Natural Philosopher]

That is massively incorrect.

Double check.

[Kal Ico]

Thanks again for your steer.

I'm with you, Roger, that I think I will have mis-measured. Yes, I was using a low voltage AVO multimeter. I have a mains tester and even an insulation tester but would have to read up how to use them. (I qualified as 16th Edition, years ago, but not made use of this stuff in a long time. What is it they say about the brain - if you don't use it, you lose it!)

If the heater element is most likely to be at fault, I can remove that (after draining down - not easy!) then test that. I expect they are not too expensive to replace, so worth a try.

My alternative is a new washer, which must be circa £350. This one has done about 8 years, so not bad. But I prefer to look after and repair stuff if I can. The modern ones are all so complicated, with LCD displays for goodness sake. It's a washer!

[Archibald Tarquin Blenkinsopp]

If you have to read up on how to use an insulation tester, you don't really have the knowledge needed to diagnose the problem.

16th edition is meaningless. Anyone can pass the regs exam, you do not have to have had even a miniscule amount of training or experience to sit and pass the wiring regs test. Unless you have training or experience, and your request for help on a very simple fault suggests you haven't, get someone to look at it that does know where to start.

On the plus point most of the "advice" doesn't seem that bad. 'Pity to have the equipment to diagnose the problem in minutes, yet not have the solution.

For the solution you have to apply logic. Electrical diagnosis comes into it, but you need a "system".

If you dig out the instructions for the Megger and have confidence using it, you are well on your way to success. I would still ask an electrically qualified aquaintance though :-)

AB

[The Natural Philosopher]

If you are gettinmg trips with the washing machine unplugged IT IS NOT THE WASHING MACHINE

[Fredxx]

Clearly the OP wants a new washing machine. Now they'll have to find another excuse to buy one.

[2987fr]

But given that he does get trips with the washing machine plugged in to a different circuit with a different RCD, it does appear that the washing machine does have a fault and that there is also a separate fault with the original circuit or whats plugged into it.

[tabbypurr]

Mains voltage insulation tester will give a much clearer picture, but it does look like you've got bad insulation in there somewhere. Once you find it it will quite likely be fixable for anything from nothing to £30 or so.

Draining is trivial, pull the hose off the standpipe and lay it down in a bowl - water runs out.

You can also eliminate the element by disconnecting it at both terminals, see if it runs. That will cause the program to stall in wash mode.

NT

[George Miles]

Mains tester plugs like this one

some leakage from live and neutral to earth so can be used to trip RCDs which are almost tripping which could be useful in finding whats going on.

But I dont know how many milliamps they leak, anyone know?

George

[Kal Ico]

Latest news:

Following the earlier steer that the most likely component to break is the heater element in the washer, I took the connections off that.

It then does not trip the RCD and I was able to select the drain programme then the spin programme, without problem.

But then the strange bit - when the spin finished I reconnected the heating element and it still didn't trip the RCD.

Testing the resistance from each terminal on the heating element to Earth, with the low-voltage meter, it was about half a Meg Ohm on each. Could this be a fault that only shows up when under power and/or heated?

Just to be clear, there have been NO further trips of the RCD when the washer is unplugged. Maybe just a coincidence or maybe that ring has high earth leakage anyway. Not sure.

[tabbypurr]

Half a meg at low voltage is not right, suspect it has a problem. That R figure will fall as higher V is applied. The heater elephant is only powered up during the wash cycle, and half a meg from N to E doesn't matter. I'd test the element resistance at full voltage. Leaky elements are cheap enough to replace.

NT

[Kal Ico]

Thanks. New element ordered. Cheers

[The Natural Philosopher]

Oh yes.

Half a meg is WAY OK.

I've seen trippy elements at around 10k

Faults I HAVE located that caused trips are as follows.

Water in sewage treatment motor. Water dripping onto boiler electrics Water dripping into lighting circuit Water dripping into motorised valve Winding to armature leak aroudn 3k in washing machine motor. Element to earth leak of around 3K in cooker grill element. Note that actual appliance issues have been fewer than other issues affecting wiring etc.

[The Natural Philosopher]

Don't be too sure. He is (as usual) talking relative bollocks.

half a meg is 500uA. Well below 30 mA.

IME trips happen around the tens of K mark.

The elements I have replaced all measured that when cold. Thats not to say they didnt get worse when hot, but they all showed up in the sub

100K zone cold.

As did my motor winding to chassis 'short'