RCD he say 'click' ?

So,
There I was, minding my own business when 'click' all the power went off in the room. I only had a side light on at the time so thought it could have been a power cut. Went to the hall and found the light on so realised it was just my power ccts. Reset the RCD and it tripped again. Switched off all the MCB's, reset the RCD and turned the MCB's back on one at a time .. upstairs ring .. 'click'. I then removed all plugs from the ring and RCD reset ok. Plugging things back in found the washing machine (there is a little utility area also on upstairs ring) was the cause (but only when switched on at the socket to it's a live <> earth fault?)
So, what is likely to be the cause of a washing machine tripping the power when it's not actually turned on itself (ie what's between the plug and the main switch in the machine .. It's an AEG OKO-Lavamat 6100 Digitronic if that makes any difference?)
I'll pull it out and have a look tomorrow but I fancied some pointers meantime?
"Place yer bets please .. " ;-)
All the best ..
T i m
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T i m wrote:

Mains input filter?
Lee
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Lee wrote:

Sounds like it to me too. Large electrolytic capacitor gone all leaky.
Andrew
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T i m wrote:

Depends on if your socket has a double pole switch or not... ;-)

Input filter as others said, or possibly water seeping into some place it should not (which would suggest an internal leak!). Any puddles under the machine when you move it?
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On Fri, 14 Jan 2005 21:03:08 +0000, John Rumm

Std MK double switched socket .. single pole? And if it is only single pole that pins it down to a live <> earth fault though eh?).

Are you all talking one of the inline sealed jobbys here .. L & N in and out, common Gnd (like you sometimes get built into IEC chassis sockets?
or possibly water seeping into some place

I'll let you know tomorrow ;-) Theres no 'visible' water leak as yet (it *has* leaked in the past .. I changed the drum bearings / seal and the water pump, both a few years ago now ..) and the drain backed up once (used the drain wand on my pressure washer). ;-)
It was working perfectly last night and wasn't on when it tripped the cct?
We will see ...
All the best ..
T i m
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Also don't forget to check and measure leakage from Neutral to Earth this is also a cause for RCD tripping....
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Tony Sayer


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wrote:

Will I need some 'special' gear for that .. only got a DMM?
If it only trips when I turn the thing on at the socket (ie netural and earth would be connected all the time) would that suggest the neutral <> earth leakage was ok (or below the trip current at least?)
All the best ..
T i m
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That leakage is quite awkward to measure, its that sometimes if theres a short between neutral and earth some current needs to flow before it will show up. Bit late to explain all the niceties about RCD's.
Bet summats got damp somewhere;)
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And it actually trips the RCD, or just the MCB for that circuit. If it's the whole house RCD then it's a fault from live to earth through a cable or loose connection somewhere. Or the mains RFI filter on the appliance as others have already said. A fault to earth through the negative conductor will only show when the supply to the appliance is actually being used. That's the nature of un-balanced current flow in both conductors. Earth and negative are usually at the same, or bloody close to the same, potential while the appliance is lying dormant. But this being a washing machine supply, then look for water as well as burn marks on the wires inside. Mice can also chew through the flex in the most inconceivable places.
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On Sat, 15 Jan 2005 00:10:15 GMT, "BigWallop"

Nope.
Possibly.
Nope.
Not always. It doesn't take much to knock the RCD out while other circuits are on load if there is a slight difference between N and E and there is a bit of a N\E fault somewhere..

*ignore all this and carry on following the advice from elsewhere in the thread. *
BW, you can have absolutely nothing pulling a load through an RCD and a NEUTRAL (not negative, that's DC), to earth fault *can* trip it.
Sorry.
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strung together this:

<<<snipped>>>
Well, I'm sorry too, because I can't find anything, anywhere, that says a standard RCD in a normal domestic installation will trip the supply unless there is a fault from Phase to Earth. If the appliance is open circuit, all switches open, then the phase should not be connected to neutral through any load, and so this can't cause an imbalance in the phase to neutral loop which the RCD is there to detect. So, for arguments sake, we'll say that neutral and earth are in the same potential state. The phase is at higher potential than both neutral and earth. Phase and neutral are "not" connected through any load (open circuit). A straight short occurs between a neutral and an earth conductor. What happens at the RCD?
Therefore, the fault must lie between phase and earth for the RCD to trip the supply, because neutral is already at, or so close to, earth potential that the RCD will not detect any difference on this side of the supply. This would only happen if there was a closed circuit between phase and neutral, and a neutral conductor passed a fault current to earth at such a low impedance, which should be highly unlikely because neutral is already, or very nearly, at earth potential.
How I was told and read how it all worked was like this. The conductors and loads in a circuit act as resistance to the passage of electrical current. Placing two resistances in series only increases the total resistance in the circuit. But, if two resistors are placed in parallel to each other, the total resistance is actually reduced by a tangible amount in the whole circuit because the electrical current has two paths to flow through on that part of the circuit rather than just one. This reduction in total resistance in the circuit by placing a parallel resistor in it is what creates the imbalance for the RCD to detect. The RCD should only have one conductor with current going out and one conductor with current coming in. By making two conductors send current out, and still have only one conductor sending current in, the circuit becomes unbalanced.
That's why I always thought an RCD was placed in line to prevent shock or damage from an imbalance on the phase to earth side of the supply, not on the neutral to earth side of the supply as well. An RCD should also give no detection of a fault across phase and neutral because such a fault would also be detected as a balanced load across them. Reading the IEE and RCD manufacturers literature would also point me to believe this is true.
Yes you can have a slight increase in potential through heavy loading on other parts of the same neutral path, but these should never be enough to create a dangerous situation for the RCD to detect and trip open because earth should also be induced by these same small increases in potential that are effecting the neutral paths. So what you are saying is that the neutral or earth of the OP's supply are not operating properly to remove the unlikely event of a low resistance current flow between neutral and earth, while the neutral conductor is being induced by some other loadings on the same part of the circuit. This would cause the neutral to have a much higher potential than earth, and so would cause an imbalance for the RCD to detect. So do you think the OP should also have the supply and wiring tested to be sure that the safety devices fitted are going to properly protect from the potential harm of an electric shock?
(BTW, I use the word "negative" for circuit descriptions nearly every day and I was wrong to use it here as we're talking AC not DC, but old habits die hard. My apologies)
http://www.safety.ed.ac.uk/policy/part3/52.html http://www.tlc-direct.co.uk/Technical/Distribution/How%20RCD%20Works.htm http://www.reo.co.uk/files/kbase/How%20an%20RCD%20works.pdf http://www.collinseducation.com/resources/teaching%20resources/Bc2%20Circuit%20Breakers.pdf http://www.tlc-direct.co.uk/Book/5.9.2.htm
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On Sat, 15 Jan 2005 04:55:43 GMT, "BigWallop"

Not sure this helps anything but when I was rewiring Dads garage a while back I fitted one of those little RCD + 2 x MCB CU's.
I had powered it all up and was using the 'lighting' CCT and had the live switched out on the MCB. I cut through the T&E on the 'Power' cct and the RCD tripped (because the RCD had detected earth current derived from the neutral potential as they were shorted by my cutters?).
All the best ..
T i m
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wrote:

unless
No it didn't, it detected induced current through what should have been a neutral conductor, but which was then a phase conductor because the lighting was still in use when you cut the cable to the socket circuit. I can bet that the lighting and power cables run along side each other on some stretch of the wiring plan, and it was either the induced current, even though very small, or a larger impedance on the earth conductors that caused the RCD to trip open. It could have either been the earth was not properly conducting the residual current away from the induced leakage through the cable insulation, and this created a higher potential in the neutral conductor, or what should have been a neutral conductor had risen more toward phase potential from some other means as yet undiscovered. This would cause a Residual Current Devices to detect an imbalance between phase and earth and activate the breaker circuitry.
If you have a look at the inner workings of an RCD you see there is no way that a neutral to earth leak will cause the device to trip open. That's unless there is an earth loop impedance fault or, to put it another way, a higher resistance path on the earth conductors than the neutral conductors, which will then causes the neutral path to become higher in potential energy than earth and so cause an imbalance between a positive potential and negative potential at earth (where common current flow specific is used). This type of fault causes what should be a neutral potential to literally become phase potential and so again cause an imbalance between phase potential and earth potential which an RCD is designed to detect. Here: http://www.memonline.com/rcd1.html for instance, shows how the device works, with a diagram of the inner parts.
The whole point of equipotential bonding using larger cross sectional area (csa') conductors than those used in the supply, is to greatly reduce the impedance along these conductors. The reduction in impedance should be to such a level that will not cause what should be a neutral potential to obtain phase potential. This use of large csa' cables for earth bonding should be capable of removing all residual current obtained by the neutral paths, either through inductance or contact with a phase potential conductor, and should also be capable of preventing the neutral path from creating an imbalanced current flow between it and earth. Neutral and earth should always remain at the same potential, or at a very negligible measure from it, no matter where it is on the whole installation plan. This is the requirement, stated in all the good guideline hand books and other literature, for the earth bonding to have proper residual current removal properties.
An example. Phase and neutral conductors can be created using, lets say, 2.5 mm csa' conductors but, to remove the residual current created by close proximity between the two supply conductors and any other means of induced current flow, the earth bonding conductor needs to be of a larger csa', of more commonly 4 mm to 6 mm, to reduce its impedance further than the supply conductors and so be capable of reducing induced current flow and prevent nuisance trips on an RCD. So, larger cross sectional area cables are used for equipotential bonding to produce a much lower impedance path to ensure proper earth leakage current detection from the phase supply. This, in turn, creates a much safer reaction time if such a leak to earth does occur. It isn't just a small safety thing to use equipotential bonding, it is also there to keep both phase and neutral paths in balance so that a higher residual current, commonly 30mA, can be detected quickly.
It is natural to have a current flow of anything up to 12 mA, or even 15 mA in some installations, between phase and earth/neutral conductors, even when they are not under load. This is due mainly to induction through their close proximity with each other inside the insulated outer sleeve of the cable. The totally bare earth protective conductor is placed in the cable to try to reduce this natural induced current flow phenomenon as much as possible. The bare conductor should also help bring the two supply conductors back in to a balanced state again. It isn't because the cable makers are stingy with the insulation materials that the earth protective conductor is left totally bare naked, it's because an insulated coating would create a much higher resistance and reduce the bare conductors capabilities in removing the residual current and so be unable to creating some kind of harmony inside the cable again. Electricity suppliers also use tests to make sure that the earth bonding at a supply is within certain limits. This is to create a proper equipotential bond between all the conductors. To high an impedance on any one of them, phase, neutral or earth, will put the whole power balance out of sync and cause problems.
So, to sum up, I still say an RCD will not trip open unless the fault current it detects is between a phase potential and earth mass.
Boy, can I go on a bit when I get started. :-) LOL !!!
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On Sat, 15 Jan 2005 11:22:16 GMT, "BigWallop"

RCD's don't detect anything between phase and earth. Most don't know what earth is so can't detect it.
I'll not bother reading the rest as it's probably all based on the incorrect fundementals again.
<snip it all>
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SJW
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strung together this:

and
So this manufacturers diagram is wrong then: http://www.memonline.com/rcd1.html I better tell them about that, because the little man in the drawing will be in really great danger. :-)

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On Sat, 15 Jan 2005 21:39:52 GMT, "BigWallop"

I said *most*, I know that MEM and MG have earth monitoring on the RCDs but that's about it.
If the earth connection was required then they wouldn't be the only two in the history of RCD making to have got it correct.
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BigWallop wrote:

The diagram is right, it agrees with what Lurch said!
The RCD does *not* detect current flow between phase and earth, it can't it is not even connected to the earth. What it detects is an imbalance in feed and return. The fact that in the case depicted in the diagram, the reason for the imbalance was a phase to earth fault (through said loweryesq character) is not actually relevant, any number of other possible reasons could result in a condition that will instigate a trip.
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strung together this:

Its not WRONG but its too simplified to give a full outline of the operation. What it does do is show to the unenlightened how a fatal shock can be prevented by an RCD. I'm not sure what your level of electrical education is but terms like Vector sum should mean something to you if you are going to "explain" RCDs to the public<g>. Basically the RCD responds to the imbalance of currents flowing in both the live and the neutral conductors passing through the "core" (thats the yellow ring on the diagram). Considering a situation during a half cycle where current flows "out" on the red wire and should therefore flow back "in" on the blue wire. If the two current magnitudes are not equal there is an imbalance and a trip current is unduced in the thin wire sense coil. This current when large enough causes the contacts to be opened. If a neutral to earth voltage exists on the unloaded incoming supply even a small one it CAN be sufficient to give rise to a fault curent flow through a N-E fault which goes "out" on the Neutral but does not come "back in" on the live so the breaker trips. If there is no N E voltage then the situation will not arise. Sometime try putting a voltmeter across N-E on your CSU incomer with the main switch open and see what you get. Depending on external conditions you may get nothing or you could get tens of volts. I once found 40 volts on a supply fed on a long overhead supply at the end of a village street many years ago and long before PME, (earths in those days all came via water pipes). Not enough to do personal damage but certainly enough to give a significant fault current.
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O

I must have a faulty one on my bench at work then, always trips on neutral to eath fault.
Dave
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strung together this:

Could be worse, I've installed loads of faulty ones, apparantly.
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