T i m wrote:
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

To put us all out of our misery; what was wrong?

Oh, and would someone please take Big Wallop's spade off him? It's time
to stop digging... ;-)

Andrew

On Sat, 15 Jan 2005 20:35:24 +0000, Dave Stanton
strung together this:

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.

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

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

SJW
Please reply to group or use 'usenet' in email subject

On Sat, 15 Jan 2005 20:13:36 +0000, Mike Tomlinson
strung together this:

You don't have to. Wire a plug with two wires, one to neutral and the
other to earth. Plug it into a socket and touch the two wires together.
Your RCD will trip; if it doesn't, it's faulty.

You might want to check your facts before jumping on the high horse
there. You're just as wrong as BW.
--

SJW
Please reply to group or use 'usenet' in email subject

"Lurch" wrote in message
...
On Sat, 15 Jan 2005 11:22:16 GMT, "BigWallop"
strung together this:

This would cause a
Residual Current Devices to detect an imbalance between phase and earth
and
activate the breaker circuitry.

RCD's don't detect anything between phase and earth. Most don't know
what earth is so can't detect it.


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. :-)


I'll not bother reading the rest as it's probably all based on the
incorrect fundementals again.

snip it all
--

SJW
Please reply to group or use 'usenet' in email subject

"Andy Wade" wrote in message
...
Stefek Zaba wrote:

Exactly so. Congratulations: you've managed to say in 5 lines what
usually takes me several screenfuls - and just took Andy W nearly as
long, but with more cases more thoroughly considered - on the frequent
occasions that this FAQ comes up!

None of it seems to have stopped Mr. Wallop continuing to post complete
******** though. I'll be sorely tempted to adopt the IMM approach next
time and resort to snip_drivel.

Having followed this thread for several minutes. I quickly realised that BW
was wrong from the beginning. I have done electrical work in this house and
I have tripped the RCD by shorting neutral to earth many years ago and many
times since :-)
I quickly learned, without re-course to a news group, that an RCD could
detect an imbalance between neutral and earth, as well as its intended
supply/return current.

This begs the question...

What are the qualifications of BW?

Dave

"Dave" wrote in message
...

"Andy Wade" wrote in message
...
Stefek Zaba wrote:

Exactly so. Congratulations: you've managed to say in 5 lines what
usually takes me several screenfuls - and just took Andy W nearly as
long, but with more cases more thoroughly considered - on the frequent
occasions that this FAQ comes up!

None of it seems to have stopped Mr. Wallop continuing to post complete
******** though. I'll be sorely tempted to adopt the IMM approach next
time and resort to snip_drivel.

Having followed this thread for several minutes. I quickly realised that
BW
was wrong from the beginning. I have done electrical work in this house
and
I have tripped the RCD by shorting neutral to earth many years ago and
many
times since :-)
I quickly learned, without re-course to a news group, that an RCD could
detect an imbalance between neutral and earth, as well as its intended
supply/return current.

This begs the question...

What are the qualifications of BW?

Dave


So you didn't read my argument properly either? Do you know the way
electricity is transmitted from the generation companies to the national
grid?

Oh, don't worry, I'm fully qualified for the work I do, and a bit more. :-)
LOL !!!

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

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. :-)

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.
--

SJW
Please reply to group or use 'usenet' in email subject

On Sat, 15 Jan 2005 21:43:14 +0000 (UTC), "Dave"
strung together this:

What are the qualifications of BW?

Absolutely none that are relevant to the issues in this thread.
--

SJW
Please reply to group or use 'usenet' in email subject

On Sat, 15 Jan 2005 22:03:12 GMT, "BigWallop"
strung together this:

So you didn't read my argument properly either? Do you know the way
electricity is transmitted from the generation companies to the national
grid?

Oh, don't worry, I'm fully qualified for the work I do, and a bit more. :-)
LOL !!!

FFS, you sure you're not IMM? You might have to have a solitary "****
off ****" response in a minute!
--

SJW
Please reply to group or use 'usenet' in email subject

In article , Lurch
writes

You might want to check your facts before jumping on the high horse
there. You're just as wrong as BW.

What's the difference between cutting a length of connected (but not
energised) T&E causing the RCD to trip, and the example I posted?

--
..sigmonster on vacation

John Rumm wrote:

tony sayer wrote:
Now do the same with the neutral output side of the trip and it won't
trip.

Errr, in fact it might. There is a very good chance that a potential
difference will exist between your earth stake and the neutral connected
to the incoming side of the RCD. Hence current can flow.

I'm glad you said that. I did too earlier, under the TT system heading.
Tony, it depends how good your earth spike is and how 'hot' the
neutral is, wrt local ground. The neutral heading back toward the
supply transformer is 'lifted' by the voltage drop caused in it by other
consumers' load currents, as well as your own.

Here I have a detached workshop building, wired as a TT system. The
neutral of the TN-S house supply is not usually more than a couple of
volts away from earth, but shorting neutral to earth in the workshop
almost always trips the 30 mA RCD. The earth electrode resistance (two
8 ft. rods in parallel) is about 7 or 8 ohms.

--
Andy

Mike Tomlinson wrote:

What's the difference between cutting a length of connected (but not
energised) T&E causing the RCD to trip, and the example I posted?

It's not that, it's the fact you said "if it doesn't [trip], it's faulty".

That conclusion isn't valid. If you put a lamp in a lampholder and it
doesn't light up, does it prove that the lamp is faulty?

--
Andy

On Sat, 15 Jan 2005 21:22:12 +0000, Andrew Chesters
wrote:


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

To put us all out of our misery; what was wrong?

Ah, sorry Andrew g, can't tell you yet as I got side tracked as Taxi
cab for my daughter, first to her recorder session and then with her
Fender P Bass and Amp to her band practice. Then getting a Dell
Inspiron (lappy) with no floppy or CD reloaded (with no apparent way
of influencing the boot sequence to accept std USB floppy or CDROM)
with 2KPro ;-(

Oh, and would someone please take Big Wallop's spade off him? It's time
to stop digging... ;-)

It does all get a bit deep ... but then there have been some pretty
serious contradictions being aired?

All I know is that when I cut the T&E on Dads garage RCD CU it tripped
the RCD (it only had a couple of m of wire on it and a couple of
flouro's on the lighting cct) ... and the (switched off on the unit)
washing machine trips my RCD (not the MCB) when the live is brought
into play .. ;-(

I hope to get on it first thing tomorrow .. when I've delivered my
daughter and her mates swimming .. sigh

All the best ..

T i m

BigWallop wrote:

"Lurch" wrote in message
...

On Sat, 15 Jan 2005 11:22:16 GMT, "BigWallop"
strung together this:


This would cause a
Residual Current Devices to detect an imbalance between phase and earth

and

activate the breaker circuitry.


RCD's don't detect anything between phase and earth. Most don't know
what earth is so can't detect it.



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. :-)

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.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

BigWallop wrote:

So, I'll start again. A neutral / earth short circuit will not cause an RCD
to trip. If a fault or high impedance earth loop is used, then the neutral

You seem to be suffering from IMM syndrome here, repeat it as many times
as you like it is still wrong!

Neutral and earth are *unlikely* to be at the same potential, so if you
connect them together a current will flow. If this is high enough it
will trip the RCD, end of story!

detect this leak and trip open. Again. Neutral and earth are at the same
potential, so a straight short across them will do nothing. If an induce

Its behind you...

current of any kind lifts the neutral conductor to phase potential, then it
no longer is at neutral potential. This can be caused, as you have

It don't need to be at phase potential, half a volt will be more than
enough!


--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Mike Tomlinson wrote:

In article , Lurch
writes


You might want to check your facts before jumping on the high horse
there. You're just as wrong as BW.


What's the difference between cutting a length of connected (but not
energised) T&E causing the RCD to trip, and the example I posted?

It will only trip if there is a potential difference between N and E,
and given that, that the impeadances of each are low enough to allow a
current of trip magnitude to flow.

On a TN-S or a TT setup there is a good chance that what you have said
is true, the RCD will trip. On a PME system with all circuits
disconnected, there is a fair chance the RCD won't trip. You can not
infer that the RCD is faulty as a result of this however.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

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

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

Good job Part P came in then Lurch G.

Dave
--
For what we are about to balls up may common sense prevent us doing it
again
in the future!!

"BigWallop" wrote in message
. uk...

"Lurch" wrote in message
...
On Sat, 15 Jan 2005 11:22:16 GMT, "BigWallop"
strung together this:

This would cause a
Residual Current Devices to detect an imbalance between phase and earth
and
activate the breaker circuitry.

RCD's don't detect anything between phase and earth. Most don't know
what earth is so can't detect it.


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. :-)



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 publicg. 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.

In article , Andy Wade
writes
John Rumm wrote:

tony sayer wrote:
Now do the same with the neutral output side of the trip and it won't
trip.

Errr, in fact it might. There is a very good chance that a potential
difference will exist between your earth stake and the neutral connected
to the incoming side of the RCD. Hence current can flow.

I'm glad you said that. I did too earlier, under the TT system heading.
Tony, it depends how good your earth spike is and how 'hot' the
neutral is, wrt local ground. The neutral heading back toward the
supply transformer is 'lifted' by the voltage drop caused in it by other
consumers' load currents, as well as your own.

Arrrrgggggghhhhhhhh!.....

Perhaps you didn't see the other posting where I omitted the finer
points of earth leakage via multi return paths in order to try and get
the "current balance" concept across to BW and others, without
complicating it further!.

Even some pro electricians haven't the correct idea of how an RCD
works;((

--
Tony Sayer

tony sayer wrote:

Arrrrgggggghhhhhhhh!.....

Arrrrgggggghhhhhhhh what?

Perhaps you didn't see the other posting where I omitted the finer
points of earth leakage via multi return paths in order to try and get
the "current balance" concept across to BW and others, without
complicating it further!.

You mean the one where you said:

Now take a wire thats connected to a good earth like a stake in the
ground outside in very damp soil and after its been raining. Touch this
to the live and the trip will immediately fire off.

Now do the same with the neutral output side of the trip and it won't
trip.

What we were pointing out is that while the first part of that is right,
the second part isn't necessarily correct at all. Touch neutral to your
earth stake and the RCD will trip if the combination of the voltage on
the neutral (relative to the stake) and the earth resistance of the
stake is such as to allow sufficient current to flow.

--
Andy

"BigWallop" wrote in message
. uk...

"Dave" wrote in message
...


Having followed this thread for several minutes. I quickly realised that
BW
was wrong from the beginning. I have done electrical work in this house
and
I have tripped the RCD by shorting neutral to earth many years ago and
many
times since :-)
I quickly learned, without re-course to a news group, that an RCD could
detect an imbalance between neutral and earth, as well as its intended
supply/return current.

This begs the question...

What are the qualifications of BW?

Dave


So you didn't read my argument properly either?

The Panto season is not yet over, so...

Oh! Yes, I did ;-)

An RCD has no recollection of earth, hence my learning of tripping it by
earthing a neutral.
It didn't take me long to understand why it happened though

Do you know the way
electricity is transmitted from the generation companies to the national
grid?

I have a limited understanding of it, but I have a greater understanding of
the PME system that is in this house.
I have tripped the RCD by earth to neutral more times than is needed.
(mainly by pulling back boxes over the wire, to change a single to a double
socket.)

Oh, don't worry, I'm fully qualified for the work I do, and a bit more.
:-)
LOL !!!

Don't tell me, you are qualified to do the work, but you are in the position
of not being qualified to certify it. What a shambles Part P has become.
:-((((

Dave

On Sun, 16 Jan 2005 23:44:27 +0000 (UTC), "Dave"
strung together this:

Don't tell me, you are qualified to do the work, but you are in the position
of not being qualified to certify it.

No, he is not qualified to do either.
--

SJW
Please reply to group or use 'usenet' in email subject

tony sayer wrote:

Andy Wade writes
What we were pointing out is that while the first part of that is right,
the second part isn't necessarily correct at all. Touch neutral to your
earth stake and the RCD will trip if the combination of the voltage on
the neutral (relative to the stake) and the earth resistance of the
stake is such as to allow sufficient current to flow.

Yes IF theres a load connected to the RCD and, if theres sufficient
induced current over the line from the substation to your local earth
due to leakage locally......

No, no, no, no, no, there's no need for there to be any load on the
output side of the RCD and no need to talk about induction or local
leakage. All you need is some load (said load being in a 3-ph system
not perfectly balanced) on the feeder causing current in some part of
the neutral between you and the transformer. Now you have the neutral
earthed at both ends - one end by the supplier's earth and the other end
to your stake, with a current sensor (i.e. the RCD's neutral coil) in
series at one end. There are two parallel current paths, one through a
dirty great copper or aluminium cable and the other through two earth
electrodes and terra firma. Most of the current goes through the cable,
but a little bit goes through the earth path and if that's high enough
the RCD will trip.

It was this bit. Perhaps you missed it?.

Errr, in fact it might. There is a very good chance that a potential
difference will exist between your earth stake and the neutral connected
to the incoming side of the RCD. Hence current can flow.

? John Rumm wrote that and I was agreeing with it!

Yes you could argue this, but ...

.... this has gone on quite long enough.

Its quite debatable as to whether or not this will happen. It won't in a
PME installation where the earth and neutral are bonded together at the
incoming board such as we have here in our office.

Whether or not what will happen? We were talking about shorting the
neutral to a local earth stake. Whether the main supply is PME or TN-S
will make not a jot of difference. But if you're now talking about a
short between N and the installation earth then it obviously will. Go
back a few dozen articles to wot i writ befo

2. TN-C-S (PME)
---------------
Here your earth comes from the supply neutral entering the premises. If
there are no loads on in your house there is no neutral current to
divert and the RCD will not trip on a N-E short.

However if you are working on one RCD protected circuit (with its phase
isolated) and there's load current flowing in another circuit protected
by the same RCD, a N-E short in the circuit you're working on will
divert some of the other circuit's load current through the earth,
causing an imbalance and tripping the RCD.

I trust you see where I'm coming from on this now?....

Trumpington, I thought...

--
Andy