Last week we had a minor? change made to the supply wires coming
into the house. The electricity company changed the supply wires
(from their pole to our incoming fuse) from the 1970's twin wires
to a modern single coaxial supply wire. The distance is about
30-40 yards.

Before the change I can't remember the last time the RCCB tripped.

After the change we now have permanent tripping, that started
on the same afternoon.

The tripping seems to be load-related, the more things we have on,
the more it is likely to trip. eg, To have a shower, (electric,
7KW), we now have to more or less turn the rest of the house off.


Note that the loadings we have on at any one time are no different
to those before the cabling change, when we did not have tripping.

It has taken me a few days to go round the house, measuring the
leakages (Megger), or selectively isolating various appliances. I
cannot find any single suspicious appliance.... except to say that
if we have enough appliances off then we do not have a trip during
a shower. Things with motors (vacuum cleaner) do seem to trigger a
trip.

L-N and N-E voltages are much the same as before the change,
242Vrms and 1-2Vrms each. Although I do feel that the 'dip'
of the lights as the shower is turned on does seem smaller
than previously.

Can anyone suggest what is going on? Could such an apparently
simple change to 30 yards of supply wiring make the trips more
sensitive? Is there any mistake they could have made?

For ref; The RCCB in the Consumer Unit is an MK LN5780, 240V
80A, with 30mA tripping current. Between the incoming fuse and
the CU is the old original trip, a Chilton "Voltage operated
Earth leakage trip, 60A Type D". The MK 30mA always trips,
and sometimes (maybe 1 in 5 times) the Chilton also trips.

--
Tony Williams. Change "nospam" to "ledelec" to email.

On Sat, 27 Sep 2003 09:42:27 +0100, Tony Williams wrote:

After the change we now have permanent tripping, that started
on the same afternoon.

Give the company that made the change a call and report it. There is
something odd going on and RCDs should not trip in relation to the
load.

A couple of points from your description.

Is the 30mA RCD in the supply to whole house? If so that should really
be a 100mA time delayed device and if you want shock protection on
some circuits a 30mA non delayed RCD should be used as required.

Where is the voltage operated trip really loacted you don't mention a
meter. If it's pre the meter it is the boards equipment and I'd argue
up to them to replace it with a 100mA time delayed RCD. Voltage
operated trips are really from the ark these days.

--
Cheers
Dave. pam is missing e-mail

One possibility is that on the old set up you were not connected to the
electricty company's earth and now you are. Small amounts of leakage current
from a number of appliance can trip a 30mA RCD. From memory I think 100mA is
recommende/requierd if covering the whole supply.

Your wiring may have been installed perfectly ok to operate without an
electricty company earth on the other hand it may not have been or the
electricty company earth may have been broken/ accidently disconnected for
years.

Earthing is complicated if it was me I would get the electricty company back
and ask them what they changed and how it may cause your RCD to trip. If
there is still a problem get professional assistance if you don't know what
you are doing.

Ian,

Can anyone suggest what is going on? Could such an apparently
simple change to 30 yards of supply wiring make the trips more
sensitive? Is there any mistake they could have made?

For ref; The RCCB in the Consumer Unit is an MK LN5780, 240V
80A, with 30mA tripping current. Between the incoming fuse and
the CU is the old original trip, a Chilton "Voltage operated
Earth leakage trip, 60A Type D". The MK 30mA always trips,
and sometimes (maybe 1 in 5 times) the Chilton also trips.

Maybe the electric company did a megga test, and fried your RCD!

I have the same model MK breaker, and have had to replace it recently, not
due to a megga test, just seemed to have died, it was about 20 years old! -
as soon as we got the new one (same model) the annoying trips stopped!

One thing though, they aint cheap!

Sparks...

In article ,
Dave Liquorice wrote:

Give the company that made the change a call and report it. There
is something odd going on and RCDs should not trip in relation
to the load.

That does look on cards. I was trying to eliminate
us as the problem first.

Is the 30mA RCD in the supply to whole house? If so that should
really be a 100mA time delayed device and if you want shock
protection on some circuits a 30mA non delayed RCD should be
used as required.

The RCD supplies the three ring mains and the shower. The
lights, boiler, cooker are not on the RCD.

Where is the voltage operated trip really loacted you don't
mention a meter. If it's pre the meter it is the boards
equipment and I'd argue up to them to replace it with a 100mA
time delayed RCD. Voltage operated trips are really from the ark
these days.

I forgot the meter. Fuse -- meter -- Chilton, -- CU.

--
Tony Williams. Change "nospam" to "ledelec" to email.

In article ,
ian nicoll wrote:
One possibility is that on the old set up you were not connected
to the electricty company's earth and now you are.

ATM I can't see this. There are two wires only going
from pole to pole. There used to be two wires coming
into the house, and there are still only two wires
coming into the house, except they are now coaxial.

Small amounts of leakage current from a number of appliance can
trip a 30mA RCD. From memory I think 100mA is recommende/requierd
if covering the whole supply.

Yes this is an all-electric house so the total load
can be high and I have a feeling that multiple RCDs
is where we might end up. No room for that in the
present CU though.

--
Tony Williams. Change "nospam" to "ledelec" to email.

In article ,
Sparks wrote:

Maybe the electric company did a megga test, and fried your RCD!

No I watched him..... he tested the new installation with
the CU isolated (by the Chilton).

--
Tony Williams. Change "nospam" to "ledelec" to email.

On Sat, 27 Sep 2003 23:30:29 +0100, Tony Williams wrote:

One possibility is that on the old set up you were not connected
to the electricty company's earth and now you are.

ATM I can't see this. There are two wires only going from pole to
pole.

Where is the transformer? Do you have your own or is it shared?

There used to be two wires coming into the house, and there are
still only two wires coming into the house, except they are now
coaxial.

The neutral will almost certainly be bonded to earth at the
transformer or at least it should be. Ours is you can see the wire
from one of the transformer LV terminals descending the pole and into
the ground.

Though with that old voltage operated breaker I suspect your earth
was/is supplied localy. Trace out the earth bonding, if you can. It
may well disappear outside to an earth rod in addition to connecting
to the incoming service pipes.

I suspect you now either have a better earth than you did before or
maybe no earth cause of a cock up somewhere in the change over.

--
Cheers
Dave. pam is missing e-mail

Tony

For some reason I can only see your reply's an not messages from other
posters.

If there is was only two single wires coming into you house you may have had
an earth from the electricity company, you may not. I gather you mean you
now have a concentric cable (one thicker single black one). This can have
either a live and neutral or live, neutral and earth. So it is quite
possible that you now have an electricity company earth when you didn't have
one before . As I said I ask the electricity company to see if they can sort
out what they did to point you in the right direction.

Ian

In article ,
ian nicoll wrote:

If there is was only two single wires coming into you house you
may have had an earth from the electricity company, you may not.
I gather you mean you now have a concentric cable (one thicker
single black one). This can have either a live and neutral or
live, neutral and earth. So it is quite possible that you now
have an electricity company earth when you didn't have one before

The incoming cable goes into the fuse and there are only
two cables going from fuse to meter. There is no sign of
a new Earth wire anywhere.

As I said I ask the electricity company to see if they can sort
out what they did to point you in the right direction.

I'm going to have to do that probably.....

--
Tony Williams. Change "nospam" to "ledelec" to email.

Tony Williams wrote in message ...
In article ,
Sparks wrote:

Maybe the electric company did a megga test, and fried your RCD!

No I watched him..... he tested the new installation with
the CU isolated (by the Chilton).

Hi


I'm not quite 100% clear about this, but I detect a possible problem
with your setup. The voltage operated ELCB works by disconnecting your
house's earthed appliances (including shower) from earth, and tripping
when the voltage between the house 'earth' loop and the real earth
exceed 50v. To be frank, if you have an electric shower, I would think
this was dangerous.

Then we have an RCD, which _relies on_ a proper earth connection
somewhere to function. The RCD doesnt need an earth connection itself,
but it does need the appilances/wiring to be earthed, one way or
another, to be effective.

Now this is one area that's stretching my knowledge a little, but from
what I understand of your setup I dont think I'd be volunteering to
take any electric showers.

If I have this right:
your shower can have upto 50v on it before the Chilton trips
your shower is disconneted from earth
your plughole probably will be earthed once the water starts running.
AND it looks like you have more than 30mA of earth leakage current
from your disconnected earth loop thats connected to the shower.

I would say you need skilled advice before you get in that shower
again.

Regards, NT

The tripping seems to be load-related, the more things we have on,
the more it is likely to trip. eg, To have a shower, (electric,
7KW), we now have to more or less turn the rest of the house off.

Probably an earth to neutral short somewhere. These tend to produce earth
leakage problems somewhat proportional to load.

Also, was the earthing type upgraded during the cable change? It sounds like
you may have gone from TT to TN-C-S. It is important to find out if you
have.

Christian.

I too am a bit perturbed by the apparent setup, with both an olde-worlde
voltage-operated earth leakage breaker, and a whole-house current-balance
one downstream. And as both Nick T and Dave P have suggested, I'd want
to ditch the voltage-operated item. Since your hassles have started after
the supply co's mods, I'd start with a friendly call to them. Don't
bother sounding too clueful on the phone - you want to get a real
person from the supply company to come visit your place with test gear
and knowledge to hand; don't expect (or accept ;-) a diagnosis over the
phone from the person slaving in call-centre hell!

HTH, Stefek

RCDs should not trip with load increasing.... although there may be
increasing leakage to earth with increasing load, which might be tripping
it.

I think the answer might well lie in the earthing arrangements being
different to what they where before.

We had exactly this job done about 2 years ago and we still have the
exact same Chilton in circuit (with no earth wires attached) so it
is just an isolator now, to be removed when I get round to it.

I put a couple of new earth rods in and connected up to the house earth.

All works perfectly.............

If the Elec Board is supplying an earth (I would be a bit surprised though)
then
the voltage drop (current flowing) would be dependent on load. However,
even this should not trip a RCD - its the imbalance that trips these.

My vote - 1) Get the board back to demonstrate the problem and ask them
to sort it
2) Try a new RCD if they can't / don't, possibly a 100mA
delayed, but
there must be something not quite right if this is
needed in the average
family house, and these are no good for shock
protection - even 30 mA
is really very unpleasant !

Nick

On Sat, 4 Oct 2003 08:35:18 +0100, "froggers"
wrote:

Related but mayjnot be relevant.

Last Sunday morning the circuit breaker tripped out and refused to
re-set. By a process of elimination the trouble appeared to be in the
ring serving the kitchend and utility room.

Having un-plugged /switched off every item on this ring, with the
exception of the built-in fridge-freezer which was plugged into a
socket mounted on the wall behind it, inside the cabinet, there was
nothing to do but pull the b****y thing out so it could be switched
off, to see if this was where the problem lay.

Just had it pulled out, it was a tight fit and required the removal of
doors and various trim pieces,when swmbo appeared to ask if the
problem could be anything to do with the vacuum cleaner, which had
been cutting out while she was using it, but was still plugged in
upstairs.

B****x

Unplugging the machine cured the fault.

There must have been a short or summat at the plug end of it's cable
as removal of the plug and trimming back the lead a few inches solved
the problem of it cutting out .

Electrics wouldn't be a strong point with me, I was off sick that
day, so perhaps someone else can understand this errant behaviour.

A few years back we had a severe problem of the breaker going off
regularly. In this case it was down to a bad connection at the mains
end of the board.

Paul Mc Cann

In article ,
wrote:
I too am a bit perturbed by the apparent setup, with both an
olde-worlde voltage-operated earth leakage breaker, and a
whole-house current-balance one downstream. And as both Nick T
and Dave P have suggested, I'd want to ditch the voltage-operated
item.

The RCCB in the CU only feeds the three ring mains and the shower.
The appliances with fixed wiring (cooker, c/heating boiler,
immersion, lights, etc), are not on that 30mA RCCB and their
possible earth leakages would be detected by the old Chilton.
It makes a sort of sense.

Since your hassles have started after the supply co's mods,
I'd start with a friendly call to them.

Yes, I got them back in last week. Three men, two vans and
a serious inspection from the pole up to the Chilton. That's
the limit of their responsibility (when for free).

They confirmed what I already thought.... they had simply
replaced a two-wire feed with another two-wire feed, but
in one cable instead of two. Their opinion was that the
fault was almost certainly in our RCCB, or downstream of it.

So I hacked an old portable RCCB into a differential current
sensor, and have been going around the house looking for
possible (multiple) perps.

The electric kettle is known to have (apparently) tripped the
RCCB at point of switchoff and it is that stupid design where
actual steam is used to heat the bimetallic element. I boiled
it a couple of times, but it only showed a differential current
of less than 1mA. It's a bit mucky inside the handle so that
one is still a maybe for an occasional trip.

Other appliances, mini oven, w/machine, tumble drier, Henry,
all show a tiny differential current, of between 0.0 and 0.5mA.
The two fridge-freezers haven't been tested yet.

The biggest perp (oh buggerit!) is this computer system. It
has a differential current of 1.3mA. And (wait for it) the
little mains filter that powers the modem actually has a VDR
across Line-Earth. I can only think that fitting a VDR in
that apparently daft place is for it to conduct whenever there
is an overvoltage surge on the mains, which would deliberately
trip the RCCB.

The number of nuisance trips have reduced over the last few
days (to zero yesterday). This may (or may not) be due to two
changes made. That VDR across L-E has been removed, and the
soil around the earthing rod has been thoroughly wetted (this
is a clay soil, which I know to be bone dry down to at least
3ft, with major cracks running through it).

Touch wood.....

Thanks for all the suggestions.

--
Tony Williams. Change "nospam" to "ledelec" to email.

Tony Williams writes
And (wait for it) the
little mains filter that powers the modem actually has a VDR
across Line-Earth.

Could have been the culprit if your earthing is recently improved.
You wouldn't like to post the make and model and approx age of this item
you?
Is it a "transformer moulded onto a 13A plug"?
--
roger

delete x's to email

The RCCB in the CU only feeds the three ring mains and the shower.

In this case, replace the ELCB with a Type S 100mA RCD.

Christian.

In article ,
ian nicoll wrote:
Earthing is complicated if it was me I would get the electricty company
back and ask them what they changed and how it may cause your RCD to
trip. If there is still a problem get professional assistance if you
don't know what you are doing.

But then I doubt you have access to a Megger as the OP has...

--
*24 hours in a day ... 24 beers in a case ... coincidence? *

Dave Plowman London SW 12
RIP Acorn

In article ,
roger wrote:

Tony Williams writes
And (wait for it) the little mains filter that powers the modem
actually has a VDR across Line-Earth.

Could have been the culprit if your earthing is recently
improved. You wouldn't like to post the make and model and approx
age of this item you? Is it a "transformer moulded onto a 13A
plug"?

Noname (yet). All I know atm is that the nuisance tripping
*appeared* to reduce when that VDR was removed. The VDR
is marked "GE U9 275L40B", which probably means a 275V(rms?)
stand-off voltage. So that should be an ok design as long
as the VDR is not faulty, and on normal mains voltages.

--
Tony Williams. Change "nospam" to "ledelec" to email.

In article ,
Christian McArdle wrote:

In this case, replace the ELCB with a Type S 100mA RCD.

Yes, other comments about replacing the Chilton have been
noted. We will be getting a leccy in to do that (and a
few other things). Thanks for a suggested specific type.

--
Tony Williams. Change "nospam" to "ledelec" to email.

Tony Williams wrote in message ...
In article ,
wrote:

I too am a bit perturbed by the apparent setup, with both an
olde-worlde voltage-operated earth leakage breaker, and a
whole-house current-balance one downstream. And as both Nick T
and Dave P have suggested, I'd want to ditch the voltage-operated
item.

The RCCB in the CU only feeds the three ring mains and the shower.
The appliances with fixed wiring (cooker, c/heating boiler,
immersion, lights, etc), are not on that 30mA RCCB and their
possible earth leakages would be detected by the old Chilton.
It makes a sort of sense.

Trust me, it doesn't. Its not nearly as simple as you just suggested.
Mixing a v-ELCB and an unbonded electric shower is not too clever.

So I hacked an old portable RCCB into a differential current
sensor, and have been going around the house looking for
possible (multiple) perps.

You have a fundamental installation problem and need it sorting out.
You might also have a faulty appliance, but that's secondary. Someone
needs to carefully look over your earthing system.

With a v-ELCB in circuit and tripping you will almost certainly have
no real earth in the place, and you may also have voltage
differentials sufficient to cause electrocution in more vulnerable
situations where human and water mix.

Understand this: the v-ELCB disconnects the whole house earth system
in order to function. Its how it works. Your house earth loop must
still be unearthed if the Chilton is tripping.

The basic use of the obsolete v-ELCBs is only secondarily for
additional protection against small earth leaks, its primarily to make
installations safe when there is an inadequate earth. When I say safe,
I mean for obsolete values of safe, and in no way safe for use with an
electric shower.

A v-ELCB on a wiring system is cause for caution. There are real
issues with them. They allow some types of dangerous situations to
occur without tripping.


The biggest perp (oh buggerit!) is this computer system. It
has a differential current of 1.3mA.

normal.


The number of nuisance trips have reduced over the last few
days (to zero yesterday). This may (or may not) be due to two
changes made. That VDR across L-E has been removed, and the
soil around the earthing rod has been thoroughly wetted (this
is a clay soil, which I know to be bone dry down to at least
3ft, with major cracks running through it).

Touch wood.....

Thanks for all the suggestions.

I've got to ask, are you still taking electric showers?


Regards, NT

ony Williams writes
And (wait for it) the little mains filter that powers the modem
actually has a VDR across Line-Earth.

Noname (yet). All I know atm is that the nuisance tripping
*appeared* to reduce when that VDR was removed. The VDR
is marked "GE U9 275L40B", which probably means a 275V(rms?)
stand-off voltage.
Yes.
So that should be an ok design
No, definitely not. Should only be between L & N.
as long
as the VDR is not faulty, and on normal mains voltages.
Normal mains voltage includes very short spikes up to several kV, and
longer ones of several 100 Volts.
During these spikes the VDR is only 100 Ohms or less, so it can put a
lot of unbalance current thro the RCD for the duration of the spike if
your earth is fairly good.
These spikes can trip RCD's anyway on occasion, due to the house-wiring
capacitance to earth and filters on electronic gear, without the help of
spurious VDRs.
If your electrician gives your installation a clean bill of health, but
trips still occur, he can ask the supplier to but a transient recorder
on site for a couple of weeks to see if your trips coincide with
incoming rubbish. Normally foc.

You really didn't want to know all that did you, but maybe it will be
useful to someone else following the thread.
--
roger

delete x's to email

In uk.d-i-y, N. Thornton wrote:
.................................................. ... When I say safe,
I mean for obsolete values of safe....

Thought you were working your way up to a fine Mark Lamar rant there, Nick...

wrote in message ...
In uk.d-i-y, N. Thornton wrote:
.................................................. ... When I say safe,
I mean for obsolete values of safe....

Thought you were working your way up to a fine Mark Lamar rant there, Nick...

I bet this guy is still taking electric showers too.

Regards, NT

In article ,
Tony Williams wrote:

Final followup;

I found an actual definitive perp. All appliances checked out ok,
so isolated the incoming mains and started prodding around inside
the CU. Found a Neutral-Earth short, disconnected all N's and
found it was on an upstairs ring main, so started hunting for
it.... Cutting a very long story, I finally found a low-R between
E+N and the head of a nail, above particular 13A socket. Removed
the nail, and all probs went away.

We've been having a lot of internal/external work done recently
and this nail went in at about the same time as the incoming
cabling was changed. I'm not blaming anyone though, because it
is only about 2ft above the 13A socket, and a good 8" to the right
of it. I now have to remember to warn people of the possibility of
diagonal cabling under the plaster.

Note that (with our very low E-N voltage) the E-N short itself
did not cause a trip, it required a certain amount of load
current on that ring before there was enough unbalance current
between the L-N wires.

Christian McArdle wrote:
In this case, replace the ELCB with a Type S 100mA RCD.

Leccy's been in and done it, as suggested, thank you.

--
Tony Williams. Change "nospam" to "ledelec" to email.