The main RCD in our consumer unit seems to be very much on a 'hair trigger'
and cuts out regularly, causing mayhem to pc users and dvd recorders!

We thought at first it was just when the heater in the washer/drier kicked
in, but closer observation shows that it trips in various combinations of
heating element devices like kettle/toaster/cooker/washer, tending most to
cut out if two of these happen to be on at once.

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

The consumer unit was fitted by a competent electrician and the problem was
not immediately apparent after the fitting.

Do the RCDs wear out?
How can they be tested?

Cheers for any tips,

S

On Apr 5, 7:51*pm, "spamlet" wrote:
The main RCD in our consumer unit seems to be very much on a 'hair trigger'
and cuts out regularly, causing mayhem to pc users and dvd recorders!

We thought at first it was just when the heater in the washer/drier kicked
in, but closer observation shows that it trips in various combinations of
heating element devices like kettle/toaster/cooker/washer, tending most to
cut out if two of these happen to be on at once.

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

The consumer unit was fitted by a competent electrician and the problem was
not immediately apparent after the fitting.

Do the RCDs wear out?
How can they be tested?

Cheers for any tips,

S

You really need to get an electrician in to do some proper
diagnostics. Whilst RCD's can develop faults, my gut feeling is that
you have some other problem.

The lighting MCB tripping when a lamp blows is quite normal though.

Steve

Agree with Steve, sounds like a neutral-earth leak somewhere.

You could try _unplugging_ appliances each in turn to see if the
tripping stops.

cheers,
Pete.

spamlet was thinking very hard :
The main RCD in our consumer unit seems to be very much on a 'hair trigger'
and cuts out regularly, causing mayhem to pc users and dvd recorders!

We thought at first it was just when the heater in the washer/drier kicked
in, but closer observation shows that it trips in various combinations of
heating element devices like kettle/toaster/cooker/washer, tending most to
cut out if two of these happen to be on at once.

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

The consumer unit was fitted by a competent electrician and the problem was
not immediately apparent after the fitting.

Do the RCDs wear out?
How can they be tested?

RCD's operate on the difference in current flow between what goes in on
the live and what comes out via he neutral - the difference being what
is leaking to earth. Enough leakage and they trip. Some of the leakage
can be deliberate in the form of filters. PC's, monitors, printers and
certain appliances etc. are fitted with filters on there mains input.

Sometimes the heating elements on kettles, washers and dishwashers can
deteriorate and start to leak current to ground.

All of the above can cause nuisance tripping of RCD's.

Lacking an insulation tester, the best way is to note what was running
at the time of the tripping and gradually work out the cause.

MCB's quite often trip when lamps suddenly burn out - they are very
sensitive and fast to respond to over current, unlike a fuse. As a lamp
burns out, it can strike up an internal arc which draws excess current,
thus causing the MCB to trip.

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk

In article ,
spamlet wrote:
The main RCD in our consumer unit seems to be very much on a 'hair
trigger' and cuts out regularly, causing mayhem to pc users and dvd
recorders!

We thought at first it was just when the heater in the washer/drier
kicked in, but closer observation shows that it trips in various
combinations of heating element devices like
kettle/toaster/cooker/washer, tending most to cut out if two of these
happen to be on at once.

The current imbalance that the RCD trips out at is additive - sounds like
you have several small leakages which are very common with certain types
of heating elements. Hence the common use of split load units that allow
things like cookers and immersion heaters to be fed from the non RCD
protected side.

Also light circuit RCD always trips when a light bulb goes, but main
also trips if the light's earth is touched when removing lamp holders
even when the lighting RCD is 'off'?

An RCD works by measuring tiny current imbalance between neutral and
earth. Short neutral to earth with the circuit switched off and you get a
tiny current flow between those but not in the line. So the RCD trips.

The consumer unit was fitted by a competent electrician and the problem
was not immediately apparent after the fitting.

Could be the 'leakage' of some appliances have increased since then.

Do the RCDs wear out?
How can they be tested?

There are devices available for this purpose. You might be able to hire
one. But probably cheaper to just replace it on spec. But I doubt it's
actually faulty.

Cheers for any tips,

S

--
*Never miss a good chance to shut up.*

Dave Plowman London SW
To e-mail, change noise into sound.

On Sat, 05 Apr 2008 18:51:54 GMT, spamlet wrote:

Also light circuit RCD always trips when a light bulb goes,

Lighting RCD? or do you mean the MCB? An MCB tripping when a bulb blows is
fairly common for the reasons already posted.

but main also trips if the light's earth is touched when removing lamp
holders even when the lighting RCD is 'off'?

I don't quite follow what you mean. What do you mean by "the light's
earth"? The metal body that the pins of a bayonet bulb twist and latch
into or one of the power connections?

An MCB is a single pole device, the neutral is still connected to the
circuit. Shorting neutral to earth can cause an RCD to trip as not all the
current going to the load in the live is coming back through the RCD on
the neutral, some is going via the short to earth. This sort of indicates
a possible problem with the supplies neutral/earth bonding or with the
earth conection.

But if you have a lot of devices with SMPSU's there could be a lot of
"normal" earth leakage which will have the affect of making the RCD appear
over sensitive. How many, PCs, printers, monitors, dvd and/or video
machines, digi boxen, TVs etc are plugged in? They don't have to be
powered on, just plugging in puts the filter components across the mains.

Do the RCDs wear out?

Yes or more correctly go out of tolerance.

How can they be tested?

Yes.

--
Cheers
Dave.

On 5 Apr, 19:51, "spamlet" wrote:
The main RCD in our consumer unit seems to be very much on a 'hair trigger'
and cuts out regularly, causing mayhem to pc users and dvd recorders!

We thought at first it was just when the heater in the washer/drier kicked
in, but closer observation shows that it trips in various combinations of
heating element devices like kettle/toaster/cooker/washer, tending most to
cut out if two of these happen to be on at once.

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

The consumer unit was fitted by a competent electrician and the problem was
not immediately apparent after the fitting.

Do the RCDs wear out?
How can they be tested?

Cheers for any tips,

S

these things have been a pain in the arse for a long time. they trip
out all the time. it is is easy to link them out and bypass, i have
done this for many year and have no problem with tripping any more, do
it and save you all the bother of lights out etc.

Chas wrote:

these things have been a pain in the arse for a long time. they trip
out all the time. it is is easy to link them out and bypass, i have

If installed and setup correctly they will hardly ever trip (apart from
the times they do so whilst saving your life)

done this for many year and have no problem with tripping any more, do
it and save you all the bother of lights out etc.

Do so and your are a fool.

Fix the problem and not the symptom. Then when something untoward does
happen they can do their job and protect you from electrocution.


--
Cheers,

John.

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

spamlet wrote:

The main RCD in our consumer unit seems to be very much on a 'hair trigger'
and cuts out regularly, causing mayhem to pc users and dvd recorders!

OK, you say "main" RCD... how many do you have?

Could I suggest you have a read through of:

http://wiki.diyfaq.org.uk/index.php?title=RCD

and check the nomenclature to make sure we are not talking at cross
purposes.

We thought at first it was just when the heater in the washer/drier kicked
in, but closer observation shows that it trips in various combinations of
heating element devices like kettle/toaster/cooker/washer, tending most to
cut out if two of these happen to be on at once.

This could indicate that you have a faulty heater element in one or more
of these devices. Alternatively you may just have too many devices /
circuits protected by the device, and hence it is normally very close to
its trip threshold.

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

Do you mean MCB here? If so that is not unusual - especially with mains
halogen bulbs. In some cases replacing the MCB with a "Type C" MCB
(normal ones are type B) can reduce this problem.

http://wiki.diyfaq.org.uk/index.php?title=MCB

If you really do mean the RCD trips on a bulb failure then that is again
an indication that the leakage current is nominally right on the trip
threshold, and even the minuscule current imbalances that can result
from the effects of surges and spikes on the supply are enough to push
it over the edge.

The consumer unit was fitted by a competent electrician and the problem was
not immediately apparent after the fitting.

Do the RCDs wear out?

They can fail, but it is not common.

How can they be tested?

Using a RCD tester is the easiest and most reliable way (especially
ensuring that they are tripping fast enough). However there are other
methods described in the RCD article above. See the section on nuisance
trips.


--
Cheers,

John.

/================================================== ===============\
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|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

In article
,
Chas wrote:
Do the RCDs wear out?
How can they be tested?

these things have been a pain in the arse for a long time. they trip
out all the time. it is is easy to link them out and bypass, i have
done this for many year and have no problem with tripping any more, do
it and save you all the bother of lights out etc.

I've yet to have a nuisance trip on my split load unit. If I had I'd
investigate why.

However, the lighting circuits do sometimes trip their MCBs when a bulb
blows. If this really is a concern they can be changed to ones which allow
a longer 'instant' overload. Or arrange the wiring so the hall and stairs
is on a separate circuit as I've done - that way a source of light is no
further away then than the nearest door.

--
*Never kick a cow pat on a hot day *

Dave Plowman London SW
To e-mail, change noise into sound.

"Chas" wrote in message
...


these things have been a pain in the arse for a long time. they trip
out all the time. it is is easy to link them out and bypass, i have
done this for many year and have no problem with tripping any more, do
it and save you all the bother of lights out etc.


Very bad advice - you are fixing the symptom and not the problem. I suggest
you look at your wiring and refrain from giving such irresponsible advice.

How much does residual current monitor RCM cost, from where?

They seem to have a readout of how much current is being lost to earth,
so could be used to see which appliances are leaking how much
(by turning them on and off)
if an RCM was installed bedore the fuseboxes..

I cant find one on ebay

--

[george]

George (dicegeorge) wrote:
How much does residual current monitor RCM cost, from where?

They seem to have a readout of how much current is being lost to earth,
so could be used to see which appliances are leaking how much
(by turning them on and off)
if an RCM was installed bedore the fuseboxes..

I cant find one on ebay

The only type I have seen are the very high sensitivity clamp meters,
that you place around the phase and neutral to your appliance / circuit
/ whatever of interest. They then measure the (very small) imbalance if
present.

Not cheep mind:

http://wiki.diyfaq.org.uk/index.php?...up_access_tips


--
Cheers,

John.

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

On Sat, 5 Apr 2008 18:51:54 UTC, "spamlet"
wrote:

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

Do you mean RCD or MCB? I guess RCD as you mention touching the earth.
RCDs will trip if neutral / earth are accidentally connected. There is
usually enough voltage.

The basis of an RCD is a current transformer carrying both live and
neutral conductors. If there is a difference in current, sufficient
voltage is developed to trip the circuit. There is little that can go
wrong with the sensor but the trip circuit can fail which is why they
should be tested regularly.

Check the circuits carefully before blaming the RCDs.

--
Jim Backus running OS/2 Warp 3 & 4, Debian Linux and Win98SE
bona fide replies to j dot backus the circle thingy jita dot
demon dot co dot uk

On Sat, 05 Apr 2008 17:12:47 -0700, Chas wrote:

these things have been a pain in the arse for a long time. they trip
out all the time. it is is easy to link them out and bypass, i have
done this for many year and have no problem with tripping any more, do
it and save you all the bother of lights out etc.

If you're after a Darwin award you could also try replacing
those flimsy fuses with more robust chunks of solid copper and dispensing
with earth conductors on your electrical system. Then, since your
lights aren't likely to trip out, what's the point of having
banisters around your stairs? Next to go those pesky smoke detectors.
Don't forget to bypass those unreliable flame sensors etc on your
boiler. In your car you can get rid of those irritating warning
lights, not to mention those awkward seat belts, and so on ...

--
John Stumbles

I can't stand intolerance

http://www.westernautomation.com/pages/demystify.htm

Problems With RCDs
As far as users are concerned, the single greatest problem with RCDs is
nuisance tripping. This problem will either be due to the design of the RCD
or due to the installation. Nuisance tripping can be a frustrating problem
for the user and there have been cases where RCDs were strapped out, removed
from installations completely or replaced with RCDs with a higher rated trip
current. All of these types of actions are very dangerous and should be
avoided. Where the problem lies with the RCD design, it is usually
attributable to factors such as voltage spikes, surges, switching
transients, noise, inrush currents, etc. Over recent years, the problem of
nuisance tripping attributable to the RCD itself have been addressed by IEC.
New tests have been introduced into the product standards to ensure that
RCDs have a reasonably high immunity to nuisance tripping. Unfortunately,
all RCDs do not comply with the new requirements. To minimise this problem,
ensure as far as possible that the RCD has compliance to IEC61008 or EN61008
(RCCBs) or IEC61009 or EN61009 (RCBOs) and also to IEC61543 or EN61543 (EMC
requirements for RCDs).
To the top

Sometimes the problem of nuisance tripping is attributable to the
installation. IEC recommend that the standing earth leakage current on the
installation should not exceed 30% of the rated trip current of the RCD
intended to be used on that installation. This means that for a 30mA RCD,
the standing earth leakage current should not exceed 10mA. Given that a 30mA
RCD may trip anywhere from 15 - 30mA, a 10mA standing leakage current will
virtually prime the RCD to trip. In general, RCDs cannot tell the difference
between a standing leakage current and an earth fault current. The sum of
these two currents is the residual current seen by the RCD and if this
aggregate current is greater than its rated trip current, the RCD will trip,
unless it's faulty. (but that's another story)
To the top

The problem of standing leakage currents is increasing. This is due to two
factors:

1.. equipment manufacturers filtering internally generated noise to earth
2.. fitting of RFI suppression to provide immunity to mains borne noise.
Recently introduced European Directives on EMC require manufacturers of
products, appliances, equipment, etc. to contain within specified limits the
levels of RFI type emissions produced by their products. Manufacturers often
have to resort to the use of filtering circuits to meet these requirements.
The filtering circuits can divert high frequency signals to earth, but can
also result in the flow of significant levels of leakage current to earth at
the standard 50Hz frequency. Under IEC rules, electrical appliances may
allow a standing leakage current of up to 3.5mA/50Hz to flow to earth. Such
current levels coupled with other sources of standing leakage currents can
give rise to nuisance tripping.
To the top

Washing machines, oil or gas burners and even immersion heaters can
contribute to nuisance tripping. Temperature and humidity may also be
factors in nuisance tripping. Other factors contributing to nuisance
tripping may be poor earth terminations, surge suppressers, neutral voltage
rising above earth potential, etc. A very sneaky problem is where an earth
fault current on the supply side of the RCDs manages to appear as a load
side fault to the RCD, causing it to trip. This problem is more usually
associated with IT systems, or on TT systems with high earth impedance.
Before changing the RCD in response to a nuisance tripping problem, check
the installation by measuring the standing leakage current and carrying out
an earth loop test. Also try to identify equipment that is likely to
contribute to standing or transient earth currents. A residual current
monitor can be fitted to an installation to detect the level of the standing
earth leakage current or even transient leakage currents.
To the top

VD - v - VI RCDs

--

[george]

~ [g] ~
~ ~
~ 07970 378 572 ~
~ www.dicegeorge.com ~
~ (c)2008 ~
~ ~

John Rumm wrote:

The only type I have seen are the very high sensitivity clamp meters,
that you place around the phase and neutral to your appliance / circuit
/ whatever of interest. They then measure the (very small) imbalance if
present.

Not cheep mind:

http://wiki.diyfaq.org.uk/index.php?...up_access_tips

Err, error no. 42: context mismatch in link destination :~) Perhaps you
meant http://www.martindale-electric.co.uk/clamp.htm#cm67

--
Andy

Andy Wade wrote:

The only type I have seen are the very high sensitivity clamp meters,
that you place around the phase and neutral to your appliance /
circuit / whatever of interest. They then measure the (very small)
imbalance if present.

Not cheep mind:

http://wiki.diyfaq.org.uk/index.php?...up_access_tips

Err, error no. 42: context mismatch in link destination :~) Perhaps you
meant http://www.martindale-electric.co.uk/clamp.htm#cm67

Ermm, yes - much closer ;-)

(damn past buffer - keep any crap some fool sticks in it!)

--
Cheers,

John.

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

"spamlet" wrote in message
. ..
The main RCD in our consumer unit seems to be very much on a 'hair
trigger' and cuts out regularly, causing mayhem to pc users and dvd
recorders!

We thought at first it was just when the heater in the washer/drier kicked
in, but closer observation shows that it trips in various combinations of
heating element devices like kettle/toaster/cooker/washer, tending most to
cut out if two of these happen to be on at once.

Also light circuit RCD always trips when a light bulb goes, but main also
trips if the light's earth is touched when removing lamp holders even when
the lighting RCD is 'off'?

The consumer unit was fitted by a competent electrician and the problem
was not immediately apparent after the fitting.

Do the RCDs wear out?
How can they be tested?

Cheers for any tips,

S


Well!
I have to say a big thankyou, and that I am very impressed with you all!
Thankyou for this excellent lesson and references to all who contributed.
I had not noticed there was even a Diy version of Wiki, and now it's been
pointed out, perhaps I will not have to trouble you with so many silly
questions in future.

Apologies for having been offline since asking the question, and for the
confusion caused by lumping RCDs and MCBs together - most of you saw what I
really meant, thanks.

It turns out that we had had two problems with elements at the same time. I
had just replaced an oven element, that had been gradually failing and was
only realised when it finally went completely open circuit.

After that replacement, I was anticipating a blissful end to the tripping,
but then I realised, after following up complaints from the 'other half'
that the washing machine was 'rubbish', that it had been washing in cold
water, and probably for some time!

A clip had come adrift inside the drum and allowed the heater element to be
rubbed down gradually, causing the leakage, but, subsequently, a damper
strut had broken, and thrown a connector off the element, thus showing up as
the 'cold water problem', and temporarily ending the tripping... Till I
went to put the connector back on (not, at that stage, noticing the broken
strut)!

I should have looked for this earth leakage problem before, but, as the
washing machine element was fairly new, I had thought that was probably ok,
and had not remembered about the clip that holds it away from the drum and
what might happen if this were to break...

So, it looks like I was taking the RCD's name in vain, and it really is
doing its job nicely (Though I do have a fair number of IT and video things
about, so I will definitely bear in mind all of what has been said in this
thread above in future).

So, now all I have to do is think of a way I might be able to retain a new
washing machine element in place without having to strip every last thing
out and split the drums, just for the sake of a little piece of stainless
'coathanger wire'. Drills and grommets come to mind, but that's for another
thread or forum.

Many thanks once again,

S