"Michael Chare" wrote in message ...
[news:uk.d-i-y added and follow-up set to uk.d-i-y]
| I am contemplating fitting an RCD (Residual Current Device /
| Earth Leakage Relay ) in the power supply to my house between
| the meter and the fuse box.

Whole-house RCDs are deprecated and are contrary to the IEE wiring
regulations. It is unacceptable to lose power to lighting and smoke alarm
circuits in the event of an earth leakage on a power circuit. If you will
google this subject on news:uk.d-i-y you will find anecdotal evidence that
whole-house RCDs may cause more deaths through sudden lighting failure
causing a person to fall, than are caused by electrocution annually.

The only requirement for whole-house RCDs is in an installation with TT
(earth electrode) earthing, when it should be a 100mA time-delay RCD and the
power circuits should be protected by 30mA RCDs such that proper
discrimination is obtained.

RCD protection should be provided to power circuits either using a 'split
load' Consumer Unit where the power circuits are run through a 30mA RCD but
the lighting circuits are not, or through individual RCBOs for each circuit,
which combine the functions of MCB and RCD.

| The problem with doing this is that it could involve some hot wiring
| which I dont much like. So I have some questions:
| a) The safest procedure looks to be to pull out the Electricity Board
| (or who ever they are now) Fuses but I would have to break the seals
| and this might annoy them. I have never tried doing this, I just
| assume that it is possible and reasonably easy.

You should only have one service fuse, and the "board" don't usually mind
too much if that is pulled. Ensure it is pulled and replaced when no current
is flowing.

| b) I could break the seals on the meter and disconnect the wires,
| coming from it. Again this would no doubt annoy the Electricity Board,
| but looks to be quite easy and would involve minimal hot wiring, and
| I would not have to tamper with the fuses.

This *will* annoy the electricity co and does not remove the need for hot
wiring; you are still handling live terminals on the meter. If you were
going to do this you should pull the main fuse, remove the meter tails from
the existing CU and connect to the RCD supply terminals, and provide new
meter tails from the RCD load terminals to the existing CU. You should not
open the seals on the meter.

| I would happily post in a more relevant news group if I could find one.

copied to and follow-ups set to uk.d-i-y That ng has an extensive FAQ
section at
http://www.diyfaq.org.uk/

Owain

On Mon, 15 Dec 2003 20:21:16 UTC, "Owain"
wrote:

You should only have one service fuse, and the "board" don't usually mind
too much if that is pulled. Ensure it is pulled and replaced when no current
is flowing.

And cover up the exposed terminals while you're working - you do NOT
want to touch the exposed supply-side one, nor drop anything into it....

--
Bob Eager
rde at tavi.co.uk
PC Server 325*4; PS/2s 9585, 8595, 9595*2, 8580*3,
P70...

Whole-house RCDs are deprecated and are contrary to the IEE wiring
regulations. It is unacceptable to lose power to lighting and smoke alarm
circuits in the event of an earth leakage on a power circuit. If you will
google this subject on news:uk.d-i-y you will find anecdotal evidence that
whole-house RCDs may cause more deaths through sudden lighting failure
causing a person to fall, than are caused by electrocution annually.

Our CU is a split load, the sockets are run off a 100A/30mA RCD (Via MCB's)

The lighting is run off a 40A/30mA RCD, again via MCB's

This was apparently installed when it became apparent I was very interested
in electricity
at a very early age!

Is this arrangement not allowed, as IMHO there is more risk of electrocution
when some dopey tw*t tries to change the dead bulb with the switch still on
than the same dopy tw*t unplugging something when it is switched on!

If someone was up a ladder, using a power drill for example, and the drill
caused an earth fault, the sockets RCD would trip, leaving the lights on in
my setup.

Just my thoughts here...

Sparks...

If someone was up a ladder, using a power drill for example, and the drill
caused an earth fault, the sockets RCD would trip, leaving the lights on
in
my setup.

Personally, I'd remove the lighting RCD. Even with it on, you'll still get
enough jolt to knock you off the ladder, and you are unlikely to electrocute
yourself with a pendant fitting.

Loss of a lighting circuit can be very dangerous, especially in a fire, or
whilst in a dangerous position, such as up a ladder.

Christian.

| I am contemplating fitting an RCD (Residual Current Device /
| Earth Leakage Relay ) in the power supply to my house between
| the meter and the fuse box.

Often, the easiest way to add RCD protection to an existing installation
(using DIN rail CU) is to replace socket circuit MCBs with single width
RCBOs, if they are available. It isn't necessarily the cheapest way,
although if there are only 1 or 2 circuits to be protected, it can still be
cost effective. It is certainly the best way to do it, however many ways
there are.

Christian.

On Tue, 16 Dec 2003 00:37:33 -0000, "Sparks"
wrote:

Is this arrangement not allowed, as IMHO there is more risk of electrocution
when some dopey tw*t tries to change the dead bulb with the switch still on
than the same dopy tw*t unplugging something when it is switched on!

It is a classic example of the original specifier not understanding
risk at all and making things more dangerous by installing "safety"
measures.

Putting an RCD in stops you being electrocuted whilst changing a
light bulb. As far as I can find out the number of people killed or
admitted to hospital from domestic premises in the UK for this reason
in the last 10 years is precisely zero.

On the other hand in the same period hundreds have died and thousands
been injured in fires at night. Many more have been killed or
injured in falls down stairs at night. Lighting RCD's regularly trip
if a bulb blows (especially on switch on) and trip very quickly in a
fire as combustion products create leakage paths in wiring. Both
circumstances create risks considerably greater than the trivial one
of electrocution while changing a bulb. The last thing you want in a
fire at night is the lights going out on you.



--
Peter Parry.
http://www.wpp.ltd.uk/

"Peter Parry" wrote in message
...

Putting an RCD in stops you being electrocuted whilst changing a
light bulb. As far as I can find out the number of people killed or
admitted to hospital from domestic premises in the UK for this reason
in the last 10 years is precisely zero.

Well, the only person I know personally who's received a serious electric
shock at home received it from a wall-mounted (i.e. fixed) light fitting,
while she was changing a light bulb.

On the other hand in the same period hundreds have died and thousands
been injured in fires at night. Many more have been killed or
injured in falls down stairs at night. Lighting RCD's regularly trip
if a bulb blows (especially on switch on)

No they don't, that's the MCBs which trip. And *their* installation is
considered to be a good thing.

and trip very quickly in a
fire as combustion products create leakage paths in wiring. Both
circumstances create risks considerably greater than the trivial one
of electrocution while changing a bulb. The last thing you want in a
fire at night is the lights going out on you.

I think that to form a balanced opinion at this point, we also need to know
what proportion of fires are caused by electrical faults which might have
been detected by an RCD.

I've just spent 9 years living in a house with a 30mA RCD covering the lot,
with a 6A MCB on the lighting circuit. The former is frowned upon, the
latter is supposed to be good.

The former *never* tripped except when there was a fault on an appliance.
The latter tripped on probably 60% of bulb failures, as often as not
requiring a journey downstairs in the dark (have you seen the number of
people that die in stair-falls) to reset the breaker. If suddenly plunging
a house into darkness is a dangerous, then so are typical 6A type-I (B,
nowadays) MCBs on lighting circuits.

You're very acurately restating uk.d-i-y received wisdom on the subject (as
a grandee, perhaps you're the origin of it :-), but it doesn't match my
experience.

Will

If suddenly plunging a house into darkness is a dangerous, then
so are typical 6A type-I (B, nowadays) MCBs on lighting circuits.

No, it is incandescent light bulbs which are dangerous and should be banned.
Lighting circuits intended to have incandescent monstrosities may be better
equiped with a 5A cartridge fuse holder (and supply of fuses).

Christian.

Putting an RCD in stops you being electrocuted whilst changing a
light bulb. As far as I can find out the number of people killed or
admitted to hospital from domestic premises in the UK for this reason
in the last 10 years is precisely zero.

Well, the only person I know personally who's received a serious electric
shock at home received it from a wall-mounted (i.e. fixed) light fitting,
while she was changing a light bulb.

I too know of someone who did the exact same thing - they were thrown
across the room (No RCD)

On the other hand in the same period hundreds have died and thousands
been injured in fires at night. Many more have been killed or
injured in falls down stairs at night. Lighting RCD's regularly trip
if a bulb blows (especially on switch on)

No they don't, that's the MCBs which trip. And *their* installation is
considered to be a good thing.

Same here, out RCD has never tripped when a bulb has popped - The MCB's do
The blowing of the bulb causes over current, not leakage.

and trip very quickly in a
fire as combustion products create leakage paths in wiring. Both
circumstances create risks considerably greater than the trivial one
of electrocution while changing a bulb. The last thing you want in a
fire at night is the lights going out on you.

I think that to form a balanced opinion at this point, we also need to
know
what proportion of fires are caused by electrical faults which might have
been detected by an RCD.

I've just spent 9 years living in a house with a 30mA RCD covering the
lot,
with a 6A MCB on the lighting circuit. The former is frowned upon, the
latter is supposed to be good.

I would always have a seperate MCB on the lights, especially if there were
inquisative kids about.

Is it a requirement to have no RCD, or is it mearly a suggestion?
(Not that it's getting changed anyway)

I fell there is far more risk of someone poking their fingers in the fitting
while it is on, then there is of a fire breaking out - how often are
[regular GLS] bulbs changed compaired to how many times fires break out
in a house?

The former *never* tripped except when there was a fault on an appliance.
The latter tripped on probably 60% of bulb failures, as often as not
requiring a journey downstairs in the dark (have you seen the number of
people that die in stair-falls) to reset the breaker. If suddenly
plunging
a house into darkness is a dangerous, then so are typical 6A type-I (B,
nowadays) MCBs on lighting circuits.

I have installed an emergancy light in the cupboard where the breakers are,
If the lighting trips (or there is a power cut) this illuminates

Sparks...

I fell there is far more risk of someone poking their fingers in
the fitting while it is on, then there is of a fire breaking out
how often are [regular GLS] bulbs changed compaired to how many
times fires break out in a house?

Yes, but the shock is rarely fatal or injurous, just painful and
embarassing. The nature of the fitting doesn't lend it to maintaining a
solid grip on you long enough to cause electrocution.

And quick frankly, if you electrocute yourself changing a bulb, you're
probably capable of removing yourself from the gene pool in a much more
spectacular fashion.

The reason not to install an RCD is because lights failing is a demonstrable
and measurable cause of death either during house fires, or from sudden
darkness during a dangerous task (such as operating machinery, or balancing
on ladders). Electrocution from changing light bulbs doesn't figure in the
statistics.

Christian.

"Christian McArdle" wrote in message
. net...
I fell there is far more risk of someone poking their fingers in
the fitting while it is on, then there is of a fire breaking out
how often are [regular GLS] bulbs changed compaired to how many
times fires break out in a house?

Yes, but the shock is rarely fatal or injurous, just painful and
embarassing. The nature of the fitting doesn't lend it to maintaining a
solid grip on you long enough to cause electrocution.

....just imagining frail old lady holding [Earthed] wall light to steady
herself with one hand,
and attempting to get the new bulb in with the other, and decides as she
cant see the hole
(its above her head) she fells around for it with her hand.

It must happen...

And quick frankly, if you electrocute yourself changing a bulb, you're
probably capable of removing yourself from the gene pool in a much more
spectacular fashion.

Well, it ain't always me that changes light bulbs, if you get my drift

The reason not to install an RCD is because lights failing is a
demonstrable
and measurable cause of death either during house fires, or from sudden
darkness during a dangerous task (such as operating machinery, or
balancing
on ladders). Electrocution from changing light bulbs doesn't figure in the
statistics.

That's why there are two RCD's - one for the lights, and a separate one for
the
sockets (and an emergency light above the CU!)

Christian.

On Tue, 16 Dec 2003 16:22:40 -0000, "Will Dean"
wrote:

"Peter Parry" wrote

Well, the only person I know personally who's received a serious electric
shock at home received it from a wall-mounted (i.e. fixed) light fitting,
while she was changing a light bulb.

Basing a judgement of low probability events on personal experience
is never wise.

On the other hand in the same period hundreds have died and thousands
been injured in fires at night. Many more have been killed or
injured in falls down stairs at night. Lighting RCD's regularly trip
if a bulb blows (especially on switch on)

No they don't, that's the MCBs which trip. And *their* installation is
considered to be a good thing.

RCD's regularly trip when bulbs blow.

I think that to form a balanced opinion at this point, we also need to know
what proportion of fires are caused by electrical faults which might have
been detected by an RCD.

Not very many. About 20 deaths a year are caused by fires where the
cause is known after proper investigation to be an electrical fault.
This is about 4% of the total who die in house fires.

The following are based on 1999 figures from the Home Office.

The number of people killed or severely injured by electrocution in
domestic accidents the UK each year is very small. Even if you
include accidents which are not electrocution but attributable to it
(such as falling off a ladder after touching a live cable) the
numbers involved in domestic accidents are still small, about 25
deaths and 2000 injuries of all severities (compare this with 70
deaths and 40,000 injuries caused by general DIY activities). Those
figures have not reduced since whole house RCD's started to be used
although the number of electrocutions in the garden (listed
separately in the figures) has fallen.

The total number of people killed in accidents in the home each year
is about 4,000, of this roughly half are due to falls and about 1,000
due to falls down stairs.

The number of people killed or injured in house fires is also
depressingly large, many times greater than those killed by
electrocution. Typically 500 people die and 18,000 are seriously
injured each year by fire in the home.

Of these deaths about 20 are attributable to electrical fires some of
which an RCD might have prevented. The remainder are caused by
non-electrical ignition.

Of the 4,000 people killed in both falls and fires each year there is
no easily available breakdown of contributory factors. However some
police and fire reports do give further information. Of these I have
seen only a very small number from one area, however within these
there were a significant minority, probably about 10-20 which
mentioned that lights were out and could not be turned back on from
the light switch when the emergency services arrived. Only one or
two of these, usually fire service reports, specifically mention
RCD's having tripped. Nonetheless it is reasonable to infer even
from this imperfect data that the number of people killed in falls
and fires in which tripped RCD's were the cause or a major
contributory factor is significantly higher than the number of people
protected by them _in the home_. In the garden or garage is quite
another matter.

I've just spent 9 years living in a house with a 30mA RCD covering the lot,
with a 6A MCB on the lighting circuit. The former is frowned upon, the
latter is supposed to be good.

The former *never* tripped except when there was a fault on an appliance.

Of the 20 odd houses I have lived in most had 30mA RCD's covering
everything and the majority of those would quite consistently knock
everything off at the slightest provocation and especially if bulbs
failed.

The latter tripped on probably 60% of bulb failures, as often as not
requiring a journey downstairs in the dark (have you seen the number of
people that die in stair-falls) to reset the breaker. If suddenly plunging
a house into darkness is a dangerous, then so are typical 6A type-I (B,
nowadays) MCBs on lighting circuits.

As has been pointed out the danger is in using inappropriate
lighting. If the design of the house or the condition of the
occupants makes a fall likely don't fit incandescent bulbs in lights
needed for safe navigation of stairs.

You're very acurately restating uk.d-i-y received wisdom on the subject (as
a grandee, perhaps you're the origin of it :-),

Indeed I suspect I am.

but it doesn't match my experience.

My experience is of lifting the burnt corpses of family out of the
way of the locked front door they had died against while trying to
break it down to escape the fire which killed them. The key was on
the floor under the body of the youngest child, the door was covered
in blood from their hands. By the time they were found there was no
consumer unit remaining but the neighbours all said they had seen no
lights on in the house as the fire developed. Did they die because
of the fathers love of securely locking the doors or because they
couldn't see where the key fell? I don't even know if the house was
fitted with an RCD but in view of the date and the fact it was a
renovated council property I suspect it had a single whole house 30mA
RCD.

However, as I said earlier, relying upon personal experience is
unwise. The reason I won't have RCD's on lighting circuits in the
house (now I have a choice) is based upon evidence, not experience.

--
Peter Parry.
http://www.wpp.ltd.uk/

On Tue, 16 Dec 2003, Christian McArdle wrote:

Loss of a lighting circuit can be very dangerous, especially in a fire, or
whilst in a dangerous position, such as up a ladder.

Seems to me that the obvious solution is to have whole-house RCD
protection and install battery-backed emergency luminaires at e.g. stair
wells.

The ultra-cautious could have 30mA RCBOs protecting each circuit
separately.

--
Alistair Riddell - BOFH
Microsoft - because god hates us

"Peter Parry" wrote

RCD's regularly trip when bulbs blow.

They shouldnt, as RCD's will trip only if there is an imbalance between the
live
and the nuterual, when a bulb blows, it causes an overcurrent, this is when
the MCB's trip
as there is no earth inside the bulb, there cant be an imbalance.


Of the 20 odd houses I have lived in most had 30mA RCD's covering
everything and the majority of those would quite consistently knock
everything off at the slightest provocation and especially if bulbs
failed.

This is not good, as has been previously mentioned - I still cant understand
why an RCD
is tripping on a bulb failure..(maybe it is faulty, or is under rated?)

The latter tripped on probably 60% of bulb failures, as often as not
requiring a journey downstairs in the dark (have you seen the number of
people that die in stair-falls) to reset the breaker. If suddenly
plunging
a house into darkness is a dangerous, then so are typical 6A type-I (B,
nowadays) MCBs on lighting circuits.

As has been pointed out the danger is in using inappropriate
lighting. If the design of the house or the condition of the
occupants makes a fall likely don't fit incandescent bulbs in lights
needed for safe navigation of stairs.

Just out of interest, why not?

Do you mean fir CFL's, or am i missing the point here!

..

My experience is of lifting the burnt corpses of family out of the
way of the locked front door they had died against while trying to
break it down to escape the fire which killed them. The key was on
the floor under the body of the youngest child, the door was covered
in blood from their hands. By the time they were found there was no
consumer unit remaining but the neighbours all said they had seen no
lights on in the house as the fire developed. Did they die because
of the fathers love of securely locking the doors or because they
couldn't see where the key fell? I don't even know if the house was
fitted with an RCD but in view of the date and the fact it was a
renovated council property I suspect it had a single whole house 30mA
RCD.

We have already agreed that a whole house RCD is bad.
This is NOT what I am suggesting here!


Sparks...

"Peter Parry" wrote in message
...

RCD's regularly trip when bulbs blow.

This is not my experience either.

Can you propose a mechanism for this? The only one which comes to mind
would be that you already had a neutral-earth leakage fault, and the rise in
neutral current caused by the bulb-failure arc was sufficient to create a
leak to earth.

As has been pointed out the danger is in using inappropriate
lighting. If the design of the house or the condition of the
occupants makes a fall likely don't fit incandescent bulbs in lights
needed for safe navigation of stairs.

It wouldn't matter what kind of lamp illuminated the stairs if the lighting
circuit had tripped.

My experience is of lifting the burnt corpses of family out of the
way of the locked front door they had died against while trying to
break it down to escape the fire which killed them. The key was on
the floor under the body of the youngest child, the door was covered
in blood from their hands. By the time they were found there was no
consumer unit remaining but the neighbours all said they had seen no
lights on in the house as the fire developed. Did they die because
of the fathers love of securely locking the doors or because they
couldn't see where the key fell? I don't even know if the house was
fitted with an RCD but in view of the date and the fact it was a
renovated council property I suspect it had a single whole house 30mA
RCD.

Yes, but you're a (former?) member of the emergency services, aren't you?
As such, I have every sympathy with the gruesome sights you might have had
to deal with in your chosen profession, but I do believe that members of
such services are uniquely *ill* placed to give general advice about risks
to ordinary people.

To a fireman, a horrible death in a house fire is a common occurence - to
me, as a resident of a non-smoking household, it's extremely unlikely to be
the cause of my, or my family's demise. Personally, if I'm doing the
neurotic parent bit I worry about road safety a darn sight more.

However, as I said earlier, relying upon personal experience is
unwise. The reason I won't have RCD's on lighting circuits in the
house (now I have a choice) is based upon evidence, not experience.

TBH, if you know of a property that has an RCD which trips when light bulbs
blow, then you ought to advice the occupants to get the wiring fixed.

Will

Well said Peter. You are probably a voice in the wilderness, like that
chief inspector who categorically stated that 'excess speed is the cause
of less than 7% of accidents' and 'speed cameras do not (statistically)
reduce road deaths'.

I am definitely with you on this. My 30mA RCD tripped about 50% of the
time when any bulb blew, with the MCB about 60%. Sometimes both.

Its bloody dangerous feeling down te saircase to get to the consumer
unit, especialy if you have left the casing off...:-)


Peter Parry wrote:

On Tue, 16 Dec 2003 16:22:40 -0000, "Will Dean"
wrote:


"Peter Parry" wrote


Well, the only person I know personally who's received a serious electric
shock at home received it from a wall-mounted (i.e. fixed) light fitting,
while she was changing a light bulb.


Basing a judgement of low probability events on personal experience
is never wise.


On the other hand in the same period hundreds have died and thousands
been injured in fires at night. Many more have been killed or
injured in falls down stairs at night. Lighting RCD's regularly trip
if a bulb blows (especially on switch on)

No they don't, that's the MCBs which trip. And *their* installation is
considered to be a good thing.


RCD's regularly trip when bulbs blow.


I think that to form a balanced opinion at this point, we also need to know
what proportion of fires are caused by electrical faults which might have
been detected by an RCD.


Not very many. About 20 deaths a year are caused by fires where the
cause is known after proper investigation to be an electrical fault.
This is about 4% of the total who die in house fires.

The following are based on 1999 figures from the Home Office.

The number of people killed or severely injured by electrocution in
domestic accidents the UK each year is very small. Even if you
include accidents which are not electrocution but attributable to it
(such as falling off a ladder after touching a live cable) the
numbers involved in domestic accidents are still small, about 25
deaths and 2000 injuries of all severities (compare this with 70
deaths and 40,000 injuries caused by general DIY activities). Those
figures have not reduced since whole house RCD's started to be used
although the number of electrocutions in the garden (listed
separately in the figures) has fallen.

The total number of people killed in accidents in the home each year
is about 4,000, of this roughly half are due to falls and about 1,000
due to falls down stairs.

The number of people killed or injured in house fires is also
depressingly large, many times greater than those killed by
electrocution. Typically 500 people die and 18,000 are seriously
injured each year by fire in the home.

Of these deaths about 20 are attributable to electrical fires some of
which an RCD might have prevented. The remainder are caused by
non-electrical ignition.

Of the 4,000 people killed in both falls and fires each year there is
no easily available breakdown of contributory factors. However some
police and fire reports do give further information. Of these I have
seen only a very small number from one area, however within these
there were a significant minority, probably about 10-20 which
mentioned that lights were out and could not be turned back on from
the light switch when the emergency services arrived. Only one or
two of these, usually fire service reports, specifically mention
RCD's having tripped. Nonetheless it is reasonable to infer even
from this imperfect data that the number of people killed in falls
and fires in which tripped RCD's were the cause or a major
contributory factor is significantly higher than the number of people
protected by them _in the home_. In the garden or garage is quite
another matter.


I've just spent 9 years living in a house with a 30mA RCD covering the lot,
with a 6A MCB on the lighting circuit. The former is frowned upon, the
latter is supposed to be good.

The former *never* tripped except when there was a fault on an appliance.


Of the 20 odd houses I have lived in most had 30mA RCD's covering
everything and the majority of those would quite consistently knock
everything off at the slightest provocation and especially if bulbs
failed.


The latter tripped on probably 60% of bulb failures, as often as not
requiring a journey downstairs in the dark (have you seen the number of
people that die in stair-falls) to reset the breaker. If suddenly plunging
a house into darkness is a dangerous, then so are typical 6A type-I (B,
nowadays) MCBs on lighting circuits.


As has been pointed out the danger is in using inappropriate
lighting. If the design of the house or the condition of the
occupants makes a fall likely don't fit incandescent bulbs in lights
needed for safe navigation of stairs.


You're very acurately restating uk.d-i-y received wisdom on the subject (as
a grandee, perhaps you're the origin of it :-),


Indeed I suspect I am.


but it doesn't match my experience.


My experience is of lifting the burnt corpses of family out of the
way of the locked front door they had died against while trying to
break it down to escape the fire which killed them. The key was on
the floor under the body of the youngest child, the door was covered
in blood from their hands. By the time they were found there was no
consumer unit remaining but the neighbours all said they had seen no
lights on in the house as the fire developed. Did they die because
of the fathers love of securely locking the doors or because they
couldn't see where the key fell? I don't even know if the house was
fitted with an RCD but in view of the date and the fact it was a
renovated council property I suspect it had a single whole house 30mA
RCD.

However, as I said earlier, relying upon personal experience is
unwise. The reason I won't have RCD's on lighting circuits in the
house (now I have a choice) is based upon evidence, not experience.

Sparks wrote:

"Peter Parry" wrote


RCD's regularly trip when bulbs blow.


They shouldnt, as RCD's will trip only if there is an imbalance between the
live
and the nuterual, when a bulb blows, it causes an overcurrent, this is when
the MCB's trip
as there is no earth inside the bulb, there cant be an imbalance.



You haven't thought it through. there is ALWAYS some neutral earth
leakage. It occurs every time an oh so rigorously RFI suppressed switch
mode power supply (TV, computer, monitor, LV lighting) or any suppresed
motor is plugged into the circuits. Enough of these and the 30mA RCD is
on a hair trigger. Any voltage surge and over she goes.


Here it was a toss up whether the RCD. MCB, or both would go.

Now with a 100mA RCD, its not gone since.

Whether or not I install RCBO's in the few circuits the regs demand
depends on the building inspector.

Proper standrads of wiring and better plugs, sockets, and particularly
the use of double insulation and plastic cases have done far far more to
reduce shock hazard than RCD's.

I can clearly remember getting shocks of metal fires, whose earthing
wwas poor or nonexistent, and whose rubber coated wires frayed all too
easily. Now we seldom have metal frames, and we don't have users
installing their own plugs nuch either.





Of the 20 odd houses I have lived in most had 30mA RCD's covering
everything and the majority of those would quite consistently knock
everything off at the slightest provocation and especially if bulbs
failed.


This is not good, as has been previously mentioned - I still cant understand
why an RCD
is tripping on a bulb failure..(maybe it is faulty, or is under rated?)



I have just explained why.




We have already agreed that a whole house RCD is bad.
This is NOT what I am suggesting here!



Actually, I think its quite good, provided it trips only when there is a
significant dangerous fault.

Its the nusiance tripping that is so serious.



Sparks...

Will Dean wrote:

"Peter Parry" wrote in message
...

RCD's regularly trip when bulbs blow.


This is not my experience either.

Can you propose a mechanism for this? The only one which comes to mind
would be that you already had a neutral-earth leakage fault, and the rise in
neutral current caused by the bulb-failure arc was sufficient to create a
leak to earth.



There is always some leakage from both L & N to earth. If nothing else
due to the capacitance between the miles of T & E laid over the house.
And more especially in all the capacitors used to RFI filter electronic
devices.

There is always some inductance in the supply, due to cable lengths

and transformer secondaries. High speed switching currents will

work with the capacitances to flip RCDs

On Tue, 16 Dec 2003 21:35:43 +0000, The Natural Philosopher
wrote:

Well said Peter. You are probably a voice in the wilderness, like that
chief inspector who categorically stated that 'excess speed is the cause
of less than 7% of accidents' and 'speed cameras do not (statistically)
reduce road deaths'.

I am definitely with you on this. My 30mA RCD tripped about 50% of the
time when any bulb blew, with the MCB about 60%. Sometimes both.

Its bloody dangerous feeling down te saircase to get to the consumer
unit, especialy if you have left the casing off...:-)



Reading this, and especially the very sad ending to Peter's post makes
me think that it would not be a bad idea to add emergency lighting as
something that should be included in Building Regulations for new
properties and incentivised for others in some way, especially for the
elderly and others with mobility difficulties..

We already have mains powered smoke detectors as an addition,
basically to get over people taking the batteries out or forgetting to
replace them.

Non-maintained small fluorescent lights are not very expensive,
although the fittings are pretty ugly. Undoubtedly this could be
improved if there were a consumer premises market for them.

It would seem to me that the populace would be better served with a
lighting measure like this rather than the mandatory low energy lamps
stuff. In fact with a bit of creativity, both objectives could be
met in a single package.

I am not sure what sort of size and power level that they would need
to be to provide sufficient light say at the top and bottom of a
staircase in a fire, but to be able to see adequately during a power
cut, then the little 8w ones are probably enough.

I have my consumer unit at the back of a cupboard in the kitchen and
it would not be easy to see in the dark.
I fitted a small maintained fitting, run from a (non-RCD ptotected)
lighting circuit and operated also by a plunger switch on the cupboard
door. Thus I have a light over the CU for when I want to work on it
with the power deliberately off and also to be able to see the
breakers after a trip.




..andy

To email, substitute .nospam with .gl

RCD's regularly trip when bulbs blow.


They shouldnt, as RCD's will trip only if there is an imbalance between
the
live
and the nuterual, when a bulb blows, it causes an overcurrent, this is
when
the MCB's trip
as there is no earth inside the bulb, there cant be an imbalance.



You haven't thought it through. there is ALWAYS some neutral earth
leakage. It occurs every time an oh so rigorously RFI suppressed switch
mode power supply (TV, computer, monitor, LV lighting) or any suppresed
motor is plugged into the circuits. Enough of these and the 30mA RCD is
on a hair trigger. Any voltage surge and over she goes.

Where does this stray energy go?
All LV Transformers I have seen only have L&N, no earth, so where does it
go?
Into capacitors??


Here it was a toss up whether the RCD. MCB, or both would go.

Now with a 100mA RCD, its not gone since.

What use is a 100mA RCD?

You die with a 40mA shock, that's why they make them 30mA


We have already agreed that a whole house RCD is bad.
This is NOT what I am suggesting here!



Actually, I think its quite good, provided it trips only when there is a
significant dangerous fault.

Just like a split load would, but it would only take out the faulty section,
not the whole lot.
(If it took out the lighing, then there are still table lamps!)


Its the nusiance tripping that is so serious.

Well I have NEVER had one single nuisance trip on my lighting RCD, and it
has been in since the 1980's
It has never tripped when a bulb has blown - the only time it did trip was
when some dickhead drilled through a cable
(A builder, NOT me!!)

We did however have a fault develop with our "sockets" RCD, this was then
tested (along with the lighting one) and it was found to be defective (over
sensitive)

Sparks...

On Tue, 16 Dec 2003 17:53:52 -0000, "Sparks"
wrote:

"Christian McArdle" wrote

...just imagining frail old lady holding [Earthed] wall light to steady
herself with one hand,
and attempting to get the new bulb in with the other, and decides as she
cant see the hole
(its above her head) she fells around for it with her hand.

It must happen...

Possibly it does, an insignificant number of times. Many more fall
down the stairs or perish in fires.

The reason not to install an RCD is because lights failing is a
demonstrable
and measurable cause of death either during house fires, or from sudden
darkness during a dangerous task (such as operating machinery, or
balancing
on ladders). Electrocution from changing light bulbs doesn't figure in the
statistics.

That's why there are two RCD's - one for the lights, and a separate one for
the sockets (and an emergency light above the CU!)

How exactly does this stop the lights going out when you need them
most?

--
Peter Parry.
http://www.wpp.ltd.uk/

On Tue, 16 Dec 2003 18:54:40 -0000, "Sparks"
wrote:


"Peter Parry" wrote

RCD's regularly trip when bulbs blow.

They shouldnt, as RCD's will trip only if there is an imbalance between the
live and the nuterual, when a bulb blows, it causes an overcurrent, this is when
the MCB's trip as there is no earth inside the bulb, there cant be an imbalance.

Of course there can be, and is. You are forgetting what happens when
a bulb goes and the effects of inductance. You are also forgetting
the effect of sensitisation by unbalanced noise filters. Indeed it
is questionable if simple 30mA protected power circuits have any
future because of this alone.

Of the 20 odd houses I have lived in most had 30mA RCD's covering
everything and the majority of those would quite consistently knock
everything off at the slightest provocation and especially if bulbs
failed.

This is not good, as has been previously mentioned - I still cant understand
why an RCD is tripping on a bulb failure..(maybe it is faulty, or is under rated?)

Perfectly serviceable.

As has been pointed out the danger is in using inappropriate
lighting. If the design of the house or the condition of the
occupants makes a fall likely don't fit incandescent bulbs in lights
needed for safe navigation of stairs.

Just out of interest, why not?

Because their most common failure mode is fail on power on and they
have poor reliability.

Do you mean fir CFL's, or am i missing the point here!

CFL, permanent low level lighting, whatever suits the need.

We have already agreed that a whole house RCD is bad.
This is NOT what I am suggesting here!

Any RCD on the lighting circuit is bad, and it is that which you do
appear to be suggesting.

--
Peter Parry.
http://www.wpp.ltd.uk/

On Tue, 16 Dec 2003 17:15:10 -0000, "Sparks"
wrote:


I would always have a seperate MCB on the lights, especially if there were
inquisative kids about.

Unfortunate, they may figure in the Darwin awards one day.

Is it a requirement to have no RCD, or is it mearly a suggestion?
(Not that it's getting changed anyway)

It is neither, the fitting of RCD's on lighting circuits is
deprecated in the IEE regulations. There is no requirement to fit
them on power circuits either - only on sockets which may be used by
equipment used out of doors. Most electricians simply take the cheap
and lazy way out.

I fell there is far more risk of someone poking their fingers in the fitting
while it is on, then there is of a fire breaking out - how often are
[regular GLS] bulbs changed compaired to how many times fires break out
in a house?

The facts on deaths and injuries are plain and speak for themselves,
I can't help it if you can't understand them.

I have installed an emergancy light in the cupboard where the breakers are,
If the lighting trips (or there is a power cut) this illuminates

Oh good, that will be really useful in a fire.


--
Peter Parry.
http://www.wpp.ltd.uk/

On Tue, 16 Dec 2003 20:29:09 -0000, "Will Dean"
wrote:

"Peter Parry" wrote in message
.. .

Can you propose a mechanism for this? The only one which comes to mind
would be that you already had a neutral-earth leakage fault, and the rise in
neutral current caused by the bulb-failure arc was sufficient to create a
leak to earth.

You don't need resistive leakage to trip an RCD and the problems of
pre-sensitisation are become more acute as more equipment includes
noise filters.

As has been pointed out the danger is in using inappropriate
lighting. If the design of the house or the condition of the
occupants makes a fall likely don't fit incandescent bulbs in lights
needed for safe navigation of stairs.

It wouldn't matter what kind of lamp illuminated the stairs if the lighting
circuit had tripped.

Indeed not, that is why you chose a lighting type of high reliability
whose failure mode is such that it would not trip protective
circuits. Incandescent bulbs have poor reliability and less than
optimal failure characteristics.

My experience is of lifting the burnt corpses of family out of the
way of the locked front door they had died against while trying to
break it down to escape the fire which killed them.

Yes, but you're a (former?) member of the emergency services, aren't you?

No.

As such, I have every sympathy with the gruesome sights you might have had
to deal with in your chosen profession, but I do believe that members of
such services are uniquely *ill* placed to give general advice about risks
to ordinary people.

Why? Because they understand the balance of risks better?

To a fireman, a horrible death in a house fire is a common occurence

Actually it isn't.

- to
me, as a resident of a non-smoking household, it's extremely unlikely to be
the cause of my, or my family's demise. Personally, if I'm doing the
neurotic parent bit I worry about road safety a darn sight more.

Quite reasonable, but risk assessment is about how much work you have
to put into circumventing a risk. Removing (or not fitting) an RCD
on a lighting circuit is trivial and although the risk of fire is
small the consequences are devastating and I suggest the minimal
effort is worth it.

TBH, if you know of a property that has an RCD which trips when light bulbs
blow, then you ought to advice the occupants to get the wiring fixed.

What's to fix? I can set up a demonstration to prove an RCD will
trip on a bulb blowing on a perfectly serviceable circuit with ease.
The point is that an RCD on a lighting circuit does no good at all
but potentially may be very harmful, a situation recognised in the
wiring regulations. What's the agrement for fitting them?

--
Peter Parry.
http://www.wpp.ltd.uk/

"Peter Parry" wrote in message
...


That's why there are two RCD's - one for the lights, and a separate one
for
the sockets (and an emergency light above the CU!)

How exactly does this stop the lights going out when you need them
most?

When are you specificlly talking about here?

On Tue, 16 Dec 2003 23:52:33 +0000, Peter Parry
wrote:



It is neither, the fitting of RCD's on lighting circuits is
deprecated in the IEE regulations. There is no requirement to fit
them on power circuits either - only on sockets which may be used by
equipment used out of doors. Most electricians simply take the cheap
and lazy way out.


I have seen this interpreted (annoyingly I can't remember where) as
meaning that all ground floor sockets should be RCD protected.

--
Niall

"Peter Parry" wrote in message
...
On Tue, 16 Dec 2003 20:29:09 -0000, "Will Dean"
wrote:

"Peter Parry" wrote in message
.. .

Can you propose a mechanism for this? The only one which comes to mind
would be that you already had a neutral-earth leakage fault, and the rise
in
neutral current caused by the bulb-failure arc was sufficient to create a
leak to earth.

You don't need resistive leakage to trip an RCD and the problems of
pre-sensitisation are become more acute as more equipment includes
noise filters.

I dont know enough about this to comment, only that as I have said before,
in my installation (With incadecent, CFL and LV switchmodes) I have never
had
the RCD trip on a bulb failure (Including with 500w halogens) - So in my
setup
I really dont see the added risk. please explain why in my setup it wouldnt
be...


TBH, if you know of a property that has an RCD which trips when light
bulbs
blow, then you ought to advice the occupants to get the wiring fixed.

What's to fix? I can set up a demonstration to prove an RCD will
trip on a bulb blowing on a perfectly serviceable circuit with ease.
The point is that an RCD on a lighting circuit does no good at all

Sorry but I totally disagree with that statment.
It will stop people getting killed by electrocution.

but potentially may be very harmful, a situation recognised in the
wiring regulations. What's the agrement for fitting them?

Please explain, in a property where there are never any nucence tips, whay
is it bad?

Sparks...

"Andy Hall" wrote
| Non-maintained small fluorescent lights are not very expensive,
| although the fittings are pretty ugly. Undoubtedly this could be
| improved if there were a consumer premises market for them.

Something like this:

http://www.tlc-direct.co.uk/Products/HS724LE.html

Smoke alarm, emergency light and Part L1 compliant.

Owain

"Sparks" wrote in message
.. .

"Peter Parry" wrote in message
...
On Tue, 16 Dec 2003 20:29:09 -0000, "Will Dean"
wrote:

"Peter Parry" wrote in message
.. .

Can you propose a mechanism for this? The only one which comes to mind
would be that you already had a neutral-earth leakage fault, and the
rise
in
neutral current caused by the bulb-failure arc was sufficient to create
a
leak to earth.

You don't need resistive leakage to trip an RCD and the problems of
pre-sensitisation are become more acute as more equipment includes
noise filters.

I dont know enough about this to comment, only that as I have said before,
in my installation (With incadecent, CFL and LV switchmodes) I have never
had
the RCD trip on a bulb failure (Including with 500w halogens) - So in my
setup
I really dont see the added risk. please explain why in my setup it
wouldnt
be...


TBH, if you know of a property that has an RCD which trips when light
bulbs
blow, then you ought to advice the occupants to get the wiring fixed.

What's to fix? I can set up a demonstration to prove an RCD will
trip on a bulb blowing on a perfectly serviceable circuit with ease.
The point is that an RCD on a lighting circuit does no good at all

Sorry but I totally disagree with that statment.
It will stop people getting killed by electrocution.

but potentially may be very harmful, a situation recognised in the
wiring regulations. What's the agrement for fitting them?

Please explain, in a property where there are never any nucence tips, whay
is it bad?


I'm quite prepared to be shot down in flames
BUT
I operate a wet area supplied via 30ma RCDs
...it has 3kw of halogen lighting - failure mode is
water spray on tubes.
it also has two water pumps
many switchmodes
many fractional HP motors
a large compressor
many incandescents
several EMI filters
many 240v 3 port valves which are damp
and the only RCD trip we ever had was from
a cable rupture in a pudle of water.
MCBs pop often with incandescant failure
but never the RCD
(it's NICIEC tested regularly)

On Wed, 17 Dec 2003 01:07:44 -0000, "Owain"
wrote:

"Andy Hall" wrote
| Non-maintained small fluorescent lights are not very expensive,
| although the fittings are pretty ugly. Undoubtedly this could be
| improved if there were a consumer premises market for them.

Something like this:

http://www.tlc-direct.co.uk/Products/HS724LE.html

Smoke alarm, emergency light and Part L1 compliant.

Owain



Hmm. Interesting pair of products.

It would be good if one could have conventional lighting and switch
in the fluorescent stuff when the power fails or the alarm goes off.

The technical design seems well thought out though



..andy

To email, substitute .nospam with .gl

On Wed, 17 Dec 2003 01:32:03 -0000, "Chris Oates" none wrote:


"

I'm quite prepared to be shot down in flames
BUT
I operate a wet area supplied via 30ma RCDs
..it has 3kw of halogen lighting - failure mode is
water spray on tubes.
it also has two water pumps
many switchmodes
many fractional HP motors
a large compressor
many incandescents
several EMI filters
many 240v 3 port valves which are damp
and the only RCD trip we ever had was from
a cable rupture in a pudle of water.
MCBs pop often with incandescant failure
but never the RCD
(it's NICIEC tested regularly)


No shooting, but was is it?


..andy

To email, substitute .nospam with .gl

"Christian McArdle" wrote in message
. net...
| I am contemplating fitting an RCD (Residual Current Device /
| Earth Leakage Relay ) in the power supply to my house between
| the meter and the fuse box.

Often, the easiest way to add RCD protection to an existing installation
(using DIN rail CU) is to replace socket circuit MCBs with single width
RCBOs, if they are available. It isn't necessarily the cheapest way,
although if there are only 1 or 2 circuits to be protected, it can still
be
cost effective. It is certainly the best way to do it, however many ways
there are.

cheapest way is to replace the CU switch
with an RCD switch
but then we don't want the light going out

see separate thread for thaat

Andy Hall wrote:

On Tue, 16 Dec 2003 21:35:43 +0000, The Natural Philosopher
wrote:


Well said Peter. You are probably a voice in the wilderness, like that
chief inspector who categorically stated that 'excess speed is the cause
of less than 7% of accidents' and 'speed cameras do not (statistically)
reduce road deaths'.

I am definitely with you on this. My 30mA RCD tripped about 50% of the
time when any bulb blew, with the MCB about 60%. Sometimes both.

Its bloody dangerous feeling down te saircase to get to the consumer
unit, especialy if you have left the casing off...:-)




Reading this, and especially the very sad ending to Peter's post makes
me think that it would not be a bad idea to add emergency lighting as
something that should be included in Building Regulations for new
properties and incentivised for others in some way, especially for the
elderly and others with mobility difficulties..

We already have mains powered smoke detectors as an addition,
basically to get over people taking the batteries out or forgetting to
replace them.

Non-maintained small fluorescent lights are not very expensive,
although the fittings are pretty ugly. Undoubtedly this could be
improved if there were a consumer premises market for them.

It would seem to me that the populace would be better served with a
lighting measure like this rather than the mandatory low energy lamps
stuff. In fact with a bit of creativity, both objectives could be
met in a single package.

I am not sure what sort of size and power level that they would need
to be to provide sufficient light say at the top and bottom of a
staircase in a fire, but to be able to see adequately during a power
cut, then the little 8w ones are probably enough.

I have my consumer unit at the back of a cupboard in the kitchen and
it would not be easy to see in the dark.
I fitted a small maintained fitting, run from a (non-RCD ptotected)
lighting circuit and operated also by a plunger switch on the cupboard
door. Thus I have a light over the CU for when I want to work on it
with the power deliberately off and also to be able to see the
breakers after a trip.




Not a bad idea actually.

However I am against having to add two provisions to fix what Peter has
probably identified is a non existent problem.




.andy

To email, substitute .nospam with .gl

Sparks wrote:


You haven't thought it through. there is ALWAYS some neutral earth
leakage. It occurs every time an oh so rigorously RFI suppressed switch
mode power supply (TV, computer, monitor, LV lighting) or any suppresed
motor is plugged into the circuits. Enough of these and the 30mA RCD is
on a hair trigger. Any voltage surge and over she goes.


Where does this stray energy go?
All LV Transformers I have seen only have L&N, no earth, so where does it
go?
Into capacitors??


Mmm. Ok, I'll take out the LV transformers. Bercause thinking about
mine, they are alos two wrire devices. That is probably why they
interfere so badly with radios.





Here it was a toss up whether the RCD. MCB, or both would go.

Now with a 100mA RCD, its not gone since.


What use is a 100mA RCD?

You die with a 40mA shock, that's why they make them 30mA



Well it trips if you get a neutral ertha short, or some other appliance
problem.

Whether you die at 40mA is not an established yes and no type thing.

Much less applied across the heart can stop it in a vulnerable subject:
Much more applied across just a finger, will burn, but not kill.

The problem with 30mA is its proneness to false triggering, especially
applied to a whole house.

The other issue is WHAT should be protected. Arguably the most dangerous
circuit in the house is lighting, where you have potentially two user
accesible terminals, and a (now rigorously earthed) metal housing in
close proximity. Grab the housing with one hand, and stck yer other
finger in the socket and Whazza! you are across the floor...




We have already agreed that a whole house RCD is bad.
This is NOT what I am suggesting here!



Actually, I think its quite good, provided it trips only when there is a
significant dangerous fault.


Just like a split load would, but it would only take out the faulty section,
not the whole lot.
(If it took out the lighing, then there are still table lamps!)


Not in my house. They have theor own lighting sockets on the relevant
lighting circits.

I like the idea of split loads, but Peter has made me rethink all of this.

Frankly, I cannot see an ideal solution.

I am very happy that the discussion continue - if a general consensus of
best practice CAN be established, then a fait accompli could be
presented to those who dream up building regs.




Its the nusiance tripping that is so serious.


Well I have NEVER had one single nuisance trip on my lighting RCD, and it
has been in since the 1980's
It has never tripped when a bulb has blown - the only time it did trip was
when some dickhead drilled through a cable
(A builder, NOT me!!)

We did however have a fault develop with our "sockets" RCD, this was then
tested (along with the lighting one) and it was found to be defective (over
sensitive)

Sparks...

"Peter Parry" wrote in message
...

It is neither, the fitting of RCD's on lighting circuits is
deprecated in the IEE regulations. There is no requirement to fit
them on power circuits either - only on sockets which may be used by
equipment used out of doors. Most electricians simply take the cheap
and lazy way out.

There's often a requirement to fit one (a 100mA one) covering the whole of a
TT installation.

Will

On Wed, 17 Dec 2003 09:16:57 +0000, The Natural Philosopher
wrote:



I am very happy that the discussion continue - if a general consensus of
best practice CAN be established, then a fait accompli could be
presented to those who dream up building regs.



Like a few of us tried to do with proposed part P?

Worth a try, I suppose, but the decision making is much more about
politics and financial control than anything about technical merit.

It kind of reminds me of the old joke were the boss is interviewing
for a secretary, has three candidates with all kinds of skills but
chooses the one with the biggest tits.


..andy

To email, substitute .nospam with .gl

"Peter Parry" wrote in message
...

What's to fix? I can set up a demonstration to prove an RCD will
trip on a bulb blowing on a perfectly serviceable circuit with ease.

JOOI, can you describe the circuit? As I say, I have many years experience
of non-nuisance-tripping 30mA whole-house RCDs, and always with a room full
of computer equipment somewhere on the circit.

The point is that an RCD on a lighting circuit does no good at all
but potentially may be very harmful, a situation recognised in the
wiring regulations. What's the agrement for fitting them?

I'm not particularly arguing for the fitting of them against the
regulations, only against the received wisdom that A. they'll give you lots
of nuisance tripping, and B. that they're the major cause of nuisance
tripping on lighting circuits. (Which we can all agree is a bad thing.)

However, my experience of whole-house RCDs is that they've given warning of
incipient problems, both with wiring and with appliances. For a start, they
detect neutral-earth failures (which one would guess represent about 50% of
insulation problems) which are not typically detected by overcurrent
protection at all. They also give early warning of thinks like heater
sheath failure in immersion heaters and electric showers - I don't consider
myself odd in thinking that I'd like to know about an immersed heater
failure while there's 50mA flowing to earth rather than 50A.

And, like I say, I know someone personally who had a bad shock off a fixed
light fitting, and a teenage girl in the village I went to school in was
killed by an electric shock from a light fitting - her parents returned to
the house after a holiday to find her dead on the living room floor.

I'm afraid I interpret your gruesome anecdote as a warning about the way one
locks ones house at night (not being clear that it has any link to lighting
circuit RCDs, anyway), and mine as warnings about earth protection on wiring
.. No doubt we both feel rather closer to our own cautionary tales.

Will

I have seen this interpreted (annoyingly I can't remember where)
as meaning that all ground floor sockets should be RCD protected.

It is not explicitly stated as such. However, I think it is considered
reasonable to assume that downstairs sockets can be used for outside
equipment, unless specific alternative provision is made for outside
equipment, such as a weatherproof RCD socket on each outside wall.

However, you should protect all socket circuits. This isn't a requirement,
but common sense. It is also common sense to ensure that it is on a
different RCD to the outside sockets, as these are quite likely to trip in
wet weather.

Christian.

What use is a 100mA RCD?

You die with a 40mA shock, that's why they make them 30mA

Firstly, it usually takes about 200mA to be killed. Secondly, a 100mA RCD is
not for supplementary direct protection. i.e. it is not intended to prevent
electrocution when you touch the live. Its purpose is to rapidly disconnect
the supply in the event of a minor earth fault, rather than relying on there
being a massive earth fault. Circuits likely to require supplementary direct
protection should use dedicated 30mA RCBOs for that circuit only. Whole
house RCDs (except 100mA Type S) and even split load consumer units are a
bodge.

Christian.

On Wed, 17 Dec 2003 01:06:06 -0000, "Sparks"
wrote:


"Peter Parry" wrote

What's to fix? I can set up a demonstration to prove an RCD will
trip on a bulb blowing on a perfectly serviceable circuit with ease.
The point is that an RCD on a lighting circuit does no good at all

Sorry but I totally disagree with that statment.
It will stop people getting killed by electrocution.

People don't get killed by electrocution from lighting circuits.
They may sometimes get a belt from them (which an RCD will reduce but
won't prevent) but they do not cause death or injury.

but potentially may be very harmful, a situation recognised in the
wiring regulations. What's the agrement for fitting them?

Please explain, in a property where there are never any nucence tips, whay
is it bad?

Because in a fire the lights all go out as the RCD trips.

Electrocution in the home kills 25 people a year and causes 2000
minor and serious injuries. I only have access to detailed figures
for 1998 and in that year none of the 23 deaths by electrocution
involved lighting circuits - all bar 6 were people dismantling live
equipment, the remaining 6 were handling faulty supply cords.

In one year 500 people die and 18,000 are seriously injured in fires
in the home.

That's why the wiring regulations don't support fitting of RCDs to
lighting circuits.

--
Peter Parry.
http://www.wpp.ltd.uk/