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.
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
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
c) I could hot wire the whole job, I am helped by the fact that there is a join
in the cables, but it would still be a bit tricky.
d) Can anyone advise me of any safe working practices for hot wiring?
e) If I paid a non Electrify Board electrician to do the job how would he
approach the problem?
I would happily post in a more relevant news group if I could find one.
"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
| 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
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
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
Just my thoughts here...
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.
Seems to me that the obvious solution is to have whole-house RCD
protection and install battery-backed emergency luminaires at e.g. stair
The ultra-cautious could have 30mA RCBOs protecting each circuit
Alistair Riddell - BOFH
Microsoft - because god hates us
It is a classic example of the original specifier not understanding
risk at all and making things more dangerous by installing "safety"
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.
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.
No they don't, that's the MCBs which trip. And *their* installation is
considered to be a good thing.
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
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).
I too know of someone who did the exact same thing - they were thrown
across the room (No RCD)
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.
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?
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
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
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
...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...
Well, it ain't always me that changes light bulbs, if you get my drift
That's why there are two RCD's - one for the lights, and a separate one for
sockets (and an emergency light above the CU!)
Unfortunate, they may figure in the Darwin awards one day.
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.
The facts on deaths and injuries are plain and speak for themselves,
I can't help it if you can't understand them.
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
Basing a judgement of low probability events on personal experience
is never wise.
RCD's regularly trip when bulbs blow.
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
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
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
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.
Indeed I suspect I am.
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
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.
They shouldnt, as RCD's will trip only if there is an imbalance between the
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.
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?)
Just out of interest, why not?
Do you mean fir CFL's, or am i missing the point here!
We have already agreed that a whole house RCD is bad.
This is NOT what I am suggesting here!
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