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.