Well the 1974 act was a good start, as up to that time the safety of
employees wasn't a particular concern of employers as my dad found out
one day when he went to adjust the height of a circular saw blade, and
discovered the hard way that it didn't have the expected guard blade
protecting its underside.
He said afterwards that he didn't feel a thing at the moment it happened
it was the shock of seeing four fingers missing that caused him to keel
Humm.... Well the earth had come off at the distribution board and the
whole house was wired with this lead sheathed cable. So presuming that
the lead sheathing was all bonded together then there would have been
quite a lot of Capactive leakage from the live to earth, as one could
assume that at some stage the un-earthed lead casing would be connected
to another earth in the house, via lets say something like an immersion
heater or similar appliance, so I reckon that their would have been
sufficient Capactive and an unknown amount of resistive leakage
sufficient to trip the RCD.
There was quite enough current there to prevent me from doing anything
about it, and FWIW I have very dry skin and my hands were very dry on
that day, so I reckon that a trip would have been taken out.
*Not strictly true, if you know how an RCD actually works. There will
still be "some" leakage current through your body that does not go back
via the neutral return so if that exceeds the RCD trip current, quite
likely, then out she goes!.....
Have *you* actually done it? I've hung on to the output of a Van de
Graaf generator while simply standing on a piece of perspex and charged
myself up to hundreds of thousands of volts if not millions - not a
tingle, until someone walks to close to you.
In reality in the house you have to be touching something metallic or
standing on a wet (probably concrete) floor to get a shock. In
ordinary shoes on a carpet you will feel *nothing* if you touch live
mains with one finger (and, yes, I have done it occasionally when
working on something live). Mostly one gets a shock because *both*
hands are touching something conductive (and that's the worst for you
too as the electricity runs across your chest).
In workplaces where live working on benches is commonplace significant
shock prevention is provided by a vinyl floor covering and training
people to use only one hand.
"tony sayer" wrote
| >> >The RCD won't *ever* trip if you put your finger across live and
| >> >neutral, it dosn't trip on that sort of fault.
| >> *Not strictly true, if you know how an RCD actually works. There
| >> will still be "some" leakage current through your body that does
| >> not go back via the neutral return so if that exceeds the RCD
| >> trip current, quite likely, then out she goes!.....
| >Standing on a ladder on a wooden (probably) floor the leakage
| >through your body to earth will be virtually non-existent.
| >You'll probably have shoes with rubber/plastic soles as well.
| Don't you believe it!. Well if you do, then grab the mains in one
| hand and note the results.
I have done exactly this in the past, standing on rubber-backed carpet tiles
on a dry suspended timber floor. I vibrated gently at 50Hz and the RCD did
not trip. This was not a glancing touch as I was holding the L wire
intending to put it into a replacement socket faceplate.
| Usual disclaimer don't they this at home unless by doing so you'll
| help the gene pool along.......
Glad I can do my bit for the gene pool without being forced into the messy
business of procreation :-)
 I pulled out the fuse and checked the first socket. Dead. Checked the
second socket. Dead. How the f'k was I supposed to guess the third socket in
the lounge was on the garage circuit (garage being on opposite side of
house, as well).
Course some people conduct better then others;!....
Theres a howler there somewhere....
On three occasions over the years I've seen someone take apparently dead
wires in their hands and mutter "I suppose this *is* dead"?. Touch them
together, and you'll soon find out SEZ I:)
On each occasion there was a flash and loud bang!, very loud in the
first instance as it was a three phase supply.
Last time was in the belfry of Ely Cathedral where once had been a
mobile phone base station. The 'err "short circuit" took out most of the
lights as well as disrupting a service.
A bit of positive spin helped lots,
"ere look arch-bish-whatever guv" "just imagine if that little lot had
gone up by accident at night eh?"
"wouldn't have any where to pray now would yer?"
Seemed to earn a lot of brownie points:)
"tony sayer" wrote
| >| Usual disclaimer don't they this at home unless by doing so
| >| you'll help the gene pool along.......
| >Glad I can do my bit for the gene pool without being forced
| >into the messy business of procreation :-)
| Theres a howler there somewhere....
I am doing my best to avoid producing little howlers and continue to enjoy a
good night's sleep, no vomit in the carpets, and no need to buy a
| Last time was in the belfry of Ely Cathedral where once had been a
| mobile phone base station. The 'err "short circuit" took out most
| of the lights as well as disrupting a service.
What's really fun is when there's no-one in the church office on a Sunday
and an incoming phone call rings round all the extensions before ending up
at the one hidden under the pulpit.
| A bit of positive spin helped lots,
| "ere look arch-bish-whatever guv" "just imagine if that little lot had
| gone up by accident at night eh?"
| "wouldn't have any where to pray now would yer?"
"You wouldn't get any better if Jesus himeself was here, he was a chippie
not a sparkie."
In typical dry indoor conditions you will feel nothing, as Chris rightly
says. I've often demonstrated this to people, sometimes to their great
surprise. It provokes thought.
Don't try it outdoors though while standing on an aluminium ladder with
its feet in damp soil...
And don't try it if the frequency of the supply is a few orders of
magnitude higher than 50 Hz or you'll discover the meanings of "earthed
via a reactance" and "skin effect" at the same time.
Not if it's the N you touch first - there'd be naff-all current passing
through you given the negligible potential between N and local earth,
together with the much higher resistance which you present as a path to
earth/transformer-return as compared to the copper path it's got. Then
when you make contact with L (other side of the finger - possible
finger-cooking but little likelihood of death; other hand - definite
risk of fatality, hence the habit inculcated into generations of
sparkies of working with one hand at a time) you become an attractive
path for L-to-N current; and by far the greater part of the flow through
you will be on the L-to-N path, which doesn't do anything to trip the
RCD, rather than the L-to-E-via-shoes/clothes/whatever which the RCD is
Definitely better than nothing, but not a cure-all, and a possible
source of a "risk compensation" effect - "oh, it's OK to work live on
the electrics, I have a whole-house RCD"...
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