On Sat, 11 Feb 2017 19:48:54 +0000, Max Demian wrote:

On 11/02/2017 19:05, Brian Gaff wrote:
No but I'd often wondered why the combined brains of the world could
not come up with a better lampholder design than ES or BC, one that
does not leave the contacts directly exposed when no bulb is present.

It's OK because lamp-holders are all high up so the kids can't stick
their fingers in.

Pendant lamp holders dangling from ceiling roses significantly reduce
the risk of electrocution (fatal electric shock - usually the result of
currents flowing across the heart, hand to hand or hand to foot paths) to
a vanishingly low level (especially true in the case of BC lamp holders).

The safety aspect of BC lamp holders dangling by wire cords from ceiling
roses is only compromised by damaged pendant cord insulation which is a
whole new "accident waiting to happen" issue altogether.

The only 'scenario' I can envisage where such "Safety" can be
compromised is when the 'Lamp Changer' has just stepped out of a shower
straight onto a set of metal step ladders sans their plastic protective
feet in a room with a bare and very damp concrete floor (the downstairs
shower room itself?) to swap out a failed lamp whilst the lamp socket is
still 'live' and fed via a fuse or mcb protected circuit unprotected
against earth leakage faults.

The more usual scenario, a dry, fully dressed 'Lamp Changer' is unlikely
to suffer anything worse than a shock localised to the unlucky fingertip
that happened to stray deep within the empty BC lamp holder with perhaps
a couple of painful burn marks on the end of said unlucky digit with
virtually no shock current reaching the chest area.

Of course, this form of protection fails in the case of an old fashioned
earth protected brass table lamp. However, since it's a fairly trivial
matter to unplug such lamps so they are visibly isolated from any mains
voltage, the 'Lamp Changer' can only have himself to blame in the event
of a "Darwin Award" styled electrocution.

The statistics on UK 'lamp changing induced fatalities by
electrocution' (0 BC and 1 ES associated deaths?) seem to bear out that
the risk is extremely low in practice in spite of the theoretical risk
case that can be made against either type of lamp holder or socket.

When a long established design and/or practice has proved itself to be
acceptably safe for many decades (seven or more?), it's unlikely to be
modified any time soon. Unless we start seeing a sudden spate of juvenile
fatalities due to misuse of electric light sockets (which would be more a
case of bad childcare rather than a deficiency of lamp socket safety),
it's very unlikely that we'll see a change in the regulations to mandate
"A Safer Lamp Socket".

At least whilst there are countless other 'safety issues' of much higher
priority waiting to be addressed by the H&S executive, this one will
remain firmly placed on the back burner. Who knows? Perhaps one day, when
*every* other potential death hazard has finally been dealt with, the
death hazard embodied by the current lamp socket design might finally
become visible above the death statistics 'noise floor' and 'Something
done about it'. :-)

If you're waiting for a safer lamp holder or socket to materialise, I'd
recommend against holding your breath in anticipation. Most, if not all
of us, here will likely be long dead of natural causes without any need
for asphyxia by the time such a design change is ever deemed necessary.

--
Johnny B Good

On 12/02/2017 20:11, Dave Liquorice wrote:
On Sun, 12 Feb 2017 16:07:37 +0000, ARW wrote:

Sports stadia, yeah. At EPL stadiums each luminaire is 2 kW so
that's
40A @ 50 V and there are around 200 of these luminairs... For top
flight Champions League or FIFA matches the lights must not go
out,
full stop. Stadiums these days have twinset on site generation
which
is hot from about three hours before kick off.

They also have an on site electrician.

Who earnt his money at Sunderland's "Stadium of Light" not so long
ago. Ordinary live to world (but not the UK) EPL fixture, so lights
are allowed to go out but should come back on again within 10
minutes, ie about how long they have to cool before being restruck
(they are "arc lamps" most variations won't restrike when hot).

That's about all they are there for.

I have not done the job for a few years but sitting in the control room
at the Keepmoat stadium and doing **** all but getting paid to watch a
football match was a nice little earner. You had to be there 2 hours
before kick-off, and stay an hour after the match finished. You got free
parking and free coffee and tea.

I once had to fix the roller shutters on one of the bars, other than
that I have done over 100 hour of getting paid to sit down and do ****
all apart from watch football and some Rugby.

I booked a holiday when Elton John played there. It was either that or
jump off a motorway bridge.

--
Adam

On 12/02/2017 15:49, Dave Plowman (News) wrote:
In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
But if you are really concerned about safety, fit an appropriate RCD.
But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...cds-explained/
appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which, of
course, may be caused by a leakage to earth.

And will not trip if you stick your fingers in a plastic BC table lamp
holder.

In a correctly working installation then what else it there other than
earth leakage to cause the RCD to trip?


--
Adam

On Sun, 12 Feb 2017 10:23:54 +0000, Dave Liquorice wrote:

On Sat, 11 Feb 2017 23:40:33 -0800 (PST), wrote:

It's OK because lamp-holders are all high up so the kids can't
stick
their fingers in.

Wrong answer. I think I was 6.

Ditto...

JOOI, did either of you suffer burns on your fingertips? Alternatively,
since you don't make this clear as to whether you were shocked by
touching a ceiling pendant light socket or handling a table lamp, did you
suffer a shock through your arm and body as a result of providing a path
to earth?

ELCBs and RCDs have been mentioned in this thread, asking how such
protective devices can work in the absence of any path to earth such as
atop a wooden step ladder when bridging the lamp contacts with a
fingertip. The answer in this case is, "They don't!".

Fortunately, in this case, they don't have to (work, that is!) since the
luckless victim does all the necessary work of 'protective action' either
by rapidly withdrawing their digit or else by dragging the lamp cord out
of the ceiling rose or even snapping it in two as they spring off the
ladder, howling in pain with nothing worse than a bruise or three to show
for their embarrassment.

I dare say that there *have* been a (mercifully) few fatalities as a
result of injuries consequent to such electric shocks over the many
decades of DIY lamp changing to date, presumably a statistically
insignificant number to warrant a 'fresh look at the problem'.

I'd imagine most such fatal cases would have been the result of failing
to take account of the higher than usual risk of death by injury
resulting from falling from a greater height such as from a set of steps
on a landing at the top of a flight of stairs and similar hazardous
locations where such precautions should have been undertaken anyway,
irrespective of the electric shock hazard of changing out a lamp.

What few of the remaining fatalities in more prosaic settings (a living
room lamp changing exercise) resulting from injuries consequent to a fall
from a ladder (step or otherwise), even when electric shock was proved to
be the trigger, have probably been determined to be a fatality due to
'unsafe ladder working practice' rather than a lack of safety in the
design of the lamp holder or socket itself.

Compared to all the other hazards associated with changing a lamp, the
risk of actual electrocution is vanishingly small, assuming no other
obvious electrical deficiencies such as damaged insulation or loose bare
wiring.

The humble lamp socket is, imho, safe enough for its purpose although
the ES types are slightly less so and the adoption of ES over BC fittings
for GLS lamps, other than in exceptionally appropriate usage cases, is a
practice that ought to be actively discouraged in spite of Ikea's
determined efforts to introduce it as a de-facto standard via the
backdoor of selective marketing.

--
Johnny B Good

On 2017-02-11, Brian Gaff wrote:

No but I'd often wondered why the combined brains of the world could not
come up with a better lampholder design than ES or BC, one that does not
leave the contacts directly exposed when no bulb is present.

I'm pretty sure such things exist (e.g., with spring-loaded bits that
break the contact when the lamp is removed), but they are slightly
more expensive to manufacture.

On Sun, 12 Feb 2017 13:40:46 +0000, (Roger Hayter)
wrote:

dennis@home wrote:

On 12/02/2017 07:42, wrote:
On Saturday, 11 February 2017 22:44:38 UTC, Roger Hayter wrote:
dennis@home wrote:
On 11/02/2017 22:25, Harry Bloomfield wrote:
Roger Hayter explained on 11/02/2017 :

Those evil foreigners who are trying to stop us having real English posh
rulers to tug our forelocks to all use 230V

After Brexit, can we all go back to our Imperial 240v please?

I want to continue with the 230V as the stuff will be cheaper than
having the limited 240V market.

But we've never changed from 240V, we just *call* it 230V now.

It's amazing how many people think we actually have 230v at the socket.


NT


At about 18:00 the voltage on my energy meter quite often says ~230V.
I have seen it down at 229V but not often.
That's before I switch on the oven, hob or kettle.

And mine used to be from 246 to 253. Still in spec for both the 230V
and the old 240V standards.

steady 245-246 here. 3v drop on the incommer when the 10.4kW shower is
running.

--

Graham.
%Profound_observation%

On Sun, 12 Feb 2017 18:49:10 +0000, Scott
wrote:

On Sun, 12 Feb 2017 15:49:15 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
But if you are really concerned about safety, fit an appropriate RCD.
But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...cds-explained/
appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which, of
course, may be caused by a leakage to earth.

Okay, thanks very much.

And current passing through a child's fingertip is most unlikely to be
fatal, but will hurt like hell and learn them not to do it again!

--

Graham.
%Profound_observation%

On Mon, 13 Feb 2017 00:43:28 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Roger Hayter wrote:
Dave Plowman (News) wrote:

In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article , Scott
wrote:
But if you are really concerned about safety, fit an appropriate
RCD. But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...electrical-ite
ms/rcds-explained/ appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which,
of course, may be caused by a leakage to earth.

But will *not* be caused by connecting a person between live and neutral.

A whole house RCD can trip on a neutral fault in a circuit with a single
pole MCB to that circuit switched off - so no connection to the line at
all.

Exactly that plunged me into darkness once while working on the
lighting circuit in my loft. I had switched off the upstairs lighting
MCB, but didn't realise a E-N short could still trip the RCD and kill
the inspection lamp I had on an extension reel.

--

Graham.
%Profound_observation%

On Mon, 13 Feb 2017 18:50:33 +0000, Graham.
wrote:

On Sun, 12 Feb 2017 18:49:10 +0000, Scott
wrote:

On Sun, 12 Feb 2017 15:49:15 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:

In article ,
Scott wrote:
But if you are really concerned about safety, fit an appropriate RCD.
But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...cds-explained/
appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which, of
course, may be caused by a leakage to earth.

Okay, thanks very much.

And current passing through a child's fingertip is most unlikely to be
fatal, but will hurt like hell and learn them not to do it again!

Thanks. All the myths about electricity are gradually being
dispelled.

On 13/02/2017 16:33, Johnny B Good wrote:
On Sat, 11 Feb 2017 19:48:54 +0000, Max Demian wrote:

On 11/02/2017 19:05, Brian Gaff wrote:
No but I'd often wondered why the combined brains of the world could
not come up with a better lampholder design than ES or BC, one that
does not leave the contacts directly exposed when no bulb is present.

It's OK because lamp-holders are all high up so the kids can't stick
their fingers in.

Pendant lamp holders dangling from ceiling roses significantly reduce
the risk of electrocution (fatal electric shock - usually the result of
currents flowing across the heart, hand to hand or hand to foot paths) to
a vanishingly low level (especially true in the case of BC lamp holders).

The safety aspect of BC lamp holders dangling by wire cords from ceiling
roses is only compromised by damaged pendant cord insulation which is a
whole new "accident waiting to happen" issue altogether.

The only 'scenario' I can envisage where such "Safety" can be
compromised is when the 'Lamp Changer' has just stepped out of a shower
straight onto a set of metal step ladders sans their plastic protective
feet in a room with a bare and very damp concrete floor (the downstairs
shower room itself?) to swap out a failed lamp whilst the lamp socket is
still 'live' and fed via a fuse or mcb protected circuit unprotected
against earth leakage faults.

The more usual scenario, a dry, fully dressed 'Lamp Changer' is unlikely
to suffer anything worse than a shock localised to the unlucky fingertip
that happened to stray deep within the empty BC lamp holder with perhaps
a couple of painful burn marks on the end of said unlucky digit with
virtually no shock current reaching the chest area.

Of course, this form of protection fails in the case of an old fashioned
earth protected brass table lamp. However, since it's a fairly trivial
matter to unplug such lamps so they are visibly isolated from any mains
voltage, the 'Lamp Changer' can only have himself to blame in the event
of a "Darwin Award" styled electrocution.

The statistics on UK 'lamp changing induced fatalities by
electrocution' (0 BC and 1 ES associated deaths?) seem to bear out that
the risk is extremely low in practice in spite of the theoretical risk
case that can be made against either type of lamp holder or socket.

When a long established design and/or practice has proved itself to be
acceptably safe for many decades (seven or more?), it's unlikely to be
modified any time soon. Unless we start seeing a sudden spate of juvenile
fatalities due to misuse of electric light sockets (which would be more a
case of bad childcare rather than a deficiency of lamp socket safety),
it's very unlikely that we'll see a change in the regulations to mandate
"A Safer Lamp Socket".

At least whilst there are countless other 'safety issues' of much higher
priority waiting to be addressed by the H&S executive, this one will
remain firmly placed on the back burner. Who knows?



Perhaps one day, when
*every* other potential death hazard has finally been dealt with

Women drivers.

--
Adam

On Mon, 13 Feb 2017 16:33:06 GMT, Johnny B Good
wrote:



The statistics on UK 'lamp changing induced fatalities by
electrocution' (0 BC and 1 ES associated deaths?) seem to bear out that
the risk is extremely low in practice in spite of the theoretical risk
case that can be made against either type of lamp holder or socket.


If there had been a problem I would have thought it may have been
revealed back in the era before power sockets were fitted in many
premises and the pendant lamp fitting was the only source of electric
in the room.
Removing the lamp and connecting the flex of an Iron or other small
appliance using a bayonet plug was common, some users used a Y piece
with two outlets that allowed the lamp to remain in place which did
leave unprotected pins when the appliance was disconnected.
Some more expensive versions did have switch.

http://www.flameport.com/electric_mu...52_adaptor.cs4

G.Harman

In article ,
wrote:
On Mon, 13 Feb 2017 16:33:06 GMT, Johnny B Good
wrote:



The statistics on UK 'lamp changing induced fatalities by
electrocution' (0 BC and 1 ES associated deaths?) seem to bear out that
the risk is extremely low in practice in spite of the theoretical risk
case that can be made against either type of lamp holder or socket.


If there had been a problem I would have thought it may have been
revealed back in the era before power sockets were fitted in many
premises and the pendant lamp fitting was the only source of electric
in the room.
Removing the lamp and connecting the flex of an Iron or other small
appliance using a bayonet plug was common, some users used a Y piece
with two outlets that allowed the lamp to remain in place which did
leave unprotected pins when the appliance was disconnected.
Some more expensive versions did have switch.

you could buy them in Woolworths!

--
from KT24 in Surrey, England

On Mon, 13 Feb 2017 21:24:20 +0000 (GMT), charles
wrote:



If there had been a problem I would have thought it may have been
revealed back in the era before power sockets were fitted
Removing the lamp and connecting the flex of an Iron or other small
appliance using a bayonet plug

you could buy them in Woolworths!

Hoover suppled a version that converted the pendant to a two pin
socket .

There is a photo of a couple at the top of this page.
http://www.vacuumland.org/cgi-bin/TD...HREAD.cgi?3412

The socket contacts look even more likely to touched by a wayward
finger than the bayonet pins alone.

G.Harman

On Monday, 13 February 2017 18:21:42 UTC, Johnny B Good wrote:
On Sun, 12 Feb 2017 10:23:54 +0000, Dave Liquorice wrote:
On Sat, 11 Feb 2017 23:40:33 -0800 (PST), tabbypurr wrote:

It's OK because lamp-holders are all high up so the kids can't
stick
their fingers in.

Wrong answer. I think I was 6.

Ditto...

JOOI, did either of you suffer burns on your fingertips? Alternatively,

no

since you don't make this clear as to whether you were shocked by
touching a ceiling pendant light socket or handling a table lamp, did you

low hanging pendant

suffer a shock through your arm and body as a result of providing a path
to earth?

yep.


NT

On Sun, 12 Feb 2017 12:49:00 -0800 (PST), wrote:

On Sunday, 12 February 2017 18:42:44 UTC, Dave Plowman (News) wrote:
In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:
In article ,
Scott wrote:
But if you are really concerned about safety, fit an appropriate RCD.
But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...cds-explained/
appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which, of
course, may be caused by a leakage to earth.

I bet we're all curious where else you think the current imbalance goes.


NT

He knows full well, his point is RCDs do not work by detecting earth
leakage directly, and he's right.

--

Graham.
%Profound_observation%

On Sun, 12 Feb 2017 19:20:08 GMT, Harry Bloomfield
wrote:

Dave Liquorice explained :
On Sat, 11 Feb 2017 23:40:33 -0800 (PST), wrote:

It's OK because lamp-holders are all high up so the kids can't stick
their fingers in.

Wrong answer. I think I was 6.

Ditto...

My first shock was around that age, from the grill of an electric
cooker, trying to light a match. A modern toaster also has bare
elements, but perhaps less easy to make contact with.

I reckon a toaster is the most dangerous domestic appliance for it's
shock potential* in normal operation.

*SWIDT?

--

Graham.
%Profound_observation%

On Mon, 13 Feb 2017 15:26:31 -0800 (PST), wrote:

On Monday, 13 February 2017 18:21:42 UTC, Johnny B Good wrote:
On Sun, 12 Feb 2017 10:23:54 +0000, Dave Liquorice wrote:
On Sat, 11 Feb 2017 23:40:33 -0800 (PST), tabbypurr wrote:

It's OK because lamp-holders are all high up so the kids can't
stick
their fingers in.

Wrong answer. I think I was 6.

Ditto...

JOOI, did either of you suffer burns on your fingertips? Alternatively,

no

since you don't make this clear as to whether you were shocked by
touching a ceiling pendant light socket or handling a table lamp, did you

low hanging pendant

suffer a shock through your arm and body as a result of providing a path
to earth?

yep.


NT

IRTA low hanging pedant.
--

Graham.
%Profound_observation%

On Mon, 13 Feb 2017 21:24:20 +0000 (GMT), charles
wrote:

In article ,
wrote:
On Mon, 13 Feb 2017 16:33:06 GMT, Johnny B Good
wrote:



The statistics on UK 'lamp changing induced fatalities by
electrocution' (0 BC and 1 ES associated deaths?) seem to bear out that
the risk is extremely low in practice in spite of the theoretical risk
case that can be made against either type of lamp holder or socket.


If there had been a problem I would have thought it may have been
revealed back in the era before power sockets were fitted in many
premises and the pendant lamp fitting was the only source of electric
in the room.
Removing the lamp and connecting the flex of an Iron or other small
appliance using a bayonet plug was common, some users used a Y piece
with two outlets that allowed the lamp to remain in place which did
leave unprotected pins when the appliance was disconnected.
Some more expensive versions did have switch.

you could buy them in Woolworths!

I had my enlarger and safelamp plugged into one under the stairs.
--

Graham.
%Profound_observation%

On Mon, 13 Feb 2017 22:21:14 +0000, wrote:

On Mon, 13 Feb 2017 21:24:20 +0000 (GMT), charles
wrote:



If there had been a problem I would have thought it may have been
revealed back in the era before power sockets were fitted
Removing the lamp and connecting the flex of an Iron or other small
appliance using a bayonet plug

you could buy them in Woolworths!

Hoover suppled a version that converted the pendant to a two pin
socket .

There is a photo of a couple at the top of this page.
http://www.vacuumland.org/cgi-bin/TD...HREAD.cgi?3412

The socket contacts look even more likely to touched by a wayward
finger than the bayonet pins alone.

G.Harman

I used to plug my shaver into one.
--

Graham.
%Profound_observation%

On Tuesday, 14 February 2017 00:46:06 UTC, Graham. wrote:
I had my enlarger

Scrolling through quickly, IRTA low hanging pedant enlarger

Owain

On Tuesday, 14 February 2017 00:24:46 UTC, Graham. wrote:
On Sun, 12 Feb 2017 12:49:00 -0800 (PST), tabbypurr wrote:
On Sunday, 12 February 2017 18:42:44 UTC, Dave Plowman (News) wrote:
In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:
In article ,
Scott wrote:
But if you are really concerned about safety, fit an appropriate RCD.
But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...cds-explained/
appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which, of
course, may be caused by a leakage to earth.

I bet we're all curious where else you think the current imbalance goes.


NT

He knows full well, his point is RCDs do not work by detecting earth
leakage directly, and he's right.

Where else do you think the leakage current goes? How often does a person connect themselves to another circuit's neutral while taking a shock? Even then the current still goes to earth.


NT

Johnny B Good expressed precisely :
JOOI, did either of you suffer burns on your fingertips? Alternatively,
since you don't make this clear as to whether you were shocked by
touching a ceiling pendant light socket or handling a table lamp, did you
suffer a shock through your arm and body as a result of providing a path
to earth?

I didn't suffer any burns - how serious a belt you receive, depends
upon the conductivity of your skin, its resistance. Unless I am very
hot and sweaty, I can touch across 240v with a barely noticeable
tingle. I have tripped RCD's without even noticing I have tripped them.

Johnny B Good brought next idea :
JOOI, did either of you suffer burns on your fingertips?

A guy I was working with once, suffered burns on his arms. He was
working from a ladder alongside a 3Ph works crane, the crane was of the
style used back then and ran the full length of a bay, using a catenary
bare copper along the full length of the track, with pickups on the
mobile crane. He had failed to isolate the crane, the ladder had
slipped a bit and had grabbed the bare live lines. He was lucky he
could let go and climb down, but you should have the howl.

On Tue, 14 Feb 2017 01:06:53 -0800 (PST), wrote:

On Tuesday, 14 February 2017 00:24:46 UTC, Graham. wrote:
On Sun, 12 Feb 2017 12:49:00 -0800 (PST), tabbypurr wrote:
On Sunday, 12 February 2017 18:42:44 UTC, Dave Plowman (News) wrote:
In article ,
Scott wrote:
On Sun, 12 Feb 2017 15:16:42 +0000 (GMT), "Dave Plowman (News)"
wrote:
In article ,
Scott wrote:
But if you are really concerned about safety, fit an appropriate RCD.
But
don't expect others to have to pay extra for stupid parents.

I'm not concerned at all. Anyway, I thought an RCD only detected
leakage to earth so why would touching both terminals trip an RCD?

You thought wrong.

http://www.electricalsafetyfirst.org...cds-explained/
appears to disagree with you.

Then it's wrong too.

A device which detects leakage to earth is an ELCB.

An RCD looks for differential current between line and neutral. Which, of
course, may be caused by a leakage to earth.

I bet we're all curious where else you think the current imbalance goes.


NT

He knows full well, his point is RCDs do not work by detecting earth
leakage directly, and he's right.

Where else do you think the leakage current goes? How often does a person connect themselves to another circuit's neutral while taking a shock? Even then the current still goes to earth.



Yes, they effectively trip on earth leakage whilst not directly
measuring it. Quite clever really.


--

Graham.
%Profound_observation%

On Tue, 14 Feb 2017 00:22:16 -0800 (PST),
wrote:

On Tuesday, 14 February 2017 00:46:06 UTC, Graham. wrote:
I had my enlarger

Scrolling through quickly, IRTA low hanging pedant enlarger

Owain

A pendulous enlargement? I think the yanks call that a "semi".
--

Graham.
%Profound_observation%

On Mon, 13 Feb 2017 18:21:39 GMT, Johnny B Good wrote:

It's OK because lamp-holders are all high up so the kids can't
stick their fingers in.

Wrong answer. I think I was 6.

Ditto...

JOOI, did either of you suffer burns on your fingertips?

No, fricking hurt and made mental note not to do it again, not that
it's prevented me getting several other belts from the mains.

Alternatively, since you don't make this clear as to whether you were
shocked by touching a ceiling pendant light socket or handling a table
lamp,

Pendant.

did you suffer a shock through your arm and body as a result of
providing a path to earth?

It's a while ago but ISTR having a painful arm for an hour or two
after so despite being on top of a wooden chest of drawers some
current did flow through me not just across my finger tip.

ELCBs and RCDs have been mentioned in this thread, asking how such
protective devices can work in the absence of any path to earth such as
atop a wooden step ladder when bridging the lamp contacts with a
fingertip. The answer in this case is, "They don't!".

I think you under estimate how easyly 230 V can shove 30 mA down the
multiple parallel paths that bypass the second winding in an RCD.

--
Cheers
Dave.

On Mon, 13 Feb 2017 15:26:31 -0800, tabbypurr wrote:

On Monday, 13 February 2017 18:21:42 UTC, Johnny B Good wrote:
On Sun, 12 Feb 2017 10:23:54 +0000, Dave Liquorice wrote:
On Sat, 11 Feb 2017 23:40:33 -0800 (PST), tabbypurr wrote:

It's OK because lamp-holders are all high up so the kids can't
stick
their fingers in.

Wrong answer. I think I was 6.

Ditto...

JOOI, did either of you suffer burns on your fingertips?
Alternatively,

no

since you don't make this clear as to whether you were shocked by
touching a ceiling pendant light socket or handling a table lamp, did
you

low hanging pendant

suffer a shock through your arm and body as a result of providing a
path to earth?

yep.


Damn those low hanging pendants! Presumably you were stretching out to
reach the pendant so I guess you disconnected yourself quick smart when
you completed the circuit, neatly limiting the experience to no more than
a nasty jolt. That's not to belittle the experience but it does highlight
why, other than for obvious misuse cases, BC and ES lampholders remain
largely unchanged in design over the past century (and virtually
unchanged over the past 6 or 7 decades at least).

--
Johnny B Good

On Tue, 14 Feb 2017 20:14:11 +0000, Dave Liquorice wrote:

On Mon, 13 Feb 2017 18:21:39 GMT, Johnny B Good wrote:

It's OK because lamp-holders are all high up so the kids can't stick
their fingers in.

Wrong answer. I think I was 6.

Ditto...

JOOI, did either of you suffer burns on your fingertips?

No, fricking hurt and made mental note not to do it again, not that it's
prevented me getting several other belts from the mains.

It never does. It just makes you wary enough of lamp sockets/holders to
treat them with a little more respect. :-)

Alternatively, since you don't make this clear as to whether you were
shocked by touching a ceiling pendant light socket or handling a table
lamp,

Pendant.

did you suffer a shock through your arm and body as a result of
providing a path to earth?

It's a while ago but ISTR having a painful arm for an hour or two after
so despite being on top of a wooden chest of drawers some current did
flow through me not just across my finger tip.

Makes you wonder how you managed to bridge yourself to earth or a
connection to a neutral via some other part of your body.

ELCBs and RCDs have been mentioned in this thread, asking how such
protective devices can work in the absence of any path to earth such as
atop a wooden step ladder when bridging the lamp contacts with a
fingertip. The answer in this case is, "They don't!".

I think you under estimate how easily 230 V can shove 30 mA down the
multiple parallel paths that bypass the second winding in an RCD.

I don't underestimate the possible sources of earth leakage paths (8K
ohms or less required btw), I was just completely discounting them in
this particular scenario where the hapless victim has managed to isolate
themselves from contact with any such earth leakage paths. This a common
enough scenario in a typical home environment when changing a pendant
lamp these days such that the hapless victim can receive a nasty jolt
without fear of tripping an RCD or ELCB or electrocution.

--
Johnny B Good

On 11/02/2017 17:48, Scott wrote:
On Sat, 11 Feb 2017 17:00:17 +0000, Graham.
wrote:

On Sat, 11 Feb 2017 16:52:05 +0000, Scott
wrote:

On Sat, 11 Feb 2017 16:41:30 +0000, ARW
wrote:

On 11/02/2017 14:38, Huge wrote:
On 2017-02-11, David Lang wrote:
Same bloke in TLC Direct in the lamp holder post, reckoned that the 18th
edition will specify that all new lighting installations after a certain
date will have to be low voltage.

240V *is* low voltage.


So is 230V.

Plus or minus. Is it +10% / -6% or something else as there seems to
be some confusion? I'm sure 240V is in there. .

That's European harmonised supply ********. Nothing to do with what is
or isn't LV.

I appreciate that but I assumed 230V was chosen for a reason and I was
commenting on that reasoning.

We use 240V and many European countries use 220V. 230V with a wide
enough tolerance means that products designed for "230V" can be sold
both here and on the continent, without having to have separate products
for each voltage.

SteveW