scott <sco### [at] scottcom> wrote:
> I don't know about Finland, but here in Germany only higher power/earthed 
> equipment uses the Schuko plug, for lower powered stuff usually the Europlug 
> is used (which also fits into the Schuko sockets fine of course).

> http://en.wikipedia.org/wiki/Europlug

  Yeah, those are common here too. Depends on the device. Things like
PSU powercords and extension cords invariably use Schuko. Smaller devices
use the europlug.

  I assume it's about the same as in Germany. After all, lots of electrical
devices are imported here from there (and I assume in some cases the other
way around too).

-- 
                                                          - Warp

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> > Oh I forgot, we also have this type in Germany too:
> > 
> > http://en.wikipedia.org/wiki/Image:CEE_7-17_plug.jpg

> Looks pretty much identical to me...

  It has no ground connectors and is smaller.

-- 
                                                          - Warp

Post a reply to this message

>> Looks pretty much identical to me...
> 
>   It has no ground connectors and is smaller.

Ah, OK. You can't really tell the scale from the image...

Post a reply to this message

"Invisible" <voi### [at] devnull> wrote in message 
news:48f33a4b$1@news.povray.org...
>
> So it seems putting 250 V through your hands isn't necessarily an instant 
> fatality like they tell you on TV.
>

Through your hands, no. Through othe parts of your body, maybe.

I've been zapped by mains current once (240V, SA standard). I was trying to 
remove the network cable from a server (10-base-2, coax), and as I turned it 
to unplug it, my wrist brushed against the power cable, which was missing 
insulation right at that point.
Next thing I was sitting with my back to the wall of the server cupboard 
(1/2 a metre from the server)

I'd been resting elbows on the floor of the cupboard, so the current only 
flowed wrist to elbow, but I couldn't write or type properly for a short 
while afterwards.

Post a reply to this message

Gail wrote:

> Through your hands, no. Through othe parts of your body, maybe.

You would have thought holding the two halves in either hand, there'd be 
a rather high chance of the current crossing your chest cavity... hell 
*I* wouldn't like to try it!

> I've been zapped by mains current once (240V, SA standard). I was trying 
> to remove the network cable from a server (10-base-2, coax), and as I 
> turned it to unplug it, my wrist brushed against the power cable, which 
> was missing insulation right at that point.
> Next thing I was sitting with my back to the wall of the server cupboard 
> (1/2 a metre from the server)
> 
> I'd been resting elbows on the floor of the cupboard, so the current 
> only flowed wrist to elbow, but I couldn't write or type properly for a 
> short while afterwards.

I bet that hurt! o_O

Actually, come to think of it, there *was* that time I was trying to 
figure out why mum's electric shower wasn't working properly. I took the 
cover off and had a look at the circuit board. I couldn't see anything 
wrong with it. Of course, all circuit boards run at a mere 5V, so it's 
quite safe to touch even thAAAAAARGH!!!! >_<

I guess standing in a fiberglass bath tub saved me. It hurt quite a bit 
though. (I mean, it stopped hurting as soon as I let go, but I nearly 
headbutted the wall!)

Post a reply to this message

"Invisible" <voi### [at] devnull> wrote in message 
news:48f3154d$1@news.povray.org...
> It's amazing what you can find out on teh interwebs...
>
> For example, that plug you use to plug normal equipment into the 
> electricity grid. Apparently there's a name for it. It's called "BS 1363". 
> (Memorable, eh?)

We use both of these:
http://en.wikipedia.org/wiki/Image:M_plug.jpg,
http://en.wikipedia.org/wiki/Image:C_plug.jpg

It's irritating, as the two require different sockets and so people tend to 
have a number of convertors lying around to allow the 2-pins to be used. All 
the wall sockets are for the 3-pin only.

Post a reply to this message

Invisible wrote:

> 
> Not something you think about every day - until you realise that less 
> civilised countries just use a plain metal stick so it's frighteningly 
> easy to pull out of the wall, plug in backwards, electrocute yourself 
> with by touching the pins while inserting/removing, insert random 
> objects into the socket, etc.
> 

Heh, that's not a jab at the U.S. style plugs, is it? Our wall sockets 
are just the right size for a determined toddler armed with only a 
screwdriver to, err, well ... That's why we invented any number of 
different solutions to prevent determined toddlers armed with 
screwdrivers from sticking the end of the screwdriver in the appropriate 
slot and causing a simultaneous power and life failure. :)

So, can't a kid stick something metallic in a British design socket?

> I guess it's like you don't realise how stringent UK health and safety 
> rules are until you see some pictures on the TV of workers in some 
> random country using blowtorches and angle grinders without any safety 
> equipment at all...

I remember on a cruise to Mexico, they were working on fixing the pier, 
they had run out to their power tools, above the salty water, what 
looked like a pair of wires, twisted together at some points to extend 
it. OSHA would have had a field day with their utter lack of regard for 
basic electrical safety.

-- 
~Mike

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> >> Looks pretty much identical to me...
> > 
> >   It has no ground connectors and is smaller.

> Ah, OK. You can't really tell the scale from the image...

  (Of course "smaller" meant "smaller in volume". Naturally the round part
has the same radius.)

-- 
                                                          - Warp

Post a reply to this message

scott wrote:

> 
> Saw a big 3-phase motor once, the supply cable was simply stripped back 
> and tied around the contacts on the motor!  No cover, nothing.
> 

My favorite are the 3-phase plugs. I had one hell of a time trying to 
unplug one, until someone walked up, twisted the plug and pulled it 
right out.

Reminds me of the test bench we had set up once. 3-phase from the 
wall-socket, neutral screwed to a big steel plate, and 3 phases into 
breakers, all nice and well exposed. Some guy from a vendor was out 
trying to diagnose some problems we were having with the bus and 
electronics on the test rack actually jammed his screwdriver straight 
into the contact of one of the phases. That had to hurt :/ Then after he 
got jolted pulled out his multimeter to see why the ground plate was 
"hot" I just told him he should be more careful when he's holding long 
metal objects around hot electrical stuff.

Man, I miss working at the equipment division sometimes. :)


-- 
~Mike

Post a reply to this message

Invisible wrote:

> OTOH, take a look at those overhead power lines. It's not so much that 
> the current involved might make your heart stop beating... it's more 
> that your body is liable to be transformed into an actual human crisp. ;-)

Somewhere on Youtube there's a video of a backhoe making contact with a 
(I think) 15kv overhead line. Needless to say, the backhoe was no more.


-- 
~Mike

Post a reply to this message

scott wrote:
> http://en.wikipedia.org/wiki/Europlug

We use those (or used to) for some devices but most have this:
http://en.wikipedia.org/wiki/Image:Australian_dual_switched_power_point.jpg

Post a reply to this message

Invisible wrote:

> That worked for about 20 minutes, and then the ends unhooked. 
> Frustrated, my dad picked up the ends again... and then got up off the 
> floor and UNPLUGED THE HEATER before repeating this action. ;-)

As a kid, about 5, for some reason still unknown to me today, I got it 
in my head that I should unplug the clock that was on top of a dresser, 
so I crawled underneath the furniture, grabbed the plug, slid my fingers 
behind it to get more leverage, and >Thump< a nice 110V hit. From that 
day forward, I've had a very healthy respect for electricity. But, no. I 
wouldn't recommend anyone make contact with live wires. It's just asking 
for a trip to the morgue.
-- 
~Mike

Post a reply to this message

Gail wrote:
> Next thing I was sitting with my back to the wall of the server cupboard 

Wow. I'm glad we only use half the voltage here. I've been shocked a few 
times in the US, and while it leaves you shaking a bit, I can't imagine 
it being bad enough to knock you down. I mean, I wouldn't want to repeat 
the experience, it's like stubbing your toe: not especially dangerous.

-- 
Darren New / San Diego, CA, USA (PST)

Post a reply to this message

Mike Raiford wrote:

>> Not something you think about every day - until you realise that less 
>> civilised countries just use a plain metal stick so it's frighteningly 
>> easy to pull out of the wall, plug in backwards, electrocute yourself 
>> with by touching the pins while inserting/removing, insert random 
>> objects into the socket, etc.
> 
> Heh, that's not a jab at the U.S. style plugs, is it?

Nooo, at at all... </sarcasm>

> Our wall sockets 
> are just the right size for a determined toddler armed with only a 
> screwdriver to, err, well ... That's why we invented any number of 
> different solutions to prevent determined toddlers armed with 
> screwdrivers from sticking the end of the screwdriver in the appropriate 
> slot and causing a simultaneous power and life failure. :)

Hmm. It's like natural selection, but backwards: the kids who get bored 
quickly enough don't figure out how to do it and survive to reproduce! :-D

> So, can't a kid stick something metallic in a British design socket?

Nope. As the Wikipedia article explains, there are sprung-loaded plastic 
covers that only move out of the way as the earth pin is inserted.

So you'd actually need *two* pointy things - one to poke the earth 
socket, and another metallic object to insert into the live socket. Oh, 
and some coordination. I'm sure if you try hard enough you can kill 
yourself, but seriously... ;-)

(Interestingly, Wikipedia also points out that the "safety covers" you 
can commonly buy are actually ideal for opening the pins so you can kill 
yourself. Neat, eh?)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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Mike Raiford wrote:

> As a kid, about 5, for some reason still unknown to me today, I got it 
> in my head that I should unplug the clock that was on top of a dresser, 
> so I crawled underneath the furniture, grabbed the plug, slid my fingers 
> behind it to get more leverage, and >Thump< a nice 110V hit. From that 
> day forward, I've had a very healthy respect for electricity. But, no. I 
> wouldn't recommend anyone make contact with live wires. It's just asking 
> for a trip to the morgue.

[Another safety feature of the BS1363: partially insulated pins. You'd 
need very thin fingers to touch live by the time it's inserted far 
enough to make contact...]

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Mike Raiford wrote:

> Somewhere on Youtube there's a video of a backhoe making contact with a 
> (I think) 15kv overhead line. Needless to say, the backhoe was no more.

If you can think of it, it's probably on YouTube.

I heard some guy has one of those mains grid transformers in a shed at 
the end of his garden. (I don't know how common this is in other parts 
of the world, but it's not "rare" in the UK.) Apparently one day the 
whole street lost power, and this shed looked "like the 5th of 
November". Apparently when the power company finally turned of the 
circuit, there was a bit of a crater.

Damn, I would *not* want to be around that crap! o_O

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Darren New wrote:

> Wow. I'm glad we only use half the voltage here. I've been shocked a few 
> times in the US, and while it leaves you shaking a bit, I can't imagine 
> it being bad enough to knock you down. I mean, I wouldn't want to repeat 
> the experience, it's like stubbing your toe: not especially dangerous.

...which reminds me of the time I stood on an upturned BS1363 plug, 
barefoot.

Trust me, it hurt.

It hurt *almost* as much as a split second later, when I grabbed a 
red-hot gas fire griddle to support myself as I hopped around in pain.

I had a griddle pattern on the skin of my hand for, like, a month after 
that...

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Orchid XP v8 <voi### [at] devnull> wrote:
> Nope. As the Wikipedia article explains, there are sprung-loaded plastic 
> covers that only move out of the way as the earth pin is inserted.

  Is it guaranteed that the difference in potential between the earth pin
and the physical ground is always very close to zero?

  Because AFAIK there may be surprisingly large potential differences
between the earth pins of neighboring buildings at some places.

-- 
                                                          - Warp

Post a reply to this message

Orchid XP v8 wrote:

> 
> Hmm. It's like natural selection, but backwards: the kids who get bored 
> quickly enough don't figure out how to do it and survive to reproduce! :-D
> 

That explains a lot, actually ... :)

>> So, can't a kid stick something metallic in a British design socket?
> 
> Nope. As the Wikipedia article explains, there are sprung-loaded plastic 
> covers that only move out of the way as the earth pin is inserted.

Sounds similar to what we have installed over our plugs. Essentially, 
you have to slid the cover over as you plug something in. The drawback 
is if you have older plugs that don't hold firmly, the plugged-in device 
will slip out.

> So you'd actually need *two* pointy things - one to poke the earth 
> socket, and another metallic object to insert into the live socket. Oh, 
> and some coordination. I'm sure if you try hard enough you can kill 
> yourself, but seriously... ;-)

Ah, so only the most determined toddlers with a good bit of hand-eye 
coordination, and manual dexterity will be successful.


-- 
~Mike

Post a reply to this message

Warp wrote:

>   Is it guaranteed that the difference in potential between the earth pin
> and the physical ground is always very close to zero?
> 
>   Because AFAIK there may be surprisingly large potential differences
> between the earth pins of neighboring buildings at some places.

I'm not an electrical engineer, so I couldn't say. I do know that on 
many appliances the earth pin is physically connected to the metal 
chasis of the appliance, so I *hope* it's similar to the 
surroundings...! o_O

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

>> Hmm. It's like natural selection, but backwards: the kids who get 
>> bored quickly enough don't figure out how to do it and survive to 
>> reproduce! :-D
> 
> That explains a lot, actually ... :)

Hmm... how depressing! :-S

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

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> "It is, in principle, possible to insert a Europlug into a BS 1363 
> socket by inserting another object (such as a screwdriver or key) into 
> the earth hole first."
> 
> :-)
Back on my holidays in Ireland I've just used the native plug of some 
hotel room equipment upside down :) Then jammed the europlug in the 
mains holes.

Post a reply to this message

"Warp" <war### [at] tagpovrayorg> wrote in message 
news:48f38551@news.povray.org...
> Orchid XP v8 <voi### [at] devnull> wrote:
>> Nope. As the Wikipedia article explains, there are sprung-loaded plastic
>> covers that only move out of the way as the earth pin is inserted.
>
>  Is it guaranteed that the difference in potential between the earth pin
> and the physical ground is always very close to zero?
>
>  Because AFAIK there may be surprisingly large potential differences
> between the earth pins of neighboring buildings at some places.

When I was at university, there was a noticable potential difference between 
the earth pins on different floors of the same building. It played hell with 
the coax network cable...

Post a reply to this message

"Darren New" <dne### [at] sanrrcom> wrote in message 
news:48f381e2$1@news.povray.org...
> Gail wrote:
>> Next thing I was sitting with my back to the wall of the server cupboard
>
> Wow. I'm glad we only use half the voltage here. I've been shocked a few 
> times in the US, and while it leaves you shaking a bit, I can't imagine it 
> being bad enough to knock you down.

It didn't really. I was sitting on the floor fiddling with the server. It 
knocked me back about half a metre

When I said server cupboard, I meant it. It was a 'room' about 2.5 m long 
and just over 1 m wide

Post a reply to this message

Gail wrote:

> When I said server cupboard, I meant it. It was a 'room' about 2.5 m 
> long and just over 1 m wide

Gee, that sounds just like *my* server room...! o_O

Tell me, is it also freezing cold in there?

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

Orchid XP v8 wrote:
> ...which reminds me of the time I stood on an upturned BS1363 plug,
> barefoot.
> 
> Trust me, it hurt.
> 
> It hurt *almost* as much as a split second later, when I grabbed a
> red-hot gas fire griddle to support myself as I hopped around in pain.
> 
> I had a griddle pattern on the skin of my hand for, like, a month after
> that...
> 

...

Dear god.

Post a reply to this message

Nicolas Alvarez wrote:

> ...
> 
> Dear god.

...and *then* everybody was mad at me for yelling my head off at, like, 
6 AM on a Sunday. O_O

I mean hell, if you spiked your foot and then burned your hand, would 
*you* care what time of day it is???

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

On Mon, 13 Oct 2008 21:26:05 +0200, "Gail" <gail (at) sql in the wild (dot) co
[dot] za> wrote:

>
>"Darren New" <dne### [at] sanrrcom> wrote in message 
>news:48f381e2$1@news.povray.org...
>> Gail wrote:
>>> Next thing I was sitting with my back to the wall of the server cupboard
>>
>> Wow. I'm glad we only use half the voltage here. I've been shocked a few 
>> times in the US, and while it leaves you shaking a bit, I can't imagine it 
>> being bad enough to knock you down.
>
>It didn't really. I was sitting on the floor fiddling with the server. It 
>knocked me back about half a metre

You probably threw yourself back and it wasn't the electric shock. Working in
the business I have had more shocks than I can remember from 110 Vac tingles to
a 660 Vac wallop from a 3 phase distribution board. The most painful was when a
loose strand of wire pricked my finger with the power off and I hurt my hand
against the case getting it out of there. I knew the power was off but try
telling that to your reactions :)
I once got a 500 Vdc belt that lifted my feet off the ground even though I was
standing on a rubber mat and wearing insulating boots. As we all know ac throws
you off and dc makes you grab on so it was a reaction that made me jump
incidentally breaking the contact with the supply. It sure does waken you up ;)
Here are a couple of tips for everyone when working on live equipment. Wear
insulating footwear and keep one hand in your pocket. That way the current is
less likely to find a path through your body.

Incidentally when you see medics using that "Stand Clear, Stand Clear" electric
defibrillator. They are not starting the heart but stopping it. Think on :)
-- 

Regards
     Stephen

Post a reply to this message

Stephen wrote:

> Incidentally when you see medics using that "Stand Clear, Stand Clear" electric
> defibrillator. They are not starting the heart but stopping it. Think on :)

It's like rebooting a computer. Gotta shut it down to make it start back 
up again in normal working order. ;-)

-- 
http://blog.orphi.me.uk/
http://www.zazzle.com/MathematicalOrchid*

Post a reply to this message

>> Nope. As the Wikipedia article explains, there are sprung-loaded plastic
>> covers that only move out of the way as the earth pin is inserted.
>
>  Is it guaranteed that the difference in potential between the earth pin
> and the physical ground is always very close to zero?

The Earth wires in your house (in the UK at least) are connected to the 
physical ground at your house, usually by being connected to the mains water 
pipe or some similar big lump of metal in the ground.  So I don't think 
there can be much of a difference, there is probably some building standard 
that gives limits on the resistance.  I assume these limits are set so that 
any potentially dangerous Earth voltage would result in the current in the 
defective device blowing a fuse.

Post a reply to this message

"scott" <sco### [at] scottcom> wrote:
> >> Nope. As the Wikipedia article explains, there are sprung-loaded plastic
> >> covers that only move out of the way as the earth pin is inserted.
> >
> >  Is it guaranteed that the difference in potential between the earth pin
> > and the physical ground is always very close to zero?
>
> The Earth wires in your house (in the UK at least) are connected to the
> physical ground at your house, usually by being connected to the mains water
> pipe or some similar big lump of metal in the ground.  So I don't think
> there can be much of a difference, there is probably some building standard
> that gives limits on the resistance.  I assume these limits are set so that
> any potentially dangerous Earth voltage would result in the current in the
> defective device blowing a fuse.

I’ve seen them connected to plastic water pipes and a fat lot of good that would
do :)
In new builds you will often find a metal rod driven into the ground as an
earthing electrode.

--

Stephen

Post a reply to this message

Stephen wrote:

> I’ve seen them connected to plastic water pipes and a fat lot of good that would
> do :)

Isn't that illegal?

> In new builds you will often find a metal rod driven into the ground as an
> earthing electrode.

"I think having a lightning conductor on a church represents an 
extrodinary lack of faith."

Post a reply to this message

Invisible <voi### [at] devnull> wrote:
> Stephen wrote:
>
> > I’ve seen them connected to plastic water pipes and a fat lot of good that would
> > do :)
>
> Isn't that illegal?
>

Yes and not very effective.


> > In new builds you will often find a metal rod driven into the ground as an
> > earthing electrode.
>
> "I think having a lightning conductor on a church represents an
> extrodinary lack of faith."

Is it not to protect the church from the devil ;)
A bit like a high tech gargoyle.

Post a reply to this message

Stephen wrote:

> Here are a couple of tips for everyone when working on live equipment. Wear
> insulating footwear and keep one hand in your pocket. That way the current is
> less likely to find a path through your body.
> 

I am not an electrician, so I know enough to be dangerous.
Actually, I studied electrical engineering - so I know enough to keep 
mostly safe.

I was thinking I would write about keeping a hand in the pocket, but you 
beat me to it.

I always have a hand in my pocket when routing wires in my main electric 
panel where I can't easily turn everything off.  It isn't enough to just 
keep a hand away - by instinct you will use it to grab on to something.



I've been lucky, I've never been hit with anything more than 110v


Tom

Post a reply to this message

Warp wrote:
> Orchid XP v8 <voi### [at] devnull> wrote:
>> Nope. As the Wikipedia article explains, there are sprung-loaded plastic 
>> covers that only move out of the way as the earth pin is inserted.
> 
>   Is it guaranteed that the difference in potential between the earth pin
> and the physical ground is always very close to zero?
> 

Some non-electricians will hook up the earth as a common - using it as 
the return path for the hot.

In this case the potential will vary with the amount of current on the wire.

Post a reply to this message

Tom Austin <taustin> wrote:
> Stephen wrote:
>
> > Here are a couple of tips for everyone when working on live equipment. Wear
> > insulating footwear and keep one hand in your pocket. That way the current is
> > less likely to find a path through your body.
> >
>
> I am not an electrician, so I know enough to be dangerous.
> Actually, I studied electrical engineering - so I know enough to keep
> mostly safe.
>
> I was thinking I would write about keeping a hand in the pocket, but you
> beat me to it.
>
> I always have a hand in my pocket when routing wires in my main electric
> panel where I can't easily turn everything off.  It isn't enough to just
> keep a hand away - by instinct you will use it to grab on to something.
>
>
>
I’m not an electrician either nor an electrical engineer but an electronic on so
I get nervous working over 5V Vcc.
That hasn’t stopped people asking me to work on power systems which was the
reason I stopped working offshore. It was getting too dangerous.

If you can’t put your hand in your pocket grab hold of the back of your
waistband.


> I've been lucky, I've never been hit with anything more than 110v
>
>
A mere tingle :P
240 V is not too bad it hurts more but is bearable if it is just through your
hand. And most of the shock is just shock people do get used to it and can even
deliberately touch live connectors to test the voltage. The trick is to do it
fast and the pain level will tell you the voltage. The same way that I learned
to see how close to boiling water is by dipping my fingers into it (FAST). The
human body is very resilient.


Stephen

Post a reply to this message

> Some non-electricians will hook up the earth as a common - using it as the 
> return path for the hot.
>
> In this case the potential will vary with the amount of current on the 
> wire.

But I think that Buildings Standards require that the resistance to ground 
be low enough that for the Earth voltage to become dangerous, enough current 
must flow to blow a fuse.  Otherwise this kind of relatively common fault 
would leave metal cases of everything in the house electrified to dangerous 
voltages!

Post a reply to this message

> Yeah, some bathrooms have special "shaver" sockets which are weird 2-pin 
> connectors fused at 2A or something. Personally, I don't know about you, 
> but my bathroom is so tiny that you'd be just as well to go somewhere 
> else... ;-)

It appears that the forthcoming 17th editiion of the building regulations 
(aren't you excited!) in the UK will allow normal 13A sockets in a bathroom, 
if they are protected by a 30mA RCD and not too close to a shower/tap...

Post a reply to this message

scott wrote:

> It appears that the forthcoming 17th editiion of the building 
> regulations (aren't you excited!) in the UK will allow normal 13A 
> sockets in a bathroom, if they are protected by a 30mA RCD and not too 
> close to a shower/tap...

How in the name of God do you know that? o_O

Post a reply to this message

>> It appears that the forthcoming 17th editiion of the building regulations 
>> (aren't you excited!) in the UK will allow normal 13A sockets in a 
>> bathroom, if they are protected by a 30mA RCD and not too close to a 
>> shower/tap...
>
> How in the name of God do you know that? o_O

My mum asked me a while ago about putting a socket in her bathroom, so I 
looked into it then.  It appears that now you are actually allowed normal 
sockets in your bathroom (Wikipedia was a bit out of date).

Post a reply to this message

"scott" <sco### [at] scottcom> wrote in message news:48f4a20e@news.povray.org...
>> Some non-electricians will hook up the earth as a common - using it as 
>> the return path for the hot.
>>
>> In this case the potential will vary with the amount of current on the 
>> wire.
>
> But I think that Buildings Standards require that the resistance to ground 
> be low enough that for the Earth voltage to become dangerous, enough 
> current must flow to blow a fuse.  Otherwise this kind of relatively 
> common fault would leave metal cases of everything in the house 
> electrified to dangerous voltages!
>

I've seen similar happen in an old flat I was renting at University. Don't 
know how it happened (not an electrician), but something in the geyser 
shorted and left all of the hot water pipes (and the water) live.
It's times like that when having a friend who's father works for the city 
council as an electricial comes in handy.

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On Tue, 14 Oct 2008 07:38:36 +0100, Orchid XP v8 <voi### [at] devnull> wrote:

>Stephen wrote:
>
>> Incidentally when you see medics using that "Stand Clear, Stand Clear" electric
>> defibrillator. They are not starting the heart but stopping it. Think on :)
>
>It's like rebooting a computer. Gotta shut it down to make it start back 
>up again in normal working order. ;-)

True
-- 

Regards
     Stephen

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"Gail" <gail (at) sql in the wild (dot) co [dot] za> wrote:
> I've seen similar happen in an old flat I was renting at University. Don't
> know how it happened (not an electrician), but something in the geyser
> shorted and left all of the hot water pipes (and the water) live.
> It's times like that when having a friend who's father works for the city
> council as an electricial comes in handy.

Wow. Reminds me of a short from The Three Stooges :)

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Stephen wrote:
> Tom Austin <taustin> wrote:
>> Stephen wrote:
>>
>>> Here are a couple of tips for everyone when working on live equipment. Wear
>>> insulating footwear and keep one hand in your pocket. That way the current is
>>> less likely to find a path through your body.
>>>
>> I am not an electrician, so I know enough to be dangerous.
>> Actually, I studied electrical engineering - so I know enough to keep
>> mostly safe.
>>
>> I was thinking I would write about keeping a hand in the pocket, but you
>> beat me to it.
>>
>> I always have a hand in my pocket when routing wires in my main electric
>> panel where I can't easily turn everything off.  It isn't enough to just
>> keep a hand away - by instinct you will use it to grab on to something.
>>
>>
>>
> I’m not an electrician either nor an electrical engineer but an electronic on so
> I get nervous working over 5V Vcc.

I've been scared of that as well - especially when the circuit that I 
wired up actually blows things up.  I got so jumpy at one point I had to 
have someone else hook it up to smoke test it.

>>
>>
> A mere tingle :P
> 240 V is not too bad it hurts more but is bearable if it is just through your
> hand. And most of the shock is just shock people do get used to it and can even
> deliberately touch live connectors to test the voltage. The trick is to do it
> fast and the pain level will tell you the voltage. The same way that I learned
> to see how close to boiling water is by dipping my fingers into it (FAST). The
> human body is very resilient.
> 
> 

Never thought of it like that, but it makes sense.
The problem is that someone without experience tries to do it and gets 
themselves hut.


Tom

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scott wrote:
>> Some non-electricians will hook up the earth as a common - using it as 
>> the return path for the hot.
>>
>> In this case the potential will vary with the amount of current on the 
>> wire.
> 
> But I think that Buildings Standards require that the resistance to 
> ground be low enough that for the Earth voltage to become dangerous, 
> enough current must flow to blow a fuse.  Otherwise this kind of 
> relatively common fault would leave metal cases of everything in the 
> house electrified to dangerous voltages!
> 

When a layman looks in an electric panel he sees that the bare copper 
ground and the white neutral (U.S. colors here) attach to the same point 
they start to think they can use the bare copper as the neutral.

While it isn't terribly shocking, it does cause a voltage on what is 
supposed to be grounded.

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Gail wrote:
> Don't know how it happened (not an electrician), but something in the 
> geyser shorted and left all of the hot water pipes (and the water) live.

I was working at a place once where we were doing CP/M development, back 
before LANs and stuff. So we had the serial ports on all the machines 
hooked to long wires that came up to what could only be called a patch 
panel (for connecting machines together, and machines to modems).

One day, "Hey, I can't get the Apple ][ to talk to the Kay-pro."
"Try the Vernace."
"Nope."
"See if the Vernace will talk to the Kay-pro."
"Nope."
"Try the Radio Shack."
"That doesn't work either."

After a few such tries, one of us got a tingle trying to plug the serial 
connector into the patch panel. Oh, jeez, house current on the serial 
port ground. We managed to fry every single serial port, except that the 
radio shack machine had 2 and we only fried one of them.

-- 
Darren New / San Diego, CA, USA (PST)

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On Wed, 15 Oct 2008 10:34:11 -0700, Darren New <dne### [at] sanrrcom> wrote:

>
>After a few such tries, one of us got a tingle trying to plug the serial 
>connector into the patch panel. Oh, jeez, house current on the serial 
>port ground. We managed to fry every single serial port, except that the 
>radio shack machine had 2 and we only fried one of them.
>

You're bringing back memories ;)
That reminds me of a job years ago (about 1975). I was using a scope to check
the current flowing through a component and had disconnected the mains earth
wire so that the scope was floating. {So that the probe's reference ground would
not be connected to earth and short out the component's power supply (before
double insulated or floating return paths on scopes. A valve job IIRC)} Every
time someone touched the scope they got a tingle. Looking into it I found that
when the scope's mains filter had been put on back to front and there was a
capacitive bridge between the live-earth-neutral making the chassis sit at 120
Volts. It was limited current but a really sharp tingling. 
-- 

Regards
     Stephen

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On Wed, 15 Oct 2008 12:39:19 -0400, Tom Austin <taustin> wrote:

>
>I've been scared of that as well - especially when the circuit that I 
>wired up actually blows things up.  I got so jumpy at one point I had to 
>have someone else hook it up to smoke test it.
>

Nothing wrong with that IMO ;)

>>>
>>>
>> A mere tingle :P
>> 240 V is not too bad it hurts more but is bearable if it is just through your
>> hand. And most of the shock is just shock people do get used to it and can even
>> deliberately touch live connectors to test the voltage. The trick is to do it
>> fast and the pain level will tell you the voltage. The same way that I learned
>> to see how close to boiling water is by dipping my fingers into it (FAST). The
>> human body is very resilient.
>> 
>> 
>
>Never thought of it like that, but it makes sense.
>The problem is that someone without experience tries to do it and gets 
>themselves hut.

Yes, you don't do it in front of children. The boiling water thing was shown to
me by someone in the catering trade. There are a couple of tricks for snapping
un-insulated wire you can do. One involves putting a kink in the wire that
fatigues it and makes it break before it cuts you and another that spreads the
pressure over your knuckle stopping it from digging in. 
Send $10 and a SAE for the secrets :)
-- 

Regards
     Stephen

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Darren New wrote:
> 
> One day, "Hey, I can't get the Apple ][ to talk to the Kay-pro."
> 

That brings back memories, BTW. One of the first computers I actually 
had my hands on was a Kaypro. I remember thinking CP/M was very similar 
to DOS, later I learned DOS was based on CP/M.

> After a few such tries, one of us got a tingle trying to plug the serial 
> connector into the patch panel. Oh, jeez, house current on the serial 
> port ground. We managed to fry every single serial port, except that the 
> radio shack machine had 2 and we only fried one of them.
> 

Ouch. How did that happen, BTW?
-- 
~Mike

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Mike Raiford wrote:
> That brings back memories, BTW. One of the first computers I actually 
> had my hands on was a Kaypro. I remember thinking CP/M was very similar 
> to DOS, later I learned DOS was based on CP/M.

Yep. Same system calls and everything. You were supposed to be able to 
re-assemble your assembly code for CP/M and have it Just Work on the 
IBM-PC.  It really wasn't *just* the Microsoft deal that made it work.

> Ouch. How did that happen, BTW?

Dunno. Something inside one of the machines touched something it 
shouldn't. It probably started with the Apple, which got opened up more 
than the other machines.

-- 
Darren New / San Diego, CA, USA (PST)

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