Circular saw won't ground, safe?

[Don Klipstein]

You are correct; 100ma is about the lethal threashold. But it is difficult
to get 100ma off 120v unless you are in saltwater.
Naturally adverse medical conditions, or just plain bad luck, will change
everything!

A few problems with this:

1. Perspiration is salty. A sweaty hand on a metal power tool could have
resistance down to about 1k ohms or so.

2. Electric shock can stimulate sweat glands.

3. Electric shock at a few 10's of mA or maybe around 10 mA can stimulate
muscles and cause you to involuntarily grip what is shocking you.

4. Most sources say 100-1,000 mA is a range of current that is likely to
cause ventricular fibrillation, with a few saying this deadly range
starts at 50 mA. (Also a few sources make the upper limit of this
"most deadly range" lower.)
The changes of death do not decrease to zero at 99 or 49 mA. I have
heard of electrocution by 30 mA from a neon sign transformer, although
people *usually* survive this.

5. Electrocution is unreliable. With electric chairs, they use enough
current to either:

* Cook vital organs
* Paralyze breathing muscles long enough to deprive the brain of
oxygen to the point that breathing will not restart when the
shock ends

Lack of electrocution is simularly unreliable.

6. The low fatality rate of 110-120V shocks lulls people into a false
sense of security that leads to this voltage achieving a body count.
On US Navy ships, most power circuits are 440V rather than 110V, and
most electrocution deaths are from 110V. (Another factor could be
that lights and ordinary outlets - where exposure to less-trained
people is greater than that of 440V stuff - are 110V.) (Yes, US
Navy ships have 110V at least nominally rather than 120V.)

- Don Klipstein ([email protected])

 

[Don Klipstein]

Absolutely. The exact same concept applies to guns: "If there's even the
slightest doubt about whether it could be loaded, then *IT IS* until
proven otherwise."

If there's even the slightest doubt that a pair of wires might be hot,
then *THEY ARE* until proven otherwise.

Any other assumption in either case is stupidity on a scale you only
read newspaper articles about. Usually articles ending "Services will be
provided by <insert name> funeral home."

I have been told there are old pilots and bold pilots, but not many who
were both. My father said the same thing about electricians.

- Don Klipstein ([email protected])

 

[Leon]

Glad I'm not the only one that does that.

And who says the breaker box was labeled correctly or labeled at all.

 

[Dr. Anton T. Squeegee]

I certainly agree that the cord should be replaced; but it is not
particularly dangerous. To get any shock, you would have to both short the

<snippety-two>

Underestimating potential hazards has probably gotten lots of
people killed.

Any cord that is frayed and cracking is dangerous. Period. That
saw should NOT be used, under any conditions, until it has been properly
repaired.


--
Dr. Anton T. Squeegee, Director, Dutch Surrealist Plumbing Institute.
(Known to some as Bruce Lane, ARS KC7GR,
kyrrin (a/t) bluefeathertech[d=o=t]calm -- www.bluefeathertech.com
"If Salvador Dali had owned a computer, would it have been equipped
with surreal ports?"

 

[spudnuty]

For info on how a GFCI works check Sam's , very complete:

http://www.codecheck.com/gfci_principal.htm

please explain why do some modern factory drills, grinders
and saws get away without a ground plug?

As above double insulated and more over usually GFCI protected.

a hot or neutral short to ground shuts down my entire electrical
system. Is this the GFCI?

Hot to ground short - how big is the spark? 15-20 Amps? Breaker. No
spark? - Possibly a GFCI
Neutral to ground short - Possibly a GFCI or total miswire
And if this is the case can't you ID the GFCI?

Incidently any electrician knows that you can be shocked from a neutral
line, especially if you're dissasembling a junction of several neutrals
even with the power turned off to the box you're in. One or more of the
neutrals can be tied back to another hot or often the other leg through
an appliance. Can be a nasty suprise if someone turns on the toaster
while you're working on a neutral. There could also be a break in the
neutral.
I recently rewired a garage where the BX was run along the ground
right under the threshold of the door. Salt corrosion rotted the
neutral wire out as well as the BX shield. Whoever did this job also
tied the neutral to conduit ground so the path was hot to device
neutral to box ground to earth through the remenents of the BX. Their
son got a nasty shock walking into the garage barefoot on a rainy night
and turning on the light!

Richard

 

[Doug Miller]

Any electrical book. Ever read one?
Electricians used to test for hot wires by touching it; a little tingle and
it was hot. Thats all it is, a little tingle.

That's right, you ass, just a little tingle IF YOU'RE NOT GROUNDED.

If you *are*, you're risking your life.

Certainly not a recommended

method with modern test equipment available, but not all that dangerous
since they used to get plenty of tingles.

You ever hear this saying?
"There's old electricians, and there's bold electricians. But there ain't no
old, bold electricians."

Measure your resistance,and then figure out the associated current. It is a
lot closer to 0ma than to 100ma.

So by that "reasoning", ground fault circuit interrupters (which trip at 20ma)
are completely unnecessary. Riiiiiiight.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

 

[Doug Miller]

You cannot get a shock from a neutral unless it is open. A closed neutral
(which it would be, unless it were broken) is such a good conductor that
virtually no current would go through you. Until a few years ago dryers and
stoves had the frames connected to the neutral. They are perfectly safe
unless the neutral is broken, and then you may be the best path to ground.

Completely false. You *can* get a shock from a neutral that is not open, if
you provide a good enough alternate, parallel path to ground. And dryers and
stoves with the frames connected to neutral are *not* safe - that's why the
NEC now prohibits that on new installations.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

 

[Doug Miller]

And who says the breaker box was labeled correctly or labeled at all.

Good point. My breaker box and subpanels are labelled correctly *now*, but
they sure weren't when we bought this house. At least a *few* of them were
labelled, and most of those correctly - the two previous houses had *nothing*
labelled.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

 

[Andy Dingley]

But it is difficult
to get 100ma off 120v unless you are in saltwater.

Sure is. The problem is that I'm made of 70% salt water




(and no jokes about 30% tequila and lime juice)

 

[WillR]

You are correct; 100ma is about the lethal threashold. But it is difficult
to get 100ma off 120v unless you are in saltwater.
Naturally adverse medical conditions, or just plain bad luck, will change
everything!

What colour of flowers would you like at your funeral? Best you let us
know now. If you believe that shit, you are going to take a chance some day.

Risks are one thing -- chance is another.

 

[Robatoy]

Any electrical book. Ever read one?

As a matter of fact I did. Many. And I have a piece of paper to prove it.
I went straight from college into a career at Ontario Hydro (the
province-wide power company) in operations.
During my tenure in operations at a 2000 MW power-station, I received an
award for identifying safety problems relating to test procedures in
station service electrical distribution. Again, paper/plaque and
pictures from a dinner in my honour to prove it.
But that's enough about me.

How about you? If you ever DID read anything about electrical
engineering, you must now read some material on interpretative skills
and memory retention, because, buddy, you do not know what you are
talking about.

 

[WillR]

A couple years ago I moved an outlet by putting a hand on each side,
contacting the hot with one and the neutral with the other. (I thought "the
other guy" had opened the breaker) I was rather surprised to be alive and
unhurt afterwards. I did some research and found out it is almost
impossible to get a lethal shock from 120v under normal circumstances.

Once again demonstrating that you have _no_business_ giving electrical advice
to anyone. _Of_course_ it's almost impossible to get a lethal shock under
"normal circumstances" because "normal circumstances" don't include doing
stupid stuff like putting your hands across a live circuit. It's _abnormal_
circumstances that are dangerous, and it is indeed quite possible to receive a
fatal shock from 120V when something has gone wrong - like installing a stove
with its equipment ground connected to the circuit neutral conductor, as you
recently told someone to do.
Aye!!

And only an idiot would assume that "the other guy" had opened the breaker,
and not check first. Hell, I check before touching even when *I* am the guy
that opened the breaker - just to make sure I opened the right one.[/QUOTE]

Good advice Doug. I do triple checks and am used the the rolled eyes
from "knowledgeable" people. F** em. It's less stress to do what you
suggest, and it's better advice to give.

And I am never embarrassed to have anyone check my work. No one has
never found me to make a wiring error, but if someone asked to check my
work I would say "thank you" and move over. Getting it right and safe is
cheaper than the alternative.

Usually it is the qualified engineers who recognize the value of safety
and QA checks and are never embarrassed to do the required checks, and
are never embarrassed to have someone check their work. It is part of
the training as I recall.

If you work on your own wiring, I hope you live alone. I'd hate to see anyone
else's life jeopardized by your ignorance.

Now now -- jus cause it's true.

 

[Andy Dingley]

Someone please explain why do some modern factory drills, grinders
and saws get away without a ground plug?

(I'm posting from Europe, your local terms may be different).


All electrical appliances must be insulated, meaning that the live and
neutral feeds are not connected to any accessible part of the appliance.
However things break, and so we must also design them to be moderately
safe even after this insulation fails.

One way it to wrap them in a conducting case and then earth this case.
If they're supplied through an appropriate fuse, then the fault current
(internal "works" to case) is then enough to blow the fuse and make the
appliance safe. For this reason the earth must not only conduct, but it
must conduct _well_.

Another approach is an RCD or GFCI. This measures "earth leakage",
usually be measuring the difference in current between live and neutral
wires. If there's a difference of more than a few mA (i.e. the current
has gone _somewhere_ it's not meant to), then something is wrong and the
RCD trips.

UK wiring has much better appliance fusing than other systems, so until
quite recently (10-20 years) we've been quite lax about using RCDs. US
wiring is a shocking abomination by design and so it's only the huge
number of GFCIs and arcing-fault breakers (a totally alien concept in
the UK) that stop your evil aluminum wiring killing the population of
Detroit weekly.

Around the late '60s, a new approach developed. Plastic was the new
thing, and plastic cased appliances were everywhere. These allowed the
economic use of "double insulated" appliances. They were still insulated
(of course) but now they also had to _remain_ insulated, even after an
internal fault. If the wire fell out of the switch and hit the case,
the case mustn't in turn become "live". Of course with plastics for
cases, this isn't that hard to arrange. Once the standards had got
sorted out and clever designers knew how to work with them, you could
even get such bizarre things as double-insulated hair curlers, where you
stick a big metal heating element on your head, without an earth wire.
Not something _I'm_ going to trust in a hurry, I can tell you.

You can spot double insulated appliances in Europe by the two nested
squares logo. It's also likely that they only have two wire cables, as
you describe. The crucial thing is their internal design though, not
merely missing off the earth wire!

 

[toller]

As a matter of fact I did. Many. And I have a piece of paper to prove it.
I went straight from college into a career at Ontario Hydro (the
province-wide power company) in operations.
During my tenure in operations at a 2000 MW power-station, I received an
award for identifying safety problems relating to test procedures in
station service electrical distribution. Again, paper/plaque and
pictures from a dinner in my honour to prove it.
But that's enough about me.

How about you? If you ever DID read anything about electrical
engineering, you must now read some material on interpretative skills
and memory retention, because, buddy, you do not know what you are
talking about.

Aside from being an electrical engineer? (or receiving dozens of 120v shocks
without any ill-effects?)
Without waving your hands and throwing another hissy-fit, dispute one single
thing I have said with documented facts. Do so, and I will never post
regarding electrical issues again.

Hint; "everyone knows" is not a documented fact.

 

[Robatoy]

I asked you:

How about you?

Answer that first.

Hint; "everyone knows" is not a documented fact.

Sometimes both are one and the same.

For instance:

Everyone knows you don't know what you're talking about AND the group
has a documented paper-trail of what you have been posting.

Besides, I never have a battle of wits with an unarmed person.

END of discussion with you.

 

[BobS]

Ya know.... this "Robatoy" is sounding more an more like a troll everyday
and appears to have an answer for everything. Not that they're always
correct answers - but he always seem to have one. From Net Nanny to now an
electrical safety expert....hmmmm... gotta wonder. Troll maybe...?

He's about bad mouthed everyone here and sure has one pissy attitude if
anyone conradicts his words of wisdom. I'm on his plonk list anyway so he
won't read this but it sure would be nice if he could provide some useful
information once in awhile instead of alway's arguing a point.

Make the correction if someone makes a mistake in a posting and get on with
life - your whinning is getting real old.

Now back to your regularly scheduled bitchin 'n moaning,


Bob S.

 

[toller]

I asked you:

Answer that first.


Sometimes both are one and the same.

For instance:

Everyone knows you don't know what you're talking about AND the group
has a documented paper-trail of what you have been posting.

Besides, I never have a battle of wits with an unarmed person.

END of discussion with you.

 

[toller]

I asked you:

Answer that first.

Do you realize you replied to your own dumb comment?

Sometimes both are one and the same.

Sure, occasionally, but it is still never used in an intelligent discussion.

For instance:

Everyone knows you don't know what you're talking about AND the group
has a documented paper-trail of what you have been posting.

Besides, I never have a battle of wits with an unarmed person.

Hey, my 9 year old said the same thing to a friend the other day!

END of discussion with you.

So, you concede you can't come up with a single fact. Then stop posting.

 

[Doug Miller]

Aside from being an electrical engineer?

The closest you've ever come to being an "electrical engineer" is driving a
Lionel train when you were a kid. You don't even know the difference between
neutral and ground.

(or receiving dozens of 120v shocks
without any ill-effects?)

The ill-effects are obvious in your posts.

Without waving your hands and throwing another hissy-fit, dispute one single
thing I have said with documented facts. Do so, and I will never post
regarding electrical issues again.

The world could only be so lucky. It's been documented already, pretty
thoroughly, in this thread. Go read some of the responses to your posts.

--
Regards,
Doug Miller (alphageek at milmac dot com)

Nobody ever left footprints in the sands of time by sitting on his butt.
And who wants to leave buttprints in the sands of time?

 

[Robatoy]

Besides, I never have a battle of wits with an unarmed person.

Hey, my 9 year old said the same thing to a friend the other day![/QUOTE]

I guess he also taught you how to have an intelligent discussion?

So, you concede you can't come up with a single fact. Then stop posting.

I conceded nothing. If you think you can get people to respect you
around here by putting words in my mouth, guess again.

I said I wasn't discussing anything with you, and I really must move on
to things that need my attention. Please stop replying to my posts,
because every time you do, I read them, thinking that you may have seen
the errors of your ways and apologized like a man for offering wrong
advice on electrical matters here and in previous threads.

Best not be holding my breath, eh?

Go play with your 9 year old. You can still impress humans at that age.