Basic Electrical Safety Question

Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack

 

[krw]

In article <639f856f-9ac9-4f6f-bedd-
36cf8bb4b26c@m16g2000vbp.googlegroups.com>, luckiejacky@hotmail.com
says...>

Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

Shouldn't. You have a problem.

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?

If there are no other faults, there shouldn't be a lethal current.
There will be *some* current (because there is *some* voltage).

 

[Lord Garth]

<luckiejacky@hotmail.com> wrote in message
news:639f856f-9ac9-4f6f-bedd-36cf8bb4b26c@m16g2000vbp.googlegroups.com...

Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack

In a typical shock situation, the persons body is in series with the hot
lead.
His body is the link between the hot and the neutral lines.

One can also get shocked when their body is connected via a virtual ground.

 

[Shaun]

<luckiejacky@hotmail.com> wrote in message
news:639f856f-9ac9-4f6f-bedd-36cf8bb4b26c@m16g2000vbp.googlegroups.com...

Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack

There are a couple of possibilities. These are assuming your testing in an
average sized house with 120 / 240 volts AC service.

If your not familiar with electricity or house wiring, I would recommend
that you call in an electrician to check things out.
If you do know enough about electricity and houses wiring, try these tests
out:

1. Hot and Nuetral are swapped. Measure HOT(black wire) - Ground(green or
bare wire), there should be 120 volts, then measure Nuetral(white wire) -
ground, you might measure a few volts, but not 120 volts. If there is more
that a few volts measured on the Nuetral, Check the plug wiring if that is
where your touching wires, then check other plugs and juction boxes that
could be connected to the same circuit for miss wiring, check the fuse panel
for Black wires, NOT WHITE, comming off the breakers.

2. If could be a bad ground (Nuetral to Ground) connection in the breaker
panel, check the connections at the Nuetral connection bar. If could even
be connection to the ground rod or not a long enough ground rod. Make sure
all connections are tightly screwed in.

3. Check that marrettes are tightly screwed on and screws are tight.

4. There could be an appliance connected to the same circuit drawing heavy
current, which puts heavy current on the Nuetral wire. Again good
connections everywhere reduces the chances of a shock hazard.

There are cheap little circuit testers with three lights on them that detect
miss wiring, they are easy to use (you just plug them into AC recepticals).
Two of the amber lights should light up under normal conditions and not the
red light. Read the instructions though in case yours is different.

Shaun

 

krw $BUmF;!'(B

In article <639f856f-9ac9-4f6f-bedd-
36cf8bb4b26c@m16g2000vbp.googlegroups.com>, luckiejacky@hotmail.com
says...
Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

Shouldn't. You have a problem.

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?

If there are no other faults, there shouldn't be a lethal current.
There will be *some* current (because there is *some* voltage).

Correct me if I have made a mistake. By nodal analysis on a simple
"resistor" circuit,
in case the resistor is 100Ohm, the main is 220V, I can calculate the
current given the neutral line is 0V with respect to the hot wire,
220V - 0V / 100ohm = 2.2A... So I assume the neutral line is 0V...
with reference to the 5V side...
Thanks

 

[krw]

In article <a9725283-de75-465c-a397-da12399ec955
@m2g2000vbp.googlegroups.com>, luckiejacky@hotmail.com says...>

krw $BUmF;!'(B

In article <639f856f-9ac9-4f6f-bedd-
36cf8bb4b26c@m16g2000vbp.googlegroups.com>, luckiejacky@hotmail.com
says...
Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

Shouldn't. You have a problem.

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?

If there are no other faults, there shouldn't be a lethal current.
There will be *some* current (because there is *some* voltage).

Correct me if I have made a mistake. By nodal analysis on a simple
"resistor" circuit,
in case the resistor is 100Ohm, the main is 220V, I can calculate the
current given the neutral line is 0V with respect to the hot wire,
220V - 0V / 100ohm = 2.2A... So I assume the neutral line is 0V...

Ideally, yes. In practice, not so much. In reality there is no 0V,
or 0ohm.

with reference to the 5V side...

5V?

 

[Shaun]

<luckiejacky@hotmail.com> wrote in message
news:639f856f-9ac9-4f6f-bedd-36cf8bb4b26c@m16g2000vbp.googlegroups.com...

Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack

I should have mentioned this FIRST

ANYTIME Your working with a screw driver around electrical wiring, or even
with live wires, the breaker(s) for that circuit MUST be TURNED OFF, then
with a voltmeter, verify that there is no power there on any of the wires.

Same thing with checking marrettes, power must be off first before you get
your hands in there.

If your checking the breaker panel, TURN OFF the Main breakers, Then verify
that there is no voltage with a volt meter. Be aware that at the top of the
breaker panel where the power comes in, there is live power; 240 volts and
atleast 100 amps or more. Be Carfull.

IF your not sure how to do any of this, call an electrician.

 

[Sjouke Burry]

luckiejacky@hotmail.com wrote:

Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack
Yes, have your house wiring checked immediately.

 

safety

 

krw $BUmF;!'(B

In article <a9725283-de75-465c-a397-da12399ec955
@m2g2000vbp.googlegroups.com>, luckiejacky@hotmail.com says...
krw $BUmF;!'(B

In article <639f856f-9ac9-4f6f-bedd-
36cf8bb4b26c@m16g2000vbp.googlegroups.com>, luckiejacky@hotmail.com
says...
Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

Shouldn't. You have a problem.

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?

If there are no other faults, there shouldn't be a lethal current.
There will be *some* current (because there is *some* voltage).

Correct me if I have made a mistake. By nodal analysis on a simple
"resistor" circuit,
in case the resistor is 100Ohm, the main is 220V, I can calculate the
current given the neutral line is 0V with respect to the hot wire,
220V - 0V / 100ohm = 2.2A... So I assume the neutral line is 0V...

Ideally, yes. In practice, not so much. In reality there is no 0V,
or 0ohm.

with reference to the 5V side...

5V?

220V

 

Lord Garth $BUmF;!'(B

luckiejacky@hotmail.com> wrote in message
news:639f856f-9ac9-4f6f-bedd-36cf8bb4b26c@m16g2000vbp.googlegroups.com...
Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack

In a typical shock situation, the persons body is in series with the hot
lead.
His body is the link between the hot and the neutral lines.

One can also get shocked when their body is connected via a virtual ground.

You meant there is a "charge leakage" bacause the circuit is broken?
So you are in series with the hot lead?
Thanks
Jack

 

Shaun $BUmF;!'(B

luckiejacky@hotmail.com> wrote in message
news:639f856f-9ac9-4f6f-bedd-36cf8bb4b26c@m16g2000vbp.googlegroups.com...
Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?
Thanks a lot
Jack


I should have mentioned this FIRST

ANYTIME Your working with a screw driver around electrical wiring, or even
with live wires, the breaker(s) for that circuit MUST be TURNED OFF, then
with a voltmeter, verify that there is no power there on any of the wires.

Same thing with checking marrettes, power must be off first before you get
your hands in there.

If your checking the breaker panel, TURN OFF the Main breakers, Then verify
that there is no voltage with a volt meter. Be aware that at the top of the
breaker panel where the power comes in, there is live power; 240 volts and
atleast 100 amps or more. Be Carfull.

IF your not sure how to do any of this, call an electrician.

Hi Shaun,
Thanks for your reply. Actually, I am not doing any plumbing, I just
came across a book on Electrical Safety and wondering what the author
is talking about...
Thanks

 

[JeffM]

luckieja...@hotmail.com wrote:

safety

People who use real newsreaders don't see what you see on Google:
http://google.com/search?q=cache:RXr79UPHu9MJ:groups.google.com/support/bin/answer.py?hl=en%26answer=46492+remove-*-*-*-irrelevant+Usenet+*.*.*.*.*-*-*-*-relevant.*+Terms+Home+your.reply+Summarize.what.you're.following.up+before.the.original.*.*+*-for-your-readers
At a minumum,
don't delete the name of the person to whom you are responding.

....and for those who DO read via Google:
http://groups.google.com/group/sci.electronics.basics/msg/cae0c4ab19130f9e?q=instead.of.using.an.email.address+mysubs+1st-line+aka

 

krw $BUmF;!'(B

In article <a9725283-de75-465c-a397-da12399ec955
@m2g2000vbp.googlegroups.com>, luckiejacky@hotmail.com says...
krw $BUmF;!'(B

In article <639f856f-9ac9-4f6f-bedd-
36cf8bb4b26c@m16g2000vbp.googlegroups.com>, luckiejacky@hotmail.com
says...
Hi,
I am hoping any of you guys can solve my puzzle.
If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

Shouldn't. You have a problem.

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain
this with a little bit of details?

If there are no other faults, there shouldn't be a lethal current.
There will be *some* current (because there is *some* voltage).

Correct me if I have made a mistake. By nodal analysis on a simple
"resistor" circuit,
in case the resistor is 100Ohm, the main is 220V, I can calculate the
current given the neutral line is 0V with respect to the hot wire,
220V - 0V / 100ohm = 2.2A... So I assume the neutral line is 0V...

Ideally, yes. In practice, not so much. In reality there is no 0V,
or 0ohm.

with reference to the 5V side...

5V?

220V Google ate my post.....

 

[Phil Allison]

<luckiejacky@hotmail.com>

Actually, I am not doing any plumbing, I just
came across a book on Electrical Safety and wondering what the author
is talking about...

** Either he is wrong, you are wrong or you have misread what he wrote.

If the "neutral line" you alluded to in your first post is INSIDE some
plug in appliance - the it must be treated as a potential shock hazard.



...... Phil

 

[Tim Wescott]

On Mon, 23 Feb 2009 14:14:46 -0800, luckiejacky wrote:

Hi,
I am hoping any of you guys can solve my puzzle. If a person is touching
the neutral line, the potential is already zero
How come he still gets shocked?

If there is a ground connection on the neutral line, and with a person
who is touching it
,how come the current will pass thru his body. The resistance of the
rest of the neutral line
is obviously less than the human body. Could anyone please explain this
with a little bit of details?
Thanks a lot
Jack

The potential on the neutral line isn't _already_ 0, it is _presumably_
0, or _supposed to be_ 0, or perhaps _often, but sometimes not_ 0.

There are a lot of faults that can put full voltage on a "neutral" wire
-- you should always treat it as hot.

I used to work in a building where there were two adjacent outlets, with
a nice low-impedance 50VAC between the _ground_ pins. There were a few
RS-485 boards burnt up over that, before people figured out what was
going on.

--
http://www.wescottdesign.com

 

[whit3rd]

On Feb 23, 2:14 pm, luckieja...@hotmail.com wrote:

If a person is touching the neutral line, the potential is already
zero
How come he still gets shocked?

The 'neutral' wire is presumably bonded, at the power
panel (i.e. one place in each building) to a ground wire.

Your hypothetical person can safely touch any grounded
item (and you do this every time you stand on a concrete floor,
touch metal door frames, water fixtures, etc.), at the
same time as touching the third-prong ground, without
completing a circuit and getting a shock.

The neutral wire, however, IS SEPARATED FROM the
ground connection by a length of wire, with (possibly
loose) connections, which carries electrical current to
some appliance. You can get induced I*R voltage
if there's resistance in the wiring, or L*dI/dt voltage
if there's significant inductance, etcetera. The
appliance current MIGHT, if you put your body in the
circuit, send part of its current through you instead of
through the neutral wire. So, handling a 'neutral' wire
is not generally safe. That's why the third wire,
the safety ground wire, is supplied: it carries no appliance
current, so it is as safe to handle as a water faucet.

 

[Chuck]

whit3rd wrote:

SNIP

The appliance current MIGHT, if you put your body in the
circuit, send part of its current through you instead of
through the neutral wire. So, handling a 'neutral' wire
is not generally safe. That's why the third wire,
the safety ground wire, is supplied: it carries no appliance
current, so it is as safe to handle as a water faucet.

While it is true as stated that the equipment grounding conductor
normally carries no appliance current, it can and often does carry
appliance leakage current.

Even a leakage current on the order of ten amps would probably not
trip a breaker and there is no simple way of knowing whether any
leakage current is present short of measuring it. Placing yourself
in series with a low impedance ground fault could even be fatal.

I would caution against becoming part of any household wiring
circuit, no matter the color of the insulation.

Chuck

 

[whit3rd]

On Feb 26, 7:44 pm, Chuck <no.s...@no.spam.at.all> wrote:

While it is true as stated that the equipment grounding conductor
normally carries no appliance current, it can and often does carry
appliance leakage current.

Even a leakage current on the order of ten amps would probably not
trip a breaker

That's why ground-fault interrupters (GFI, GFCI, whatever)
are required for places (bathroom, outdoors, kitchen) where
people make body contact with water pipes and other
grounded items. A GFI will trip on small leakage current.

The scenario of dangerous third-prong ground is unlikely,
but all modern construction (in my municipality) is protected
against it anyhow.

 

[Chuck]

whit3rd wrote:
SNIP

That's why ground-fault interrupters (GFI, GFCI, whatever)
are required for places (bathroom, outdoors, kitchen) where
people make body contact with water pipes and other
grounded items. A GFI will trip on small leakage current.

Yes, GFCIs offer protection where they are installed. I would guess
that something like 99.9% of domestic branch circuits are not
protected by a GFCI in the US.

The scenario of dangerous third-prong ground is unlikely,
but all modern construction (in my municipality) is protected
against it anyhow.

I'm not sure what exactly is meant by "dangerous third prong
ground". If the equipment grounding conductor (third prong) is wired
properly, it will be close to ground (earth) potential even when
carrying lethal currents. Under those circumstances, touching the
EGC should be safe. But inserting your body in series with the EGC
when it is carrying lethal currents is quite dangerous.

Readers are left with the option of a) measuring EGC current before
placing their body in series with the EGC; or b) relying on
whit3rd's assertion that such a scenario is unlikely. Doubters might
contact their local plumbers who sometimes find their body between
two sections of metal pipe through which is passing a significant
leakage current. For safety's sake, they routinely attach a bonding
wire across the pipe joint before separation.

Chuck