I have a quick question and wondered if somebody can explain this to
me. While working on some wiring today, I got a bit of a jolt from
the neutral wire. When I tested it with my voltmeter, it read zero (I
had the breaker off). But then, when I grabbed the neutral, I got a
I took my voltmeter and tested it, and it peaked up around 1 to 2
volts, then dropped back to zero. Did it again a few minutes later
and the same thing.
Upon further investigation, I found that there was one neutral that
was going to the furnace (on one circuit) and then up to the sockets
on the other circuit. One circuit (the furnace one) was live while
the other was dead.
Just so I understand, is the reason why I got a tingle was because
electricity was flowing through the live circuit? If I turned off the
circuit for the furnace along with the other one, would this have
prevented me from getting a little shock? I read one posting that
said to use the clamp to check for amps. Should I have done this
along with checking out how many volts are running through it?
*The neutral is a current carrying conductor. It sounds as if the one that
you are referring to is part of a multiwire circuit that is shared with the
furnace. When the furnace comes on there will be current flowing through
it. You should treat it like a live wire even when the circuit breaker is
This is a good rule to practice...but how do you test for this?
*No test. When handling the conductors treat them as though juice was
flowing. Tape up the bare ends, don't touch the ends, don't let them come
in contact with anything else, keep one hand behind your back, etc. I am
used to working with hot wires so it is easy for me.
On Wed, 31 Dec 2008 06:54:34 -0500, John Grabowski wrote:
This is probably why the new electrical code does not allow sharing
neutrals between circuits. You may want to check to make sure the light
circuit is on a different phase than the furnace. Neutrals should never be
shared on common phase circuits.
Also, get off googlegroups. Many wise NG users block googlegroups because
google refuses to deal with NG abusers. Blocking all posts originating
from googlegroups eliminates about 90% of the trash posts!
Thats why rules are codified. Ask them to show you what rule disallows
shared neutrals. About the only common requirement for the typical
residential shared neutral installation is that the circuit breaker
handles must be interlocked if the outlets are split wired.
Back in 1975 I was a brand new service tech just out of high school
and fresh from manufactuers training, I was nervous but wanted to do
EVERYTHING just right!
Went to a stock broker in downtown pittsburgh working by reception
desk and this gorgeous beautiful model type who was the
long blonde hair, big heels and short dress, but tasteful she
decorated the office:)'
Anyhow In servicing the machine I followed my new training closely:)
INTENTIONALLY overheated the machine to test the safety switches,
which worked fine. let the machine cool, crouched down to reach the
pushed it and a ball of fire came out of machine, no electric shock
but stunned I went from crouched down to flat out on floor, looking up
The entire office of perhaps 50 people went silent, probably thinking
someone just died, and fireball was large:( the click clak of
typewriters stopped you could hear a pin drop
Dumb blonde kept asking if I was electrocuted.... third time she asked
I was getting up and said if I were I wouldnt be talking to you:)
Anyhow didnt know what I did wrong I finished fast got out of there
and went back to our office, when I told my boss what happened he said
call the guy who trained you.... Hey I get to call chicago on this
Trainer when told of my excitement said after you guys left we
realized we forgot to tell you guys to always unplug machine before
resetting! otherwise a fire ball will come out of machine:(
Well it does and it did we agreed he should call the other trainees,
and warn them:)
its rare to remember a specific thing that happened so long ago.
excitement wise it ranks right up there with the day I ran a borrowed
gasoline garden tiller into the service entrance of our house:(
The 2008 NEC makes no change to using common neutrals - they are still
As several people have said, the 2008 NEC requires a common disconnect
which can be a handle tie.
AFCI circuits can't use a common neutral (unless the AFCI breaker is
240V). That is a limitation of the breaker, not the NEC. (AFCIs include
ground fault detection, typically at 30mA.) Because the 2008 NEC vastly
expands where AFCI protection is required in houses, the use of common
neutrals is effectively much limited.
The NEC applies to new wiring, not existing. (A jurisdiction can change
Also, remember this is not a purely
resistive circuit. You have a motor
and even some inductance in the wires.
Even turning on an incandescent
lamp produces a short high current until
the filament warms up. So, you
can get current spikes when starting
motors and lamp, which can produce
voltage spikes on the neutral of a
circuit which is not purely resistive. .
On Tue, 30 Dec 2008 20:18:27 -0800 (PST), " firstname.lastname@example.org"
Just for clarity can you explain how you were "electrocuted" and are
still able to post to Usenet?
Was the 'death of Usenet that we've been hearing about for a decade a
statement on the status of the posters?
A 'bit of a jolt' is hardly electrocution.
A Multi-Wire Branch Circuit (MWBC) is two hot wires on separate breakers
sharing one neutral.
If just one breaker is turned off, the neutral is still carrying electricity
for the other circuit. If you disconnect the neutral and something is turned
on upstream to the still energized circuit, the upstream neutral will be
like a hot wire!
For this reason, new code requires a double pole breaker for a MWBC or both
breakers to be tie bared. Then both circuits must be turned off at the same
And for this reason it is a good idea to turn off power to the entire house
before doing electrical work.
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