Heres a good question from Mike Fox in Indiana and I would appreciate your answers:
"Subject:
Neutrals from different panels
Date:
Wed, 09 May 2001 15:03:19 -0500
From:
FoxM@Mail.ips.k12.in.us
To:
codeviolations@netscape.net
Joe,
I enjoy your "Code Violations" section and wanted to quiz you on a certain point. Several times in my career as an
electrician I have run into this potentially dangerous situation. This usually occurs in a commercial or industrial
plant where there are many distribution panels through out the building. An electrician is asked to change a panel
interior due to age and availability of breakers. After the proper wire bending radius is checked and OK'd with the
new interior manufacturer the electrician has the go to put the new interior in the old tub. He locks and tags out
the feeder to the panel but ends up getting shocked when lifting the panel neutral. The reason he was shocked is due
to another electricians mistake. Someone inadvertently tied the grounded conductor from another panel to the neutral
of the panel being upgraded. Even with the panel feeder de-energized current is passing through the neutral of the
panel being upgraded. Of course when the neutral is lifted you have the potential of the phase voltage in your hand.
If the electrician didn't see the spark he could potentially become a series load to ground. I have talked to other
experts about this and they act as though this is common knowledge and not a big deal. I can tell you I teach code
courses and each year I pose this situation to my students. Many of them are seasoned electricians and usually only a
few have encountered this. I think we need to identify the grounded conductors with suitable wire tags corresponding
to the proper panel number. What are your feelings on this? Thanks, Mike Fox (Indiana Electrical License Prep)
Added note by mike: "The electrician would be shocked by the neutral bar not the neutral feeder conductor."
[This message has been edited by Joe Tedesco (edited 05-16-2001).]
