"Ben" wrote in message
ups.com...
I thought I was pretty good when it comes to wiring. I thought I knew
enough to be safe and have good quality work when I do it on my own.
Then I learned about shared neutral lines for different hot phases. I
am shocked I never heard of this. No book I ever read mentioned shared
neutrals for household wiring.
Given that a shared neutral is a possibility, I don't understand how
anybody can do electrical work without shutting off power to the
entire house.


Shutting off power to the entire house is not a guarantee that the neutral
won't be hot. Under rare circumstances if your neighbor lost his neutral
connection it is possible that his return current would travel through the
earth to your neutral connection and then back to the transformer.


You can test for hot wires and verify at least one
circuit is off, but then somebody comes along and turns on a light and
suddenly the neutral is live. Not to mention the fact that if somebody
came along who didn't know about split neutrals who knows what they
may have mistakenly done in the past.

So what is the best way to proceed when trying to determine if a box
has any live wires or wires which could become charged if somebody
turns on a light upstream?


Always treat the wires as though they are hot. Every once in a while I get
zapped by a neutral. Even though the ground and neutral are bonded together
at the main you don't know what the condition of the neutral going back to
the transformer is. You also don't know how good the neutral connections
are at the panel. There is always the possibility of having a difference in
potential between the ground and neutral at the load. In an old house it is
a good idea to be extra cautious as you don't know what changes have been
made over the years.



Are shared neutrals avoided where possible?


Some states are requiring arc fault circuit interupter circuit breakers for
bedroom wiring. You cannot use a shared neutral on these circuits.


An electrician is about to rewire just about my entire house. Should I
request no shared neutrals or is this a silly request?


It is not a bad idea to discusss with him what his plans are. Afterall you
are paying for it, you have a right to ask.