As an example, I am looking at a ceiling fan box that says that it is rated
for up to five #12 wires.
Does that include the bare ground wires that will be going into the box, or
is it just the conducting wires (such as the black and white wires)?
Yes. (But... :) )
You don't have to count wires under #14 from a fixture to wires in the box.
A wire originating in and terminating in the same box (ground from green
terminal of an outlet to box ground, for example) doesn't count.
A wire running thru a box w/o splice or tap counts as only one wire
(from which one can deduce the answer to the original question, btw).
And, of course, the limit for #14 would be higher than for #12 (probably
by one altho I didn't check tables).
There are other conditions/adjustments but those are the highlights that
are probably the pertinent ones for the application.
Not quite. The rule is "no part of which leaves the box". I grant that it
would be highly unusual, perhaps unique, for a conductor to leave the box in
which it originates and return and be terminated in that same box, but any
such hypothetical conductor that might exist must be counted as two.
Not necessarily. The OP said the box is marked for up to five #12 conductors,
which means that its capacity is at least 5 * 2.25 cubic inches per conductor,
or 11.25 cubic inches -- but that is *not* big enough for six #14s at 2.00
cubic inches each.
Note the distinction: circuit conductors are counted. Fixture conductors (the
leads to a lamp, for example) are not.
- a conductor that both enters and leaves the box, without being spliced, is
counted only once
- any conductor, no part of which leaves the box, is not counted at all.
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