"Existential Angst" wrote in message
...
Awl --

A two-part Q:

Due to some remodeling, I'm forced to splice/lengthen some old bx cable
that has #14 wire in it, and re-connect to the fuse box.
Should I splice the #14 with #14, or splice with #12?

The reason I would continue with #14 wire is just to remind me and future
people that Hey, this old wire is a little lighter than modern #12, and to
not take liberties with 20 or 30 amp fuses or breakers. Other than that,
#12 would be fine with me.

Next, is there a rule of thumb for how many hot wires can share one
neutral of the same gauge? If using different gauges, is there a "gauge
ratio", ie, some formula for cross sectional area between total hots and
total neutrals?

tia.
--
EA
keep the conductors the same size as is existing

14ga is and has always been fine for 15 amp circuits

12ga is and has always been fine for 20 amp circuits (even in NYC)

NYC, prior to 2005 has always used the NEC as the basis for electric code.
Only certain areas did they require more stringent rules.

Your neutral can be shared by as many hot legs as your service has,
typically 2