Existential Angst wrote:
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.

There's nothing "unmodern" about 14 for 15A circuits.

I'd recommend sticking w/ same gauge as the original circuit for the
reason mentioned.

Remember to not bury connections in inaccessible places.

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?


Don't follow this question. Each hot needs its own return neutral.
If you're talking about 3-wire ("Edison") circuits, if properly wired
the return is in effect a neutral w/ a balancing currents from the two
sides if both are loaded equally; hence only the same size conductor is
required for a single-sided load.

If that isn't it, I have no clue what you're thinking.

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