According to jJim McLaughlin :
Charles Bishop wrote:

A friend of mine asked me a question I didn't know the answer to, so I
told her I'd ask you guys.

She has a stove-oven/microwave combination. She is going to get a new
stove/oven and a microwave but the microwave will be separate. Currently
(heh) she has just the 220V outlet for the stove. Can she take one leg of
the 224V circuit and run an outlet for the microwave? Her reasoning is
that she should be able to since it was done before, just inside the
stove.

What say those more knowledgeable?

Not a good idea.

Run a separate 20 amp 12 gauge line from a breaker serving only the
microwave.

Or see if the new stove has a 120V outlet on it that's rated high
enough for the microwave (check the instructions). Stoves always
used to have one, but auxiliary outlets are a lot rarer these days
(if not non-existant).

Even if it does, she might consider the cord over the top of
the stove objectionable anyway.

Running another circuit is the best way. Electrical codes
forbid the use of 120V and 240V devices on the same circuit
_except_ when the 240V device has a UL/CSA approved 120V outlet
on it. While the codes will permit turning a four wire
240V/120V stove circuit into a feed to a subpanel (with its own breakers)
to supply both 240V and 120V, that will NOT be permissible
with an old style 3 wire stove feed, and probably not with
4 wire unless the circuit ampacity is enough for _both_ the
stove and microwave circuits simultaneously at full. You
might get away with a 4 wire 60A feeding a breakered-for
40A stove and breakered-for 15A microwave circuit, but 60A
stove circuits are rather rare - the more normal 40A stove
circuits for 40A stoves aren't enough.

In Canada, builtin microwaves have to have their own
dedicated circuits anyway. That may be true now in the US
as well.
--
Chris Lewis,

Age and Treachery will Triumph over Youth and Skill
It's not just anyone who gets a Starship Cruiser class named after them.