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
What say those more knowledgeable?
Don't know about those more knowledgeable, but I say NO. Before ,the
microwave was integral to the stove, and U.L. approved as a unit. It was
also probably fused inside the stove as well . In any event she'd now need
to run a dedicated circuit for the microwave
NO. The stove breaker would allow 40 or 50 Amps before it trips. Wiring
for the microwave would only be 20A or even 15A. An overload on the
microwave could cause a fire.
I am pretty sure a tap off is not allowed even if you were to add a
smaller breaker after the stove outlet. Also some older stove outlets do
not have the neutral wire that would be needed for the 120V.
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
Age and Treachery will Triumph over Youth and Skill
No. The microwave must be on a 120 volt 15 or 20 amp circuit depending on
the unit's nameplate rating. I am familiar with these types of changeouts
because those combo units were installed in quite a few townhouses in my
area that I service. In most cases I have found that there already is a 120
volt 20 amp circuit wire in the wall above the stove. I surmised that the
electricians who wired these units were told to wire for a hood fan or a
microwave and installed the wiring for such during their rough-in. You
might want to investigate that.
When my customers change from the combo stove/microwave to a separate stove
with a overhead microwave, they usually have to get some overhead cabinet
work done. The new microwave is supported by a wall bracket and by two long
bolts that come through the shelf inside of the top cabinet. In the cases
that I have seen there is no top cabinet, just a fascia board that matches
the cabinets. Your friend may have a similar situation.
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