I am replacing my built in oven/microwave combo with a separate thermal oven
and a microwave. The oven will take 220 V, the Microwave is a plug-in
(built-in) above the oven and requires 110V.
Can I extract 110 V for the MW from the 220 V junction box (line to 220V
thermal oven )? The 220 V line has a 40 Amp Circuit- breaker.
This house is 25 years old. I cannot tell if 3 or 4 wires go from the main
panel to the junction box.
.. but you need to find that out first. With 3 wires, it's impossible to do
it safely and legally (you need, but don't have, a neutral). With 4 wires,
it's merely impractical.
Here's the problem you run into with four wires: the microwave almost
certainly is intended to plug into a 15A (or maybe 20A) 120V circuit, but your
existing wiring is likely 8-gauge. 120V receptacles aren't rated for wires
that large, and cannot grip them securely, so you'll have to have 12- or
14-gauge wires going to the receptacle for the microwave -- but it's a Code
violation to put anything smaller than 8-ga on the 40A circuit that you now
Doug Miller (alphageek at milmac dot com)
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