Previously in alt.home.repair, unkbloc (HaHaHa)
proclaimed :


Not the old style microwave/range combination units popular in the late 80's.
They were one unit, as tall as a refrigerator.

...the one that we're getting rid of is a "over and under" unit. Where
the upper oven is an oven/exhaust fan combination that is connected to
the lower oven/range. The entire until was fed by a single 220v line.


Those older units utilized the 40/50a 220v for everything.

They're no longer common, probably not made anymore as a critical defect in one
component would require either a house call from an authorized dealer/repairman
or junk the whole kit and kaboddle.


...that probably explains why we couldn't find a similar, more modern
replacement and had to go with two separate units.



Seems strange to me that your microwave draws almost as much as the oven..
Hummmm maybe more than an microwave?
Electrical connection for the new microwave if as you described should be an
outlet and maybe an breaker change out.
Electrical connection for oven will probably need an new run as the new
ovens require and neutral and ground conductor. (4 wires).
Check with the manufacture/ local authority to see what is required.

I think the OP is simply converting from an all-in-one appliance containing a
microwave on top, and a standard convection oven/4 burner cooktop on the
bottom.


...actually it even more basic than that. The all-in-one is just an
upper and lower oven setup. No convection or microwave (hey this
thing was made in the late 70's). ;-)

It's actually worked quite well all these years and didn't start
acting up until lately when the thermostats for both ovens started
acting up and the knobs have started to deteriorate and when we had a
technician come out to replace a faulty timer assembly, he said that
the wiring is shot and recommended either replacing the entire control
unit or just consider replacing the entire range. I took the control
unit apart and the wires are indeed shot. Since the entire unit is a
little long in the tooth and my wife really wanted a more modern unit,
we ordered a new flattop convection oven with a combo oven/microwave
for the upper unit. It's a really nice combination actually. It's
just the wiring situation has become a little more complicated than we
had thought it would.





Replacing with 2004 unit will require only running a new 20a 120v line and
receptacle for the new, stand-alone, "over-the-stove" microwave/range hood.

The original, existing 40/50a 220v 3-wire circuit for the original range can
remain.

Code changes cover new installations of circuits, not the replacement
appliances. The new range can be connected just as the old range was, on a
standard 2-wire with ground circuit.

But if replacing the old 3-wire circuit with a new 4-wire circuit is a piece of
cake as the OP describes, might as well just do it anyway.





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