sean_n wrote:
In the last 2 years, our microwaves have been breaking very quickly.
We suspect that it might be our electrical wiring. I've noticed that
the microwave and refrigerator are sharing the same neutral wire.
What's the chances of this being the cause of our microwave problems?
I believe sharing the neutral wire was common practice in the old
days--but is against code. Is this true? The microwave and
refrigerator are on circuits that are out of phase--I believe that
makes a difference but would like confirmation on this. We've had
this setup for the last 17 years and only in the last 2 years we've
been having microwave problems. I would hate to have to run another
wire unless it's absolutely necessary.

Describe the microwave failure.
Shared neutral circuit are fairly common in older homes.
I mostly see them on dishwasher/disposal circuits. I believe in Canada
they are very common or required in kitchen counter circuits.
A full load on both circuits will completely cancel each other and
neutral will be at 0 current. A load of say 2 amps on one and 3 amps on
the other will leave 1 amp on the neutral etc...
As the other reply mentioned, if the neutral gets disconnected down
stream then you will get up to 240V at the appliance plug depending on
what is plugged into the circuits. This could certainly damage both the
refrigerator and microwave.
Kevin