GrumpyHoser

With regards to 'not much you can do about that' (both have 3 wires), keep in mind that a true 220v machine that does not have any internal components that require 110v (typically something with just a 220v motor, like a grinder or compressor, well pump, etc) requires just the 2 hot wires - no neutral is used. I suspect your ground wire is really just a ground - all the current is just going through the 2 hots, and it would probably continue to work fine with the ground disconnected. For something that uses both 220v and 110v (like a dryer, with a 220v heating element but 110v for the controls/motor etc) then you should have 2 hots, 1 neutral (for the 110v components only), and a ground. Running something on just 2 hots with no neutral doesn't seem intuitive - at least it didn't to me originally, when I was looking in my breaker box and didn't see any neutral wire going to the well pump. To understand why it works like that, you need an understanding of how split-phase transformer works, which is what 220v residential power comes from.