I agree with your diagnosis. I used to run into this when I was
repairing dryers, people had the supply installed by a "handyman" or did
it themselves and wondered why the dryer didn't dry.

James P. Javery wrote:
I'm considering setting up a 240 volt appliance in my garage and I need to
determine whether it is being supplied with 220-240 volt service. The
breaker box in the garage has three wires coming in from elsewhere in the
building, one white wired to the neutral bus bar and two black wired to a 70
amp double pole breaker.

1. multimeter shows ~116 volts from hot to neutral for each of the two poles
on the main breaker
2. multimeter shows 0 volts from hot to hot between the two poles on the
main breaker
3. multimeter shows 0 ohms resistance between from hot to hot between the
two poles on the main breaker

Am I not testing this properly, or is it possible that my garage is not
wired for "three wire single phase" as I suppose electricians prefer to call
it? My understanding would lead me to believe that the two hot wires are
connected upstream to the same half of my building's electrical supply, so
I'm only getting 120 in my garage despite the two hot wires.

Any ideas? Are there any other tests I can perform to verify or invalidate
my conclusions? Thanks for any help you may provide...

-James