I have assembled an Ultimate Bundle - OpenEVSE P50-D Kit Level2 50A, but my electrician hasn't installed the 50amp plug yet. Can I hook this up to my 120volt/30amp plug to test if my assembly works?
Something like this
The P50D Level 2 kit will only work from 208-240v. 120v is not enough to close the contactor.
Your home has 240 VAC "split-phase" service. For testing only, you can plug into the receptacle used by a 240 VAC appliance such as your clothes dryer or electric range. If you have no such receptacle, you can also use two 120 VAC receptacles as long as the two receptacles are NOT on the same pole of the split phase. You can determine this by checking with your DMM. The voltage across the "Hots" of the two plugs will be 240 if on opposite poles, or (roughly) 0 if on the same pole. The two plugs' 120 VAC circuits should have the same size breakers. Do not try this unless you know what you are doing, and do not use this setup except for testing: there are too many ways to screw it up. Your testing will be limited to the amperage of the smaller of the two circuit breakers.
I did it the boring way and waited for a 240volt to be installed. A little nervous about jimmy rigging two 120 volts together as explained.