Dont have the model number handy, may have to slide the chassis partly out to get it.
I realize this is not a 3-phase unit, and the power delivered to the (220v/20a) outlet is not 3-phase.
But if on a 3-phase 120/208v system 2 phases are used as the hot wires then the voltage will be 208v single-phase.
Which may be what was done in this building - it was built in the 70's, is a low-end building originally build as apts so possibly the only requirement for 220v back then was for the electric heat which would tolerate a lower voltage. (A/C is on the same circuit as the heat, there was no more breaker box space left so maybe the circuit was added later).
thanks for replies...