al hildenbrand said:
The secondary windings of the two transformers will be hooked up in the classic open delta. The customer will receive, typically, 120 / 240 V , 4 wire 3 ? with a wild leg.
Great, just after it was decided that 208Y/120V was correct, now the 120/240V versus 240/120V pops up.
Al, from what you said above, a 3-ph, 4-wire system is correctly stated as 240/120V. which, is not to be confused with your standard single phase service of 120/240V.
As far as "open wye" it is mentioned in Note d) to Table 1 in ANSI C84.1. that should be authoritative enough.
It is a single phase service provided by the utility, from a 3-ph, 4-wire system. Hence you have a single phase service with 208V line-line, and 120V line-neutral. This would be differing in that the line voltages are still 120 deg apart, versus a 120/240V service with a line-line voltage of 240V, and a phase difference of 180 deg.