Greg, out my way such discos are a little light on neutrals.
There is a perfectly good ground in there tho and an HVAC tech on a hot roof doesn't know or care that there is a difference.
If one of those phases to ground is 120v, it will run his vac pump and he is outta there. Hot wire in a receptacle on the line side and off you go.
... at least that was what they were joking about.
I always assumed that was why we wanted a real receptacle up there.
210.63 appeared in the code in 87. There are plenty of buildings around here older than that, considering we were 2 cycles behind most of the time.
