Karl Townsend wrote:

"The Kid" is putting in underground wiring to his outbuildings. For
now, power will come from the house to the shop.

The shop sits twenty feet from a three phase line. future plans is to
install a three phase service to the shop, cut the ordinal transformer
out, and then feed one phase back to the house from the wiring being
installed now.

OK, a one phase house service has two 110 legs on the same phase
opposite polarity to get 220 across the two hot wires, neutral is the
center tap. As I understand it you in effect get three 110 hot wires
120 degrees apart in the phasing for three phase with the center tap
for neutral.

So, can you run single phase 220 off this? Need any special provisions
installed now? He's putting in conduit - four wires - two hot, neutral
and ground.

Karl

Two legs and neutral of 120/208V Wye three phase service is generally
considered to be equivalent to 120/240V single phase service for most
uses. 120V only appliances will see no difference at all, 240V
appliances will be minimally affected and many have dual 208/240V
ratings anyway these days since apartments often have 120/208V service.

The key thing to watch out for with three phase service is the rates
such as the common peak metered commercial rates where you end up paying
for your highest use day, not your actual use. The four wires are
correct since either way, one end is the service end with ground and
neutral bonded and the other is a sub.