Crown Air Conditioning

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This is the most common four-wire three-phase delta service and is essentially a 240 volt, three-phase, three-wire delta service with one of the 240 volt transformer winding center tapped to provide two 120 Vac circuits, which are 180 degrees out of phase with each other. The voltage measured from this center tapped neutral to the third “wild” leg is 208 Vac.

There is two types of three phase winding connections, delta and wye.

You apparently have not been around wye systems all that much. With no wild leg we can use all three lines for 120 volt loads, the compromise here is line to line volts is only 208. If you have a majority of loads being 120 volts it is preferred.

The delta system can be corner grounded and have no 120 volts at all, or mid point of one phase can be grounded and that leaves us with one high leg and two 120 volt to ground legs. It would be more preferred when 120 volts are somewhat minimal and a lot of 240 volt load is present.

Voltage to neutral times square root of three is what line to line voltage will be = so for 120 line to neutral that gives us 208 line to line. Like I said earlier if line to neutral is 125 then line to line will be about 216, right about what you said you had.