The nominal voltage between the breaker in space 4 and the neutral bar is ___ volts.

The nominal voltage between the breaker in space 4 and the neutral bar is ___ volts.

• A. 120
• B. 208
• C. 0
• D. 240

Answer: (B)

In a four-wire delta service with a center-tapped winding, the neutral is tied to the center of the 240 V winding. That creates 120 V to neutral from two of the phases, while the third phase (the high leg) is about 208 V to neutral. So if the breaker in that space is on the high leg, the nominal voltage to the neutral bar is 208 volts. This is a standard characteristic of high-leg delta systems; in a 120/208Y system you’d see 120 V to neutral instead, and there is no such 208 V to neutral in a simple three-wire delta with no center tap.

In a four-wire delta service with a center-tapped winding, the neutral is tied to the center of the 240 V winding. That creates 120 V to neutral from two of the phases, while the third phase (the high leg) is about 208 V to neutral. So if the breaker in that space is on the high leg, the nominal voltage to the neutral bar is 208 volts. This is a standard characteristic of high-leg delta systems; in a 120/208Y system you’d see 120 V to neutral instead, and there is no such 208 V to neutral in a simple three-wire delta with no center tap.