Definition of "Branch Circuit, Multiwire"


Old 07-10-04, 03:55 PM
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Definition of "Branch Circuit, Multiwire"

The NEC definies:
<blockquote><b>Branch Circuit, Multiwire.</b> A branch circuit that consists of two or more ungrounded conductors that have a voltage between them, and a grounded conductor that has equal voltage between it and each ungrounded conductor of the circuit and that is connected to the neutral or grounded conductor of the system.</blockquote>
I would presume that a circuit with 2 hot wires, but no neutral wire, would not be considered a multiwire branch circuit, but that if the neutral were present, it would. But what about a three phase WYE circuit where the neutral is not included? What about a 4 wire center tapped delta where the grounded conductor is is the center tapped one, thus making the voltages unequal?
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Old 07-10-04, 04:26 PM
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You are correct that if there is no neutral, then it is not a multiwire circuit.

The center of the WYE is a grounded conductor, with equal voltage to each leg. So this fits the definition. But an Open WYE has no neutral, so it would not be a multiwire circuit.

If one leg of the delta is grounded, the voltage from the other two legs to this leg are equal. So that seems to fit the definition.

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