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The Advantages of a Multiwire Branch Circuit

A multiwire branch circuit consists of at least two ungrounded or hot conductors connected to the same grounded or neutral conductor. A potential difference exists between each neutral conductor, likewise the same potential difference is found between the neutral and hot conductors. The two most likely places to find multiwire branch circuits are in disposable circuits and dishwashers. Other locations include kitchen counters and lighting circuits.

  1. Multiwire Branch Circuit Theory

    • The theory behind multiwire branch circuits is centered on the idea that the load imbalances from circuits supplied by different service phases will be carried by one neutral conductor. Hence in theory, the proper installation and maintenance of a multiwire branch circuit will ensure protection from over-voltage in both neutral and hot conductors.

    Cost Advantage

    • Multiwire branch circuits are particularly used in areas that require power for multiple small appliances, such as kitchen counters. This eliminates the additional material and labor costs of installing another circuit in the same location. Multiwire branch circuits also require fewer current-carrying conductors in a raceway. It also uses smaller raceways, which saves on space.

    Other Advantages

    • In a multiwire branch circuit, the voltage drop is lowered by up to 50 percent compared to dedicated neutral circuits. This reduces the risk of over-voltage transmission to appliances or equipment plugged in to the circuit. Multiwire branch circuits are also easily identified using color-coded marking tapes and tags approved by the National Electrical Code (NEC).

    Precautions

    • The voltage protection offered by multiwire branch circuits is compromised, resulting in a potential fire hazard when the continuity of the neutral conductor is broken. All hot conductors must be simultaneously disconnected during installation or repair, to prevent the risk of shock. Conductor insulation material must also be monitored, as overheating reduces its effectiveness.

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