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Thread: service disconnect verses main disconnect.

  1. #1
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    service disconnect verses main disconnect.

    transfer switches with breaker in them are being called main disconnect by inspectors.
    but you turn it of and generator comes on in 30 or so seconds.
    so the main disconnect should be the main breaker in the breaker panel.
    I would like proper clarification.
    thanks.qugh devaj

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    Transfer switches with main breakers are called "service rated" because the main breaker can be the "service disconnect" for the utility power but is not necessarily so.

    If there is no disconnect between the meter and the transfer switch, the main breaker in the transfer switch is the "service disconnect". If there is a disconnect ahead of the transfer switch, the main breaker in the transfer switch is a "main disconnect".

    The generator itself has a main breaker which is a "service disconnect" according to 230.72(B).

    230.72 Grouping of Disconnects.
    (B) Additional Service Disconnecting Means. The one or
    more additional service disconnecting means for fire
    pumps, emergency systems, legally required standby, or optional
    standby services permitted by 230.2 shall be installed
    remote from the one to six service disconnecting means for
    normal service to minimize the possibility of simultaneous
    interruption of supply.

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    service disconnect

    the ATS breaker is for servicing the transfer switch after locating the generator and turning of the breaker and disconnecting the battery.
    the main disconnect for the breaker is still the main in the panel.
    this is how I see it.
    you cannot have a main disconnect and a breaker to also turn on in two different locations.

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    I think if you look at the NEC definition of services, service conductors, and service disconnects, the 1st point of disconnect (of service conductors) is going to be the "Service Disconnect" ("meter disconnects" as allowed by 230.82 being an exception).
    If the ATS is service rated and connected to the service conductors, the ATS main is the Service Disconnect.
    I don;t recall a NEC definition of a "Main Disconnect"
    Last edited by augie47; 01-24-19 at 10:15 PM.
    At my age, I'm accustomed to restaurants asking me to pay in advance, but now my bank has started sending me their calendar one month at a time.

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