All questions and answers are based on the 2014 NEC.
Q. What are the requirements for a building service disconnecting means?
A. The service disconnecting means must open all service-entrance conductors from the building premises wiring [230.70]. It must be placed at a readily accessible location either outside the building or inside nearest the point of service conductor entry [230.70(A)(1)] (Fig. 1).
WARNING: Because service-entrance conductors don’t have short circuit or ground fault protection, they must be limited in length when installed inside a building. Some local jurisdictions have a specific requirement as to the maximum length permitted within a building.
The service disconnecting means isn’t permitted to be installed in a bathroom [230.70(A)(2)]. In addition, overcurrent devices must not be located in the bathrooms of dwelling units or guest rooms/guest suites of hotels or motels [240.24(E)].
If a remote-control device (such as a pushbutton for a shunt-trip breaker) is used to actuate the service disconnecting means, the service disconnecting means must still be at a readily accessible location either outside the building, or nearest the point of entry of the service conductors as required by Sec. 230.70(A)(1) [230.70(A)(3)] (Fig. 2). See the definition of “Remote Control” in Art. 100.
The service disconnecting means must consist of a manually operated switch, a power-operated switch, or a circuit breaker that’s also capable of being operated manually [230.76].
Each service disconnecting means must be permanently marked to identify it as part of the service disconnecting means [230.70(B)]. When a building has multiple services and/or feeders, a plaque is required at each service or feeder disconnect location to show the location of the other service or feeder disconnect locations. See Sec. 230.2(E).
Each service disconnecting means must be suitable for the prevailing conditions [230.70(C)].
There must be no more than six service disconnects for each service permitted by Sec. 230.2, or each set of service-entrance conductors permitted by Sec. 230.40 Ex 1, 3, 4, or 5. [230.71(A)].
The service disconnecting means can consist of up to six switches or six circuit breakers mounted in a single enclosure, in a group of separate enclosures, or in or on a switchboard, or in switchgear.
CAUTION: The rule is six disconnecting means for each service permitted, not for each building. If the building has two services, then there can be a total of 12 service disconnects (six disconnects per service).
The up to six service disconnecting means for each service must be grouped [230.72(A)].
To minimize the possibility of simultaneous interruption of power, the disconnecting means for fire pumps [Art. 695], emergency [Art. 700], legally required standby [Art. 701], or optional standby [Art. 702] systems must be located remote from the one to six service disconnects for normal service [230.72(B)]. Because emergency systems are just as important as fire pumps and standby systems, they need to have the same safety precautions to prevent unintended interruption of the supply of electricity.
In a multiple-occupancy building, each occupant must have access to their service disconnecting means [230.72(C)]. Exception: In multiple-occupancy buildings where electrical maintenance is provided by continuous building management, the service disconnecting means can be accessible only to building management personnel.
The service disconnecting means can consist of [230.76]:
- A manually operable switch or circuit breaker equipped with a handle or other suitable operating means.
- A power-operated switch or circuit breaker, provided it can be opened by hand in the event of a power supply failure.
The service disconnecting means must indicate whether it’s in the off (open) or on (closed) position [230.77]. The service disconnecting means for a building must have an ampere rating of not less than the calculated load according to Art. 220, and in no case less than [230.79]:
A) For installations consisting of a single branch circuit, the disconnecting means must have a rating not less than 15A.
B) For installations consisting of two 2-wire branch circuits, the disconnecting means must have a rating not less than 30A.
C) For a one-family dwelling, the disconnecting means must have a rating not less than 100A, 3-wire.
D) For all other installations, the disconnecting means must have a rating not less than 60A.
A shunt-trip button doesn’t qualify as a service disconnect because it doesn’t meet any of the above requirements.
Holt is the owner of Mike Holt Enterprises, Inc. in Leesburg, Fla. He can be reached at www.mikeholt.com.
