Stumped By the Code? Number of Service Disconnects Allowed on a Service
All questions and answers are based on the 2020 NEC.
Underlined text indicates revisions made in the 2020 Edition of the NEC.
Q. What Code rule applies to the number of service disconnects allowed on a service?
A. Section 230.71 provides guidance on the number of disconnects allowed on a service.
Each service must have only one disconnecting means except as permitted in Sec. 230.71(B).
(A) General. For the purpose of this section, a disconnecting means installed as part of listed equipment and used solely for the following is not considered a service disconnecting means:
(1) Power monitoring equipment.
(2) Surge-protective device(s).
(3) Control circuit of the ground-fault protection system.
(4) Power-operable service disconnect.
(B) Two to Six Service Disconnecting Means. Up to six service disconnects are permitted for each service allowed by Sec. 230.2, or for each set of service-entrance conductors permitted by Sec. 230.40, Exceptions No. 1, 3, 4, or 5.
The two to six service disconnecting means may consist of a combination of any of the following:
(1) Separate enclosures with a main service disconnecting means in each enclosure
(2) Panelboards with a main service disconnecting means in each panelboard
(3) Switchboard(s) where there is only one service disconnect in each separate vertical section where there are barriers separating each vertical section
(4) Service disconnects in switchgear or metering centers where each disconnect is located in a separate compartment
Informational Note 2: Examples of separate enclosures with main service disconnecting means in each enclosure include but are not limited to, motor control centers, fused disconnects, circuit breaker enclosures, and transfer switches that are suitable for use as service equipment.
The rule is six disconnects for each service, not for each building. If the building has two services, then there can be a total of 12 service disconnects (six disconnects per service) (see Figure below).
This revision retains the previous permission to have two to six service disconnects for each service or each set of service-entrance conductors but provides the increase in safety that a single service disconnect provides. The previous six main disconnect rule for a single enclosure made it impossible to work in service equipment when applying electrical safe work practices in accordance with NFPA 70E, unless the line side of the multi-disconnect enclosure was disconnected by the electric utility.
This revision also reflects the electrical hazards inherent while working on service equipment where there is more than one service disconnect in a single enclosure. This, combined with the rule in Sec. 230.62(C) that requires line side barriers, is a significant safety improvement toward reducing the risk to electricians by limiting their exposure to energized parts.
