There are long-standing general rules in the National Electrical Code that apply specifically to service disconnects. One of the first things to realize is that the word “service” in the phrases “service disconnect,” “service drop” and “service lateral,” by definition, implies that a serving utility is involved.

“Utility” is not defined in the NEC, but it is used enough times to be a good candidate for an Article 100 definition, based on requirements in the NEC Style Manual. This article reviews some critical requirements in the Code related to the service disconnect—more specifically, location access for occupants, routing of service conductors and so forth. 

Service conductors include a connection to the utility source, typically a pole-top or pad-mounted utility transformer. Service conductors are provided little to no protection by the serving utility, other than cutouts or fuses on the primary side of the utility transformer(s). One of the main reasons for this is to ensure continuity of service and reduce outages for utility customers. 

The NEC provides requirements that apply to service conductors and generally requires them to remain outside of a building or structure served. Key requirements in play  are Section 230.2, which generally requires each building or structure to have one service. Although there are multiple conditions allowing more than one, the long-standing  rule of “one building, one service” still exists. =

Location rules

Let’s take a closer look at the location rules for service disconnects. Part VI of Article 230 addresses service disconnects. Section 230.70 generally requires a means of disconnect for all ungrounded service conductors serving a building or structure. 

Sections 230.70(A)(1) and (2) get more specific and address the location of the service-­disconnecting means. This rule clearly emphasizes that the service­disconnecting means be located at a readily accessible location either outside of the building or structure or inside nearest the point of entrance of the service conductors. 

“Readily accessible” is a defined term and included in this rule. It is explained (in part) as capable of being reached quickly for operation, which generally applies to and benefits the occupants, but could concern first responders in some cases. 

Additional provisions

The second aspect of this rule addresses limiting the length of service conductors from extending excessive distance inside the building from the point of entrance of the service conductors. The NEC does not place a specific maximum length because service(s) come in a variety of sizes. This means that while keeping the distance short for service conductors routed inside a building for a 100A service, maintaining the service conductors for a 4,000A service is not as practical. The Code just requires the disconnecting means to be as close as practicable (without a distance specified) to the entrance of the service conductors. This allows flexibility and application for installers and authorities having jurisdiction. 

Another provision is what each service disconnect must be composed of, regarding throws of the hand, to accomplish disconnecting the power. Years ago, the Code required only one single service disconnect, and the rules subsequently evolved to permit more (up to six currently), but they all must be grouped in the same location, as indicated in Section 230.71(A) and (B). This allows for ease of accomplishing disconnecting the power with no more than six hand motions. 

This is another rule in the NEC for the AHJ to exercise practical judgment regarding the grouping requirement. Nowhere in this rule is a maximum distance between grouped service disconnects addressed, nor is an “in sight from” requirement apparent. Each service is unique. The grouping rule must carefully be applied to achieve compliance. 

As indicated in Section 230.70(B), each service disconnect must be identified as one (often referred to as a main in the field). This applies to every service disconnect as permitted by the provisions in 230.2. 

Section 230.2(E) contains essential requirements for permanently installed plaques denoting the location of each service-­disconnecting means, including remote ones. This rule expands the identification requirements from service disconnects to all feeders and branch circuits supplying the same building or structure. 

This is critical, as there is an ever increasing number of power sources (other than utility supplied) present in buildings or structures. Power sources such as generators, solar photovoltaic systems and energy storage systems are often present and active even when the utility service disconnect is placed in the open (off) position.

michael johnston