There were two exceptions inserted into Section 230.40 for the 1984 NEC. These exceptions were designed to cover installations where there were multiple occupancies in the same building and where separate service disconnecting means enclosures were installed as permitted by the six disconnect rule in Section 230.71.

The first exception dealing with multiple occupancies in the same building was worded as follows in the 1984 NEC: “Buildings of multiple occupancies shall be permitted to have one set of service- entrance conductors run to each occupancy or to a group of occupancies.”

The second exception dealt with separate service enclosures and read as follows from Section 230.45 in the 1984 NEC: “Where two to six service disconnecting means in separate enclosures supply separate loads from one service drop or lateral, one set of service-entrance conductors shall be permitted to supply each or several such service equipment enclosures.” For the 1987 NEC, the text in Section 230.45 was converted into the text for 230.40, Exception No. 2, with some minor revisions. This exception remains relatively unchanged since its inception for the 1987 NEC and through the 2005 NEC.

What has changed is the text for Section 230.40, Exception No. 1, with a minor change in the 1999 NEC, a major change in the 2002 NEC and then another major change for the 2005 NEC, all dealing with multiple occupancies in a single building. Each text change, as well as the ramifications of each change, will be discussed in detail so the reader can determine the effects each change might have for their own applications.

The 1999 NEC 230.40, Exception No. 1, read as follows: “Buildings with one or more than one occupancy shall be permitted to have one set of service-entrance conductors for each class of service run to each occupancy or group of occupancies.” The words “for each class of service” was added to the text with the exception still permitting multiple occupancies to have a set of service-entrance conductors run to each occupancy from a single service drop or service lateral.

Since the phrase “for each class of service” was not used or defined in the 1999 NEC, a change in the 2002 NEC to delete this phrase resulted in the greatest change in 230.40, Exception No. 1, since it was inserted into the NEC in 1987.

In the 2002 NEC, Section 230.40, Exception No. 1, was reworded as follows: “A building with one or more than one occupancy shall be permitted to have one set of service-entrance conductors for each service of different characteristics, as defined in 230.2(D), run to each occupancy or group of occupancies.”

This change removed permission for sets of service-entrance conductors to be installed from the service drop or lateral to each occupancy, unless there were multiple services each with different characteristics, such as different voltages, frequencies or phases, or with multiple services having different uses, such as different rate schedules. For the first time since this exception was inserted into the NEC, buildings with multiple occupancies but with a single service could not have individual sets of service-entrance conductors installed to each occupancy.

Even though this restriction occurred in the 2002 NEC, it was never the intent of Panel 4, the Code-Making Panel with jurisdiction over Article 230, to restrict this exception to multiple services with different characteristics. A change to Section 230.40, Exception No. 1, in the 2005 NEC has resulted in the return to text that is very similar to the original text from the 1984 NEC. The text for the 2005 NEC reads as follows: “Exception No. 1: A building shall be permitted to have one set of service-entrance conductors for each service, as defined in 230.2, run to each occupancy or group of occupancies.”

The reworded text for the 2005 NEC has returned the text and the permission for service-entrance conductors to be run from each service to as many different occupancies as may exist in a building. Remember, the service-entrance conductors may be run on the exterior of the building for any distance but must be connected to the service disconnecting means at a readily accessible location either outside the building or structure, or located inside nearest the point of entrance of the service conductors into the building or structure. EC

ODE is a staff engineering associate at Underwriters Laboratories Inc., in Research Triangle Park, N.C. He can be reached at 919.549.1726 or at [email protected].