Ecmweb 2307 501ecm31fig1
Ecmweb 2307 501ecm31fig1
Ecmweb 2307 501ecm31fig1
Ecmweb 2307 501ecm31fig1
Ecmweb 2307 501ecm31fig1

Code Quandaries

Jan. 1, 2005
Q. Where should the high-leg conductor from a 120/240V, 3-phase, 4-wire delta-connected system be landed? My utility requires it to be in the right hand or phase position at the meter. A. The NEC requirements are as follows: Panelboards. Since 1975, panelboards supplied by a 3-phase, 4-wire delta-connected system must have the high-leg conductor (208V) terminate to the (center) phase of a panelboard



Q. Where should the high-leg conductor from a 120/240V, 3-phase, 4-wire delta-connected system be landed? My utility requires it to be in the right hand or “C” phase position at the meter.



A. The NEC requirements are as follows:

Panelboards. Since 1975, panelboards supplied by a 3-phase, 4-wire delta-connected system must have the high-leg conductor (208V) terminate to the “B” (center) phase of a panelboard [408.3(E)] (Fig.1 at right).

An exception to 408.3(E) permits the high-leg conductor to terminate to the “C” phase when the meter is located in the same section of a switchboard or panelboard.

Disconnects. The NEC doesn't specify the termination location for the high-leg conductor in switch equipment (Switches — Art. 404), but the generally accepted practice is to terminate this conductor to the “B” phase.

Warning: When replacing equipment in existing facilities that contain a high-leg conductor, care must be taken to ensure that the high-leg conductor is replaced in the original location. Prior to 1975, the high-leg conductor was required to terminate on the “C” phase. Failure to re-terminate the high-leg in accordance with the existing installation can result in 120V circuits inadvertently connected to the 208V high-leg, which can have disastrous results.

Identification. On a 3-phase, 4-wire delta-connected system, where the midpoint of one phase winding is grounded, the conductor with the higher phase voltage-to-ground (208V) must be durably and permanently marked by an orange outer finish or another effective means. Such identification must be placed at each point on the system where a connection is made if the grounded neutral conductor is present (110.15, 215.8, and 230.56) (Fig. 2 above).

The high-leg conductor is also called the wild-leg, stinger-leg, or bastard-leg.

Utility equipment: As I understand it, the ANSI standard for meter equipment requires the high-leg conductor (208V-to-neutral) to terminate on the “C” (right) phase of the meter enclosure. This is because the demand meter needs 120V, which it gets from the “B” phase.

About the Author

Mike Holt

Mike Holt is the owner of Mike Holt Enterprises (www.MikeHolt.com), one of the largest electrical publishers in the United States. He earned a master's degree in the Business Administration Program (MBA) from the University of Miami. He earned his reputation as a National Electrical Code (NEC) expert by working his way up through the electrical trade. Formally a construction editor for two different trade publications, Mike started his career as an apprentice electrician and eventually became a master electrician, an electrical inspector, a contractor, and an educator. Mike has taught more than 1,000 classes on 30 different electrical-related subjects — ranging from alarm installations to exam preparation and voltage drop calculations. He continues to produce seminars, videos, books, and online training for the trade as well as contribute monthly Code content to EC&M magazine.

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