Identification of Disconnecting Means

One of the most important NEC requirements (and yet one most often ignored) is 110.22: Identification of Disconnecting Means. It reads: “Each disconnecting means shall be legibly marked to indicate its purpose unless located and arranged so the purpose is evident. The marking shall be of sufficient durability to withstand the environment involved.”

In commercial and industrial occupancies, this is not too difficult to comply with at panelboards or switches. In a commercial occupancy there are floor numbers and room numbers, so circuit identification is a simple matter; in an industrial occupancy there are machine descriptions (numbers, sizes) and it may appear that it is more important that these circuit disconnects be quickly identified. There is software available so those panel directories can be made on a personal computer. Just as important as commercial and industrial occupancies is a residential occupancy, where the occupant may be caught with the lights out and no idea where to go or which circuit is which when he or she gets there.

In a dwelling unit, it is not unusual to find at the circuit breaker panel these descriptions: “lights,” “plugs” (should be “receptacles,” but that is too long to write out) or simply “lights and plugs.” These might be in felt-tip marker, stick-on plastic labels or any number of makeshift methods. What is needed, to aid the occupant, and a troubleshooter, (who may later turn out to be you, the installer) is a legible brief description of the area or loads served by each circuit.

The 2002 NEC Handbook includes this in the commentary: “Proper identification needs to be specific. For example, the marking should indicate not merely ‘motor’ but rather ‘motor, water pump’ [and] not merely ‘lights’ but rather ‘lights, front lobby.’ Consideration should also be given to the form of identification. Marking often fades, or is covered by paint after installation.” Just how the installer is to protect against future painting over the switch or panelboard markings is not clear, but I suppose this is included in the commentary to indicate that the marking requirement is for the lifetime of the installation. As the facility ages and changes are made (additions, alterations, new equipment), it is important that these markings be kept up to date.

For a dwelling unit, it is not proper to mark “Ethel’s Bedroom.” The typical family in the United States moves on the average of once every seven years, and it is not likely that the next occupant of that bedroom will be named Ethel. Mark the disconnects “front and rear bedroom” or “east and west bedroom,” and in a three- or four-story house be sure to note the floor. In other cases, there may be some confusion when the room is not used as shown on the plans. Many bedrooms are actually used as computer rooms or offices. Often the installer and the occupant have no opportunity to communicate, so the proper action for the installer is to mark the circuit disconnects for the areas as shown on the plans. It is hoped that the occupant will correct the markings as necessary. Most do-it-yourself books urge the occupant to survey the wiring and make sure the markings at the panelboard are correct.

On another subject, the question of emergency wiring for a dental office has come up. In the 2002 NEC, in Part III of Article 517, Health Care Facilities, the Scope of 517.25 Essential Electrical Systems indicates that dental offices are included in the list of functions which are required to have an essential electrical system which consists of providing lighting and power considered essential for life safety and orderly cessation of procedures during the time normal electrical service is interrupted for any reason. NEC 517.30 covers Essential Electrical Systems for Hospitals, while 517.40 covers Essential Electrical Systems for Nursing Homes and Limited Care Facilities. Also, 517.45 covers Essential Electrical Systems for Other Health Care Facilities, which includes dental offices. 517.45(A) covers the requirement for a battery or generator system. Section (B) covers Life Support Equipment, (C) covers Critical Care Areas, and (D) refers to Article 700 for batteries and 517.30 through 517.35 for generators.

Do dental offices require this standby source, automatic transfer equipment? The only way to find out is to refer to NFPA 99-1999, Standard for Health Care Facilities.

It depends on the degree and type of patient care given. Oral surgery where the patient may be anaesthetized will have a different requirement from the normal dental office where dental hygiene and tooth repairs are done. EC

SCHWAN is an electrical Code consultant in Hayward, Calif. He can be reached at


About the Author

W. Creighton Schwan

Former Code Columnist
W. Creighton Schwan was a long-time contributor to ELECTRICAL CONTRACTOR magazine and an important figure in the electrical code world. His first article written for ELECTRICAL CONTRACTOR was published in January 1980 issue. He wrote a total of 326...

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