210.62 Show Windows
Requirements specifying the placement of receptacle outlets are covered in 210.52 through 210.63. The majority of these provisions pertain to dwelling units. Section 210.52 has eight subsections covering general and specific requirements for the placement of receptacle outlets inside and outside dwelling units. Receptacle outlets in guest rooms of hotels, motels and similar occupancies must be installed in accordance with the provisions in 210.60(A) and (B). As stipulated in 210.60(A), some of the dwelling requirements are also applicable in guest rooms. This month’s In Focus is the 11th part in a series discussing required receptacle outlets. The first nine covered dwelling units, the 10th covered the last dwelling area and also guest rooms in hotels, motels and similar occupancies. Compared to the number pertaining to dwelling units, Article 210 contains a small number of receptacle-placement provisions for commercial occupancies. The only requirements in Part III of Article 210 pertaining to required receptacles in commercial occupancies are in 210.62 and 210.63. While the first section covers show windows, the second covers areas around heating, air-conditioning and refrigeration equipment. This month’s In Focus discusses show windows.
The National Electrical Code mentions show windows in eight places: once in Articles 100, 210, 314, 400 and 410; and twice in Article 220. Show windows are also mentioned in Annex D, Examples. Article 100 defines a show window as any window designed or used to display goods or advertising material. It can be enclosed (fully or partially), or entirely open at the rear. Show windows can incorporate platforms that are raised higher than the street-floor level, or can be even with the street-floor level. (See Figure 1.)
Article 220 provides requirements for computing branch-circuit, feeder and service loads. Show windows are mentioned twice in this article. Branch circuits supplying show windows must be calculated in accordance with 220.3(B)(7). The branch circuit must be computed either by the unit load per outlet as required by other provisions in 220.3(B), or at 200 volt-amperes per 1 foot (300 mm) of show window. The feeder (or service) procedure for computing show-window loads is stipulated in 220.12(A). For show-window lighting, a minimum rating of 200 volt-amperes/linear foot (660 volt-amperes/linear meter) must be included for each show window. This computation includes all show windows, regardless of size. The measurement must be taken horizontally along the base of the show window. Article 314 (previously 370) contains a specification for floor boxes. [314.27(C) Exception.] Flexible cords permitted in show windows are listed in 400.11.
Article 410 covers luminaires (fixtures), lampholders and lamps. Section 410.7 covers luminaires used in a show window. Although all types of luminaires are installed in show windows, only one type can have external wiring. Other than fixture wires that run through the chain of a chain-supported luminaire, no external wiring is permitted on those installed in show windows. (See Figure 2.) This provision eliminates luminaires from being wired with small extension cords and plugged into receptacle outlets.
The last mention of show windows is in Annex D, which contains examples of branch-circuit, feeder, and service load calculations. In the 1996 and earlier NEC editions, these examples were located in Part B of Chapter 9. In the 1999 edition, they were relocated to Appendix D. The term “Appendix” was changed to “Annex” in the 2002 edition. The examples are included in the Code book for informational purposes only.
As stipulated in 210.62, one or more receptacles will be required above certain show windows. At least one receptacle outlet must be installed directly above a show window for each 12 linear feet (3.7 m) or the major fraction of show-window area measured horizontally at its maximum width. The receptacle must be installed directly above the show window. Since the placement is not specified, the receptacle can be wall or ceiling mounted. Receptacles installed in (or around) the show-window floor do not satisfy the requirements of this section. If the show window meets the minimum dimension, the receptacle must be installed directly above the show window. (See Figure 3).
Upon first reading this specification it appears as if a receptacle is not required if the show window is less than 12 feet (3.7 m), but that’s not the case. A receptacle must be installed if the show window is a major fraction of 12 linear feet (3.7 m). Six feet constitutes a major fraction of 12 feet. A major fraction of 3.7 meters is 1.8 meters. Therefore, if the show window measures at least 6 linear feet (1.8 m), a receptacle is required. For example, a small retail store has a show window measuring 6 linear feet at its maximum width. Because this dimension is a major fraction of 12 feet, at least one receptacle is required. (See Figure 4.) While receptacles are not required above show windows measuring less than 6 feet (1.8 m), they are permitted.
To determine the show window’s linear distance, measure horizontally along the widest point. Although most show windows are straight, there are exceptions. Regardless of the show window’s curve or angle, measure horizontally at its maximum width. For example, a store’s show window is made up of three windows that are similar to a bay window. Each end window is set on a 45-degree angle extending out from the store. While each end window has a linear measurement of 3 feet, the middle measures 10 feet. Since this show window measures 16 feet total, at least one receptacle outlet is required. Because the remaining distance beyond 12 feet is not a major fraction of 12 feet, only one receptacle is required. (See Figure 5.)
A receptacle must be installed for each 12 linear feet (3.7 m) or major fraction of a show-window area. If the distance is great enough, more than one receptacle outlet will be required. Six linear feet (1.8 m), as discussed earlier, makes up a major fraction of 12 linear feet (3.7 m). At least two receptacles are required above a show window measuring 18 feet. If the show window is 18 feet (5.5 m) and less than 30 feet (9.1 m), two receptacles are required; if it is 30 feet (9.1 m) and less than 42 feet (12.8 m), at least three receptacles are required; if the show window is 42 feet (12.8 m) and less than 54 feet (16.5 m), at least four receptacles are required; etc.
A show window can include more than one window on more than one wall. If the show-window area continues around a corner, measure around the corner to determine the total linear distance. For example, a show window in a store features two windows. The side window is perpendicular to the front window. The front window measures 5 linear feet and the side window measures 4 linear feet. Since the total measurement of this show window is more than a major fraction of 12 linear feet (3.7 m), a receptacle is required. (See Figure 6.)
Next month’s In Focus, resuming with 210.63, will conclude the series on required receptacle outlets. EC
MILLER, owner of Lighthouse Educational Services, teaches classes and seminars on the electrical industry. He is the author of “Illustrated Guide to the National Electrical Code” and NFPA’s “Electrical Reference.” He can be reached at 615.333-3336, charles@charlesRmiller.com or www.charlesRmiller.com.