The National Electrical Code provides minimum requirements for electrical systems installed in places of assembly. The first item to review is what constitutes such a place, based on NEC requirements. 

Section 518.1 clarifies what occupancies fall into this category. The key aspect is the text indicating that buildings, or portions of buildings or structures, designed or intended for a gathering of “100 persons or more” for any purpose, including those that are or are not indicated in the scope. This is a good example of the Code remaining open-ended: to be considered as exclusive of those assembly occupancies that qualify as assembly types and must be included and covered. 

As indicated in Section 518.1, Article 520 covers theaters and audience areas of motion picture and television studios, performance areas and similar locations and is excluded from the rules in Article 518. Section 518.2 provides a noninclusive list of occupancies that qualify as assembly types and would be covered by Article 518. 

A clarification and observation: the term “pool rooms” as indicated in 518.2(A) list item (18) should probably be replaced with “billiards rooms” or something similar, to avoid confusion. The term “pool rooms” can mean a room(s) where there is a pool for swimming and result in misapplication of Article 518.

Occupant load and means of egress 

The NEC’s purpose is to protect people and property from hazards arising from the use of electricity. In assembly occupancies, the safety and protection or people is the key concern—more specifically, the means of egress and the ability to exit the assembly occupancy during abnormal, emergency events such as a power failure or fire. 

NFPA 101, the Life Safety Code, provides important information about determining maximum occupant loading (population capacity) and how many means of egress are needed. Section 12.1.7 of NFPA 101 has important information to assist with designs that meet or exceed the minimum requirements of NFPA 101 and NFPA 70. The objective is to get people out as fast as possible. 

This differs from healthcare occupancies, such as hospitals, covered by Article 517. Those occupancies are designed using a defend-in-place philosophy, meaning that for other than a portion of the area that may need to be evacuated for safety, the patients and staff are remaining in the building. 

Applying the NEC

A review of the concepts addressed in Section 90.3 is in order, as it is fundamentally applicable to Article 518. Section 90.3 clarifies that NEC chapters 1–4 have general application and chapters 5–7 can amend or supplement those requirements. Given the use and application context of 90.3, it becomes clear that the general Code rules for electrical installations apply to all assembly occupancies, and additional rules with Article 518 must be followed. 

A couple of examples of how the general rules are modified are the qualifiers for applicability of Article 518, meaning the “100 persons or more clause” and the more restrictive “wiring methods” required for occupancies or spaces within buildings or structures where the occupant load would be 100 or more people. 

Another example of amended wiring requirements is the reference to Article 590 for temporary wiring, such as that installed in exhibition halls for trade shows, display booths, demonstrations or other purposes.

Wiring methods

Section 518.4(A) provides requirements for wiring methods installed in places of assembly. Key aspects are that it must be a metal raceway or flexible metal raceway or be nonmetallic and encased in not less than 2 inches of concrete. The other requirement is that the wiring method itself qualifies as an equipment grounding conductor (EGC) in accordance with Section 250.118, or it must contain a wire-type EGC sized in accordance with Table 250.122. MI, AC and MC cables are permitted in accordance with this section. 

The reasoning behind the more robust wiring requirement is more resiliency during a fire event. These types of wiring must be installed in areas of assembly occupancies required to be fire-rated construction in accordance with the applicable building code. In addition to the wiring permitted in 518.4(A), nonmetallic-sheathed cable, electrical nonmetallic tubing and rigid nonmetallic conduit shall be permitted in areas not required to be of fire-rated construction. 

A more restrictive illumination requirement applies for equipment such as service equipment, switchboards, switchgear, panel­boards or motor control centers installed outdoors and serve assembly occupancies. See Article 518 for these requirements. It is also a good idea to consult the applicable authority having jurisdiction for additional requirements or local amendments.

Mselected / stock.adobe.com