Every three years, most members of the industry involved with electrical installations in homes, businesses, and industry take the opportunity to participate in an NEC changes education program to make sure they are acquainted with the changes that are likely to be enforced by the local electrical inspector or other authority having jurisdiction (AHJ).  They look for a good instructor with some knowledge about the substantiation and history to help them understand the reason for the change, since they might “have been performing an installation in a certain way for 30 years and it doesn’t need to be changed now.” Having had the opportunity to serve on a number of NEC code panels and to listen to the discussion, possibly the most valuable insight I have gained is: there are underlying principles that guide these changes. This article will help explain a few of these guiding principles that the Code-Making Panel(s) have consistently used over multiple code development cycles in making their decisions.

Receptacle Outlet Locations

For dwelling units, the NEC contains very specific requirements for placement of receptacle outlets in 210.52. The performance objective of these requirements is:

“Locating receptacles in a manner that eliminates or significantly reduces the need for a homeowner  to use extension cords to supply power to their cord- and-plug-connected appliances, or in other words, as a substitute for permanent wiring”

There is logical rationale for the numbers specified in the NEC. For basic receptacle placement in habitable rooms, receptacles are required by 210.52(A) to be spaced every 12 feet along the wall space. This means that no space along the wall is more than 6 feet away from a receptacle outlet. Six feet is important because it is the standard cord length for appliances such as table and floor lamps. 

In the kitchen, receptacles are required by 210.52(C) to be spaced on countertops so that no point along the counter is more than 24 inches from a receptacle outlet. Again, the value is important, because most kitchen appliances such as toasters, electric skillets, coffee pots, and similar appliances are equipped with 24 inch long cords. 

Are Outlet and Receptacle Synonymous?

One of the most misused terms in residential electrical construction is “outlet.” When this term is used incorrectly, it can result in reading and interpreting the Code rules improperly. The following definitions can be found in Article 100:

Outlet. A point on the wiring system at which current is taken to supply utilization equipment.

Receptacle. A receptacle is a contact device installed at the outlet for the connection of an attachment plug. A single receptacle is a single contact device with no other contact device on the same yoke. A multiple receptacle is two or more contact devices on the same yoke.

An installation can have various types of “outlets,” including receptacle outlets, lighting outlets, and specific purpose outlets. Contrasting two areas in the NEC will help illustrate the importance of keeping these terms independent. 

Section 210.8(A) establishes the requirements for ground-fault circuit-interrupter (GFCI) protection of receptacles located in areas of dwelling units that are considered to have a higher degree of shock hazard. The protection for a particular receptacle can be provided at any point between the power source and the receptacle itself. So whether a GFCI receptacle or a GFCI circuit breaker is used, the GFCI requirement of 210.8(A) can be met. The performance objective of this requirement, which drives the proper use of the term, is:

“Protecting people from electrocution due to ground faults in cord- and plug connected utilization equipment.”  

Had the requirement stated that “outlets” in those specified locations must be provided with GFCI protection, the protection would be broader. The term “outlets” would include points of connection in addition to receptacles – such as outlets for lighting and smoke alarms. 

In contrast, there are requirements in the NEC that are specific to outlets. Section 210.12(B), for instance, establishes that 120-volt, 15- and 20-ampere branch circuits supplying outlets in specified areas of a dwelling unit must be protected by arc fault circuit interrupters (AFCIs). This requirement extends protection beyond branch circuits that supply “receptacles” to include branch circuits that supply any “outlets.” This would include lighting outlets, smoke alarm outlets, receptacle outlets, and even outlets for fixed appliances. Again, the proper use of the term is driven by the underlying performance objective, which in this case is:

“Protecting the entire branch circuit from becoming a fire ignition source due to an electrical arcing condition.” 

The hazard exists not only in a circuit supplying a receptacle, but also in fixed wiring serving luminaires and other loads. An arcing fault does not discriminate by location or by the type of load supplied.

Summary

Understanding the performance objectives that drive the NEC Code-Making Panels to establish requirements provides significant insight into why requirements do or do not exist. Nearly every NEC Code-Making Panel works from these performance objectives; this article has afforded the opportunity to explore only a few of these performance objectives, those behind residential branch circuit requirements. I encourage readers to explore other areas of the NEC and the substantiation for changes contained in the Report on Proposals (ROP) and Report on Comments (ROC). A knowledge of the intent of these performance objectives leads to a better understanding of why the latest NEC safety requirements exist as they do today.

Mr. Manche is a registered Professional Engineer and Director of Industry Standards at Schneider Electric. He currently serves on NEC Code-Making Panel 10 and has formerly served on CMP-8 and CMP-20. He is also a member of the NFPA 110, NFPA 70B, and NFPA 73 Technical Committees.