National Electrical Code Articles and Information
National Electrical Code Top Ten Tips:
Article 210 -- Branch Circuits
by Mark Lamendola
Please note, we do quote from copyrighted material. While the NFPA
does allow such quotes, it does so only for the purposes of education
regarding the National Electrical Code. This article is not a substitute
for the NEC.
These are the 10 NEC Article 210 items we deem most important, based
on the pervasiveness of confusion and the potential costs of same.
- This Article contains Table 210.2, which identifies
specific-purpose branch circuits. When people complain that the Code
"buries stuff in the last few Chapters and doesnít provide
you with any way of knowing," that is usually because they didnít
pay attention to this table.
- NEC 210.4 Multiwire Branch Circuits. This is a circuit that
"consists of two or more ungrounded conductors that have a
voltage between them, and a grounded conductor that has an equal
voltage between it and each ungrounded conductor of the circuit, and
that is connected to the neutral or grounded conductor of the
system." The conductors of such circuits must originate from
the same panel. These circuits can supply only line-to-neutral
- NEC 210.8 Ground-Fault Circuit-Interrupter Protection for
Personnel. Crawl spaces, unfinished basements, and boathouses are
just some of the 8 locations requiring GFCI protection. If you donít
know the others, youíll find out what they are in 210.8.
- NEC 210.11. Branch Circuits Required. With three subheadings,
210.11 gives summarized requirements for the number of branch
circuits in a given system, states that a load computed on a VA/area
basis must be evenly proportioned, and covers rules for dwelling
- NEC 210.12. Arc-Fault Circuit-Interrupter Protection. An AFCI
provides "protection from the effects of arc faults by
recognizing characteristics unique to arcing and by functioning to
de-energize the circuit when an arc fault is detected." It is
not a GFCI, though combination units do exist. The purpose of an
AFCI (30 mA) is to protect equipment. The purpose of a GFCI (4 to 6
mA) is to protect people.
- NEC 210.19. ConductorsóMinimum Ampacity and Size. The rules for
ampacity require some study. One item many people overlook is that
branch conductorsóbefore the application of any adjustment or
correction factorsómust have "an allowable ampacity not less
than the noncontinuous load plus 125 percent of the continuous
load." The Code does have an exception for this, but the rule
- NEC Table 210.21(B)(2) shows that the maximum load on a given
circuit is 80% of the receptacle rating and circuit rating. Thus, if
you are planning to supply 20A on one circuit, that circuit must be
at least 30A.
- NEC 210.23 Permissible Loads. Read on down to (A)(2):
"Utilization Equipment Fastened in Place. The total rating of
utilization equipment fastened in place, other than luminaries
(lighting fixtures) shall not exceed 50 percent of the
branch-circuit ampere rating where lighting units,
cord-and-plug-connected utilization equipment not fastened in place,
or both are also supplied." The idea here is to prevent a
circuit overload just because someone plugs in a lamp or vacuum
cleaner. Proper planning and good engineering practices will prevent
needing to be concerned with this aspect of the Code. Place lights
on separate circuits, dedicated (fastened in place) loads on
separate circuits, and convenience receptacles on separate circuits.
The added cost really isnít that much. In residential
construction, the goal is to build as cheaply as possible. However,
if presented to Realtors and buyers correctly, a good electrical
plan (vs. the standard plan, which may meet Code but is barely
functional) will provide a selling edge. Even if the sale price isnít
higher, the number of days on the market will be less and cash flow
- NEC Table 210.24 Summary of Branch-Circuit Requirements allows you
to see everything at a glance. You just look up the circuit rating
(which you will base on the load you plan to supply), and the table
tells you the minimum conductor size. For that circuit rating, it
also tells you the size of the taps, overcurrent protection, and
maximum load. It also tells you which lampholders are permitted, and
what the receptacle rating must be. Donít leave home without it!
- NEC 210.52. Dwelling Unit Receptacle Outlets. An area rife with
confusion is receptacle spacing. "Receptacles shall be
installed so that no point measured horizontally along the floor
line in any wall space is more than 1.8 meters (6 feet) from a
receptacle outlet." This means you canít have receptacles
more than 12 feet apart along a wall line. 210.52 notes certain
exclusions, describing what a wall space is and is not. You can
exceed this requirement by mounting two receptacles to every stud,
if you so desire. But, you cannot space them any less than 12 feet
apart along a wall as defined by the NEC. Note, doorways and certain
other items do not count in the 12 feet.
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How the NEC is arranged
- The first four Chapters of the NEC apply to all installations.
- Article 90 precedes Chapter One, and establishes the authority of the NEC.
- Article 80 follows the body of the NEC; it exists as Annex H. It provides the requirements for administration.
- Chapters 5, 6, and 7 are the "special" chapters, covering special: occupancies, equipment, and conditions (in that order).
- Chapter 8 provides the requirements for communications systems.
- Chapter 9 provides tables.
- The appendices provide mostly reference information.
- Appendix D contains examples that every NEC user should study.
Try your NEC moxy:
- Do you know the difference between bonding and grounding? Hint: Look in the NEC, Article 100.
- Does the NEC refer to grounding incorrectly in any of its articles? Yes! So be careful to apply the Article 100 definitions. Don't ground where you should bond.
- When doing motor load calculations, which Article covers hermetic motors? Answer: While Article 440 covers the application of hermetic motors, it does so only by amending Article 430 because hermetic motors are a special case of motors. For motor load calculations, refer to Article 430.
- Does the NEC provide a voltage drop requirement? Yes! It does so in a special case, which is Article 648 Sensitive Electronic Equipment. But for general applications, it does not provide a requirement; it merely provides a recommendation in a couple of FPNs.
- Take our Code Quizzes.
Remember other applicable codes, rules, standards, and references:
- OSHA's electrical worker safety rules.
- IEEE standards.
- NETA standards.
- NFPA standards.
- International Codes (if applicable to the installation).
- State Codes (if the state has them).
- Local ordinances and permit requirements.
- Local fire codes.
- Manufacturer requirements or guidelines.
- Customer security requirements.
- Industry standards.
- Your company's own internal standards, practices, and procedures.
- Engineering drawing notes.
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