National Electrical Code Top Ten Tips:
Article 210 -- Branch Circuits
by Mark Lamendola
Based on the 2020 NEC
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 210.3, 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.
- 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 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
- 210.8 Ground-Fault Circuit-Interrupter Protection for
Personnel. Crawl spaces, unfinished basements, and boathouses are
just some of the many locations requiring GFCI protection. If you donít
know the others, youíll find out what they are in 210.8. There are 10 identified in "Other Than Dwelling Units" alone.
- 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
- 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.
- 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
- Table 210.21(B)(2) shows that the maximum load on a given
circuit is 80% of the receptacle rating and circuit rating (not spelled out that way, but look at the numbers and do the math). The maximum load on a 20A OCPD is 16A (as the table shows). Thus, if
you are planning to supply 20A on one circuit, that circuit must be
at least 30A (next available size up OCPD from 20A).
- 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 usually 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
- 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!
- 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.
Meeting this requirement doesn't necesarily mean you did a good job. This requirement is woefully inadequate for the typical dwelling. Consider the paucity of receptacles in the typical bathroom; this usually means the occupant must run cords across the sink or vanity. Yes you can get by with doing that, but is doing such shoddy work why you became an electrician? Go beyond the Code requirement and imagine where loads will actually be used in a given room. Installing a receptacle placed to service those loads is part of doing a good job. If you stop and think about it, 3 duplex receptacles in a bathroom means underserving that room. The Code requires only one, but caring about how the occupant will actually use that space requires at least 4. It's not the 1950s anymore, install receptacles accordingly.