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Outside Branch Circuits
and Feeders
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How to apply the NEC rules for Art. 225
By Mike Holt, NEC Consultant
utdoor conductors run
ning to buildings aren’t
necessarily service con
ductors. They may be
feeders or branch circuit
conductors originating
in another building. They may provide
power for area lighting, outdoor equip
ment, or a separate structure.
To determine if outdoor conductors
are service conductors, identify where the
electric utility service point is, and review
the Art. 100 definitions for feeders, branch
circuits, and service conductors. If they’re
service conductors, use Art. 230. Other
wise, use Art. 225, which covers outside
feeders and branch circuits (Fig. 1).
Minimum size. You can use conductors
10 AWG or larger for overhead spans up to
50 ft. For spans more than 50 ft, use 8AWG
or larger (unless supported by a messenger
wire) [225.6(A)(1)], as shown in Fig. 2.
Unless supported by messenger wire,
overhead conductors for festoon lighting
must be at least 12AWG. Spans longer than
40 ft must be supported by a messenger
wire with strain insulators [225.6(B)].
Support and attachment. Do con
ductors pass over a roof? If so, use sub
stantial structures to securely support
them. If practicable, make the supports
independent of the building [225.19,
and 230.29]. Don’t use trees or other
vegetation to support overhead conduc
tors [225.26].
The point of attachment for overhead
conductors must be at least 10 ft above
finished grade. Locate it so the whole span
maintains the minimum conductor clear
ance required by 225.18 [225.16(A)].
Attach open conductors to fittings
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Outside Branch Circuits and Feeders Scope
225.1
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Overhead Branch Circuit or Feeder Conductors
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Underground Branch Cwcuit or Feeder
Fig. 1. Article 225 contains the installation requirements for outside branch circuits and feed
run on or between buildings, structures, or poles.
Outside Branch Circuits and Feeders
Conductor Size Overhead Spans
225. 6(A)(1)
-
Minimum of 8 AWG or larger for
spans over 50 ft. (no messenger wire)
Minimum of 10 AWG or larger for
spans up to 50 ft. (no messenger wire)
Fig. 2. For spans over 50 ft, use 8 AWG or larger (unless supported by a messenger wire).
identified for use with conductors, or to noncombustible,
nonabsorbent insulators securely attached to the structure
[225.16(B) and 230.27]. This point of attachment must meet
the minimum clearances specified in 225.18 and 225.19— and
in no case be less than 10 ft above finished grade.
If you use a mast for overhead conductor support, it must
have adequate mechanical strength, braces, or guy wires to
withstand the strain caused by the conductors. Only feeder or
branch circuit conductors can be attached to the feeder and/or
branch circuit mast [225.17], as shown in Fig. 3 on page 18.
Clearances from grade. Overhead conductor spans must
maintain these vertical clearances from grade [225.18]:
10 ft above finished grade, sidewalks, platforms, or projec
tions from which they might be accessible to pedestrians for
120V, 120/208V, 120/240V, or 240V circuits [225.18(1)].
• 12 ft above residential property and driveways, and those
commercial areas not subject to truck traffic for 120V, 120/20
8V,
120/240V, 240V, 277V, 277/480V, or 480V circuits [225.18(2)).
• 18 ft over public streets, alleys, roads, parking areas subject
to truck traffic, driveways on other than residential property;
and other areas traversed by vehicles (such as those used for
cultivation, grazing, forestry, and orchards) [225.18(4)].
• 24½ ft over track rails of railroads [225.18(5)].
For overhead conductors above poois, outdoor spas, out
door hot tubs, diving structures, observation stands, towers, or
platforms, follow the clearance requirements in 680.8.
Clearances from buildings. Overhead conductors must
maintain a vertical clearance of 8 ft above the surface of a roof.
Maintain that for a distance of at least 3 ft from the edge of the
roof [225.19(A)], except:
• If the roof is subject to pedestrian or vehicular traffic,
follow 225.18 [225.19(A) Ex 1].
‘vVhen the slope of the roof meets or exceeds 4 in. of verti
cal rise for every 12 in. of horizontal run, you can reduce the
overhead conductor clearances above the roof to 3 ft instead
of 8 ft [225.19(A) Ex2].
• When no more than 6 ft of conductor of 120/208V or
120/240V circuits passes over no more than 4 ft of roof, you
can reduce the clearance above only the roof overhang to
18 in [225.19(A) Ex 3], as shown in Fig. 4 on page 18.
• If the point of attachment is on the side of the building
below the roof, the 3 ft clearance from the roof edge doesn’t
apply [225.19(A) Ex4].
Overhead conductors must maintain a clearance of at least
3 ft from:
• Signs, chimneys, radio and television antennas, tanks, arid
other nonbuilding or nonbridge structures [225.19(B)].
• Windows that open, doors, porches, balconies, ladders,
stairs, fire escapes, or similar locations [225.19(D)(1)].
Also, overhead conductors must:
Maintain a vertical clearance of at least 10 ft above plat
forms, projections, or surfaces from which they might be
reached. Maintain this vertical clearance for 3 ft measured
horizontally from the platforms, projections, or surfaces from
which they might be reached [225.19(D) (2)].
Not be installed under an opening through which materials
might pass [225.19(D) (3)].
Not be installed where they will obstruct an entrance to
building openings [225.19(D)(3)].
Raceways. Raceways on exterior surfaces of structures must
be arranged to drain and be suitable for use in wet locations
[225.22]. Underground raceways (used or unused) entering
structures must be sealed in accordance with 300.5(G) to pre
vent moisture from contacting energized live parts [225.2
71.
Number of supplies. If more than one building or other
structure is on the same property, each building/structure must
be served by no more than one feeder or single or multiw
ire
branch circuit [225.30]. However, there are five exceptions
to
this. You can have additional supplies for:
1. Special conditions [225.30(A)]. These are:
Fire pumps.
• Emergency systems.
• Legally required standby systems.
• Optional standby systems.
Parallel power production systems.
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Systems designed for connection
to multiple sources of supply for the
purpose of enhanced reliability.
2. Special occupancies. Multipleoccupancy buildings where there’s no
available space for supply equipment
accessible to all occupants, or a build
ing/structure so large that two or more
supplies are necessary
but only with
special permission [225.30(B)].
3. Capacity requirements. ‘\‘Vhere the
capacity requirements exceed 2,ODOA
[225.30(C)].
4. Different characterjstics. Different
voltages, frequencies, or uses, such as
control of outside lighting from multiple
locations [225.30(D)].
5. Documented switching procedures.
Additional supplies are permitted where
documented safe switching procedures
are established and maintained for dis
connection [225.30(E)].
Disconnects. A disconnecting means
is required for all conductors that enter
a building or structure [225.31]. Install
it at a readily accessible location (either
outside or inside) nearest the point of en
trance of the conductors [225.32]. There
are four exceptions to this rule:
1) If documented safe switching
procedures are established, maintained,
and monitored by qualified persons, the
disconnecting means can be located else
where on the premises [225.32 Ex 1].
2) The building or structure qualifies
under the provisions of Art. 685 [225.32
Ex2].
3) For towers or poles used as light
ing standards, the disconnecting means
is permitted to be located elsewhere on
the premises [225.32 Ex 3].
4) For a pole or similar structure used
only for the support of signs installed in
accordance with Art. 600, the disconnect
ing means is permitted to be located else
where on the premises [225.32 Ex 4].
The building/structure disconnect
ing means can consist of no more than
six switches or six circuit breakers in a
single enclosure or separate enclosures
for each supply grouped in one location
as permitted by 225.30 [225.33].
The building/structure disconnecting
means must be grouped in one location,
and marked to indicate the loads they
serve as required byl 10.22 [225.34(A)].
Mast as Support for Power Conductors
225.17
VIOLA11ON
Only branch circuit or
feeder conductors can be
attached to a power mast.
Fig. 3. Only feeder or branch circuit conductors can be attached to the feeder and/or bran
circuit mast.
Clearance Above Roof
225.19(A) Ex 3
Maximum 6 ft of
Conductors Over Roof
Maximum 4 ft
Over Roof
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Fig. 4. For 120V/208V or l2OV/240V circuits, conductor clearance can be 18 in., if no more th
6 ft of conductor pass over no more than 4 ft of roof.
To minimize the possibility of ac
cidental interruption of critical power
systems, the disconnecting means for a
fire pump or for standby power must be
located remotely away from the normal
power disconnect [225.34(B)].
In a multiple-occupancy building,
each occupant must have access to the
disconnecting means for their occupancy
[225.35]. But if building management
provides electrical maintenance und
continuous supervision, manageme
can make access available only to buil
ing management [225.35 Ex].
The building/structure disconnecti
means must be comprised of a circi
breaker, molded case switch, general-u
switch, or snap switch “suitable for use
service equipment (225.36].”
If more than one supply feeds
•—büiBASICS
building/structure, a permanent plaque
or directory must be installed at each
feeder disconnect location denoting all
other feeders or branch circuits supply
ing that structure and the area served by
each [225.37].
The disconnecting means can consist
of a manual switch or a power-operated
switch or circuit breaker capable of being
operated manually [225.38(A)].You can
use a shunt-trip pushbutton to open a
power-operated circuit breaker. In this
case, the breaker (not the pushbutton)
is the disconnecting means. The discon
necting means for a building supplied by a
feeder must plainly indicate whether it’s in
the open or closed position [225.38(D)].
Rating. A single disconnecting means
for a building/structure must have -an
ampere rating at least equal to the cal
culated load as determined by Art. 220.
If the disconnecting means consists of
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more than one switch or circuit breaker,
the combined ratings must be no less
than the calculated load as determined
per Art. 220 [225.39].
Minimum ratings for disconnecting
means:
• For installations consisting of a
single branch circuit, the disconnecting
means must have a rating of at least 1 5A
[225.39(A)].
• For installations consisting of two
2-wire branch circuits, the feeder discon
necting means must have a rating of at
least 30A [225.39(B)].
• For a one-family dweffing, the feeder
disconnecting means must have a rating
of at least bOA, 3-wire [225.39(C)].
• For all other installations, the feeder or
branch circuit disconnecting means must
have a rating of at least 60A [225.39(D)].
Three’s a charm. It’s easyto overlook
a detail in Art. 225. To avoid that, check
your design to ensure you’re meetin
these three goals:
1. Maintain clearances. Outdoc
conductors present dangers from po
sible contact that indoor conductoi
don’t.
2. Support conductors. Outdoor cor
ductors are subject to stresses that indo
conductors aren’t.
3. Follow all rulesfor the installation
disconnects. This is essential in order i
provide a convenient and safe means I
disconnect sources of electric power i
case of fire or electrocution hazards.
Methodically walk through your di
sign, looking at all of the clearances fi
conformance to Art. 225. Then repu
with support requirements and discos
EC&I
nect rules.
Holt i5 the owner ofMike HoltEnterpris6
Inc., Leesburg, F/a. He can be reached
www. mikeholt. corn.
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