ELECTRICAL
INSTALLATION OF RESIDENTIAL SERVICES
Ref. 2004 California Electric Code
SERVICE ENTRANCE
Minimum
Size of Residential Service and Feeder Conductors
[CEC 310.15(B)(6)]
| Copper
AWG |
Amps
|
| 4
|
100 |
| 2 |
125 |
| 2/0 |
200 |
Conductor
Types must be rated for wet locations. Conductors
exposed to sunlight must be listed/marked sunlight
resistant. [310.8] e.g.:
Type THWN conductors
See
Table 310.15(B)(6) for complete list of amperes and
conductor types.
CLEARANCES
FOR SERVICE DROPS
[CEC
230.9 & 230.24]
-
3
ft. from openable windows, doors, porches, balconies,
ladders, stairs, fire escapes & similar locations.
-
8
ft. above any roof surface with a pitch of less than 4
in 12.
-
3
ft. above any roof surface with a pitch greater than 4
in 12.
-
18
when passing over the overhang (eave) portion of the
roof, regardless of the pitch, provided the overhang
does not exceed 4 ft. and the length of the drop above
the overhang does not exceed 6 ft.
-
10
ft. above grade at the service entrance, also at lowest
point of the drip loop, and above areas that are
accessible only to pedestrians.
-
12
ft. above residential property and driveways.
-
1
ft. from communications wires/cables at any point in the
span including the point of attachment to the building.
[800.10(A)(4)]
Service
Mast [230.28]
Only
service conductors shall be attached to the mast.
SERVICE
GROUNDING/BONDING
1.
An unspliced main bonding jumper shall be used to
connect the equipment grounding conductor(s) and the service
disconnect enclosure to the grounded conductor (neutral) of
the system within the enclosure. [250.28]
2.
Service equipment, enclosures and raceways must be
bonded. [250.92(A)] Bonding
shall apply at each end, and to all intervening raceways,
boxes, and enclosures, between the service equipment and the
grounding electrode.
The
following are acceptable bonding techniques: [250.92(B)]
-
Bonding
jumpers and main bonding jumpers connected to the
neutral bus
-
Threaded
hubs or condulet to threaded conduits
-
Threadless
conduit fittings, both setscrew and compression types.
Note:
Standard locknuts must be upgraded to the bonding type.
Grounding
Electrodes [250.52]
In
the City of Daly City, grounding electrodes for residential
service must be A, and
either B or C below:
A.
A metal underground water pipe in direct contact with
the earth for 10 ft. or more and electrically continuous by
bonding around insulating joints to the points of connection
of the grounding electrode conductor. Interior
metal water piping located more than 5 ft. from the point of
entrance to the building shall not be used as a part of the
grounding electrode system or as a conductor to interconnect
electrodes that are part of the grounding electrode system.
B.
A
concrete encased electrode an electrode encased by at
least 2 of concrete, located within and near the bottom
of a concrete foundation or a footing that is in direct
contact with the earth, consisting of at least 20 ft. of one
or more bare or zinc galvanized steel reinforcing bars or
rods (rebar) of not less than ½ inch in diameter, or of at
least 20 ft. of bare copper conductor not smaller than 4
AWG. Rebars
shall be permitted to be bonded together by the usual steel
tie wires or other effective means.
C.
A
ground rod, copper or copper clad plated steel, ½ to
5/8 in diameter and 8-10 ft. long, driven at least 8 ft.
into the ground.
Note:
For other types of grounding electrodes and installation
procedures refer to NEC 250.52 & .53
Note:
Two different types of grounding electrodes are required;
for service upgrades this usually means the water pipe and a
ground rod.
The
Grounding Electrode Conductor (GEC)
Materials
(DCMC
15.24.070)
Installation
-
#8
AWG (min. size) requires physical protection
[250.64(B)]
-
#6
AWG requires protection if subject to physical
damage
-
#4
requires protection if subject to severe physical
damage (e.g. along driveway).
Protection
is usually in the form of EMT, armor cable or rigid conduit.
All of these methods must be properly bonded at both
ends. [250.64(E)]
GEC
Connection to Electrode
1.
The connection is to be accessible unless buried or
encased in concrete. [250.68 (A)]
2.
The connection is to be made with listed lugs, clamps
or other listed materials.
Note:
If buried, the lug or clamp must be listed for ground
contact. [250.70]
GEC
Connection at the Service
1.
The GEC shall be connected to the grounded service
conductor (neutral). [250.24(C)]
This
connection typically occurs at the neutral terminal of the
main disconnect enclosure.
Capacity
of GEC
(Table 250.66)
-
#8
AWG is rated for a #2 AWG size service entrance
conductor; #6 AWG up to size #1/0, and #4 AWG up to#3/0.
-
The
GEC to a ground rod need not exceed #6 AWG in size
[250.66(A)]
-
The
GEC to a concrete encased electrode need not exceed #4
AWG in size [250.66(B)]
Other
Bonding Requirements [250.104]
Bonding
of Piping Systems
(A)
Metal Water Piping systems installed in, or attached to
a building, shall be bonded to the service equipment
enclosure, the grounded conductor (neutral) at the service,
the GEC where of sufficient size, or to the one or more
grounding electrodes used. The bonding jumpers shall be sized in accordance with Table
250.66.
Other
Bonding Requirements [250.104]
(B)
Other Metal Piping, where installed in or attached to a
building, including gas piping, that may become energized
shall be bonded to the service equipment enclosure, the
grounded conductor (neutral) at the service, the grounding
electrode conductor where of sufficient size, or to the one
or more grounding electrodes used.
The
points of attachment of the bonding jumper(s) shall be
accessible.
Working
Space Required at the Service
[110.26 (A) (E)]
-
66
headroom
-
30
minimum width
-
36
minimum depth measured from the face of enclosure
-
Meter
height 48 66 (PG&E)
-
Illumination
shall be provided for working space at service equipment
installed indoors.
Daly
City Municipal Code Requirements
1.
(DCMC 15.24.030) Service entrance conductors
shall be enclosed in rigid metal conduit (RMC). Note:
PG&E requires a minimum of 1-1/4 diameter service
mast.
2.
(DCMC 15.24.070) Conductor material shall be
copper only.
3.
(DCMC 15.24.040) The meter and main disconnect must be
accessible from the exterior.
Note:
A lockable, gated entry compromises this access requirement.
4.
(DCMC 15.24.040) The service equipment must be
screened from public view by an enclosure.
Other
Items
Panel
Directory/Circuit Directory [408.4]
All circuits shall be legibly identified as to the purpose
or the use on a circuit directory located on the face or
inside of the panel door.
Grounded
Conductor
Color
- An
insulated grounded (neutral) conductor of 6 AWG and smaller
shall be identified by a continuous white outer finish along
its entire length [200.6(A)]. This
means you cannot
re-color a conductor to make it white for these sizes.
An
insulated grounded (neutral) conductor larger than 6 AWG can
be re-colored in the field; this re-coloring must occur at
all termination points.
Terminations
Each
grounded (neutral) conductor shall terminate within the
panelboard in an individual terminal that is not also used
for another conductor [408.21]. I.e.
One conductor, one screw
Circuit
Breakers & Size of Conductors [240.4(D)]
14
AWG size conductors are limited to 15 ampere rated breakers.
12
AWG size conductors are limited to 20 ampere rated breakers.
Service
Drop
[230.54]
Service
heads shall be located above the point of attachment of the
service conductors to the building.
Rating
of Cabinet/Service Equipment All cabinets installed
outdoors must be rated NEMA 3 (this includes cabinets within
enclosures designed to screen equipment from public
view).
Building
Division Telephone Number:
(650)
991-8061
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