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INDEX
INTRODUCTION
ELECTRIC SERVICE
BRANCH CIRCUIT WIRING
REQUIRED BRANCH CIRCUITS
REQUIRED RECEPTACLE OUTLETS
REQUIRED LIGHTING OUTLETS
GROUND FAULT PROTECTION
REQUIRED DISCONNECTION MEANS
CONDUCTOR FILL
EQUIPMENT GROUNDING CONDUCTOR MAKE-UP
ELECTRIC HEAT CIRCUITRY
ROUGH-IN INSPECTION
FINAL INSPECTION
DOWNLOAD THIS INFORMATION IN ENGLISH OR SPANISH
DO NOT HESITATE TO ASK YOUR INSPECTOR QUESTIONS
This guideline has been prepared to assist the lay person in complying with the requirements of all Longmont adopted Electrical Codes, and assure the installation of a safe and reliable electrical system. This guideline is not inclusive for every installation and is not an instruction manual.
Along with meeting NEC requirements, the permit and inspection process defined by ordinance must be followed. If for some reason, the job does not meet the requirements of the NEC and an extra visit is necessary, a re-inspection fee may be required before the inspector can return.
See the currently adopted codes and local amendments on our web site. In addition, check with Longmont Power and Communications (303-651-8386) for their requirements.
ELECTRIC
SERVICE
The service equipment must be large enough to supply the connected load, which
is calculated using Article 220 of the NEC. The most common sizes of residential
service equipment are 100, 125, 150, and 200 amperes. The minimum wire size
for service entrance conductors are listed below:
Conductor Types and Sizes for 120/240-Volt, 3-Wire, Single-Phase Dwelling Services
RH, RHH, RHW, RHW-2, THHN, THHW, THW, THWN, XHHW, USE*
*Type "USE" (Underground Service Entrance) conductors are not permitted to enter a building unless they are triple rated with the additional markings RHH and RHW.
| COPPER |
ALUMINUM
AND COPPER CLAD ALUMINUM |
SERVICE
RATING IN AMPS |
| AWG
|
AWG |
|
| 4 |
2 |
100 |
| 3 |
1 |
110 |
| 2 |
1/0 |
125
(min for new home) |
| 1 |
2/0 |
150 |
| 1/0 |
3/0 |
175 |
| 2/0 |
4/0 |
200 |
The
service equipment must be grounded in accordance with Article 250 of the NEC,
which, in general, says the neutral must be bonded to the service enclosure
and the grounding electrode system as defined in Article 250-50.
The main service equipment panel shall be mounted either outside or inside
the dwelling, as near as possible to the point of entrance of the service
conductors to the building. All service equipment and electrical panels shall
have a clear area 30" wide and 36" deep in front. This clear area
must extend from floor to ceiling with no intrusions from other equipment,
cabinets, counters, appliances, etc. Panels are NOT permitted in clothes closets
or bathrooms.
In the main service equipment, the neutral and equipment grounding conductors
are bonded together; in sub-panels, the neutral is isolated from ground. The
cold water pipe and the supplementary grounding electrode (ground rod), are
also bonded to the neutral at the service equipment. The electric meter enclosure
should be mounted at 5' 6" above finish grade, at the center of the meter
opening. Overhead drops should have a clearance of 10' above finish grade
to the bottom of the drip loop.
BRANCH
CIRCUIT WIRING
Type NM cable (also known as romex) is the wiring method most frequently used
in residential dwellings. Type NM cable must have a 90 degree conductor insulation
rating, which is designated on the cable sheath by a "B".
Type NM-B #12/2 w/ground and #14/2 w/ground are used for lighting and general
purpose receptacle circuits. #10/2 w/ground is commonly used for electric
water heaters, #10/3 w/ground for electric dryers, and #8/3 w/ground &
#6/3 w/ground for ranges and wall mounted ovens. Type "SER" cable
with an insulated neutral is permitted for electrical ranges, wall ovens and
dryers.
The cables must be protected by over-current devices (circuit breakers), which
do not exceed their rated ampacity. The rated ampacities for cable types are
listed below:
| COPPER NM CABLE | TYPE S.E. AND S.E.R. ALUMINUM CABLE |
| 15 amperes for #14 | 40 amperes for #8 |
| 20 amperes for # 12 | 50 amperes for #6 |
| 30 amperes for #10 | |
| 40 amperes for #8 | |
| 50 amperes for #6 |
It
is important to note that if you begin a circuit with #12, you must use this
same wire size throughout. You can not mix different wire sizes on
the same branch circuit.
Type NM cable must be stapled within 12" of metal boxes, 8" of plastic
boxes and every 4½ feet thereafter. Proper connectors must be used
where NM cable enters metal cabinets, boxes or panel boards.
When Type NM cable is installed parallel to framing members, or in bored holes,
it shall be located at least 1¼" from the nearest edge of the
framing member, where nails or screws may penetrate the cables. If this distance
cannot be maintained, the cable shall be protected by a steel plate or sleeve
at least 1/16" thick. Article 300-4(d).
Cable or raceway-type wiring methods installed in a groove, to be covered
by paneling, carpeting, or similar finish, shall be protected by a 1/16-inch
steel plate, sleeve, or equivalent, or must be recessed in the groove 1 ¼-inch
for the full length of the groove in which the cable or raceway is installed.
Exception: Raceways as covered in articles 345,346, 347, and 348. Article
300-4(e).
Ceiling mounted paddle fans weighing 35 pounds or less may be supported by
outlet boxes identified for such use. Fans weighing more than 35 pounds must
be supported independently of the box. Article 422-18.
a. Small Appliance Branch Circuits - The NEC requires a minimum of two 20 ampere branch circuits to feed receptacle outlets for small appliance loads, including refrigeration equipment in the kitchen, pantry, breakfast room, and dining room. These circuits, whether two or more are used, shall not supply anything other than receptacles in these areas. Lighting outlets and built-in appliances such as garbage disposals, hood fans, dishwashers, and trash compactors are not permitted on these circuits. Kitchen counter top receptacles must be supplied by at least two small appliance branch circuits. See electrical code amendments.
b. Laundry Branch Circuit - One 20 amp branch circuit must be provided for the laundry. This circuit is limited to receptacles within the laundry room. No other outlets are permitted on this circuit.
c. Bathroom Receptacles - At least one 20 amp circuit for bathroom receptacle outlets shall be supplied, such circuits may have no other outlets.
d. Exception: Where the 20 ampere circuit supplies a single bathroom, outlets for other equipment within the same bathroom shall be permitted to be supplied in accordance with 210-23a. (This circuit would not be used to supply a whirlpool bath or a hot tub!)
e. Central Heat - Central heating equipment shall be supplied by an individual branch circuit.
f. General Lighting Branch Circuits - Shall be computed on a three watts per square foot basis. You may wire up to 600 square feet of living area on a 15 ampere branch circuit or up to 800 square feet on a 20 ampere circuit. These branch circuits may supply lighting outlets in all areas of the dwelling and receptacle outlets, other than those covered in (a) - (d) above.
a. At least one outlet shall be installed in bathrooms within 36 inches of the outside edge of each basin. The receptacle outlet shall be located on a wall that is adjacent to the basin location.
b. At least one outlet in every attached garage, and one outlet in every detached garage with electric power.
c. At least two outlets installed outdoors, one on the front and one on the back of the dwelling, accessible at grade level.
d. At least one receptacle must be installed in the unfinished portion of the basement. This receptacle is in addition to any receptacles that may be installed for laundry or other specific purposes.
e. In every kitchen, family room, dining room, living room, parlor, library, den, sun room, bedroom, recreation room or similar room, or area of dwelling units, receptacle outlets shall be installed so that no point along the floor line in any wall space is more than six feet horizontally, measured from an outlet in that space, including any wall space two feet or more in width, and excluding only that space occupied by sliding panels in exterior walls. The wall space afforded by fixed room dividers, such as freestanding bar-type counters or railings, shall be included in the six foot measurement. No outlets may be installed over an electric baseboard heater.
f. In kitchens and dining areas, a receptacle outlet shall be installed at each counter space wider than 12". Countertop receptacles shall be installed so that no point along the wall line is more than 24" measured horizontally from a receptacle outlet in that space. Peninsular bars and islands 12" or wider shall have at least one receptacle.
g. Receptacles installed in the floor must use a box-receptacle combination designed specifically for that purpose. Receptacles installed in the floor within 18" of the wall may be used in place of wall mounted receptacles. A receptacle outlet is required in any dwelling unit hallway that is ten feet or more in length.
h. At least one 15 or 20 ampere, 125 volt GFCI protected receptacle must be installed at an indoor spa or hot tub location, not closer than five feet from the inside wall of the unit and not more than ten feet away from it. Light fixtures, outlets and ceiling fans over spas and hot tubs shall be a minimum of 7'6" above the maximum water level. Outdoors spa or hot tubs have the same requirements as a swimming pool. Check with your inspector for those requirements.
i. Dwelling Unit Bedrooms. All branch circuits that supply 125 volt, single phase, 15- and 20- ampere outlets installed in dwelling unit bedrooms shall be protected by an arc-fault circuit interrupter(s).
Arc-Fault Circuit-Interrupter Protection - Definition. An arc-fault circuit interrupter is a device intended to provide 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.
a. At least one wall switch-controlled lighting outlet shall be installed in every habitable room; in bathrooms, hallways, stairways, attached garages, detached garages with electric power, and at outdoor entrances or exits. The lighting outlet for interior stairways shall have a wall switch at each floor level where the difference between floor levels is six steps or more.
b. At least one wall switch controlled lighting outlet shall be installed in an attic, under-floor space, utility room, and basement, where these spaces are used for storage or contain equipment requiring servicing. The switch shall be located at the point of entry to these areas, and the lighting outlet located at or near the equipment requiring servicing.
Identification of switch leg: Circuits of 50 Volts or More. The use of insulation that is white or natural gray or that has three continuous white stripes for other than a grounded conductor for circuits of 50 volts or more shall be permitted if part of a cable assembly and where the insulation is permanently re-identified to indicate its use as an ungrounded conductor, by painting or other effective means at its termination, and at each location where the conductor is visible and accessible.
All receptacles listed below must be protected by a ground fault circuit interrupter:
a. Bathrooms receptacles.
b. All outdoor receptacles.
c. Garage receptacles except those not readily accessible such as ceiling mounted receptacles or single receptacles in dedicated spaces for appliances.
d. Kitchen receptacles that serve counter top surfaces.
e. Counter top receptacles within 6 feet of a wet bar sink.
f. All receptacles in an unfinished basement or crawl space at or below grade, with these exceptions:
g. Single receptacle within a dedicated location and identified for specific use by a cord and plug connected appliance.
h. Single receptacle serving a permanently installed sump pump.
i. Hydro-massage bath tubs.
j. Spas and Hot tubs, water features and associated electrical components.
Disconnects are required insight of the following equipment:
a. Electric hot water heaters.
b. Central heating equipment (furnaces, boilers).
c. Spas, hot tubs and water features.
d. Hydro-massage bath tubs.
e. Air conditioners
Outlet and junction boxes shall be of sufficient size to provide free space for all conductors and devices enclosed in the box. All outlet boxes have a specific volume, measured in cubic inches. For example, if you have two #12/2, with ground NM-B cables entering a box with one duplex receptacle, you would need a box with a minimum volume of 15.75 cubic inches. Each #12 that enters the box needs 2.25 cubic inches with the exception of the grounding conductor which requires one 2.25 cubic inch for all of the grounds. Also, each strap containing one or more devices is counted as the equivalent of two conductors; therefore, 2.25 x 7 = 15.75.
VOLUME REQUIRED PER CONDUCTOR:
· #6 - 5 cubic inches
· #8 - 3 cubic inches
· #10 -2.5 cubic inches
· #12 -2.25 cubic inches
· #14 - 2 cubic inches
EQUIPMENT
GROUNDING CONDUCTOR MAKE-UP
All equipment grounding conductors must be connected together with solder-less
pressure connectors such as wire-nuts or crimp sleeves, leaving sufficient
extra conductor for attachment to the metal box and/or device. When crimp
type connectors are used, they must be crimped using the tool recommended
by the manufacturer.
Please note that all metal junction and outlet boxes must be grounded by attaching
the equipment grounding conductor out of the NM cable to the metal box using
an approved screw or grounding clip. When circuit conductors are made up,
six inches of free conductor measured from the back of the box, must be left
for use in make-up and for the attachment of devices.
ELECTRIC
HEAT CIRCUITRY
Electric heat may be installed on 15, 20, or 30 amp branch circuits. Listed
below is the maximum wattage that may be installed on each size branch circuit.
(All circuits are figured at 240 v):
· 15A - 2,880 watts maximum
· 20A - 3,840 watts maximum
· 30A - 5,760 watts maximum
For example, if you are installing baseboard heaters which are rated 250 watts a linear foot, you could install 15 feet on a 20 amp, 240 volt circuit. 250W x 15 = 3,750 watts.
ROUGH-IN
INSPECTION
At the time you call for rough-in inspection, you should have all wire pulled,
stapled properly, and all splices made up and ready to accept devices and
fixtures. Please DO NOT install any devices or cover any wiring with insulation
or wall coverings, i.e., drywall or paneling. Requirements of # 9 above must
be completed prior to the rough inspection.
The building code requires hard wired battery backup smoke detectors, one
on each level, one in the hallway or area serving a sleeping room and one
in each sleeping room. Additionally in areas where the ceiling height changes
24" or more on the same level another smoke detector must be installed
in the upper ceiling level. Check the manufacture's installation instructions
for smoke detectors placement. For remodel projects check with the electrical
inspector for smoke detector requirements.
FINAL
INSPECTION
The electrical installation should be complete at the time of request. All
devices and fixtures installed, service equipment complete, and labeled properly.
All wiring shall be free from short circuits, ground faults and open circuits.
All light fixtures are required to be grounded along with light switches that
are within five feet of a grounded object.
IMPORTANT: You MUST have the Adobe Acrobat Reader on your system prior to selecting the report in order to be able to view these files.
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Last Updated: 11/14/07