National Electrical Code®
(NEC®)
Electrical Blueprints Reading
UPRB
Professional Studies Program
Prof. Jaime Jose Laracuente-Diaz
NEC®
• 1879
– Thomas Alva Edison - First practical incandescent light bulb
– National Association of Fire Engineers met to discuss standards
for electrical installation.
• 1895
– There were five separate codes in the USA.
• 1896
– A meeting was held between various organizations to define a
code.
• 1897
– The National Electrical Code was adopted and is often referred
as the Code.
NEC®
• National Fire Protection Association
(NFPA) is now the sponsor association for
the Code.
• It is officially endorsed by the American
National Standards Institute (ANSI).
• The NFPA Electrical Code Committee
NEC® is named as the ANSI Standards
Committee C1.
NEC®
• Purpose:
– “practical
safeguarding of persons
and property from hazards arising
from the use of electricity”
• It is meant as a legal document which
could be interpreted by governmental
bodies and agencies with jurisdiction on
this matter (electrical installations).
NEC®
• The Code generally applies to the
installation of electrical conductors and
equipment within private and public
facilities up to the connection point to the
power source.
NEC®
• NEC Areas:
– Introduction
– (1) General
– (2) Wiring and Protection
– (3) Wiring Methods and Materials
– (4) Equipment for General Use
– (5) Special Occupancies
– (6) Special Equipment
NEC®
•
•
•
•
•
(7) Special Conditions
(8) Communication Systems
(9) Tables
Annex A: Product Safety Standards
Annex B: Information for Ampacity
Calculation
• Annex C: Conduit and Tubing Fill table
• Annex D: Examples
NEC®
• Annex E: Types of Construction
• Annex F: Cross Reference Tables
• Annex G: Administration and Enforcement
NEC® Coverage Diagram
Generation Area
Substation Area
Figure concept taken from Reference [1].
Coverage Area
NEC® Coverage
• It is important to mention that the NEC is
the most used standard in the USA and it
is basically complemented with local
codes and regulations in different states,
cities or counties.
• Other
regulations
applies
to
the
generations and distribution process of
electrical power.
NEC®
• Introduction (Article 90)
• Permissive rule
– One allowed but not required (an alternative)
– These alternatives are highlighted using the
term “shall be permitted”.
NEC® - General Portion
• General Portion
– (Articles 100): Definitions
– (Articles 110): Requirements for electrical
installation.
NEC® - General Portion
sub-feeder
main-feeder
Power
supply
source
feeder
Power
Panel
board
Panel
board
branch ckts
Panel
Board
Fixed
Overcurrent
Protective
device
branch ckts
NEC® - General Portion
• Overcurrent
– Any current in excess of rated current.
• The selection of proper conductor size is
extremely important to avoid this situation.
– AWG = American Wire Gage
NEC® - General Portion
• Example:
– We have a wire of unknown gage but the give
diameter is 0.2591 [cm]
• Convert the diameter from [cm] to [inches].
• Use the AWG table to identify the AWG number
given the wire diameter in inches.
NEC® - Wiring and Protection
• Wiring and Protection
– (Article 200): Grounded Conductors
– (Article 210): Branch Circuits
– (Article 215): Feeders
– (Article 220): Branch Circuit, feeder and
service calculations
– (Article 225): Outside Branch Circuits and
Feeders
– (Article 230): Services
NEC® - Wiring and Protection
– (Article 240): Over-current Protection
– (Article 250): Grounding
– (Article 280): Surge Arresters
– (Article 285): Transient Voltage surge
suppressors
NEC® - Wiring and Protection
Grounded Conductors
• Grounded Conductor
– It is intentionally grounded.
– For example: the neutral wire of an electrical
system
– It is identified by a white o natural gray outer
finish or by three continuous white stripes on
other than green insulation (See Article
200.6).
NEC® - Wiring and Protection
Grounded Conductors
• Grounding Conductor
– It is used to connect equipment or the
grounded circuit (neutral) of a wiring system
to a grounding electrode and which is colored
green (See Articles 100 and 250.119).
NEC® - Wiring and Protection
Branch Circuits
• How do I calculate the number of branch
circuits required in a building?
– The section 210.11 of the Code is used for
this purpose.
– For example:
• A dwelling unit is required to have two or more 20A small appliance branch circuits beyond that
calculated, one 20-A branch circuit for laundry and
one 20-A branch circuit for each bathroom.
(Section 210.11 C)
NEC® - Wiring and Protection
Branch Circuits
• Ground Fault Circuit Interrupter
GFCI
Trip.
Branch
Circuit
Power
supply
Current travelers
Utilization equipment
NEC® - Wiring and Protection
Branch Circuits
• Ground Fault Circuit Interrupter
– Are required to be installed outdoors and in
dwelling units bathrooms, garages, crawl
spaces, unfinished basements, kitchens, wet
bar sinks, and boat houses. (See Section
210.8 (A)).