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National Electrical Code

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Title: National Electrical Code


1
National Electrical Code (NEC)
  • Electrical Blueprints Reading
  • UPRB
  • Professional Studies Program
  • Prof. Jaime Jose Laracuente-Diaz

2
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.

3
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.

4
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).

5
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.

6
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

7
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

8
NEC
  • Annex E Types of Construction
  • Annex F Cross Reference Tables
  • Annex G Administration and Enforcement

9
NEC Coverage Diagram
Generation Area
Substation Area
Coverage Area
Figure concept taken from Reference 1.
10
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.

11
NEC
  • Introduction (Article 90)
  • Permissive rule
  • One allowed but not required (an alternative)
  • These alternatives are highlighted using the term
    shall be permitted.

12
NEC - General Portion
  • General Portion
  • (Articles 100) Definitions
  • (Articles 110) Requirements for electrical
    installation.

13
NEC - General Portion
sub-feeder
main-feeder
Panel board
Power Panel board
Power supply source
branch ckts
Panel Board Fixed Overcurrent Protective
device
feeder
branch ckts
14
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

15
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.

16
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

17
NEC - Wiring and Protection
  • (Article 240) Over-current Protection
  • (Article 250) Grounding
  • (Article 280) Surge Arresters
  • (Article 285) Transient Voltage surge
    suppressors

18
NEC - Wiring and ProtectionGrounded 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).

19
NEC - Wiring and ProtectionGrounded 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).

20
NEC - Wiring and ProtectionBranch 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
    20-A 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)

21
NEC - Wiring and ProtectionBranch Circuits
  • Ground Fault Circuit Interrupter

Utilization equipment
GFCI
Trip.
Branch Circuit Power supply
Current travelers
22
NEC - Wiring and ProtectionBranch 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)).
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