National Electrical Code NEC

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)).