national electrical code® (nec®) electrical blueprints reading uprb professional studies program...
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National Electrical Code® (NEC®)
Electrical Blueprints ReadingUPRB
Professional Studies ProgramProf. 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 Coverage Area
Figure concept taken from Reference [1].
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
Power supply source
Panel board
Power Panelboard
sub-feedermain-feeder
feeder
branch ckts
branch ckts
Panel Board
Fixed OvercurrentProtective
device
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 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).
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).
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)
NEC® - Wiring and ProtectionBranch Circuits
• Ground Fault Circuit Interrupter
Trip.GFCI
Utilization equipment
Current travelers
BranchCircuitPower supply
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)).