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 Coverage Area Figure concept taken from Reference .
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 Panel board Panel board Power supply source branch ckts Panel Board Fixed Overcurrent Protective device feeder 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 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 Utilization equipment GFCI Trip. Branch Circuit Power supply Current travelers
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)).