EE24 BASIC ELECTRICAL ENGINEERING FOR CE LECTURE NO. B-2 Basic Electrical Code Provisions
Codes/Standards/Organizations PEC Philippine Electrical Code NEC National Electrical Code IEEE - Institute of Electrical and Electronics Engineers IEC Commission Electrotechnique Internationale ANSI American National Standards Institute CENELEC Comite Europ en de Normalisation Electrotechnique 2
Electrical Plans and Specifications SHEET SIZES: 760mm x 1000mm, 600 x 900 mm, 500 mm x 760 mm PLAN REQUIREMENTS: 1) Location and Site Plans Bordering areas showing public and well-known streets, landmarks and/or structures Location of service drop, service equipment and nearest pole of the utility company furnishing electrical energy; location of the meter as well as sizes of service entrance wires, conduits and service equipment Clearance of the path or run of service drops and entrance wires to adjacent, existing and or proposed structures 3
Electrical Plans and Specifications 2) LEGEND & SYMBOLS 3) GENERAL NOTES AND SPECIFICATIONS Nature of Electrical Service, including number of phases, number of wires, voltage and frequency Type of wiring, method of grounding Special equipment Type and rating of disconnection means, circuit protection etc. Other information important for designer, owner and contractor 4
Electrical Plans and Specifications 4) ELECTRICAL LAYOUT Floor Plan showing location of equipment and their interconnection POWER LAYOUT motors, ACUs, receptacles, appliances, etc. LIGHTING LAYOUT Lighting, fixtures, switches, etc. FIRE DETECTION AND ALARM CIRCUITS SCHEDULE OF LOADS shows list of loads with required voltage, phase, frequency, current, conductor and protection needed, conduit sizing DESIGN ANALYSIS Feeder and branch circuit wire/cabler sizing, fuse/circuit breaker/overload sizing and setting, Short Circuit Analysis, voltage drops ONE-LINE DIAGRAM Single line or schematic diagram of supply, panelboard, wire, protection, load, etc with information 5
Electrical Plans and Specifications 4) TITLE BLOCK 40 MM high at the bottom of the sheet Name and Location of installation or project Name, signature and address of the owner/manager/operator Title of the Sheet Name, signature and seal of Professional Electrical Engineer together with Professional Regulations Commission professional license number and validity, Professional Tax Receipt Number and Tax Identification Number Scale used, date drawn and Sheet number 6
Conductor Ampacity (Art 3.10) 7
Example #1 Basic Electrical Code Provisions What is the raw ampacity of 14.0 mm2 THHN wire? Ans. 70 Amperes What is the raw ampacity of 38.0 mm2 THWN wire? Ans. What is the maximum allowable temperature of THHN wire? Ans. What is the maximum allowable temperature of THWN wire? Ans. 8
Temperature Correction Factor 9
Example #2 Basic Electrical Code Provisions If the ambient temperature is 40C, determine the new maximum allowable ampacity of a 14mm2 THHN wire. Ampacity = new Ampacity old xcf ambient Ampacity new = 70 x0.91 = 63.70 10
Example #3 Basic Electrical Code Provisions If the ambient temperature is 45C, determine the new maximum allowable ampacity of a 38mm2 THWN wire. 11
Branch Circuit Conductor Sizing PEC 2.10.2.1 Branch circuit conductors shall have an ampacity not less than the maximum load to be served. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the minimum branch circuit conductor size, before the application of any adjustment or correction factors, shall have an allowable ampacity equal to or greater than the noncontinuous load plus 125 percent of the continuous load. 12
Branch Circuit Protection Sizing PEC 2.10.2.2 Branch circuit conductors and equipment shall be protected by overcurrent protective devices that have a rating or setting that complies with the following: (a) Continous and Noncontinuous Loads. Where a branch circuit supplies continuous loads or any combination of continuous and noncontinuous loads, the rating of the overcurrent device shall not be less than the noncontinuous load plus 125% of the continuous load. 13
Conductor and Protection Sizing VITAL #1: The ampacity of branch circuit conductors must not be less than the maximum load to be served VITAL #2: The maximum load to be served by the branch circuit conductors must not be more than 80% of the ampacity of the conductors. VITAL #3: The Ampacity of the branch circuit conductors must not be less than the rating of the branch circuit. VITAL #4: The rating of a branch circuit is established or defined by the rating of setting of its protective device. 14
Example #4 Basic Electrical Code Provisions Engr. Erik Libranda needs to put up an electrical circuit for his girlfriend. Her girlfriend wants to add nineteen (19) HOT incandescent bulbs with following ratings: 3 pieces 50 Watts Incandescent Bulb 15 Pieces 100 Watts Incandescent Bulb 1 Piece 25 Watts Incandescent Bulb Source Voltage is 230V Single Phase. a)determine the wire that he must use b)determine the circuit breaker he needs to buy c)if he intends to use fuse as protection, determine the rating that he needs to buy 15
Solution Basic Electrical Code Provisions 50W 100W 25W I total = 3 + 15 + 1 = 7. 28Amperes 230V 230V 230V Ampacity Re quired = 1.25 x7.283 Amperes = 9. 10Amps Use 2.0 mm2 THWN wire with Ampacity of 20 Amperes and can be loaded up to 20Amps x 0.8 =16 Amps at Ambient Temperature of 30C. Use 15 Ampere Trip 2 Pole Molded Case Circuit Breaker, 15AT 2P MCCB. You can also use 10AT 2P MCCB but not 5AT 2P MCCB. Use 15 Ampere or 10 Ampere Fuse. 16
Example #5 Basic Electrical Code Provisions Engr. Ben Mendoza to put up an electrical circuit for his ex-girlfriend. Her ex-girlfriend wants to add Ten (10) 40 Watts fluorescent lamps. The ambient temperature at the area of installation is 40C. a) Determine the total load current of the circuit b) Determine the wire that he must use c) Determine the circuit breaker he needs to buy d) If he intends to use fuse as protection, determine the rating that he needs to buy 17
Solution Basic Electrical Code Provisions Fluorescent Lamp = 40W Magnetic Ballast for 40W Fluorescent Lamp = 0.48A x 230V = 110.4W So, 1 Fluorescent Lamp is 40W + 110.4W = 150.4W I 150.4 = 12 = 7. Amperes total 230V 85 Ampacity Re quired = 1.25x 7.82 Amperes = 9. 80Amps If you intend to use 2.0mm2 THWN, the corrected ampacity = 20 x 0.88 = 17.6A And you can load it up to 17.6 x 0.8 = 14.08 Amperes Use 15AT Molded Case Circuit Breaker. 18
Example #6 Basic Electrical Code Provisions Engr. JB Co to put up an electrical circuit for his ex-friend. Her exfriend wants to add convenience outlets with following specifications: 2 Single Convenience (1 CO in 1 strap) 4 Duplex Convenience (2 CO in 1 strap) 6 Triplex Convenience (3 CO in 1 strap) Ambient temp is 40C a) Determine the total load current of the circuit b) Determine the wire that he must use c) Determine the circuit breaker he needs to buy 19
Provision Governing Dwelling CO PEC Article 2.20 Receptacle outlets shall be computed at not less than 180 Volt-Amperes for each single or multiple receptacles on one strap. A single piece of equipment consisting of a multiple receptacle comprised of four or more receptacles shall be computed at not less than 90 Volt-Amperes per receptacle. 20
Solution Basic Electrical Code Provisions 2x180VA + 4x180VA + 6x180VA I total = = 9. 39Amps 230 Ampacity Re quired = 1.25 x7.82 Amperes = 11. 74Amps If you intend to use 2.0mm2 THWN, the corrected ampacity = 20 x 0.88 = 17.6A And you can load it up to 17.6 x 0.8 = 14.08 Amperes Use 15AT Molded Case Circuit Breaker. 21
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