ee24 basic electrical engineering for...

Mapua Institute of TechnologySchool of Electrical, Electronics and Computer Engineering

Engr. John C. Placente, MSEE

BASIC ELECTRICAL BASIC ELECTRICAL

ENGINEERING FOR CEENGINEERING FOR CE

LECTURE NO. B-2

Basic Electrical Code Provisions

EE24

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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 Electro-technique

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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

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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

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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

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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

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Conductor Ampacity (Art 3.10)

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Example #1

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.

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Temperature Correction Factor

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Example #2

If the ambient temperature is 40C, determine the new maximum allowable ampacity of a 14mm2 THHN wire.

ambientoldnew xCFAmpacityAmpacity =

70.6391.070 == xAmpacity new

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Example #3

If the ambient temperature is 45C, determine the new maximum allowable ampacity of a 38mm2 THWN wire.

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Branch Circuit Conductor Sizing

PEC 2.10.2.1Branch 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.

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Branch Circuit Protection Sizing

PEC 2.10.2.2Branch 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.

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Conductor and Protection Sizing

VITAL #1: The ampacity of branch circuit conductors must not be less thanthe 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.

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Example #4

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

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Solution

AmperesV

W

V

W

V

WItotal 28.7

230

251

230

10015

230

503 =

+

+

=

AmpsAmperesxquiredAmpacity 10.9283.725.1Re ==

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.

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Example #5

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

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SolutionFluorescent Lamp = 40W

Magnetic Ballast for 40W Fluorescent Lamp = 0.48A x 230V = 110.4W

So, 1 Fluorescent Lamp is 40W + 110.4W = 150.4W

AmperesV

Itotal 85.7230

4.15012 =

=


If you intend to use 2.0mm2 THWN, the corrected ampacity = 20 x 0.88 = 17.6AAnd you can load it up to 17.6 x 0.8 = 14.08 Amperes

Use 15AT Molded Case Circuit Breaker.

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Example #6

Engr. JB Co to put up an electrical circuit for his “ex-friend”. Her “ex-friend” 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

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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.

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Solution

AmpsVAxVAxVAx

Itotal 39.9230

180618041802 =

++=


If you intend to use 2.0mm2 THWN, the corrected ampacity = 20 x 0.88 = 17.6AAnd you can load it up to 17.6 x 0.8 = 14.08 Amperes

Use 15AT Molded Case Circuit Breaker.

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