ENGINEERING
UTILITIES 1
CHAPTER 1
ELECTRICITY
– a form of energy tied to the existence of
electrical charge and is related to magnetism
– the behavior of positively and negatively
charged elementary particles of an atom
CLASSICAL THEORY:
FLOW OF ELECTRONS
• Law of Charges
– opposite charges (positively charged
electrons) attract each other and
like charges (negatively charged
electrons) repel each other
• Electrical Flow
– electrical current
– electrons in outer orbital shells
experience a weaker attraction and
are more easily freed
MODERN THEORY:
FLOW OF CHARGED PARTICLES
– electricity is tied to even smaller subatomic
particles that possess either a positive or
negative electromagnetic charge
ELECTRIC CURRENT
– a flow of electric charge through a conductor
CONDUCTOR
– carries electrical current without providing
too much resistance to current flow
INSULATOR
– materials that resist the flow of electricity
– rated by voltage from 300 to 15000 V
SEMICONDUCTOR
– neither good conductors nor good insulators
KINDS OF ELECTRICITY
1. STATIC ELECTRICITY (FRICTION)
– rubbing two materials together
2. THERMOELECTRICITY
– from heat
3. PIEZOELECTRICITY
– from pressure
4. ELECTROCHEMISTRY
– from chemical reaction
5. PHOTOELECTRICITY
– from light
6. MAGNETOELECTRICITY
– from magnetism
UNITS OF ELECTRICITY
1. VOLTAGE / ELECTROMOTIVE
FORCE (E / EMF)
– VOLT (V)
– the driving force behind current flow
2. AMPERAGE / INDUCTIVE FLOW (I)
– AMPERE (A)
– the rate of current flow in a closed
electrical system
3. RESISTANCE
– OHM (Ω)
– affected by the length of a conductor
(wire), the diameter of the conductor,
type of conductor material, and
temperature of the conductor
OHM’S LAW
– the mathematical relationship between
current, voltage, and resistance
𝑽 = 𝑰𝑹
𝑰=
𝑽
𝑹
𝑹=
𝑽
𝑰
where V (voltage), I (amperage) and R (resistance)
ENERGY
– the amount of work or consumption value
– WATT (W)
𝒒 = 𝑷𝒕 = 𝑽𝑰𝒕
where q (energy), t (time) and P (power)
POWER
– the rate at which work is accomplished
– WATT (W)
𝑷 = 𝑽𝑰
where V (voltage), I (amperage) and P (power)
ELECTRIC CIRCUIT
– a continuous path along which an electric
current can flow
• Power Source
– e.g. battery or generator
• Load
– an electrical component that
consumes electricity
– e.g. a lamp or appliance
• Set of Conductors
– carry current from the source to the
load
– e.g. wires
TYPES OF ELECTRIC CIRCUIT
1. CLOSED CIRCUIT
– an uninterrupted path that allows a
continuous current flow through
an electrical conductor
2. OPEN CIRCUIT
– if the path of current flow in a circuit
is interrupted or turned off
3. SWITCHED CIRCUIT
– switch allows the circuit to open or
close to control operation
𝑹𝒆𝒒 = 𝑹𝟏 + 𝑹𝟐 + 𝑹𝟑 + ⋯ + 𝑹𝒏
𝑰𝒆𝒒 = 𝑰𝟏 = 𝑰𝟐 = 𝑰𝟑 = ⋯ = 𝑰𝒏
𝑽𝒆𝒒 = 𝑽𝟏 + 𝑽𝟐 + 𝑽𝟑 + ⋯ + 𝑽𝒏
𝑽𝟏 = (
𝑹𝟏
) (𝑽)
𝑹𝟏 + 𝑹𝟐
𝑹𝟐
) (𝑽)
𝑽𝟐 = (
𝑹𝟏 + 𝑹𝟐
2. PARALLEL CURCUIT
– current branches off to individual
components in the circuit
– if one lamp fails, the circuit remains
closed and all other lamps remain lit
(domino effect)
– same voltages
– Kirchhoff’s Current Law
CONTROL DEVICE
– either opens or closes the path of the circuit
PROTECTIVE DEVICE
– used to protect either the load or the
𝑹𝒆𝒒 =
conductors from excessive heat from high
amperage conditions
TYPES OF CIRCUIT CONFIGURATION
1. SERIES CIRCUIT
– current passes through each
component in the circuit without
branching off to individual
components in the circuit
– if one lamp fails, the circuit becomes
open and all lamps go out
– same currents
– Kirchhoff’s Voltage Law
𝑹𝒆𝒒 =
𝟏
𝟏
𝟏
𝟏
𝟏
+
+
+ ⋯+
𝑹𝟏 𝑹𝟐 𝑹𝟑
𝑹𝒏
𝑹𝟏 𝑹𝟐
𝑹𝟏 + 𝑹𝟐
𝑽𝒆𝒒 = 𝑽𝟏 = ⋯ = 𝑽𝒏
𝑰𝒆𝒒 = 𝑰𝟏 + 𝑰𝟐 + 𝑰𝟑 + ⋯ + 𝑰𝒏
𝑰𝟏 = (
𝑹𝟐
𝑹𝟏
) (𝑽) 𝑰𝟐 = (
) (𝑽)
𝑹𝟏 + 𝑹𝟐
𝑹𝟏 + 𝑹𝟐
KIRCHHOFF’S LAWS
– established by Gustav Kirchhoff in 1857
1. KIRCHHOFF’S VOLTAGE LAW (KVL)
– the sum of the potential differences
(voltages) in a complete circuit must
be zero
– the voltage drops around any closed
loop in a circuit must equal the
voltages applied
– the relationship between voltage
drops and voltage sources in a
complete circuit
2. KIRCHHOFF’S CURRENT LAW (KCL)
– At any specific instant at any
junction (e.g., connection), the total
current (amperage) flowing into the
junction is the same as the total
current leaving the junction
– all the current leaving that junction
must equal the current arriving at
that junction
– when a charge enters a junction, it
has no place to go except to leave
MAGNETISM
– a force of attraction between ferromagnetic
metals and a force of repulsion between
diamagnetic materials
DIRECT CURRENT
– current flow in one direction in an electrical
circuit
– from the negative to the positive terminals of
the power source
ALTERNATING CURRENT
– a continuous reversal of the direction of
current flow such that at a point in time the
current flow is in one direction and at
another point in time it is in the reverse
direction
1. SINGLE-PHASE ALTERNATING
CURRENT POWER (1Φ)
– all the voltages of the supply vary in
IMPEDANCE (Z)
– a measure of resistance to current flow on
an AC circuit due to the combined effect of
resistance, inductance and capacitance
– OHMS (Ω)
𝑽 = 𝑰𝒁
where V (voltage), I (amperage) and Z (impedance)
unison
2. THREE-PHASE ALTERNATING
CURRENT POWER (3Φ)
– three separate lines of single-phase
power with each line out of phase by
120° (1⁄3 of a cycle)
TRANSFORMER
– an electrical device that transfers an
alternating current and voltage from
one circuit to another using the induction
phenomenon
– serves as an efficient way of converting
power at a primary voltage and amperage to
the equivalent power at a different
secondary voltage and amperage
– used in transmitting and distributing power
from the power plant to a substation
𝑬𝒑 𝑬𝒔
=
𝑵𝒑 𝑵𝒔
INDUCTOR
– a coil of wire that creates an
electromagnetic field
CAPACITOR
– composed of metal plates separated by air
– stores electrical energy in an electrostatic
field and release it later
INDUCTIVE EFFECT
– peak amperage lags peak voltage
CAPACITIVE EFFECT
– peak voltage lags peak current
COMPONENTS OF AC POWER
1. REAL POWER
– working power
– performs useful effort in a circuit
(e.g., creating heat, light, and
motion)
– Watts (W) or Kilowatts (kW)
2. REACTIVE POWER
– generates the magnetic field
required for inductive devices to
operate
– dissipates no energy in the load, but
which returns to the source on each
alternating current cycle
3. APPARENT POWER
– power available to use
– Volt-amperes (VA) or
Kilovolt-ampere (kVA)
POWER FACTOR (cosϕ)
– performs useful effort in a circuit
(e.g., creating heat, light, and motion)
– Watts (W) or Kilowatts (kW)
𝑷𝑭 =
𝑷𝑭 =
𝒓𝒆𝒂𝒍 𝒑𝒐𝒘𝒆𝒓
𝒂𝒑𝒑𝒂𝒓𝒆𝒏𝒕 𝒑𝒐𝒘𝒆𝒓
𝒘𝒂𝒕𝒕𝒔
𝑾
𝒗𝒐𝒍𝒕𝒔
)
𝒂𝒎𝒑𝒔
(
=
𝑽𝑨
POWER DEMAND CHARGE
• Maximum Demand
– the user’s highest rate at which
energy is consumed over a small
time interval
• Demand Charge
– the billing fee related to maximum
demand
ENERGY CHARGE ($energy)
– the cost of electrical energy consumed
$
$
$𝒆𝒏𝒆𝒓𝒈𝒚 = (𝒒) (
= (𝑷𝒕) (
)
)
𝒌𝑾𝒉
𝒌𝑾𝒉
DEMAND LIMITING
– disconnecting loads that are not needed
during periods of high demand
LOAD SHEDDING
– nonessential equipment and appliances are
deliberately switched off to maintain a
uniform load
LOAD SHIFTING
– moves nonessential loads to periods of low
demand
TIME-OF-USE RATE
– rewards the user for reducing power
consumption during periods with high
demands
ADDITIONAL SURCHARGES
– covers the cost of metering and bill
collecting activities
CHAPTER 2
POWER STATION
– an industrial facility that houses equipment
to generate electrical energy
GENERATOR
– a mechanical device that converts
mechanical energy into electrical energy
– rotates an armature to produce current flow
ARMATURE
– a shaft with conductor windings wrapped
around an iron core
TURBINE
– a rotary engine connected to the generator
and drives the rotation of the armature shaft
STEAM TURBINE
– high pressure steam moves through the
turbine, driving rotation of discs attached to
the turbine shaft
STEAM
– produced by heating water
SERVICE ENTRANCE
– includes the components that connect the
utility-supplied wiring to the service
disconnect
SERVICE ENTRANCE EQUIPMENT
– receives the service entrance conductors
– includes a method of measuring power
(metering equipment), a method of cutting
off power (main disconnect or switch gear),
and overcurrent protection devices
(circuit breakers or fuses) that protect the
service entrance conductors
ELECTRIC METER
– an instrument that is used by the utility
company to measure and record electrical
energy consumed
SWITCHBOARD
– a large cabinet designed to divide large
amounts of electrical current into smaller
amounts
PANELBOARD
– one or more metal cabinets that serve as a
single unit
SERVICE ENTRANCE CONDUCTORS
– run between the service point and the
service equipment
SERVICE DROP
– overhead service
– an overhead electrical line running from a
utility pole
SERVICE LATERAL
– underground service
– consists of the underground service
conductors between the street main and the
first point of connection
STEP-DOWN TRANSFORMER
UTILIZATION EQUIPMENT
– secondary voltage < primary voltage
– designed to perform a specific mechanical,
chemical, heating, or lighting function
through the use of electrical energy
STEP-UP TRANSFORMER
– secondary voltage > primary voltage
APPLIANCE
– an end-use piece of utilization equipment
SINGLE-PHASE TRANSFORMER
designed to perform a specific function
– has a single primary winding and a single
1. FIXED APPLIANCES
– permanently attached installations
2. STATIONARY APPLIANCES
– situated and used at a specific
secondary winding
THREE-PHASE TRANSFORMER
– has three primary and three secondary
location but can be moved to
another outlet
windings
1. DELTA-CONNECTED
TRANSFORMER
– connected in series in the form of a
3. PORTABLE APPLIANCES
– can be easily carried or moved
ELECTRICAL DEVICE
– designed to carry but not use electricity
triangle
OUTLET
– the location in a branch circuit where
electricity is used
RECEPTACLE
– a female connecting device with slotted
2. WYE-CONNECTED
TRANSFORMER (Y)
– connected at a common point, called
a neutral or star point
OVERCURRENT RATING
– the highest amperage it can carry
continuously without exceeding a specific
temperature limit
– e.g. without overheating
INTERRUPTING RATING
– for the maximum possible fault-current
(short-circuit)
contacts
– installed at an outlet to easily establish an
electrical connection with an inserted plug
PLUG
– a male connecting device connected to a
flexible cord that’s attached to a portable
appliance
6. OCCUPANCY SENSORS
– control a lighting installation by
sensing occupants in a space
7. INFRARED SENSORS
– respond to the motion of an infrared
heat source
8. ULTRASONIC SENSORS
– emit a high-frequency sound ranging
from 25 to 40 kilohertz, above the
capacity of normal human hearing
ELECTRICAL CONDUCTOR
1. WIRE
– a common electrical conductor
– circular mil, the cross-sectional
area of the wire
2. BUS BAR
– (usually copper or aluminum)
– serves as a common connection for
two or more electrical circuits
3. BUSES
– used for power distribution
SILVER
– the best electrical conductor material and
has the least resistance of common
materials
• The type of conductor insulation determines the
environment in which it can be used safely, as it
prevents loss of power and the danger of short
circuits and ground faults.
SWITCH
– placed between electrical conductors in a
CABLE
circuit to safely and intentionally open or
close the circuit
– contains more than one conductor bundled
1. AUTOMATIC SWITCHES
– deactivate a circuit after a preset
1. NONMETALLIC-SHEATHED CABLE
– Romex
– type NM (dry, indoor applications)
time period has lapsed
2. DIMMER SWITCH
– to vary the intensity of light emitted
by the lights
3. TIME CLOCKS
– used to control the time period of
operation
4. ELECTRONIC TIMERS
– can easily be set for 7-day cycles
5. PHOTOCELL CONTROLS
– sense light and open or close a
circuit with the presence of light
together in a factory assembly of wires
and type NMC (dry and damp
applications, but not wet and
exposed conditions)
2. UNDERGROUND FEEDER CABLE
– flame retardant and moisture,
fungus, and corrosion resistant
– looks much like NM/NMC except
that the sheathing fully encases the
insulation-covered conductors
3. SERVICE ENTRANCE CABLE
– suitable for exposed above-grade
conditions
4. UNDERGROUND SERVICE
ENTRANCE CABLE
– used in underground service
applications
5. ARMORED CABLE
– BX cable
– type AC (if the insulation is rubber)
and type ACT (if the conductor
insulation is thermoplastic)
6. METAL-CLAD CABLE
– similar to armored cable except it is
not limited to the number sizes of
conductors it can carry
7. FLAT CONDUCTOR CABLE
– composed of very thin cable with
three or more conductors and
special connectors and terminals
8. THERMOSTAT CABLE
– used in applications with voltages
less than 30 V
– generally contains No. 16 AWG or
No. 18 AWG conductors
CORDS
– contains more than one conductor bundled
together in a factory assembly of wires
CONCEALED KNOB-AND-TUBE WIRING
– wiring technique using insulated conductors
strung between glass or porcelain knobs and
tubes
– the ungrounded (hot) wire is run along one
side of the joist/stud bay and the neutral is
run along the other
CONCEALED KNOB-AND-TUBE WIRING
– wiring technique using insulated conductors
strung between glass or porcelain knobs and
tubes
– the ungrounded (hot) wire is run along one
side of the joist/stud bay and the neutral is
run along the other
CONDUCTOR POWER LOSS (LINE LOSS)
– equivalent to heat produced
– the voltage must also drop
𝟐
𝑷𝒍𝒐𝒔𝒔 = 𝑰 𝑹 =
𝑽𝟐
𝑹
𝒒 = (𝟑. 𝟒𝟏𝟑)(𝑷𝒍𝒐𝒔𝒔 )
𝟏 𝑾 = 𝟑. 𝟒𝟏𝟑 𝑩𝒕𝒖/𝒉𝒓
• Feeder Busway
– used to deliver large
amounts of power with low
voltage drop (600 A to
several thousand amps)
• Plug-in Busway
– used to provide power
tap-offs at multiple points
(100 A to 3000 A sizes)
RACEWAY
– an enclosed channel designed for holding
wires, cables, or bus bars
1. RIGID METAL CONDUIT (RMC)
– looks like the galvanized steel pipe
used for plumbing applications
CONDUCTOR’S AMPACITY
– a conductor’s maximum current-carrying
capacity
• Wire Thickness
• Type of Conductor Material
• Insulation & Sheathing Type
• No. of Conductors Bundled
• Temperature and Exposure of the
Conductor
𝑰𝒂𝒎𝒑𝒂𝒄𝒊𝒕𝒚 = 𝑰𝒏𝒐𝒓𝒎𝒂𝒍 (𝑭𝒕 )(𝑭𝒏 )
ENCLOSURES
– electrical boxes and cabinets that provide
protection for conductors, and other
electrical equipment from accidental contact,
wear, corrosive atmospheric exposure, and
sunlight
1. ELECTRICAL BOXES
– hold devices and safely permit
wiring connections
– available in four primary shapes:
square, rectangular, octagonal, or
round
2. BUSWAYS
– a standardized, factory-assembled
enclosure
– used in service equipment or as
feeders, designed to carry large
amounts of current
2. INTERMEDIATE METAL CONDUIT
(IMC)
– has a thinner wall than RMC
3. ELECTRICAL METALLIC TUBING
(EMT)
– in nominal diameters up to 4 inches
4. ELECTRICAL NONMETALLIC
TUBING (ENT)
– a flame-retardant corrugated plastic
tube that is semiflexible such that it
can be bent by hand
5. RIGID NONMETALLIC CONDUIT
(RNC)
– a thin-walled pipe of PVC
– joined with fittings that are solvent
welded
6. FLEXIBLE METAL CONDUIT (FMC)
– installed without cables or wiring in
it that must be pulled
7. LIQUID TIGHT FLEXIBLE METAL
CONDUIT (LTFMC)
– covered with a plastic, watertight
jacket that is sunlight resistant
8. LIQUID TIGHT FLEXIBLE
NONMETALLIC CONDUIT (LTFNC)
– a flexible plastic conduit used in a
manner similar to FMC
9. CELLULAR CONCRETE FLOOR
RACEWAYS (CCFR)
– hollow voids in floors made of
precast concrete slabs (core slabs)
WIREWAYS (WIRE GUTTERS)
– sheet metal or nonmetallic, flame-resistant
plastic troughs that serve as a housing that
encloses and protects conductors
ELECTRIC MOTORS
– used in electrical gadgets (e.g. refrigerators)
– in HORSEPOWER (hp)
1. UNIVERSAL MOTOR
– a fractional horsepower (< 1hp)
motor designed to operate on both
AC and DC power
– available in four primary shapes:
square, rectangular, octagonal, or
round
2. SPLIT-PHASE MOTOR
– operates on single-phase AC only
– not capable of starting heavy loads
3. CAPACITOR MOTOR
– have a capacitor that stores and
discharges energy to help start the
motor rotor
4. INDUCTION MOTOR
– uses electromagnetic induction to
cause the motor rotor to turn
5. MOTOR CONTROLLER
– a switching device designed to start,
stop, and protect the motor
6. VARIABLE-FREQUENCY DRIVE
– a solid-state electronic power
conversion device used for
controlling the rotational speed of an
AC electric motor
• Electrocution occurs when a small amount of
electrical current (0.006 to 0.2 A) flows through
the heart for 1 to 3s.
GROUND FAULT CIRCUIT INTERRUPTER
(GFCI)
– an electrical device that detects an
extremely low leak (6 mA) of electrical
current and acts quickly to shut off power
1. RECEPTACLE OUTLET TYPE
– used in place of standard duplex
convenience outlets that are
commonly found throughout the
house
2. CIRCUIT BREAKER TYPE
– gives protection to the entire branch
circuit
– interrupts power in the event of a
ground fault and trips when a short
circuit or a power overload occurs
3. PORTABLE TYPE
– can be plugged into a convenience
outlet so an electrical appliance
plugged into the GFCI is protected
ARC FAULT
– an unintentional electrical discharge
characterized by low and erratic current
– caused by the breakdown of the protective
insulation that surrounds household wiring
1. PARALLEL ARCING FAULTS
– result from direct contact of two
wires of opposite polarity
2. GROUND ARCING FAULTS
– arcs between a single conductor and
ground
3. SERIES ARCING FAULTS
– occur across the break of a single
conductor
TEMPER-RESISTANT RECEPTACLES
– have built-in shutter systems that prevent
foreign objects from touching electrically live
components when these are inserted into
the slots
ARC FAULT CIRCUIT INTERRUPTER
(AFCI)
– provides enhanced protection from fires
– detects low-level arc faults that traditional
OCP devices cannot detect
GROUND FAULT
– the unintentional flow of electrical current
between a power source
– occurs when electrical current leaks or
escapes to ground
1. CONVENIENCE OUTLET TYPE
– for protecting connected cord sets
and power supply cords
2. CIRCUIT BREAKER TYPE
– with protection provided to branchcircuit wiring
3. PORTABLE TYPE
– for protecting connected cord sets
and power supply cords that can be
moved from outlet to outlet
4. CORD-MOUNTED TYPE
– for protecting the power-supply cord
connected to it
NUISANCE TRIPPING
– the tendency for GFCIs and AFCIs to trip
frequently
EXTREMELY LOW-FREQUENCY
ELECTROMAGNETIC FIELDS (EMF)
– silent, invisible magnetic fields produced any
time electricity runs through a wire, an
appliance, or piece of equipment
GROUND FAULT PROTECTION (GFP)
– designed to detect and rapidly interrupt
low-level equipment ground faults
POWER SURGE
– a sudden increase in electrical current or
voltage that is very short in duration
– may be caused by a lightning strike or from
a sudden power spike
SURGE PROTECTION DEVICE (SPD)
– prevents power surges from reaching
electric and electronic equipment
– diverts the surge by allowing the current to
flow past rather than through the protected
equipment
1. METAL OXIDE VARISTOR (MOV)
– has surge ratings ranging from a few
hundred to many thousands of amps
2. GAS DISCHARGE TUBES (GDT)
– a primary surge protection
component
– comprised of a sealed tube
containing a special gas that breaks
down at a given voltage rise time
3. ZENER DIODE
– a secondary surge protection
component
– used for accurate clamping of surge
voltages
4. HYBRID CIRCUIT
– comprising different types of surge
protection component, taking
advantage of each component’s
strengths
INRUSH CURRENT
– the peak instantaneous current drawn by an
electrical appliance when it is first turned on
CHAPTER 3
THE ELECTRICAL CODE
– design of an electrical system involves
applying the standards written into the
building code
– specifies the minimum provisions necessary
for protecting people and property from the
improper use of electricity and electrical
– applies to both the manufacture and
installation of electrical equipment
NATIONAL ELECTRICAL CODE (NEC)
– a set of specifications and standards in the
form of a model code that can be adopted
into local law
PHILIPPINE ELECTRICAL CODE (NEC)
– establish basic materials quality and
electrical works standards for the safe use of
electricity
– ensure safety and prevent electrical fires
– practical safeguarding of persons and
property from hazards arising from the use
of electricity
MANUFACTURING STANDARD
– an approved product meets minimum
safety standards as determined by
extensive testing by an independent
testing company or organization
NATIONAL ELECTRICAL
MANUFACTURING ASSOCIATION (NEMA)
– the leading trade association in the
United States representing the interests
of electrical manufacturers
LICENSING
– the person must have a minimum number of
years of experience working with a licensed
electrician and must pass a written test that
deals with the electrical code being used and
with methods of installation
– assurance that the electrician knows, at a
minimum, the code requirements and the
installation procedures
PERMITS
– issued before any electrical installations may
be made on a project
– a complete electrical construction drawing
may also be required for review and
approval by a plans examiner
– have electrical inspectors who check the
project during regularly scheduled visits and
inspect the installation after the rough wiring
is in
ELECTRICAL CONSTRUCTION
DRAWINGS
– show the layout and design of an electrical
installation
– needed to convey design information to the
contractor
• Complete Plans and Specifications of
All Electrical Work
• Labeling Criteria of All Electrical
Equipment
• Light Floor Plans
• Power Floor Plans
• Exit Signs and Power Supply
• Lighting Fixture Schedule
• Symbol Schedule and Diagrams
SUPPLY VOLTAGES
– nominal voltage as it varies slightly
– used when power is delivered by the utility
company to the user
SYSTEM VOLTAGES
– the target voltage entering the service panel
– the principle voltages available in a building
• Medium & High Voltage Systems
– carry voltages above 600 V
– found in industrial and commercial
installations (e.g. large signage)
• Low Voltage Systems
– carry voltages less than 600 V
CIRCUIT WIRING
1. UNGROUNDED CONDUCTOR (HOT)
– the current-carrying conductor in an
alternating current system
– feeds current to the circuit
– provides power to the load
2. GROUNDED CONDUCTOR
(NEUTRAL)
– the ground leg of the circuit
– completes the circuit by connecting
the ungrounded conductor to ground
– serves more than one circuit
– carries the unbalanced load
between two ungrounded
conductors
– provides a path from the load back
to the power source
3. GROUNDING CONDUCTOR
(GROUND)
– provides additional protection
– energized only on a temporary,
emergency basis when there is a
fault between an ungrounded (hot)
conductor and any metal
• System Grounding
– that part of a building
electrical system that
provides protection against
electrical shock, lightning,
and fires
• Equipment Grounding
– grounding path that
connects the
noncurrent-carrying metal
components of equipment
480 Y/277 V AC, 3PHASE-4W
– a common electrical service in most modern
medium to large commercial buildings
– the 480 V three-phase power is used to
power specially designed heavy machinery
600 Y/346 V AC, 3PHASE-4W
– used to also power specially designed heavy
machinery, but 600 V and 346 V are
available in the circuit or feeder
configurations
UTILIZATION VOLTAGE
– accounts for anticipated voltage drops on
branch circuit conductors
LINE VOLTAGE
– measured voltage at an outlet or connection
MAXIMUM VOLTAGE
– the highest voltage to which a wiring device
can be exposed
LOAD BALANCING
120 V AC, 1PHASE-2W
– used to serve outbuildings and farm
buildings because its use is limited to
buildings with loads up to 6000 VA (50 A)
– the practice of dividing loads as evenly as
possible between the ungrounded
conductors
120/240 V AC, 1PHASE-3W
– the most common residential electrical
service in use today
– used on a limited basis in light commercial
buildings (e.g. small office buildings,
churches, and retail shops and stores)
– a 120 V branch circuit : convenience outlets,
small appliances,
and light fixtures
– a 240 V branch circuit : large appliances and
equipment
– a 120/240 V branch circuit : both 120 V and
240 V to an
appliance
208 Y/120 V AC, 3PHASE-4W
– an older electrical service found in small
commercial buildings and high-rise buildings
where three-phase motors (motors above
about 1⁄2 horsepower) and equipment are
used
DOUBLE INSULATION
– protects the user from electric shock by
creating a nonconducting barrier between
the user and the electric components
RESIDENTIAL SYSTEMS
– normally served by a 120/240 V, three-wire,
single-phase service entrance
MULTIFAMILY DWELLINGS
– e.g. apartments and condominiums
– power is brought from a utility transformer to
the building service equipment
– divided at a main distribution panel, passes
through individual meters, and is distributed
to the individual dwelling units through
feeders
COMMERCIAL/INDUSTRIAL SYSTEMS
BUNDLING CORRECTION FACTOR
– electrical power is provided to a transformer
– must be applied for four or more conductors
located outside the building
– enters a transformer vault located at the
service level in the building
in a raceway or cable installed in the same
raceway or conduit or any bundled cables
that are more than 24 in (0.63 m) long
– enters a transformer vault located at the
service level in the building
GOOD ELECTRIC CONDUCTORS
– substances with extremely low resistance to
current flow
1. Silver
2. Copper
3. Aluminum
4. Nickel
5. Brass
6. Zinc
7. Platinum
8. Iron
9. Lead
10. Tin
KINDS OF INSULATORS
1. Rubber
2. Porcelain
3. Varnish
4. Slate
5. Glass
6. Mica
7. Latex
8. Asbestos
9. Paper
10. Oil
11. Wax
12. Thermoplastic
AMBIENT TEMPERATURE
– the temperature of a surrounding medium
affecting allowable current-carrying capacity
of a conductor
AMBIENT TEMPERATURE RATING
– the normal temperature range in the
environment in which that conductor is to
be used
VOLTAGE DROP
𝑉𝑑𝑟𝑜𝑝 =
2𝐿𝑅𝐼
1000
INSULATION COLOR CODING AND
IDENTIFICATION MARKINGS
– the commonly used but not mandatory color
sequence of conductors serving single
phase circuiting
BRANCH CIRCUIT
– extends beyond the final overcurrent
protection device that is protecting a circuit
– power from a circuit breaker or fuse
1. INDIVIDUAL BRANCH CIRCUIT
– serves only one receptacle or piece
of equipment
– dedicated or special purpose circuit
2. GENERAL PURPOSE BRANCH
CIRCUIT
– supplies two or more outlets for
lighting and appliances
– lighting circuit
3. APPLIANCE BRANCH CIRCUIT
– supplies energy to outlets to which
appliances are to be connected
– supplies fixed electric equipment
– cannot exceed 20 A
4. MULTIWIRE BRANCH CIRCUIT
– consisting of two or more
ungrounded conductors having a
voltage between them and a
common grounded conductor
5. LIFE SAFETY BRANCH CIRCUIT
– provides adequate power to patients
and personnel
6. CRITICAL BRANCH CIRCUIT
– intended to provide power to task
illumination, special power circuits,
and selected receptacles serving
areas and functions
7. SPLIT WIRING RECEPTACLES
– fed with a 120/240 V circuit having
two ungrounded (hot) conductors, a
grounded (neutral) conductor, and a
grounding conductor
CONNECTED LOAD
– the sum of all loads connected in a circuit