Electrical Flashcards
1
Q
Which of the following building types would have the most stringent requirements for fire alarm and fire suppression systems? A. motel B. nursing home C. office building D. print shop
A
B. Nursing home Occupants of institutional buildings, such as hospitals, prisons, and nursing homes, often have limited mobility and require more warning and time to evacuate.
2
Q
What are transformers used for?
A
Used to change ac voltages up or down
3
Q
Information regarding the minimum number of plumbing fixtures required for various occupancies may be found in which of the following sources? A. building codes B. plumbing codes C. both plumbing and building codes D. the local authority having jurisdiction
A
C. both plumbing and building codes
12
Q
Interior doors are not to exceed _____ opening force.
A
5 lbs
13
Q
- Which one is not a disadvantage of aluminum conductors? a) Cold flow under pressure b) Splicing and terminating difficulties c) Vulnerability to oxidation d) Weight
A
d) Weight
14
Q
What is a disadvantage of Cable tray? a) It is free-air rated b) Installation and maintenance is costly c) It is not accessible easily d) It does not work for high wattage
A
c) It is not accessible easily
15
Q
Which statement is correct ? a) Conduits can have diameter 1/3 of the slab thickness. b) Conduits running parallel can be spaced as close as .5” far apart. c) Min cover over conduit shall be 3⁄4”
A
c) Min cover over conduit shall be 3⁄4”
16
Q
How much cost under floor duct system would add to the building’s electric system cost? 1) 10% 2) 30% 3) 40% 4) 50%
A
4) 50%
17
Q
What is the appropriate length of ground Rod ? a) 2’min – 4’ Max b) 4’min – 6’ Max c) 6’min – 8’ Max d) 8’min – 10’ Max
A
d) 8’min – 10’ Max
18
Q
What are the max height of switch box and min height of the receptacle above the finished floor? a) 48” max- 15” min b) 44” max- 18” min c) 48” max- 18” min d) 44” max- 15” min
A
a) 48” max- 15” min
19
Q
What is the min space requirement around high voltage switchgear? a) 3’-6” b) 5’ c) 6’ d) 8’-6”
A
c) 6’
21
Q
When is electric wiring system being inspected by local authorities? I) After raceways been installed II) After the entire job is complete III) After the equipment is installed a) I, II b) I, III c) II, III d) I, II, III
A
a) I, II
22
Q
Which one is not the characteristic of Parallel circuits? a) It has one branch connected between the same two points. b) Loads on the current are additive c) The same voltage is imposed on each load. d) It is the standard circuit arrangement in all building wiring.
A
a) It has one branch connected between the same two points.
25
Q
What is the predominant use of electrical power in a building? a) Motor b) Lighting c) Heating d) HVAC
A
b) Lighting
26
Q
What is the minimum gauge wire allowed in construction? a) 12 b) 14 c) 16 d) 18
A
b) 14
27
Q
Name the 3 different plant types a. Electric, hydronic, and forced air b. Boiler/chillers, Refrigeration cycle, Heat pump c. Single pipe, two pipe, three pipe d. Single duct, electric reheat, dual duct
A
b. Boiler/chillers, Refrigeration cycle, Heat pump
28
Q
The Hydronic system that may only be extended a very limited distance because each subsequent register gets colder is: a. single pipe b. two pipe c. three pipe d. four pipe
A
a. single pipe
29
Q
If both heating and cooling are desired a separate two pipe system can be provided for each, Resulting in a ______ a. Single pipe system b. Two pipe system c. Three pipe system d. Four pipe system
A
d. Four pipe system
30
Q
A ______ mixes both the hot and cold in a common return pipe. a. Single pipe system b. Two pipe system c. Three pipe system d. Four pipe system
A
c. Three pipe system
31
Q
True or False: electrical systems are the most expensive first costs and the least expensive in life cycle cost.
A
False
32
Q
A small Valve in the base of the cooling tower is called a ______ a. Evaporator b. Downdraft c. Condenser d. Blowdown
A
d. Blowdown
33
Q
- the Heat Pump ______ a. Creates heat energy b. Moves heat energy c. Harnesses heat energy
A
b. Moves heat energy
34
Q
A Prescriptive code: a. State what the final results need to be and how it will be measured, but does not specify how the result is to be achieved. b. States how to build a building.
A
b. States how to build a building.
35
Q
Makeup air handling unit is ______ a. An HVAC system that pulls outside air into the serviced room through the mechanical unit. Used with large buildings that would otherwise require extensive ducting. Used when separate utility bills are required. b. Refers to the cooling air, the treatment of the air for temperature and humidity control, air quality and circulation. c. Air handling unit specifically design to apply 100% outside air to the space. This outside air replaces air lost through exhaust fans or the building envelope. d. Air handling unit specifically design to apply 50% outside air to the space. This outside air mixes with internal in the building.
A
c. Air handling unit specifically design to apply 100% outside air to the space. This outside air replaces air lost through exhaust fans or the building envelope.
37
What is the requirement for ductwork in a fire rated wall? a. Fire damper b. Fire blanket c. Fire stopping d. Fire Alarm
a. Fire damper
42
What does a compression tank do for a boiler?
Accommodates the expansion of the water in the system
44
How is an EMT conduit system joined together?
Set screw and pressure fittings
45
Why is EMT and IMC conduit more cheaper to install over rigid steel conduit?
Both are lighter and both have larger inside diameters (ID) and therefore easier wire pulling
46
True or false. Ordinary steel pipe may be used for conduit?
False
47
When steel conduit is installed in direct contact with earth, how should the conduit be treated?
is is advisable to coat joints with asphaltum. If earth is wet, the entire system should be coated with waterproofing. Alternatively, a plastic jacket conduit can be used
48
Conduit size depends on what?
maximum permissible temperature of the contained conductors. number and diameter of the wires that may be drawn into the conduit without injuring the wire
49
True or false. It is preferred to wait for wire installation until conduit inspection has finished
True
50
What are the advantages of using aluminum conduit?
better corrosion resistance in most atmospheres non magnetic generally doesn't require painting
51
What is the main drawback of using aluminum conduit?
it has a deterious effect on many types of concrete when embedded It is also inadvisable to bury aluminum conduit in earth without asphalt or another coating because of corrosion
52
Where is flexible metal conduit most often used?
used for motor connect and other connections where vibration is present
53
Where is nonmetallic conduit most often used?
indoor exposed use PVC plastic conduit can be used for outdoor and underground use
54
What is the main drawback for nonmetallic conduit?
a separate ground wire must be provided because the ground provided by a metallic conduit is absent
55
The simultaneous production of electricity and heat from a single fuel source is known as what?
Cogeneration
60
What precautions should be taken if aluminum wiring is used in a building ?
Leads should be cleaned prior to making connections, licensed electricians should be used for installation, larger sizes of copper wire is necessary to carry same amperage
61
Codes limit the number of conductors permitted in a conduit for what reasons?
Control heat buildup, prevent damage to conductors being pulled through conduit
62
What is load control?
A technique used to avoid peak demand electrical charges by automatically or manually shutting off nonessential electrical loads before the peak demand is reached
63
When is multiple metering used?
It is used only for multi tenant spaces
64
What type of space would you find a ceiling raceway used for electrical distribution?
Spaces that require frequent layout and programmatic changes (merchandising space, educational classrooms)
65
What is the primary advantage of ceiling raceways?
Even more flexible than underfloor counterparts, energize lighting, provide telephone and power facilities, can supply outlets to floor above
66
What are the advantages and disadvantages of under carpet wiring systems?
Advantages include simple, low cost installation Disadvantages include interfacing problems with conventional wire
67
What are full access floors?
Floor constructed of light weight die cast aluminum panels supported on a network of adjustable steel or aluminum pedestals
68
What criteria does a building need to meet in order to justify the usage of full access floors
Heavy cabling requirement, particularly if frequent recalling and reconnection are required
69
What are the primary advantages of both cellular metal floor raceway and precast cellular concrete floor raceways?
Large capacity, versatility in that each cell is a potential raceway, and flexibility in outlet placement and movement
70
Because underfloor duct systems are expensive, what criteria must a building meet in order to justify its usage?
1) floor areas with a requirement for outlets at locations removed from walls and partitions 2) 2) under carpet wiring is inapplicable 3) outlets from ceiling systems are unacceptable 4) frequent rearrangement of furniture and other items requiring electrical and signal service is anticipated
71
What are the primary disadvantages of underfloor electrical distribution systems?
They are expensive, and become inflexible once the system is cast into concrete
72
What is an underfloor duct?
An arrangement of parallel rectangular metal or heavy plastic raceways laid on the structural slab and covered with concrete
73
What are ceiling raceways? And what are the advantages of them in electrical distribution?
Very flexible and most economic as compared to under floor distribution systems
74
Outlets within 6’ of sink must be protected using what?
Ground Fault Circuit Interrupter
75
No point is no more than what distance away from an outlet
6 ft
76
What is the typical distance between outlets?
12 ft
77
Where are surface metal raceways most typically used? What is the typical voltage contained within this type of conduit?
Only in dry, nonhazardous, noncorrosive locations. Typically contains wiring below 300 V
78
What are the principle applications of surface metal raceways?
1. Where economy in construction weighs very heavily in favor of surface raceways and where expansion is anticipated 2. Where outlets are required at frequent intervals and where rewiring is required and anticipated 3. Where access to equipment in the raceway is required and/or where necessary due to the nature of the wiring 4. Where we wish to avoid the extensive and expensive cutting and patching required to bury a raceway during rewiring
79
What is a switchgear?
A central electrical distribution center that serves to distribute power to parts of a large building.
80
Electrical systems in single family homes and duplexes commonly use which type of conductor?
nonmetallic sheathed cable
81
What is the trade name for nonmetallic sheathed cable? What is it?
Romex. It constists of two or more conductors and a ground wire encased in a plastic jacket. This type of unprotected cable is permitted in wood framed residential buildings and buildings not exceeding three stories as long as it is conealed behind wll and ceilings.
82
What type of conductors are typically used in commercial construction or in hazardous areas?
Individual conductors placed in rigid metal conduit, such as electric metal tubing (EMT), intermediate metal conduit (IMC), or rigid steel conduit.
83
What is the trade name for flexible metal clad cable? Where is it typically used\>
BX. It consists of two or more conductors inside a continuous inside a continuous spiral wound strip of steel cable. This cable is used where metal shielding is required along with the flexibility to remodel or to connect fixtures that may need to be moved.
84
What is this switch?
3 pole solid neutral
85
What is this switch?
single pole single throw
86
What is this switch?
double pole double throw
87
What is this switch?
single pole double throw center off
88
What is this switch?
single pole double throw (3 way switch)
89
What is this switch?
2 three way switches
90
Where are wye-delta transformers used?
Commonly used in a step-down transformer, wye connection on the HV side reduces insulation costs, the neutral point on the HV side can be grounded,
91
Where are delta wye transformers used?
stable with respect to unbalanced loads.
92
Where are delta delta transformers used?
Commonly used in a step-up transformer for the same reasons as above.
93
Where are wye-wye transformers used?
Offers the advantage that one of the transform- ers can be removed while the remaining two transformers can deliver three-phase power at 58% of the original bank.
94
What is this transformer system?
delta delta system
120v/240v
3 phase 4 wires
without the neutral this can be a 240v 3p 3w ora 480v 3p 3w
95
What transformer system is this?
delta wye
120/208 v 3p 4w
277/480v 3p 4w
96
what is this?
120/208 v 3p 4w
97
What is this?
120/240v 1p 3w
98
In a simple alternating current circuit serving incadescent lamps, the amperage in the circuit is calculated by
dividing the total wattage by the circuit voltage
W=IV
99
A power distribution system is to be specified for an open office area. Which of the following is the most flexible and economical?
ceiling raceway system with pole raceways
100
What is a full access floor?
It's an electrical distirbution system that consists of indivudal panels, typically 24 in square, supported on adjustable pedestals above the structural floor. These systems provide unlimited flexibility for routing power, communications, and air supply, but are expensive and not justified unless a great deal of cabling is involved or future changes will be extensive (such as in a computer room)
101
What is a an underfloor raceway?
An electrical distribution system that consists of a series of parallel rectangular metal raceways laid on the structural slab and covered with concrete.
102
What is a cellular metal floor raceway?
It is similar to an underfloor racewayin that it consists of a series of parallel rectangular metal raceways but it is part of the structure.
103
What are electrical raceways?
raceways are similar to standard metal decking and serve as conduits for power and communication cabling. In both underfloor and cellular metal floor systems, the raceways are tapped when power and communitaction outlets are required.
104
Electrical operating costs in a single-tenant commercial building can be minimized by using which of the following techniques?
I. daylighting
II. indirect lighting
III. load control
IV. multiple metering
I. daylighting III. load control
105
What is load control?
It's a way of avoiding peak demand electrical charges by automatically or manulayy shutting off nonessential electrical loads before the peak demand is reached
106
Codes limit the number of conductors permitted in a conduit for which two of the following reasons?
I. to maintain maximum ampacity
II. to control heat buildup
III. to minimize problems with harmonic currents
IV. to prevent damage to conductors when they are pulled through the conduit
II. to control heat buildup
IV. to prevent damage to conductors when they are pulled through the conduit
107
When are harmonic current a problem?
Only with unconventional electrical loads such as computers, electronic lighting ballasts, and other electronic equipment
108
Which of the following precautions should be taken if aluminum conductors are used in a building?
I. leads should be cleaned prior to making connections
II. Special conduit should be specified
III. Licensed electricians should be required to perform the installation
IV. All joints should be soldered
V. Larger sizes will be needed than if copper conductors were used.
I. leads should be cleaned prior to making connections
III. Licensed electricians should be required to perform the installation
V. Larger sizes will be needed than if copper conductors were used.
Because of the potential for oxidation, the leads of alumnum conductors must be cleaned prior to installation. The special requirements of aluminum conductors and the danger of incorrect installation make it necessary that a licensed electrician do the work. ALuminum conductors must be larger than copper conductors to carry the same amperage.
109
High voltages are used in commercial buildings because...?
...conductors and conduit can be smaller.
As volages increase, current may be decreased and the system will provide the same amount of power. Lower current require smaller conductors. For large commercial building, smaller conductors translate to less expense in conductors and conduit, as well as easier installationof smaller wires.
110
Which would be the best location for a transformer for a large school building?
A. on the power pole serving the building
B. in a separate room near the exterior wall
C. outside, on a transformer pad close tot he main switchgear
D. in a protective shed where power from the utility company enters the property.
B. in a separate room near the exterior wall
A transformer vault near the exterior wall woulf be the best choice for protection, ventilation, and ease of installation and removal. A large school building would require high voltage service from teh utility company and step down transformers provded by the owner. This type of transformer could not be installed on a pole. Althoguh the transformer could be placed on a pad outside the building, this would leave it exposed to vandalism and might present danger to srudents.
111
Electrical equipment and fixtures should meet the standards of which testing agency?
Undewriter's Laboratory (UL)
112
What is cogeneration?
Cogeneration allows heat and electricity to be produced at the same time from one ful source. Either heat or electricity is considered "free energy" because it is a by product of producing the other. As a fossil fuel is converted to heat, then to steam, then to mechanical energy, then to electrical energy, a vast amount of heat is produced. Cogeneration captures this heat and uses it for heating a building or for hot water heating.
113
Transformers installed in unit substations, both indoor and outdoor are called what?
Load center transformers
114
Transformers that are mounted on a pole or on a concrete pad outdoors are called what?
Distribution transformers
115
What are substation transformers?
They are always large and conrete pad mounted
116
A transformer is specified by what?
type, phase, voltage, kVA rating, sound level, and insulation class
thus, a 12.5-kVA, three-phase, 480/120-208-V, air cooled, indoor dry-type transformer with 428 deg F insulation system and 207 deg F, 45 lb maximum sound level, is an adequate transformer description.
117
5 kV transformers are usually liquid filled or dry type?
transformers above 5kV = liquid filled
transformers in the 600-V class = dry type
118
What are the advantages of outdoor transformers?
- no building space required
- reduced noise problem within the building
- lower first cost
- ease of maintenance and replacement
- no interior heat problem
- opportunity to use low cost, long-life, oil-filled units
Things to consider: frequently easier to find space indoors than to find suitable exterior location, exposure to direct sunlight decreases transformer's rating, exterior appearance may be objectionable
119
What disadvantages must an architect consider when situatiing an oil filled transformer indoors?
Oil insulated transformers present a fire hazard because flammable oil can spread from a tank leak or rupture. To prevent this, most oil-filled transformers must be installed in a fire resistant vault, the constrocution of which involves a heavy cost.
120
What are the advantages of oil-insulated transformers?
The advantages are the transformer's small size, low first cost, low losses, long life, excellent electrical characteristics, low noise level, and high overload capacity.
Despite this, the vault requirement has had the effect of restricting oil filled units to industrial facilities and other structures where electrical considerations favor its use.
121
All oil insulated transformers have to be installed in a fire-resistant vault. Tru or False.
False. Transformers rated 35kV or less that are insulated with a liquid whose fire point is not less than 572 deg F may be installed indoors withou a vault.
122
What are the principal advantages of dry-Type transformers?
Ease of installation and almost unrestricted choice of location
123
What are the disadvantages of dry type transformers?
- Shorter life
- higher losses
- high noise level
- greater weight
- larger size than liquid filled
124
Watt
the standard measurement of power, equivalent to 1 joule per second
1 watt = 3.412 BTU
the standard measurement of power, equivalent to 1 joule per second.
• Power is a measure of the rate at which energy flow
• Watts are basically the “miles per hour” measurement of an electrical circuit, they tell
you how fast electrons are moving around the circuit. They: • Represent a unit of energy over time
• Imply a rate (a “per second” value)
• Measure something at an instant
• Examples:
• A lightbulb might consume about 60 watts
• A medium size car might consume about 100,000 watts • A small gas generator puts out about 2,000 watts
125
Kilowatts:
1,000 watts
126
Horsepower:
A measure of power equal to 746 watts
127
Circuit:
a conductor, flow of energy, an electric potential difference (voltage), and some
type of medium that creates resistance to flow.
128
Ohm’s Law:
the building block to energy. It states that current is directly proportional to
voltage and indirectly proportional to resistance. If voltage goes up, current goes up. If
voltage goes down, current will go down.
129
Current (I):
measured in amps, it’s the amount of flow through a circuit
130
Voltage (V):
measured in volts, the amount of force or potential in a circuit
131
Resistance (R/Ω):
measured in ohms, the amount that slows down the current
132
Power (P):
the rate of energy transfer, expressed as energy / time (in hours)
133
Amp:
when one column of charge passes a point in one second
134
DC Current:
current that flows in one direction with constant voltage (e.g.: batteries).
Typical for low voltage applications which are less dangerous as there’s less current
135
AC Current:
Direction of the flow can be reversed rapidly by reversing the voltage
resulting in a sine wave when plotted. The standard form of electrical current supplied by
the utility grid and by most fuel powered generators.
136
Single Phase Electric Power:
distribution of AC power using a system in which all the
voltages of the sully vary in unison, used when loads are mostly lighting and heating with
few large electric motors.
137
3 Phase AC Current:
ike an AC current but three different circuits each 120 ̊ out of
phase with the other and one neutral circuit
138
Impedance:
the resistance in an alternating current, measured in Ohms.
139
Power Factor (PF):
he phase difference between voltage and current in AC circuits.
aka: cosine of the angle between the voltage wave and resultant current wave, ranges
from 0.0 to 1.0 and expressed as a percentage
140
Load Factor:
the ratio between the average and maximum power demands of a building
141
Reactance:
part of the electrical resistance in an alternating current circuit cased by
inductance and capacitance
142
Motor:
a machine that converts electrical energy into mechanical energy
143
Generator:
a machine that converts mechanical energy into electrical energy
144
Alternator:
AC generator that commercially produces AC current by converting
mechanical energy to AC
145
Transformer:
device that transfers energy from one circuit to another by magnetic
coupling with no moving parts. It changes the voltage (or force) of an AC circuit to a
higher or lower value
146
Volt-Ampere (VA):
the unit used for the apparent power in an electrical circuit, only
useful in the context of AC circuits.
147
KVA:
a rating for transformers equal to the product of volts and amperes divided by 1000. The product of the KVA and the power factor gives the power in kilowatts
148
Demand factor:
ratio of maximum demand or expected power usage to the total connected load
149
AC circuit Power (watts) W =
IxVxPF
150
Wye:
used when all the loads in an AC system
are connected at a single point and a neutral cable is connected at that center point where the three phases meet. Most low voltage distribution lines are Wye
151
Delta:
used when three phases are connected like a triangle and don’t have a neutral cable
Primaries are usually connected to a Delta
152
120V / 240 V Single Phase (one transformer), Three Wire System
Most common power for residential and very small buildings
• Single phase systems come from a three wire secondary
• Consists of two hot wires, each carrying 120V and 1 neutral wire
• Appliances that requires 240V use both hot wires
• Used where actual load does not exceed 80A, although some service is
considered for 100A
• 120V is used for plugs, lights, and some small equipment
• The feed is simple, and the panel is simple
153
When do you go to 240V system?
When the current draw is huge • When you can save $ on wire
• When there’s no other choice... • Typical 240V loads include:
• Air conditioning / electric heating systems • Electric dryers/ Electric water heaters
• Large appliances (microwaves and stoves)
154
208 / 480 V Three Phase (three transformers) System
Three circuits carry three alternating currents which reach their instantaneous peak values at different times
• Has an effect of giving constant power transfer over each cycle of the current and makes it possible to produce a rotating magnetic field in an electric motor.
155
The difference between single phase and three phase:
Single phase power is 60 cycles / second (called hertz)
• Three phase power is 60 cycles / second (again, called hertz) in three phases that are separated in time. Each phase is 1/3 cycles apart
• 3 phase system give a wider set of options for use
• Small Buildings usually get 120/240 single phase
or 120/208 three phase service
• Larger Commercial/Industrial require higher
voltage and get the three phase services like
277/480 volts
• Higher voltage allows for a larger number of
fixtures to be on a single circuit without an
increase in current.
156
120 / 208 V three phase (three transformers), four wires system
Used in larger buildings because it allows for a variety of electoral loads
157
277 / 480 V Three Phase (three transformers), four wires system
The same as 120/208V except for higher voltage
• Smaller feeders, conduit, smaller switchgear because of higher voltages
• Higher voltages result in small currents the equipment needs to carry
• Buildings usually have 277 V fluorescent lighting that requires smaller wiring
• Small step down transformers are used where 120 V service is needed for
receptacles and equipment
158
A circuit of plugs in your home has two floor lamps (300 watts each), a home entertainment center (750 watts), a computer work station (900 watts) and the occasional vacuum (600 watts). What is the current expected from this circuit? What size should the breaker be?
Figure out the load:
• 2 (300 watts) + 750 watts + 900 watts + 600 watts = 2,850 watts
• Convert to amps to find the current:
• 2,850 watts / 120 volts = 23.76 amps
• Size the breaker:
• Breakers come in 10A, 15A, 20A, and 30A so you’ll need a 30A for the circuit
Step Two: Design the system based on a single circuit or triple circuit system • Step Three: Rough In the System (the first part of construction), includes:
• Circuits and separation
• Outdoor and Indoor on different circuits
• By space, type and zone
• Inspections, there are usually two, sometime three • Expansion
• Organization
• Step Four: Finish and Close Out, includes:
• Inspections need to happen
• Temporary power and safety (most dangerous on job site)
• Coordination with other trades
• Punch list and closeout with architect
• Equipment startup (Which can be very time consuming for large buildings) • Switching to permanent power
159
ratchet clause
(where the demand charge is based on the highest measured demand, or percentage of, over the previous year) is disadvantage for users with a low yearly load factor
160
Transducer:
device which converts power in one kind of system to power in another form, such as loudspeaker which converts electric power to acoustic power.
161
American Wire Gauge System:
A standardized wire gauge system used since 1857 for the diameter of round, solid, nonferrous, electricity conducting wire
• Cross Sectional area of each gauge in an important factor for determining its current carrying capacity
• Increasing gauge numbers give decreasing wire diameters
• No. 36 AWG = 0.005 inches
• No. 0000 AWG (aka 4/0 pronounce “four aught”) = 0.46 inches
162
Use (blank) gauge minimum in buildings
14
163
Romex
Residential, Wood Framed less than 3 stories
Nonmetallic sheathed cables
• 2+ plastic insulated conductors and ground surrounded
by a moisture resistant sleeve
• No conduit required, it’s an alternative
• Must be protected from damage within walls, etc.
164
Flex Metal Clad Cable (BX)
Remodel/ Residential
• Flexible metal clad cable
• 2+ plastic insulation conductors encased in spiral wound
strip of steel tape
• No conduit is required
• Can be easily pulled
165
Busbar
* Rectangular bars of copper that carry high voltage
* Used in place of very large cables and high currents
166
Busway
• Multiple busbars in a metal housing
167
Rigid Steel Conduit
* The safest type
* After pipe is installed (indoor/outdoor) wires are pulled through • Connections are rigid and threaded like pluming pipes
* Connect to J-boxes and devices
168
Intermediate Metallic Conduit
* Steel conduit with thinner walls but same outside diameter as Rigid • More economical
* Use with threaded fittings
169
Flex (Flexible Metal) Conduit
• Used everywhere except underground
• Reduces vibration transmission from equipment where not possible
to install rigid
170
Electric Metallic Tubing
* Thinnest metal conduit
* Too thin to thread, connections are made with clamps • Easy/fast install
* Not allowed in hazardous areas
171
• Grounding:
* A common return path for current and/or a direct physical connection to the earth • Done to prevent user contact with dangerous voltage if electrical insulation fails
* Limits the build up of static electricity
* Electrical circuits are connected to the ground (earth)
172
Panelboard (Breaker Box):
a component of an electrical supply system which divides and electrical power feed into subsidiary circuits while providing a protective fuse or circuit breaker for each circuit, in a common enclosure
173
Branch Circuit:
the insulated wires that run between the outlet and the panel board
174
Circuit Breaker:
a switching device that can make, carry, and break current under
normal circuit conditions
175
Fuse:
a thin strip of metal that melts and breaks an electrical circuit if a current exceeds
a safe level
176
Ground Fault Interrupter (GFI):
detects small current leaks and disconnects the hot
wire, typically used in kitchens, bathrooms, and outdoor outlets
177
Emergency Power System:
type of system which may include lighting, generators to provide backup power resources in a crisis or when regular systems fail.
178
Uninterruptible Power Supply (UPS):
an electrical apparatus that provides emergency power to a load when the input source fails. Typically used to protect computers, data centers, telecom equipment, or wherever power outage can disrupt business
179
• Primary Distribution:
A central electrical distribution center that consists of an assembly of switches, circuits
breakers and cables that distribute power to the building is called switchgear
• A load center pad-mounted unit substation would typically have a primary voltage
range of 2.5-15 kV
• The most popular form of exterior transformer installation for individual buildings is
mounted on a concrete pad
• In a typical building electrical power system wiring closet, dry-type transformers are
typically placed between plug in busways and 120V panelboards
• A meter and transformer are included in with it to split power into separate circuits,
each with a master switch and circuit breaker for protection
• Switchgear also distributes power to substations for further transforming and
distribution as part of a secondary distribution system
180
Secondary Distribution System:
• Power is distributed from the main switchgear to panelboards
• Panelboards (or breaker box) divides the electrical feed into subsidiary circuits while
providing a protective fuse or circuit breaker for each circuit
• Typical power voltages of 120V, 240V, and 277V
• Distribution is made with wires in conduit, underfloor raceways, or flex cables
• Protected by circuit breakers typically 15A and 20A, also come in 10A and 30A...with
100A for main disconnects
• Breakers should be oversized when a motor in involved
• When designing a system, plan ahead. Where will it come in from, where is the main
panel, and how much will it grow?
• Typically you should oversize systems by about 25% for future expansion • 25% of the breaker box should be empty holes for new circuits
• In commercial spaces, an electrical closet might be preferable to a stand-alone panelboard for a building of 6 or more stories.
181
• Branch Circuits
• Every circuit has a hot, neutral, and ground wire
• Ground and neutral have two unique functions in an appliance connection
• Hot wire is the start of the lead, neutral is the other side of the lead together these
power the appliance (e.g.: power goes in the hot, to the appliance, and out the neutral
back to the panel)
• Third prong on a plug is the ground, which protects life safety
• If the neutral leg breaks, the ground still is there to keep it safe
• Protection for circuits:
• Ground: provides a path for fault, both ground wire and neutral wires are grounded at the bulling service entrance to a grounding electrode
• To avoid the risk of electric shock, it is recommended that appliance housings be grounded to a cold water pipe
• Ground Fault Interrupter (GFI/GFCI):
• Detects a continual current lost to the ground, even after power is shut off
• Might not trip a circuit or burn a fuse but still not good
• Typically used on any 15 or 20 amp circuit where water is or might be present
(eg: bathrooms, garages, outdoors)
• If an outlet is within 6’-0” of a water source then it must be GFCI to eliminate
potential shock hazard
182
Equation for power (E)
E=Wt
183
A low load factor implies what?
Inefficient use of energy and high demand charge.
184
Methods for avoiding peak electricity use are...?
load control, load shedding, peak demand control, and peak load regulation.
185
Most residential outlets operate under how many amps?
15
186
Low voltage Switching:
operated on 24V circuit and controls relays that provide the
120V switching.
• Same light can be controlled from several remote positions
• Central control station can be set up for monitoring and override
• Less expensive than line-voltage wiring and devices for large installations that
need to be flexible.
187
If the number of conductors in a cnduit exceeds 3, the NEC requires what?
The NEC requires that ampacity (current-carrying capacity) be derated
188
Photovoltaic:
200 watts each panel (not much produced!)
• Solar energy
• Sun shines on Solar Panels - no moving parts - goes to generator to make energy
• Can be cells, panels, arrays, fields
• A huge array of panels is needed to do any good
• Increases in PV module efficiency, new materials, and other initiatives have
brought the cost of PV (per peak Watt) to about $0.25 - 0.50
• Today's commercial two-layer PV arrays have a maximum insolation-to-electric
energy conversion rate of 12%
• The tilt angle of a PV array, to capture maximum insolation when the sun is lowest,
should be equal to the site latitude plus 15 degrees
page 78 of 142 :: created 11.2012 :: revised 05.2013 :: are 4.0 :: organized by twitter/areforum member @jennypdx
AREndurance STUDY NOTES
! building systems
• A PV system battery is generally expected to supply all of an installation's electrical requirements for a period of 3 days of cloudy weather
• Sealed PV system battery types require the least maintenance
189
Wind Power
* Newest system with big potential
* Wind - turns a wheel - which goes to generator
* Wind has to be strong and steady
* A noisy contraption
* Blades are 90 feet and one ton each...can cause some serious damage • Found in the northwest
190
Nuclear Power
* A complex process
* Split atoms - which hit other split atoms - which makes heat
* Water runs around uranium rods - makes steam - which makes heat
* Eventually rods run out of uranium and are toxic
* Was supposed to be the cure for our energy problem
* Accidents happened everywhere and the insurance industry panicked (e.g.: 3 Mile Island, Browns Ferry, Challenger, Chernobyl (the big one))
* No new orders for nuclear power have been placed since 1990
* In the US power plants have to have insurance, not one insurance company will insure nuclear power
191
Electrical demand is based on ...
...how big the service needs to be (wires, transformers, etc)
Residences are easy, it’s all small wires and units
• Bigger customers (industrial, commercial, etc) have bigger wires and takes time and
money to install and maintain
• The utility department has an obligation to provide power that covers the peak need
of a user. The user, of course, has to pay for it.
• The most power that an installation pulls at any given time over a month is
measured in kilowatts (kW)
• Your demand is measured every 15 minutes by the utility company and you pay the
largest demand they measured that month
• Residential Cost = Basic Charge + (kWh) x ($/kWh)
• Commercial Cost = Basic Charge + peak kW demand $ + (kWh) x ($/kWh)
192
What type of electricity do PV cells convert sunlight into initially?
galvanic cuurent and direct current
193
Which statements are correct about conduits?
1- Rigid conduits and IMC conduit both use threaded fittings for connections
2-EMT uses set-Screws and pressure for connections.
3- EMT and IMC conduit yield a larger inside diameter.
4- Conduits can be as small as 1” nominal trade diameter could be used.
a) 1, 2
b) 2, 3
c) 1, 2, 3
d) 1, 2, 3, 4
c) 1, 2, 3
194
Which one is not a driving factor in application of surface metal race ways:
## Footnote
a) Durability
b) Architectural restrictions
c) Economy
d) Access and flexibility
a) Durability
195
Which one is not a main factor in determining the method for service delivery from a utility line?
a) Weather condition
b) Customer participation in the cost of service installation c) Local ordinances
d) Service W attage
d) Service W attage
196
Which one is not a self Cooled rating transformer?
a ) Liquid filled
b) Soil filled
c) Dry-type ( Air- filled)
d) Cast coil
b) Soil filled
## Footnote
197
Which one is not the characteristic of oil insulated transformer?
a) has high first cost
b) needs fire resistant vault
c) has small size
d) has low noise level
c) has small size
198
If ......... Service is purchase, all equipment necessary to provide the voltage is furnished by the utility.
a) Low voltage
b) High Voltage
c) Low and high voltage
d) None of the above
a) Low voltage
199
The advantage of contactor over switches are the facility for:
a) Heavy duty
b) Remote control
c) Time control
d) Automatic transfer
b) Remote control
200
What are the 3 type of steel conduit and how do they differ?
1.Heavy wall steel conduit ( rigid steel conduit) 2. Intermediate metal conduit (IMC) 3. Electric metal tubing (thin wall conduit or EMT) They differ primarily by weight
201
Which one is not the purpose of conduits?
a) Provides grounded metal enclosure for the wiring.
b) Protect the enclosed wiring from the fire hazard
c) Provide system ground path
d) Protect surrounding against fire hazard
b) Protect the enclosed wiring from the fire hazard
202
If the Voltage between the neutral and the peak of a three-phase current is 120 volts, what is the voltage between two phases?
208 Volts
203
Typically, the use of load scheduling and duty cycle control are applied to what?
To control HVAC loads, lighting loads, and process loads in small commericial and insitutional and industrial buildings
204
What are the disadvantages of automatic instantaneous demand control
loads are pregrogrammed to shed, resulting in an inability to readlity adapt to varying load patterns resulting from variable production schedules, time schedules, chnages in weather, etc. System is most useful in applications where operating modes do not changes (stores, supermarkets, warehouses)
205
Advantages of forecasting systems for controlling electrical loads.
if programmed properly, they can make a small, accurate load changes throughout an interval, resulting in minimum load cycling and maximum efficiency.
206
Advantages of underground electrical service
attractiveness( no visible wires)
service reliability
long life
207
The number of poles is in a switch indicate what?
the number of separate circuits controlled by a switch
208
The number of throws in a switch indicate what?
The number of separate positions the switch can adopt.
209
When drawing a switch, convention calls for switches to be connected to the hot or dead blade?
dead
210
From low to high, name the frequencies of light energy?
radio, radar, infrared, visible light, ultraviolet, xray
