Mid Term Topics Flashcards
(265 cards)
1
Q
True/False: We are required to look at the service drop and service laterals.
A
True
2
Q
True/False: Service entrance conductors run from the service drop to the service box or service panel.
A
True
3
Q
True/False: The service size is determined by the amperage and voltage ratings of the service.
A
True
4
Q
List five things that make electrical inspections challenging.
A
- Electricity is invisible
- Terminology is complex
- Electricity is dangerous
- Rules for working with electricity are complicated, constantly changing and detailed (electrical codes)
- Enforcement by the authority is not always consistent
5
Q
The goal of our electrical inspection is to ensure that
A
the electrical system is safe and convenient for modern lifestyles
6
Q
The yardstick for the recommendations you make to your client should be
A
What would you do if it were your house?
7
Q
How much electrical current does it take to kill you?
A
Less than an amp.
8
Q
List five safe practices to protect you during your inspection.
A
- Wear rubber soled shoes.
- Do not stand in water when touching electrical equipment.
- Use insulated tools.
- Do not let your client stand beside a panel you are working on.
- Touch electrical equipment with the back of your right hand first.
9
Q
Aluminum wiring was first commonly used when?
A
Mid 1960s
10
Q
Knob-and-tube wiring was used up until when?
A
1950
11
Q
What are the components of an electrical system?
A
- service drop & entrance
- grounding system
- electrical service box (main disconnect, fuses, breakers)
- distribution panels
- branch circuit wiring
- lights, outlets, switches, junction boxes
12
Q
What type of wiring should you report as a potential safety hazard?
A
- aluminum wiring (except stranded #8 gauge or larger)
- smaller solid conductors have previously been troublesome
- overheating & starting fires
13
Q
How many light fixtures should you inspect?
A
- atleast 1 per room indoors
- on each wall outdoors
14
Q
What are the 11 items excluded in an electrical inspection?
A
- inspecting service laterals (except at ends)
- meter
- quality or continuity of service grounding
- testing/verifying performance of overcurrent protection devices
- floor / table lamps
- reporting on stranded #8 gauge or larger aluminum wires
- copper wires
- smoke alarms:
- testing
- how its connected
- remote control devices (garage door operators, lights, blinds)
- alarm systems
- measuring amperage, voltage, resistance
15
Q
Define “service drop”
A
- wires that come to the house from the utility pole
16
Q
Define “service laterals”
A
- utility wires that come to the house underground
- only visible at the ends
17
Q
Define service entrance conductors
A
- run down the outside of the house & into a service box
- may or may not be in conduit
- usually the responsibility of the homeowner
18
Q
Define “service size”
A
- amperage & voltage rating of a service
- usually 240 volts
- common amps:
- 60, 100, 125, 150, 200, 400
- odd sizes: 50, 70 90
19
Q
Define “service equipment/service boxes”
A
- box that contains the main fuses / circuit breaker
- houses the main disconnects
- some house don’t have a main disconnect
20
Q
Define “combination panel”
A
- contains:
- service equipment
- main disconnect
- distribution fuses
- breakers
21
Q
Define “service grounding”
A
- system parts:
- grounding electrode conductor
- runs from the service box to the grounding electrode
- grounding electrode
- water pipe, ground rod
- equipment grounding wires
- grounding electrode conductor
22
Q
Define “distribution panels”
A
- include:
- service panels
- subpanels
- fuse panels
- breaker panels
- most dangerous part of inspection; rarely able to turn off power before
23
Q
Define “conductors”
A
materials that electricity can move through easily
24
Q
What do black/red wires mean?
A
hot (underground conductors)
25
What do white/gray wires mean?
neutral (grounded conductors, identified conductors)
26
What do green wires mean?
bare, ground, grounding conductors
27
What is a cable?
group of conductors
28
What are the types of cables?
- non-metallic heated cable (Romex)
- armoured cable (BX)
29
Define "overcurrent protection devices"
fuses, breakers
30
What does GFCI stand for?
ground fault circuit interrupters
31
What does AFCI stand for?
arc fault circuit interrupters
32
What is the benefit of photoelectric detectors?
pick up smouldering fires quicker than ionization detectors
33
Define "impedance"
technically correct term for electrical resistance
34
Define "amp"
measures how much electricity is flowing through a circuit
35
Define "electrical potential"
volts, voltage, force, electromotive force
36
What is an ohm?
An ohm is a measure of resistance to electrical flow
37
Electricity can perform three very different tasks. What are they?
1. Light
2. Heat
3. Mechanical work
38
True/False: Electrical wiring in a house is direct current.
False. alternating current
39
Define "watt"
A watt is a measure of the rate of electrical energy being consumed or released
formula: voltage x amps = watts
1,000 watts = 1 kilowatt (kW)
40
Give two formulas that describe the relationships between volts, amps, ohms and watts.
V = I X R
P = V X I
V = voltage
I = current (amps)
R = resistance (ohms)
P = power (watts)
41
True/False: A 120-volt circuit uses a black and red wire.
False
42
True/False: Larger appliances usually have 240 volts.
True
43
When the switch is turned off, is the circuit open or closed?
Open
44
True/False: The wires should be considered the brains of the circuit.
False. breakers/fuses
45
The size of the fuse should be –
the same as the rating of the wire
46
Turning on another light bulb in the same circuit should not dim the bulbs that are already on because
They are wired in parallel.
47
A wire that is nicked is -
likely to overheat when carrying normal current loads.
48
A loose connection is
likely to overheat when carrying normal current loads.
49
Energy travels at nearly the speed of -
light
50
How does electricity flow?
From areas of high electrical energy to low electrical energy
51
Why does electrical energy always seek to move to the ground?
Ground has zero electrical energy
52
What is the function of fuses / breakers?
- to prevent overheating of wires (conductors)
- important to have the right size to the wire
- too large = won’t cut off electrical current soon enough
- too small = electrical current shuts off prematurely
53
What are the 3 benefits of using alternating currents in houses?
1. can produce a high voltage
2. transport it over long distances
3. lower it to safer levels
54
What are the characteristics of an alternating current?
- 240V split to 120V in a house b/w live wires (black/red)
- each supply electricity in alternating currents from each other
- pulse, rest, pulse…
- if one wire is pulsing, the other is resting
- no neutral wire (white/gray) needed
55
How do we pay for electricity?
in kilowatt-hours (kWh)
56
List the types of conductors
1. wires
2. metals (copper, aluminum, silver, gold)
3. water
4. people
57
What do overcurrent protection devices protect against?
- overloading
- ground faults
- short circuits
58
What happens when more resistance is introduced into an electrical circuit?
more resistance electricity encounters = less current
59
What happens when there is too much electrical current in a circuit?
can melt wire; fire hazard
60
What is an open circuit?
- where there is no electrical current (amps) flowing
- circuits can change from open to closed (switch)
61
What is a short circuit?
- when there is low/no resistor in the circuit
- high electrical current (amps)
- often results in a blown fuse or tripped breaker
62
What are the 3 types of short circuits?
- when the resistor is bypassed
- when a nail is driven in the cable, bridging the black & white wires
- electrical current is able to bypass resistor
- ground fault
- when electrical current moves through a path to ground than was intended
63
What is electrical resistance?
- insulators have enough resistance to electricity to prevent its movement
- conductors also have some resistance (some types more than others)
- measured in ohms
- resistance factors:
- size
- length
- temperature
- material
64
What is a synonym for voltage?
electromotive force
65
Why is electricity dangerous?
- electrical force always exists, even when no electricity is flowing
- needs a conductor to release this force to ground
- why electricity is dangerous
66
What are the characteristics of a parallel circuit?
- electricity current had multiple paths to follow to ground
- burnt out bulbs don’t impact the circuit
- more resistors don’t impact lighting
67
What are series circuits?
- electricity current has to flow through each light bulb in sequence
- if one bulb is defective, this creates an open circuit
- adding more bulbs to the circuit makes other bulbs dimmer
- this adds more resistance to the circuit
- i.e. Xmas lights
68
What is a filament?
very fine wire
69
What is frequency?
- electrical pulses in a wire move 60 cycles per second
- means energy travelling through the wire changes direction 120x per second
- measured in Hertz (Hz)
70
What is an insulator?
materials that electricity cannot move through easily
71
What are the types of insulators?
- air
- distilled water
- rubber
- glass
- ceramics
- wood
- plastics
72
What is a resistor?
- when something within a circuit is installed to convert electrical energy to:
- heat
- light
- mechanical work
- designed to allow a certain amount of electricity to flow
73
What happens during a circuit overload?
- occurs typically on circuits with several electrical receptacles/outlets
- if too many appliances are plugged in, current flow will be > the wire can handle
- fuses are generally set up to accept 80% of a 15-amp circuit
74
Is the service drop overhead or underground?
Overhead
75
Are service laterals overhead or underground?
Underground
76
True/False: The drip loop is typically part of the service drop.
False
77
True/False: The wire size for the service drop must be the same as the wire size for the service entrance conductors.
False
78
How many wires would you typically find in a 240-volt service drop?
3
79
What would four wires mean in a service drop?
Three phase electricity
80
What would two wires usually mean in a service drop?
120 volts service
81
List eight common problems with service drops
1. Overhead wires too low.
2. Overhead wires too high.
3. Damaged or frayed wires.
4. Trees or vines interfering with wires.
5. Wires too close to doors or windows.
6. Wires not well secured to the house.
7. Poor connection between service drop and service entrance.
8. Inadequate clearance from roofs.
82
List the service drop clearances above ground, swimming pools and roofs applicable to your area.
- < 30 ft above grade for wires attached to a building
- 18 to 20 ft above roadways
- 13 to 15 ft above driveways
- 12 to 15 ft above pedestrian only areas (walkways, lawns)
- 8 to 10 ft above flat roofs
- 8 to 10 ft above porches & balconies
- should not run above roofs (unless special permission given)
- permitted over overhangs; > 2 ft
- 3 ft away from the sides of windows, doors, fire escapes
- no rules over swimming pools
83
What is the purpose of the service drop?
obtain electricity safely from the utility and into the house
84
Why are service drop wires often smaller than the service entrance wires?
- can carry more electrical current since the wires can cool faster in open air than in-house wires
85
Can you use common wire sizes & amperage when inspecting service drop wires?
no. wire sizes & amps used by inspectors reserved for wires in conduit or cable
86
What are the two different arrangements for a 3-wire service drop?
- 2 hot (black), 1 neutral (white)
- neutral wire may support hot wires
- may be bare (no insulation)
- smaller
- 3 hot
- may be a separate cable as support
87
What are synonyms for service drop?
- overhead wires
- overhead service
88
Where does the service drop end?
terminates at the drip loop
89
Where should splices be made to connect the service drop to the service entrance wires?
- splices for the service drop & service entrance wire connections should be made just before the drip loop
- to avoid water collecting, connection should not be made at the lowest point
90
List the characteristics of service laterals
- usually some slack at points of connection for:
- frost heaving
- building settlement
- cable may be in conduit
- allows for easy replacement/upgrade
- bushing present at bottom so cable doesn’t get cut
- may also head straight into the house to the main disconnect
- there will be no service entrance conductors
- can:
- run up the exterior wall surface
- inside the wall cavity
- inside the building
91
What are the 3 components of a service drop?
- service entrance conductors
- drip loop
- service cap
92
What is evidence of a damaged or frayed service drop?
pieces of insulation hanging off
93
What are the implications of trees or vines interfering with the service drop?
- mechanical damage
- reduced ability to dissipate heat
94
What are some causes of the service drop not being well secured to the house?
- install issue
- building settlement
- rotting wood
- rusting metal parts
- trees falling on wires
95
What would you look for to see if the service drop is not well secured to the house?
- look for movement from the connection to the house
- connectors pulling away or have more sag should be noted
- watch for absence of drip loop; suggests wire under tension
- electrical tape at connection may indicate amateur work
- utilities use heat-shrink seal
96
What is a common problem with service laterals?
Mechanical damage or pulling loose
97
What can cause service lateral connections to become loose?
- building movement
- backfill settlement
- soil expanding
- frost heave
98
How would you inspect if the service lateral connection is loose?
- look for:
- stretched or crimped cable
- cracked conduit
- supports pulled loose
99
Define "splice"
- two wires joined together
- synonym:
- service point
100
Define "drip loop"
- u-shaped bend in the wires to allow water to drip off
- prevents water entering the service entrance
101
What are characteristics of a drip loop:
- responsibility of the homeowner
- part of the service entrance (not the service drop)
- confirms a secure connection & are relaxed
- older houses may not have a drip loop
- service wire may be connected directly to the roof surface
102
What are synonyms for a service cap?
- masthead
- entrance cap
- pothead
- weatherhead
- servicehead
103
The service entrance conductors run from where to where?
From the service drop to the service box.
104
All service entrance conductors must be in conduit.
False
105
All service entrance conductors must be attached above roof level.
False
106
The drip loop should be as close to the roof surface as possible.
False
107
List 11 common problems with service entrance conductors.
1. No drip loop
2. No mast head
3. Mast head not weather-tight
4. Service entrance wires too close to the roof
5. Mast or conduit bent
6. Mast or conduit rusted
7 Mast rotted (if wood)
8. Mast conduit or cable not well secured
9. Mast conduit or cable not weather-tight
10. Conduit or cable not well sealed at house/wall penetration
11. Cable frayed, damaged or covered by siding
108
List four common areas of water penetration into service entrances.
1. Conduit joints
2. Mast head
3. Roof flashing
4. Meter base
5. House entry
109
List two functions of the drip loop.
1. Prevents water entry into the conduit or service entrance conductors
2. Shows that the service drop wires are not straining the splices
110
True/False: The meter should be sealed & weathertight
True
111
What is the difference between service conductors & service entrance conductors?
service conductors = wires on the exterior
service entrance conductors = when wires pass through a wall from the outdoors
112
How is the amperage service size determined?
amps determined by gauge of service entrance wires
113
How often should service entrance conductors be secured to the wall when in conduit?
every 5 - 6 ft
114
How often should service entrance conductors be secured to the wall when in cable?
30“ to 5 ft (manufacturer recommendations)
115
Why shouldn't cables & conduits be covered by siding?
fasteners could be driven into cables
116
How should a drip loop be arranged?
- service entrance wires should extend at least 30 inches out of the service cap
- gooseneck used when no conduit or masthead
- bottom of drip loop at least 24 inches above roof surface
117
How should a masthead be arranged?
- required when service drop is higher than roofline
- required when masts are > 5 ft:
- guy wires used to hold mast straight
- flashing around mast when there is a hole in the roof
- service drop wires attached to mast within 12 inches from top
118
What are the causes for a mast/conduit to be bent?
- service drop force
- inadequate guy wires supporting mast
- mechanical failure of fasteners/clamps. Reasons:
- rust
- rot
- inappropriate connectors
119
What are the strategies when a mast or conduit is rusted?
- look for rust at electrical connections
- most likely to occur at horizontal surfaces
- where water sits
- pay attention to threaded connections
- don’t touch mast; electrical shock potential
120
What are the causes for why a mast, conduit or cable is not weather-tight?
- install issue
- movement of components
- deterioration of materials overtime
- building settlement
121
What are the implications when a conduit or cable is not well sealed at house wall penetrations?
- water entry into the electrical system
- water into the basement
- rusting of service equipment
122
What should you do when a conduit of cables wall penetration entry is below grade?
check inside when looking at the service equipment
123
What are the implications when the service entrance conductor cable is frayed, mechanically damaged or covered by siding?
- electrical shock potential
- if live portions touch metal siding, entire skin of building could become electrically charged
- if cable is covered by wood siding, driving nails could create a shock hazard
124
Are service entrance conductors allowed to run behind siding when in conduit?
conduits may be allowed to run behind siding (area dependant)
125
According to most standards, the size of the electrical service has to be reported.
True
126
Roughly 999 out of 1,000 houses:
1. have 240 volts available
2. have three service entrance wires
127
Load calculations are part of a home inspection.
False
128
Implications of an undersized service include –
nuisance tripping of the main fuses or breakers
129
The main fuses or breakers are most likely to trip –
when many large appliances are on
130
When is a 60-amp service acceptable?
On small homes without many large electrical appliances.
131
What is the largest single-phase service that you are likely to find in a home?
400-amps
132
What is a reliable way to identify the service size?
the service entrance conductor size
133
Aluminum is an acceptable service entrance conductor material.
True
134
A fused 200-amp service has two 100-amp fuses in the service box.
False
135
If you can’t read the size of the fuses in the service box, you should remove them to try to get a better look.
False
136
Is this a safety issue: The main fuses have a higher rating than the service entrance wire.
yes
137
Is an under-sized electrical service a safety hazard?
No
138
Where is a 100-amp service commonly found?
- generally good for a 3 bed, 2 storey house
- may be insufficient if there is a 2nd unit
- not longer meets larger family, modern lifestyles
139
Where is a 125 & 150-amp service commonly found?
- small houses with electric heat
- larger houses without electric heat
140
Where is a 200-amp service commonly found?
- found on electrically heated houses
141
Where is a 400-amp service commonly found?
- largest single-phase service
- found on large houses (6000 sq ft)
142
A 14-gauge wire is larger than a 12-gauge wire.
False
143
What are the wire sizes under the American Wire Gauge system?
14, 12, 10, 8, 6, 4, 3, 2, 1, 0, 00 (2/0), 000 (3/0), 0000 (4/0)
144
When are 1000 Circular Mils used as a wire measurement?
used for wire sizes larger than 4/0 AWG
145
What are the wire sized under the MCM system?
250, 300, 350, 400, 500, 600
146
What do wire ratings mean?
wire ratings designate the max temperature the wire can be exposed to
147
Free air affect a wires ability to carry electrical current.
True
148
What are the minimum requirements for conduit sizing for:
60-amp
100-amp
200-amp
1. 1 inch diameter
2. 1 1/4 inch diameter
3. 2 inch diameter
149
What 7 methods should not be used to determine the service size?
- the size of the service drops wires
- the size of the service entrance conduit
- size of the meter base
- rating of the meter
- service box rating
- rating of the distribution panel
- total ratings of all fuses, breakers the distribution panel
150
Why can't the service box rating be used to determine service size?
this is the max service size that can be used; not what it is currently
151
What methods should be used to determine the service size?
- check service entrance wires
- check main fuses or breakers:
152
What method is the best indication of service size?
service entrance wires
153
Is checking the main fuses or breakers for service size accurate? why not?
Not 100% accurate. fuses/breakers may be over-sized or under-sized
154
If there are main fuses, how do you determine service size?
- if fused, there will be 2 fuses in the service box
- 1 is for the red service entrance conductor
- 2nd is for the black wire
- don’t add ratings of 2 fuses
- they both should have matching numbers
155
Why should you not touch anything in the service box?
- electric shock can kill
- service entrance conductors will be live even if power is off
156
If the service size is too small, what may need to be replaced?
- service drop / laterals
- service entrance conductors
- service box
- grounding conductor
- distribution pane
157
What is the formula for a simple base load calculation?
House load = basic load + large appliances + special loads
158
What is included as a basic load?
- include:
- lights, outlets
- small appliances
- central vacuum
- oil/gas furnace
- based on house size (sq ft)
159
What is included as large appliances?
- electric stove
- electric dryer
- electric water heat
160
What is included in as a special load?
- sauna
- electric heaters (baseboard heaters)
- electric furnace
- central A/C
161
What are the steps to determine basic load?
- obtain house total sq ft
- include 75% of basement floor
- no outside wall measurement; calculate interior space
- 1st 1,000 sq ft
- allow 5000W
- every 1,000 sq ft, or part of after
- allow 1000W
162
What are the steps to determine large appliance load?
- 6000W for the stove
- 1000W for the dryer
- 750W for the electric water heater
- 1500W for additional stoves
163
What are the steps to determine the special loads?
- data plate has amp load for each appliance
- if data plate can’t be found, use supply cable, or fuse/breaker rating
- for baseboard heaters:
- add watts on each data plate / 240V = amps
- for central A/C:
- use FLA (full load amps)
164
What are the steps to determine the total house load?
1. Calculate basic load
2. Calculate large appliance load
3. basic load + large appliance load / 240V = amps
4. Calculate special loads
165
What is a common problem with service size?
undersized service
166
What are some of the causes of an under-sized service?
- old houses
- houses with additions
- larger appliances (central A/C) added after construction
167
What are the strategies for an under-sized service?
- determine service size & evaluate whether its sufficient
- recommend:
- upgrading if under-sized
- trial period if its marginal
- nothing if adequate
168
The service box can be inside, outside or in a garage.
True
169
There can be up to 10 throws to disconnect all of the electricity in the house.
False
170
The service box may stand alone or may be combined with the distribution panel.
True
171
List 17 common conditions you might find in a service box.
1. Poor access or location
2. Loose
3. Rust or water in box
4. Unprotected opening
5. Inappropriate support material
6. Damaged parts
7. Overheating
8. Incorrect fuse or breaker size; box rating too small
9. Service entrance wires exposed in the house
10. Poor connections
11. Illegal taps
12. Neutral wire bypasses service box
13. Fused neutral wire
14. Fuses upstream of disconnect switch
15. Obsolete box
16. Exterior box not weather-tight
17. Box not rated for aluminum
172
Define "carrier current controller"
- switch activated by a radio signal from the utility
- used for water heaters
- is switched on/off to relieve demand from the electrical grid
173
What are the characteristics of new house service boxes?
- new houses have combination panels:
- mains + breakers/fuses
- meter is upstream of the service box
174
What are the characteristics of older house service boxes?
- have separate mains & fuse panels
- don’t always have a single main disconnect switch
- meter may be downstream of the service box
175
Where is the service box typically located?
- usually located on the opposite side as the exterior meter
- can be indoors, outdoors, or in garages
- must weather tight if outside
- might be locked if outside
176
Where should service boxes not be located?
- bathrooms
- closets
- kitchen cupboards
- stairwells
- behind refrigerators
177
What are the clearances for services boxes?
- 3 ft away from indoor gas meters & outdoor gas relief vents
- sparks can cause a explosion
- should be mounted at eye level
- 30 to 36 inches from the left & right sides
- 3 ft in front
178
Why is it better to mount service box/panels to drywall?
drywall is non-combustible
179
Is it ok for service entrance conductors to run through the house before reaching the service box?
No
180
If the service box is upstream of the meter, what could potentially happen? Is there any exceptions?
stealing electricity without it being metered
Yes. flat rate water heaters
181
What can happen if there are multiple taps in a breaker/fuse?
high potential for loose connections
182
Where should neutral wires be attached?
- should be attached to a terminal in the service box
- not the distribution panel
- should not run through a fuse in the service box
183
Should main fuses/breakers be upstream or downstream of the main disconnect switch?
downstream
184
What are synonyms for a service box?
- service equipment
- service panel
185
What are some causes of a service box becoming loose?
- install issue
- failure overtime due to vibration
- mechanical damage
- rust
- rot
186
What are some causes of rust or water in the service box?
- water carried from the service entrance conductors
- if outside, weather tight failure
- if below-grade; moisture coming through foundation wall
- often around the conduit opening in the foundation wall
187
What are some causes of unprotected openings in a service box?
- install issue
- mechanical damage
- vibration causes loose components
188
What is your strategy for when there is inappropriate support material behind a service box?
determine whether non-combustible mounting surfaces are required & retroactive in your area
189
What are some causes for damaged parts in a service box?
- mechanical damage
- age
- vibration
- rust
190
What is your strategy for when there is damaged parts in a service box?
look for damage; especially at fuse holders & switch parts
191
What are some causes of overheating in a service box?
- loose connections
- overloading
- overfusing
- damaged conductors
192
What would you look for to identify signs of overheating in a service box?
- look for blackened, melted, charred surfaces
- wire sheathing often discoloured
- concern if the box is warm
193
If the size of the fuse, breaker is incorrect, or if the service box rating is too small, what is your strategy?
- ensure breakers are right-sized for the wire & service box
- box rating must be at least as big as the fuse & service entrance wires
- some breakers may be slightly over-sized due to the exact size not being available
- service box & breaker brand should be the same
194
What are some causes of poor connections at the service box?
- install issue
- vibration
- corrosion
- amateur retrofit
195
What are the implications of a poor connection at the service box?
- loose connection often result in a fire
- voltage drop
196
What are the implications of improper taps at the service box?
- loose connections
- legal action from the utility
197
What are the implications of fused neutral wires in the service box?
- fire hazard
- electrical shock potential
198
What is your strategy when you see fused neutral wires in the service box?
- ensure only live wires (blk/red) are fused in the service box
- recommend:
- replacing old boxes with fused neutrals
- rearranging fused neutral in modern houses
199
What are the implications of fuses upstream of the disconnect switch?
- electric shock when changing fuses
- may think the fuse holders are de-energized after switching off the main disconnects
200
What is your strategy when you notice moisture penetration in an exterior service box?
- any evidence of moisture penetration should recommend improvements
201
Two main functions of equipment grounding systems are –
* Grounding provides an emergency safety route for stray electricity, backing up the neutral wires in the distribution system.
* Grounding allows electricity to flow and allows fuses to blow and breakers to trip.
202
The functions of earth grounding systems include –
* Grounding systems can help dissipate electricity from lightning.
* Grounding systems can help avoid the build up of static electricity.
203
The grounding electrode conductor may also be called –
earth ground wire or ground wire.
204
The difference between bonding and grounding is –
Grounding connects things to ground, which has zero electrical potential.
Bonding connects things so that they will have the same electrical potential, but not necessarily zero volts.
205
You are allowed to ground to the gas piping.
False
206
The grounding systems are connected to the house neutral at the -
Service box
207
From the point where the ground and the neutral wires connect, there are two paths to ground. What are they?
- neutral service wire
- often the chosen path
- through the ground wire to the grounding electrode
- bare copper wires often used
- aluminum wires in Canada not permitted
208
List five destinations where ground wires can terminate.
1. Metal water supply pipes
2. Metal rods driven into the ground
3. Wires buried in the footings of buildings (UFER ground)
4. Buried grounding plates or rings
5. The frames of metal buildings (not common in houses)
6. Metal well casings
209
A 100-amp service would typically:
have a/an 8 gauge copper ground wire.
210
List 12 common problems found with grounding systems.
1. No grounding
2. Ground wire attached to plastic pipe
3. Ground wire after meters and valves with no jumper
4. Spliced ground wire
5. Ground wire attached to abandoned pipe
6. Poor connection
7. Ground connections not accessible
8. Ground rod cut off
9. Corroded ground rod
10. Undersized ground wire
11. Neutral bonded to ground wire after service box
12. Neutral wires not bonded to ground wire at service box
13. Service box not bonded to ground wire
14. No ground in sub panel feeder wires
211
What are the two types of grounding systems?
1. equipment grounding system
2. earth grounding system
212
What are the characteristics of the equipment grounding system?
- network of bare, uninsulated wires
- part of the branch circuit wiring
- considered an emergency path for electricity
- assumes electricity will reach the wrong place (an area humans might touch)
213
How does the equipment grounding system prevent conductive surfaces from having electrical potential?
grounding system attaches to these surfaces to provide an easy path to ground for electricity (i.e. service box panels)
214
What are the characteristics of the earth grounding system?
- connects the house electrical system to the earth with:
- water pipes
grounding rods
- acts as a path for lightning or static electricity
- not intended to carry the emergency current from the equipment grounding system to ground
215
When will the earth grounding system carry electricity?
- fault in the house causing current to flow through the ground wires in the distribution system
- neutral service wire out to the street was broken
216
Define "grounded"
- grounded = white neutral wire:
- carries current on a daily basis as part of a normal circuit
- electricity collected at the neutral bus bar in the distribution panel
- flows to the neutral connection in the service box
- then joined to the neutral service entrance wire
- neutral service entrance wire goes out to the transformer at the street
= normal electrical flow
217
Define "grounding"
- grounding = green/bare ground wire:
- available for emergency use only
- will carry electricity to the neutral service wire at the service box
218
What is the grounding electrode conductor?
bare wire that connects the service box to the grounding rods/water pipes
219
What is the equipment grounding conductor?
ground wires on each branch circuit
220
What are the characteristics of grounding?
- connecting something to the ground
- has zero electrical potential
- anything that is grounded is connected to ground and can have no electrical energy stored
- the goal is to ensure no house wiring or conductive material have stored electrical potential
221
What are the characteristics of bonding?
- joining two electrical conductors together
can be:
- two wires joined together
- wire & a pipe
- etc
- ensure both have the same electrical potential (voltage)
- prevents electricity build-up in one area
- no current flows b/w two bonded bodies b/c they have the same potential
- doesn’t protect anything
- gas piping must be bonded to the electrical grounding system
- don’t want piping to develop a electrical charge
- potential for an explosion if a spark develops
- usually accomplished with a wire attached to the hot/cold supply pipe
222
What is the relationship between arcing & sparks?
- sparks occur when there is a build up of enough electrical potential in one conductor that the electrical current will jump through air to reach the second conductor close to it.
- this is referred to as arcing
- can be good:
- for spark ignitions
- can be bad:
- when arcing occurs around anything flammable
- loose connections often start fires due to arcing
223
What things should you be aware of with metal water supply pipes?
- some metal pipes are beginning to be replaced with plastic
- clamp to pipe upstream of:
- meters
- valves
- pressure regulators
- jumper wires:
- should be used to bridge around dielectric connectors
- installed around a water meter if the electric service is grounded downstream of the meter
224
What things should you be aware of regarding metal rods drive in the ground?
- 2 x 10 ft long
- if grounding rods have been cut short, recommend further investigation
- check condition of clamp if accessible
225
What should you be aware of in regards to frames of metal buildings?
metal siding should be bonded to the grounding system
226
What should you be aware of when it comes to metal casings of private water supply wells?
- must be:
- 3 inches in diameter
- pump motor in well must be at least 50ft deep
227
Distribution panels are also called (list six other names if you can) –
Service panels
panelboards
auxiliary panels
sub panels
fuse boxes
fuse panels
breaker panels
228
Why would we not run the service entrance conductors throughout the entire house to feed the electrical needs in every room?
1. Too expensive
2. Too difficult to wire
3. Lack of localized control
229
Which devices are considered the brains of the electrical system?
Fuses and circuit breakers
230
Wires run directly from the service box to the branch circuits.
False
231
What is the advantage of a 240-volt circuit?
More electricity can flow at lower amperage ratings.
232
What size copper wires are adequately protected by –
a. 15-amp breakers?
b. 20-amp breakers?
c. 30-amp breakers?
d. 40-amp breakers?
a. 14 gauge
b. 12 gauge
c. 10 gauge
d. 8 gauge
233
What size wire is found on most general purpose outlets for lights and receptacles?
14 gauge
234
Subpanels must be immediately adjacent to the main panel.
False
235
Typical distribution panels have 60 circuits.
False
236
For each of the following, indicate whether the description fits fuses, breakers or both.
a. can be reset
b. we commonly find the wrong kind installed
c. they can be tested
d. they are not susceptible to mechanical failures
a. Breakers
b. Fuses
c. Breakers
d. Fuses
237
How is a Type S fuse different from a conventional fuse?
S-type fuses have a special base that screws permanently into fuse panel
and permits only the right size fuse to fit.
238
How is a Type D fuse special?
is a time delay fuse that will allow over-current to flow through it for a short period.
239
Do we normally shut off the power when looking at an electrical system in the house? Why or why not?
We do not shut off the power. This would be a significant inconvenience to the occupant.
240
List 16 conditions that may be found in all panels.
1. Obsolete and/or fused neutrals
2. Damaged panel or components
3. Loose panel
4. Inappropriate support material
5. Loose or missing door
6. Openings in panel
7. Panel too small
8. Overheating
9. Rust or water in panel
10. Circuits not labeled
11. Panel crowded
12. Poor access
13. Upside down
14. Not suitable for aluminum wiring
15. Poor location
16. Exterior panel not weather-tight.
241
Explain why fused neutrals are a bad idea.
These are dangerous because only the fuse on the neutral side blows. The circuit may not work, but there may be voltage throughout the entire circuit.
242
What is the implication of a panel that is too small for the service?
The panel may overheat.
243
Should the neutral and the ground wires be bonded together at the subpanel?
No. Because electricity may flow through the ground wire under normal
circumstances. The ground wire should be reserved for emergency situations.
244
How should the feeder wires to a subpanel from the main panel ideally be protected?
a) No fusing is necessary.
b) The main house fuses or breakers will protect the wire.
c) Fuses should be provided at the subpanel.
d) Fuses should be provided at the main panel.
e) None of the above.
d) Fuses should be provided at the main panel.
245
What are the implications of oversized breakers?
Oversized breakers will allow wires to overheat without tripping.
246
What does the term “double tap” mean?
Two wires are connected to a single terminal.
247
The red and black wires of multi-wire circuits should be on separate bus bars.
True
248
List four common problems found only with fuses.
1. Fuses bypassed
2. Fuses loose
3. Fuse holders loose or broken
4. Fuses for multi-wire circuits not linked
249
List four common problems found only with breakers.
1. Multi-wire circuits not linked
2. Too many breakers
3. Wrong breaker in panel
4. Loose breakers
250
List six problems found with wires in panels.
1. Sheathing not removed
2. Overheating
3. Loose connections
4. Damaged
5. Not well secured
6. Wires crossing bus bars
7. Abandoned wires in the panel
251
What is a split receptacle?
A split receptacle has the top part of the outlet on one circuit and the bottom part on a different circuit.
252
What is meant by 'linking' in multi-wire branch circuits?
Linking means that the fuses or breakers for multi-wire branch circuits have to be shut off in pairs.
253
Define "twin breaker"
two breakers that occupy a single slot in the panel
254
Describe the tree analogy
- service drop & service entrance conductors = tree trunk
- distribution wires = tree branches
- distribution panels = where branches attach to the trunk
255
Where are the blk/red wires connected in a panel?
connected to fuses or breaker terminals
256
Where are the white wires connected in a panel?
connected to the neutral terminal / bus bar
257
Where is the green wire connected in a panel?
connected to the panel enclosure
258
Cables should be:
- clamped where they enter the panel
- secured < 12 inches of the panel
259
Wires should not run across the bus bar
True
260
What are the advantages of a 240V circuit?
- able to deliver power to large appliances while keeping amps & wire size small
- minimize voltage drop
- does not need a white neutral wire
- pulse/stop b/w the live wires can act as a neutral wire
261
What are the disadvantages of a 240V circuit?
- two fuses/breakers required per circuit
- must pull out both to shut of power to appliance
- white neutral wire needs when the appliance has components that need 120V
262
What are the common copper wire to fuse/breaker sizes for:
- 14 gauge =
- 12 gauge =
- 10 gauge =
- 8 gauge =
- 6 gauge =
- 14 gauge = 15-amp
- 12 gauge = 20-amp
- 10 gauge = 30-amp
- 8 gauge = 40-amp
- 6 gauge = 60-amp
263
What are the causes for a damaged bus bar?
- bus bars:
- can be damaged from over-tightened fuses
- when one fuse is overtightened, this can cause of other fuses to have a loose connection to the bus bar
264
What are the causes of overheating in a panel?
- loose connections
- overused circuits
- damaged wire
- both sides of multi-wire branch circuits attached to the same bus bar
- aluminum wire in panels not rated for aluminum
265
What are common copper wire sizes (AWG) for:
- water heater =
- dryer =
- stove =
- central A/C =
- sauna =
- water heater = #12, 10
- dryer = 10
- stove = 8
- central A/C = 12, 10, 8
- sauna = 10, 8
