NEC Commercial Electrical Test #2
Bored holes in joists, rafter, and in wood studs for cables must be bored in the center of the stud a distance from the nearest edge of not less than ________ inch. 300.4
1 1/4 inch
Feeders containing a common neutral are permitted to supply how many sets of a 4-wire feeders? (215.4)
1 to 2
What is the minimum AWG copper size conductor that may be connected in parallel? 310.10 H 1
1/0
Given: A 150 KVA transformer with primary voltage of 480 volts, 3-phase, 3-wire has a secondary voltage of 120/208 volts, 3-phase, 4-wire. The transformer serves a pane-board with a 600 ampere main. The secondary conductors serving the panel-board consist of two parallel sets of 350 kcmil copper installed in separate raceways. What is the minimum size grounded conductor in each raceway installed from the transformer to the panel-board?
1/0 awg (You have 2 sets of parallel 350 kcmil copper. Go to Table 310.15 (B)(16) look up 350 kcmil copper (left hand side column) is 310 amps for copper 75*C column. You have 2 sets (310 x 2= 620 amps). Then go to Table 250.122 look up 800 amps, since there is no 620 amps you go next size up, the answer is 1/0 copper for minimum grounded conductor)
Connections of conductors by means of wire binding screws are permitted for number ________ awg or smaller conductors. 110.14
10 awg
The neutral conductor of a 3-wire branch circuit supplying a household electric range shall not be smaller than ______ awg. 250.140 exception 2
10 awg
Service drop conductors, when not in excess of 600 volts to ground, accessible to pedestrian that pass over residential sidewalk must have a minimum clearance of _______ feet. (230.24 B 1)
10 ft
Lighting load for demand factors for dwelling units on the first 3000 volts, required a demand factor of ______ percent. Table 220.42
100 %
For a one-family dwelling, the service disconnecting means shall have a rating of not less than ___ amps, 3-wire. (230.79 C)
100 amps
Doors or covers of enclosures shall be locked, bolted and underground box covers that weigh over ____ pounds shall be considered as meeting this requirement. 110.32 D
100 lb
What is the maximum load for a cord and plug connected load to a 15 amp receptacles? Table 210.21 B 2
12 amps
The point of attachment of 120/240 volt service drop over residential; property or driveways, shall provide conductors to a building with a clearance of ______ feet above finish grade. 230.24 B 2
12 feet
Branch circuit that supply a single motor used in a continuous duty application shall have an ampacity of not less than _______ percent. 430.22
125%
Feeder conductors shall have an allowable ampacity not less than the non-continuous load plus ______ percent of the continuous load.
125% (ask armen)
Branch circuit conductors that supply loads other than cooking shall not be smaller than ________ awg.
14 awg
Disregarding exceptions, screw shell lamp holders are permitted to be used with infrared heating lamps of up to _______ watts rating. 422.14
150 watts
Residential small appliance loads are calculated at _______ watts each. (220.52 A)
1500 watts (volt-amperes)
What is the maximum load for a cord and plug connected load to a 20 amp receptacles? Table 210.21 B 2
16 amps
A tap conductor for individual luminaries (fixtures) outlets and lamp-holders shall have a tap not over _______ inches long. 219.14 exception
18 inches
In Class 1, Division 1 locations, conduit seals shall be located in each conduit run of two inch size or larger that enter the enclosure and within no more than _____ inches of the enclosure. 501.15 1
18 inches
The minimum depth for direct buried cable under a two-family dwelling driveway is ______ inches. table 300.5
18 inches
Where compressed natural gas vehicles are repaired, and there is NOT ventilation of 4-air changes per hour, the area withing ______ inches of the ceiling is classified as Class I, Division 2. 511.3 C 1
18 inches
When used outside, aluminum grounding electrode conductors shall not be installed within _______ inches of the earth. (250.64 A)
18"
The minimum size grounding electrode conductor for an AC system with a 250 kcmil copper service entrance conductor is No_______ copper. (Table 250.66)
2 awg
Heavy-duty type lamp-holders are required on branch circuits have a rating in excess of _______ amperes. 210.21 A
20 amperes
Lamp-holders where connected to a branch circuit having a rating in excess of ______ amperes, lamp-holders shall be of a heavy-duty type. 210.21.A
20 amperes
Small appliance branch circuits in dwelling units are required to be rated at ______ ampere. 422.11 E
20 amps
Show windows shall be computed at ______ amperes per 1 ft of show window. 220.43 A
200 amp
Lighting systems operating at 30 volts or less shall be supplied from a maximum _______ ampere branch circuit. 411.2
25 amp
In all cases where there are live parts normally exposed on the front of switchboards or motor control centers, the working space in front of such equipment shall not be less than _________. Table 110.26 A 1
3 ft
In a solid channel cable tray with an inside width of 6 inches, the maximum fill area for three multi-conductor cable is _________ square inches. Table 392.9 F
3.2 sq. inches
Electrodes shall not be installed less than 8 feet in length and shall be buried in a trench not less than _____ inches. 250.53 G
30 inches
The working space shall be not less than ______ inches wide in dead front of the electric equipment. 110.26 2
30 inches
The minimum size copper conductor required for the connection between a 400-amp service and concrete encased grounding electrode is a number ______ awg. 250.66 B
4 awg
Given: A 75 KVA transformer with primary voltage of 480 volts, 3-phase, 3-wire has a secondary voltage of 120/208 volts, 3-phase, 4-wire. The transformer serves a panel-board with a 250 ampere main. The secondary conductors serving the panel-board are 250 kcmil copper. What is the minimum size copper requirement of a bonding jumper from the transformer to the panel-board? Table 250.122 Min. Size Equipment Grounding Conductors for Grounding Raceway and Equipment
4 awg (from the table 250.122 select 300 amps, since the main is 250 amps you select the next size up, and for copper it is 4 awg)
The minimum branch circuit rating for electric ranges with a nameplate rating of 8 3/4 kW or more is ________ amperes. (210.19 A 3)
40 amp
What is the minimum general lighting load permitted in a 1500 square foot single-family dwelling? Table 220.12
4500 (3 x 1500 = 4500)
The total rating of utilization equipment fasten in place, other than luminaries (lighting fixtures), shall not exceed ____ percent of the branch circuit ampere rating. 210.23 A 2
50 %
If an apartment complex contains 40 units with a 12 Kw range in each, what is the total kw rating for all the ranges that must be used in calculating the electric services? (Table 220.55 Demand Factor for ranges, ovens etc.)
55 kw (Go to Column C - 31-40 appliance = 15kw + 1kw for each range. Therefore 15kw + 40 kw "40 units" = 55 kw)
For a single family and two family dwelling at least one outdoor receptacle outlet shall be accessible at grade level and not more than ______ feet above grade. 210.52 E 1
6 1/2 feet
Dedicated electrical space equal to the width and depth of the equipment and extending from the floor to a height of _______ feet above the equipment or to the structural ceiling. 110.28 E 1
6 feet
Where a swimming pool is installed at a dwelling unit and the dimensions of the building lot prelude meeting the required clearance for locating receptacles, a receptacle outlet is permitted to be installed at least ____ feet from the inside wall of the pool. 680.22 2
6 feet
At least _______ inches of free conductor shall be left at each outlet, junction box and switch point for connection of fixtures or devices measured at what point. 300.14
6 in
The allowable number of service disconnecting means shall consist of not more than _________ sets of circuit breakers. (230.71)
6 sets
Appliance loads in dwelling units shall be permissible to apply a demand factor of _____ percent to the nameplate rating load of four or more appliance fasten in place, other than electric ranges, clothes dryer, ac or heating equipment that serve by the same feeder or service in a one-two or multi-family dwelling. 220.53
75%
If three 8 3/4 kw electric ranges are used in a three unit apartment complex, what is the total kw rating that must be used for all of these ranges in calculating the electric service? Table 220.55 ?
8 3/4KW = 8.75KW=8750(8.75 X 1000) 3 X 8750 Watts=26,250 Watts / Go to Table 220.55 - look up Column B, 3 appliances = 55% / 26,250 x .55 = 14,437 watts =14.437kw (14,437 divided by 1000)
The minimum size conductor permitted for bonding swimming pool steel is ______ awg. 680.26
8 awg
When outside overhead wiring is used on insulators, with a # _______ awg for a span of 50 foot messenger cable, 600 volts or less what is the minimum size copper wire allowed. 230.24 13
8 awg
Direct buried conductors and cables emerging from the ground shall be protected by an enclosure or raceway a distance above the ground of ______ feet. 300.5 D 1
8 ft
Exposed non-current-carrying metal parts of fixed equipment likely to become energized shall be grounded where within ______ feet horizontally of ground or grounded metal objects and subject to contact by persons. 250.110
8 ft
Service conductors that pass over a flat roof must have what clearance of _____ feet from the highest point of roof over which they pass. (230.24 A)
8 ft
The rating of any one cord and pug connected utilization equipment shall not exceed _____ percent of the branch circuit ampere rating. 210.23
80 % (not fastened 80%) (fastened 50%)
A 30 ampere branch circuit that rating of any one cord and plug connected utilization equipment shall not exceed _____ percent of the branch circuit ampere rating. 210.23 B
80%
For feeder or service supplying household electric ranges, wall mounted oven, counter mounted cooking units, and electric dryers, the maximum unbalanced load shall be considered as ______ percent of the load on the un-grounded conductors. Table 220.55
80%
In dwelling units, over-current devices shall not be located in the vicinity of easy ignitable material, such as _______ . 240.32 B
Clothes closets
Where circuit breakers are used as switches for high-intensity discharge lighting, the circuit breakers shall be listed and marked ________. 240.82 D
HID
In dwelling unit bedrooms, arc-fault circuit interrupter protection is required for protection of the entire branch circuit serving _________. 210.12
Receptacles
A conductor insulation suitable for use in wet location is ________. 310.10 C
THW
At a dwelling unit swimming pool, ground fault circuit interrupter (GFCI) protection required for all of the following, except ___________. 680.22 4
a luminaire rigidly attached to the house 6 feet horizontally from the inside wall of the pool and 6 feet above the maximum water level.
Given: An eight foot wide switchboard contain 1200 ampere over-current devices and is located in an electrical equipment room. The code requires that the equipment room shall have _________. 110.26 3
a personnel door which open in the direction of egress
Given: A 75 KVA transformer with primary voltage of 480 volts, 3-phase, 3-wire has a secondary voltage of 120/208 volts, 3 phase, 4-wire. The transformer secondary is protected at 225 amperes. The secondary conductors are 25 feet long and terminate in a single set of fuses. What is the minimum size of THHN aluminum secondary conductors?
a. 75 KVA = 75,000 VA b. 75,000 VA / (208 x 1.732) = 208 amps c. Table 310.15 (B) (16) look up THHN (90 C column / aluminum) 208 amps - select 230 amps will require 250 kcmil. Answer is 250 kcmil.
Ground fault circuit interrupter (GFCI) protection is required for ________. 210.8 B 1
all 125-volt 20 ampere receptacles in commercial kitchens.
A feeder is ___________. 100
all circuit conductors between the service and the final branch-circuit over-current device
The connection between the grounding terminal of a grounding-type receptacle and grounded box is accomplished by using _______. 406.4 C
an equipment bonding jumper (equipment grounding conductor)
Type NMC cable is NOT permitted to be installed ______. 334.12
as an open run in a suspended ceiling in an office building
Unless other voltages are specified, for purposes of computing branch circuit and feeder loads, nominal system voltage of ______ volts shall be used.
ask armen
A single ground rod with a resistance to ground of 25 ohms or less, is approved as a grounding electrode system shall be ______. 250.53
augmented by one additional electrode
Given: An eight foot wide switchboard contain 1200 ampere over-current devices and is located in an electrical equipment room with a personnel door. The code requires that the equipment room personnel door shall _______________. 110.26 C 3
be equipped with hardware that is normally latched but will open under simple pressure
The code allows wall-switched controlled receptacles in dwelling units in lieu of lighting outlets in all _______. (210.70 Habitable rooms)
bedrooms
Where the service equipment does not have concentric knockouts ______ are accessible for maintaining electrical continuity. 250.92 B 4
bonding type lock nuts and bushing
A device designed to open and close a circuit by n non-automatic means and open to open the circuit automatically on a predetermined over-current without damage to itself when property applied within its rating is called a ________. 100
circuit breaker
Unless not specified in this code, conductors normally used to carry power shall be of ________. 110.5
copper
All of the following are permitted as a type of equipment grounding conductor, except the _________. 250.118 Types of Equipment Grounding Conductors
copper sheath of mineral-insulated, meta-sheathed cable
In a hospital, receptacles or their cover plates must have a distinctive color or marking so as to be readily identifiable where supplied from the ________. 517.31 4 E
emergency systems
Where an electric sign ballast is located above a suspended ceiling, the ballast shall NOT be connected to the branch circuit by ________. 600.21 F
flexible cord
Supply conductors provisions shall be made to route the service-entrance, service lateral, or feeder where the point of attachment is known __________.
for servicing? (check the code)
Receptacles outlets installed in bathroom of garage area always require ______. 210.8
ground-fault circuit-interrupter protection (GFCI)
Connected to earth or some conducting body that serves in place of the earth is the definition of ________ . 100
grounded
If three conductors flexible cord used in a light fixture has one conductor marked with ridges or grooves, to identify it as the ________ conductor. 400.21F
grounded
What must be provided for all working spaces above service equipment? 110.26 D
illumination
Given: An eight-story office building is completely sprinklered on all floors. The fire sprinkler system is in compliance with NFPA 2010. Electrical non-metallic tubing is permitted to be used in this office building _________. 362.10 exceptions
in all locations exposed or concealed
A grounding connection shall not be made to any grounded circuit conductor on the _______ side of the service disconnecting means: (no exceptions noted). 250.30?
load
Given: A 15-ampere rated dimmer switch is installed to control a 15-ampere rated duplex receptacle on a 20-ampere circuit in a living room where a lamp will be cord-and- plug-connected. Would the installation of this dimmer switch comply with code provisions? 404.14 E
no, because a dimmer switch is permitted to control only permanently installed luminaries
Non-metallic sheath cable is required to be concealed within wall, floors or ceiling that provide a thermal barrier of material having at least a 15 minute fire rating where installed _________. 334.10 3
on a two story office building of type III, IV or V construction
In an office building, a switchboard or panel-board likely to required servicing while energized shall be field marked indicating________. 110.16
potential electric arc flash hazard
Accessory building that has a floor located at or below grade level not intended for habitation and limited to storage areas, work areas, and areas of similar use are required to have outlets that are __________. (210.8 A)
provided with ground-fault circuit interrupter protection (GFCI)
Ground-fault circuit-interrupter protection for a circuit to heated floor in spa or hot tub area is ________. 680.43 3 also see 424.45 G
required on all of these locations regardless of the floor covering:
Given: The location of the telephone service to a dwelling unit is 25 feet away from the electric service and power system grounding electrode. Which of the following installations would meet the code requirement for grounding the metallic sheath of the phone service cable at the dwelling unit? 800.100
run a 14 awg primary grounding conductor to a separate communications ground rod installed and bonded between it and the power grounding electrode system with a 6 awg copper conductor.
For devices with screw shells, the terminal for the grounded conductor shall be the one connected to the ________. 410.90
screw shell
The floor area for each floor of lighting loads ______ computed from the outside dimensions of the building, dwelling and other area involved. 220.12
shall be
Given: The entrance to a business has a permanently installed decorative fountain. The owner wishes to advertise with a portable sign. This portable electric sign ________. 680.57 2
shall be located at least 5 feet away from the inside wall of the fountain
In panel-boards and switchboards where the conductors are NOT paralleled, the grounded conductors of each branch circuit ________. 408.41Exception
shall be terminated in separate terminal that is not also used for another conductor
Aluminum electrode ______ be permitted for grounding. 250.52 B 2
shall not
A grounding electrode at two or more buildings ______ required where only one branch circuit is supplied. 250.32
shall not be
Branch circuits feeding lighting , central alarm, signal, communication, or other public or other purposes for public or common areas of a two-family or multifamily dwelling _________ supplied from equipment that supplies an individual dwelling unit or tenant space. (210.25 B)
shall not be
Conductor of dissimilar metals _______ intermixed in a terminal splicing connector where physical contact occurs between dissimilar conductors. 110.14
shall not be
Metal underground gas piping system _______ used as a grounding electrode. 250.52 B 1
shall not be
Conductor supplying several motors or a single motor shall have the current of the motors and loads to be operated at __________ . 430.7 D 1
the same time
A strut-type channel raceway is permitted to be used in all of the following installation, except ___________. 384.12
where concealed behind walls, floors and ceilings
When branch circuit conductors of different systems are installed in the same raceway, each other system grounded conductor shall be identified by ________. 200.10 2
white insulation with non-green stripes
