Unit 10: Commercial Load Calculations Flashcards
Applying NEC® demand factors and calculation methods to size service, feeders, and branch circuits for commercial buildings, ensuring proper load distribution and compliance with code requirements.
Fill in the blank:
Where exceptions are not applicable, when a metal pole supports a luminaire, the pole shall be provided with an accessible handhole of NOT less than ________ near the base of the pole.
2 in. x 4 in
What is the MINIMUM wire bending space required at the top and bottom of a panelboard that has one (1) size 3/0 AWG conductor connected to each busbar in the panelboard?
6 1⁄2 inches
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A type of conductor insulation approved for use in both dry and wet locations is ________.
THWN
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Equipment or materials to which has been attached a symbol or other identifying mark of an organization that is acceptable to the authority having jurisdiction is defined as ________.
labeled
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Disregarding exceptions, the MAXIMUM distance permitted for seven (7) current-carrying multiconductor cables to be bundled together without requiring the ampacity of the conductors to be derated and adjustment factors be applied is ________.
24 inches
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On the job-site the cut ends of electrical metallic tubing (EMT) are required to be ________.
I. reamed
II. threaded
I only
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Unless permitted by local code regulations, Type AC cable shall be secured within ________ of every box, cabinet, or fitting and at intervals not exceeding 41⁄2 feet where installed on or across framing members.
12 inches
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Given: A 120/240-volt, single-phase, one-family dwelling service has a metal chain link fence opposite exposed live parts of the service equipment. The required depth of the clear working space in front of the service equipment must be at LEAST ________.
3 ft
Fill in the blank:
Branch circuits serving patient bed locations in the general care (category 2) spaces of hospitals shall ________.
not be part of a multiwire branch circuit
What MINIMUM size ungrounded (phase) THWN copper service-entrance conductors are required for a 208Y/120-volt, three-phase commercial service with a demand load 72,000 VA?
3/0 AWG
I = P ÷ E x 1.732
I = 72,000 VA/ 208 x 1.732
= 72,000/ 360.25
= 199.8 amperes
Size 3/0 AWG THWN conductors with an ampacity of 200 amperes should be selected from Table 310.16.
Given: A retail jewelry store has two (2) large show windows having a length of 15 feet each. One show window is on each side of the front entry/exit door. How many singlephase, 125-volt, 15- or 20-ampere rated receptacles must be provided for the show window lighting?
two per window
One receptacle is required for each 12 ft. of show window or major fraction thereof therefore, 2 receptacles are required for each 15 ft. show window.
Type NM cable is permitted to be used under all the following conditions or locations EXCEPT:
a. as a feeder.
b. in Type V construction.
c. in a wet or damp location.
d. in multifamily dwellings.
c. in a wet or damp location.
What size copper grounding electrode conductor is required for a service where size 350 kcmil copper conductors are used as the service entrance conductors?
2 AWG
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In kitchens of dwelling units, receptacle outlets serving each wall countertop and work surface shall be installed so that no point along the wall line is more than ________ measured horizontally from a receptacle outlet in that space.
24 inches
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Where portions of a raceway are known to be subjected to different temperatures and where condensation is known to be a problem, the raceway shall be ________.
filled with an approved material to prevent the circulation of air
Determine the ampacity of six (6) current-carrying size 4/0 AWG XHHW aluminum conductors where installed underground in a PVC conduit.
210 amperes
Size 4/0 AWG XHHW AL – (75°C ampacity, wet location) = 180 amperes
180 amperes x .8 (adjustment factor) = 144 amperes
Fill in the blank:
Given: A six (6) foot high chain-link fence topped with razor-wire, used to deter access by persons who are not qualified, encloses an outdoor installation of electrical apparatus rated 12 kV. The razor-wire above the chain-link fence shall be at LEAST ________ in height to comply with the NEC® standards.
12 inches
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Where electrical metallic tubing (EMT) is installed under metal-corrugated sheet roof decking, the EMT shall be installed so there is NOT less than ________ clearance from the lowest surface of the roof decking to the top of the EMT
1 1⁄2 in.
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Remote disconnecting controls shall not be required for critical operations data systems when ________.
an approved fire suppression system suitable for the application is in place
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Unless listed and identified otherwise, terminations and conductors of circuits rated 100 amperes or less, or marked for conductor sizes 14 AWG through 1 AWG, shall be considered rated for ________.
60°C
In a dwelling, which of the following receptacles, if any, require GFCI protection?
I. 240-volt, 30-ampere clothes dryer receptacle
II. 240-volt, 50-ampere electric range receptacle
Both I and II
Fill in the blank:
The NEC® requires a MAXIMUM spacing between supports for trade size 4 in. rigid polyvinyl chloride conduit (PVC) to be ________.
7 feet
Determine the MINIMUM size copper branch-circuit conductors required to supply a 5.0 kW, 240-volt, single-phase storage-type residential electric water heater. Use Type NM cable and consider all terminations to be rated 60°C.
10 AWG
I = P ÷ E
I = (5 kW x 1000)/ 240 volts
= 5000/ 240
= 20.8 amperes x 1.25 = 26 amperes
Size 10 AWG NM cable with an ampacity of 30 amperes should be selected
Fill in the blank:
As indicated in the NEC®, locations of dwelling units require AFCI protection on the 120-volt, single-phase, 15- and 20-ampere branch circuits supplying outlets or devices EXCEPT ________.
bathrooms and garages
