Unit 10: Commercial Load Calculations Flashcards
Using NEC® demand factors and calculation methods to properly size services, feeders, and branch circuits for commercial buildings, ensuring safe and efficient electrical system design.
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?
61⁄2 inches
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A type of conductor insulation approved for use in both dry and wet locations is _____.
THWN
Fill in the blank:
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
Fill in the blank:
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 corrected and adjustment factors be applied is _____.
24 inches
On the jobsite, the cut ends of electrical metallic tubing (EMT) are required to be _____.
I. reamed
II. threaded
I only
Fill in the blank:
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
True or False:
Branch circuits serving patient bed locations in the general care (Category 2) spaces of hospitals shall be part of a multiwire branch circuit.
FALSE
What 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-phase current formula
Table 310.16 pg. 187
I = P ÷ E x 1.732 I = 72,000 VA = 72,000 = 199.8 amperes
208 x 1.732 360.25
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 single-phase, 125-volt, 15- or 20-ampere rated receptacles must be provided for the show window lighting?
two per window
No point along the top of the window shall be farther than 6 ft. from a receptacle 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
Fill in the blank:
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.
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 NEC standards.
12 inches
Fill in the blank:
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.
11⁄2 in.
Fill in the blank:
For information technology information equipment rooms, 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
Fill in the blank:
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
Determine the maximum number of 1/0 THWN copper conductors permitted to be installed in a trade size 11⁄4 in. rigid metal conduit run more than 24 inches in length.
three
Determine the 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
Single-phase current formula Table 310.16 pg. 187
I = P ÷ E I = 5 kW x 1000 = 5000 = 20.8 amperes x 1.25 = 26 amperes 240 volts 240 Size 10 AWG NM cable with an ampacity of 30 amperes should be selected.
As indicated in the NEC, all of the following listed locations of dwelling units
require AFCI protection on the 120-volt, single-phase, 15- and 20-ampere branch
circuits supplying outlets or devices except:
a. parlor, library and den
b. sunroom, closet and hallway
c. bathrooms and garages
d. dining room, living room and multimedia room
c. bathrooms and garages
