Unit 10: Commercial Load Calculations Flashcards
Solve commercial service load calculations, assess total demand requirements, and apply NEC standards for different occupancy types.
Fill in the blank:
At carnivals and fairs, service equipment shall not be installed in a location that is accessible to unqualified persons, UNLESS the equipment is ________.
lockable
Fill in the blank:
Where the NEC® specifies that one equipment shall be “within sight from” or “within sight of” another equipment, the specified equipment is to be visible and not more than ________ from the other.
50 feet
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As a general rule, where a cable is installed parallel to framing members, the cable shall be installed so that the nearest edge of the cable is not less than ________ from the nearest edge of the framing member.
1 ¼ in.
Generally, how many grounded conductors are permitted to be terminated under an individual terminal within a switchboard or panelboard where the equipment operates at less than 1,000 volts?
one
Fill in the blank:
The service equipment provided for a mobile home shall be located in sight from and not more than ________ from the exterior wall of the mobile home it serves.
30 feet
What is the MAXIMUM number of size 1/0 AWG THH/THWN copper current-carrying conductors allowed by the NEC® at any cross-sectional area of a 4 in. x 4 in. metallic wireway?
17
4 in. x 4 in. = 16 sq. in. x 20% (percent of fill allowed) = 3.2 sq. in.
3.2 sq. in. (wireway)/.1855 sq. in. (1wire) = 17.2 = 17 size 1/0 THHN/THWN conductors permitted
Fill in the blank:
Where electrical boxes are installed in a wall having a combustible finish and located above a kitchen wall countertop they shall be installed ________.
flush or projected from the finish surface
Fill in the blank:
A single-phase, 125-volt, 15- or 20-ampere receptacle outlet shall be installed at each residential kitchen, breakfast room, or dining room wall countertop and work surface that is at LEAST ________ or wider.
12 in.
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A one-family dwelling unit is to have the following fastened in place appliances installed: 1,200 VA dishwasher 4,000 VA water heater 1,150 VA garbage disposer 700 VA attic fan 1,920 VA garage door opener The demand load, in VA, on the ungrounded (line) service entrance conductors for the listed appliances is ________ when applying the general method of calculations for dwelling units.
6,728 VA
1,200 VA dishwasher
4,000 VA water heater
1,150 VA garbage disposer
700 VA attic fan
1,920 VA garage door opener
8,970 VA connected load x 75% (demand factor) = 6,728 VA
demand load
Fill in the blank:
Nonmetallic cable trays shall be made of ________ material.
flame-retardant
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Switches are to be located a horizontal distance of at LEAST ________ from the inside walls of an indoor placed spa or hot tub.
5 feet
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Direct buried cables installed under an open field vacant property must have a MINIMUM cover depth of ________ when the applied voltage is not more than 600 volts.
24 in.
Fill in the blank:
Shore power for boats docked in marinas and boatyards shall be provided by single receptacles that are of the locking- and grounding-type, mounted at least 12 inches above the deck surface, and rated not less than ________.
30 amperes
Fill in the blank:
For electrical systems over 1000 volts, where pulls of conductors in junction boxes are being made, the length of the box shall not be less than ________ the outside diameter of the largest shielded or lead-covered conductor or cable entering the box.
48 times
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Each grounding electrode plate of bare or electrically conductive coated iron or steel material shall expose not less than ________ sq. ft. of surface to exterior soil.
2
Fill in the blank:
Installation of direct buried cables in an area that is subject to movement by frost or settlement of the soil shall be ________.
placed with “S” loops or provide an adequate allowance for movement
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Busways shall be securely supported at intervals not exceeding ________ unless the raceway is otherwise designed and marked.
5 feet
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At LEAST ________ of free conductor, measured from the point in the box where it emerges from its raceway, shall be left at each junction box or device box for splices or connections to devices.
6 in.
What type of PVC conduit should be used for fixed wiring above bulk storage tanks?
Schedule 80
Fill in the blank:
Electrical installations which are controlled by lock(s) or other approved means, shall be considered to be accessible to ________.
qualified persons only
Fill in the blank:
The size of an equipment grounding conductor of the wire type is based on the rating of the ________, ________, and ________.
branch-circuit, short-circuit, groundfault protective device
The NEC® mandates expansion fittings for rigid PVC conduit shall be provided to compensate for thermal expansion. In an environment where the normal annual change in temperature is 100°F, and the length of the PVC is 100 feet, how much allowance for thermal expansion must be considered?
4.06 in.
Fill in the blank:
Where an enclosure housing a motor controller is located outdoors and subjected to exposure to heavy rain, sleet and snow, the enclosure must have a MINIMUM listing as a ________ enclosure.
Type 3
Fill in the blank:
The MINIMUM clearance between luminaires installed in clothes closets and the nearest point of a closet storage space shall be ________ where surface-mounted incandescent or LED luminaires are installed.
12 in.
