Unit 9: Multi Family Dwelling Service Calculations Flashcards
True or false:
Every panelboard circuit and circuit modification shall be legibly identified at the panelboard or adjacent to the panelboard.
TRUE
Fill in the blank:
Installation of direct-buried cables in an area that is subject to movement by frost or settlement shall be ________.
placed with “S” loops or adequate allowance for movement
Fill in the blank:
As a general rule, the disconnecting means for an air-conditioning or refrigerating equipment is required to be a MINIMUM rating of ________ of its nameplate rated-load current.
115%
Fill in the blank:
Electrical equipment rooms or enclosures housing electrical apparatus that are controlled by a lock(s) shall be considered accessible to ________.
qualified persons only
What MINIMUM size copper THW conductors are required to supply a single-phase, 240- volt, 5 hp motor and a single-phase, 240-volt, 1kW, non-continuous non-motor load?
8 AWG
FLC of motor = 28 amperes x 125% = 35.0 amperes
Non-motor load I = P÷E I = 1000 ÷ 240 = 4.1 amperes
Total load = 39.1 amperes
Size 8 AWG THW CU conductors with an ampacity of 50
amperes should be selected from Table 310.16.
Fill in the blank:
When buried under a driveway of a dwelling, rigid metal conduit shall have a MINIMUM ground cover of ________
18 inches
Fill in the blank:
Cable splices made and insulated by approved methods shall be permitted to be located within a cable tray, provided they are ________
accessible
Fill in the blank:
Metallic surface-type cabinets for electrical equipment in damp or wet locations shall be mounted so there is at LEAST ________ air space between the cabinet and the wall or other supporting surface.
1⁄4 in.
Fill in the blank:
Given: An equipment disconnecting means is mounted at a height of 6 feet on a remote wall in an aircraft storage and maintenance hangar. The disconnect switch is 10 feet horizontally away from any aircraft fuel tanks. The disconnect switch is located in a/an ________ area.
unclassified
Fill in the blank:
The size of an equipment grounding conductor is most dependent upon ________.
available fault-current
Fill in the blank:
Busways shall be securely supported at intervals NOT exceeding ________ unless the raceway is otherwise designed and marked.
5 feet
Size 2 AWG THWN = 0.1158 sq. in. x 3 wires = 0.3474 sq. in.
Size 8 AWG THWN = 0.0366 sq. in. x 1 wire = 0.0366 sq. in.
Total = 0.3840 sq. in.
The 40% Column of Table 4 shows a trade size 11⁄4 in. PVC with a permitted fill of 0.581 sq. in. should be selected.
Given: You are to install an underground 50 ft. run of Schedule 40 PVC conduit that will contain three (3) size 2 AWG THWN circuit conductors and one (1) size 8 AWG THWN equipment grounding conductor. In compliance with the NEC®, what is the MINIMUM trade size PVC required for this installation?
1 1⁄4 in.
Fill in the blank:
A single-phase, 125-volt, 15- or 20-ampere receptacle outlet shall be installed at each residential kitchen countertop and work surface that is at LEAST ________ or wider.
12 inches
Fill in the blank:
The short-circuit and ground-fault protective device protecting an air-conditioner motor compressor branch circuit shall have sufficient ________ to permit the motor-compressor and other motors to start and accelerate their loads.
Time delay
Fill in the blank:
Non-heating leads of heating cables, if any, of electric space-heating cables shall be at least ________ in length.
7 feet
Fill in the blank:
At least one 15-volt, single-phase, 15- or 20-ampere-rated receptacle outlet is required to be installed within 18 in. of the top of a show window for each ________ linear feet or major fraction thereof of horizontal show window area.
12 feet
Fill in the blank:
Where junction or pull boxes enclose conductors of size 4 AWG or larger the boxes are to be sized by the raceway(s)
entering the box and not by the size of the conductors contained in the box. Where splices, angle or U-pulls are made, the distance between each raceway entry in the box and opposite wall of the box shall NOT be less than ________ times the largest raceway in a row plus the sum of the additional raceways in the row.
six
Fill in the blank:
Circuit protection must be designed and capable of disconnecting motors and their controllers from the circuit.
The disconnecting means of motors and their controllers shall open ________ supply conductor(s) of the circuit.
simultaneously all ungrounded phase
Fill in the blank:
A feeder tap less than 25 feet long does not require overcurrent protection at the tap if the ampacity of the tap conductor is at LEAST ________ of the rating of the overcurrent device protecting the feeder conductor.
One-third
Fill in the blank:
As a general rule, overhead spans of open conductors and multiconductor cables, of not over 1000 volts, shall have a vertical clearance of NOT less than ________ above the roof surface of a building or structure.
8 1⁄2 feet
Given: A 75 kVA transformer will supply a 225 ampere rated panelboard with size 4/0 AWG THWN copper conductors. What MINIMUM size copper system bonding jumper is required for the transformer?
2 AWG
Fill in the blank:
In a Class I, Division 1 location, each conduit entry into an explosionproof enclosure shall have a conduit seal installed within ________ from the enclosure.
18 inches
Fill in the blank:
Each commercial building accessible to pedestrians shall have an outside electric sign circuit rated at LEAST ________ that supplies no other load.
20 amperes
Fill in the blank:
As a general rule, overhead service conductors, installed as open conductors, must have a clearance of at LEAST ________ laterally (to the side) from windows that are designed to be opened, doors, ladders, stairs and porches.
3 feet
