Unit 2: Branch Circuits Flashcards
Identify branch circuit classifications, compute proper circuit sizes, and apply updated NEC 2023 regulations. (25 cards)
Fill in the blank:
Where conduits enter a floor-standing switchboard, switchgear or, panelboard at the bottom, the conduits, including their end fittings, shall not rise more than _________ above the bottom of the enclosure.
3 in.
Fill in the blank:
For emergency systems where internal combustion engines are used as the emergency power source, an on-site fuel supply shall be provided with an on-site fuel supply sufficient for not less than _________ operation of the system.
2 hours
Fill in the blank:
Conductors supplying outlets for arc and xenon motion picture projectors of the professional type shall be a minimum size of _________ and shall have an ampacity of not less than the projector current rating.
8 AWG
Fill in the blank:
Thermostatically controlled switching devices serving as both controllers and disconnecting means for fixed electric space heating equipment shall be _________.
designed so that the circuit cannot be energized automatically after the device has been manually placed in the OFF position.
Fill in the blank:
A bonding jumper connected between the communications grounding electrode and power grounding electrode system at the building or structure service where separate electrodes are used shall not be smaller than size _________ copper.
6 AWG
3 in. (largest conduit) x 8 = 24 inches
Given: A straight pull of size 4 AWG and larger conductors is to made in a junction box that will have a trade size 3 in. conduit and two (2) trade size 2 in. conduits entering on the same side and exiting on the opposite wall. Nosplices or terminations will be made in the box. Which junction boxes is required for this installation?
24 in. x 24 in.
Given: A dairy farm supplied with a 120/240-volt, single phase electrical system will have the following three loads supplied from a common service;one – 18,000 VA, one - 16,000 VA, and one – 10,000 VA. What is the total demand load, in amperes, on the ungrounded service-entrance conductors?
152 amperes
18,000 VA x 100% = 18,000 VA
16,000 VA x 75% = 12,000 VA
10,000 VA x 65% = 6,500 VA
Demand = 36,500VA ÷ 240 volts = 152 amperes
Fill in the blank:
In compliance with the Code, all 15 or 20-ampere, single-phase, 125-volt receptacles located within _________ of the edge of a decorative fountain shall be provided with GFCI protection for personnel or SPGFCI protection
20 feet
Fill in the blank:
The emergency electrical disconnects for attended self-service gasoline stations or convenience stores with motor fuel dispensing facilities must be located not more than _________ from the motor fuel dispensers that they serve.
100 feet
Given: A dry-type transformer is fed with four (4) parallel size 500 kcmil conductors per phase. The conductors enter the enclosure on the opposite wall of the terminals. What is the wire-bending space required for the conductors?
16 in.
Fill in the blank:
Branch circuit conductors that supply a single motor used in a continuous duty application shall have an ampacity of not less than _________ of the full-load current rating of the motor.
3 AWG
Fill in the blank:
Where time-delay (dual-element) fuses are used for short-circuit and ground-fault protection for both windings of a part-winding synchronous motor, the fuses shall be permitted to have a rating not exceeding _________ of the full-load current of the motor.
150%
Where a conductor is marked RHW-2 on the insulation, what does the -2 represent?
The conductor has a maximum operating temperature of
90ºC.
Apply the general method of calculation for dwellings and determine the demand load, in kW, on the ungrounded service-entrance conductors for four(4)household electric ranges rated 19 kW each.
23 kW
19 kW – 12 kW = 7 kW x 5% = 35% increase in Column C
17 kW (4 appliances in Col. C) x 135% = 22.95 kW demand
Fill in the blank:
As a general rule regarding movie theaters, all switches for controlling the emergency lighting systems shall be permitted to be located _________.
in the lobby
Fill in the blank:
Single-conductor cable Type _________ shall be permitted in exposed outdoor locations in photovoltaic source circuits for photovoltaic module interconnections within the photovoltaic array.
USE-2
What percent of electrical supplied spaces in a recreational vehicle parks must be equipped with at least one (1) 30-ampere 125-volt receptacle outlet?
70%
Fill in the blank:
Each operating room of a healthcare facility shall be provided with a minimum of _________ listed “hospital grade” receptacles.
36
Where a 3-phase, 25 kVA rated transformer with a 480-volt primary anda 208Y/120-volt secondary is to be installed where both primary and secondary protection is required to be provided, determine the maximum standard ampere rating of the secondary overcurrent protection as permitted by the NEC®.
90 amperes
Fill in the blank:
Where ungrounded conductors are run in parallel in multiple raceways,the wire-type equipment grounding conductor, where used, shall be _________.
run in parallel in each raceway
Fill in the blank:
Where track lighting is installed in a continuous row, each individual section of not more than _________ in length shall be securely supported, unless identified for supports at greater intervals.
4 feet
Determine the minimum size THWN copper feeder conductors required by the NEC® to supply the following 480-volt, continuous duty, 3-phase, induction-type, Design C, motors.
- one - 40 hp
- one - 50 hp
- one - 60 hp
4/0 AWG
Fill in the blank:
In health care facilities, essential electrical systems shall have a minimum _________.
of two (2) independent sources of power
Fill in the blank:
Where compressed natural gas vehicles are repaired in a commercial major repair garage, the area within _________ of the ceiling shall be considered unclassified where adequate ventilation is provided.
18 in.
