Unit 4: Conductor Ampacity and Sizing Flashcards
Retrieve NEC 2023 ampacity tables, analyze derating factors, and determine conductor sizes based on environmental conditions. (25 cards)
Fill in the blanks:
Unless otherwise permitted, overcurrent protection for size 18 AWG non-power-limited fire alarm (NPLFA) circuit conductors shall not exceed _________ and the overcurrent protection for size 16 AWG NPLFA circuit conductors shall not exceed _________.
7 amperes, 10 amperes
Fill in the blank:
The general rule is where raceways and cables are exposed to direct sunlight on or above rooftops, and the distance above the roof to the bottom of the raceway or cable is less than 3/4 in., a temperature adder of 33°C(60°F) shall be added to the outdoor temperature to determine the applicable ambient temperature for application of the correction factors. An exception to this NEC® rule is _________.
where the insulated conductors or cables are Type XHHW-2
Fill in the blank:
An emergency system is required to have no more than _________ to have power available in the event of failure of the normal supply system.
10 seconds
Fill in the blank:
In an area of a hospital where flammable anesthetics are used, the entire area up to a level of _________ above the floor is considered to be a Class I, Division 1 location. The remaining area up to the structural ceiling is considered to be above the classified (hazardous) area.
5 feet
Fill in the blank:
Elevator driving motors used with a generator field control are rated as _________ duty motors.
intermittent
Fill in the blank:
Where a direct burial cable has a voltage of 45 kV, the NEC® mandates the minimum burial depth of the cable to be at least _________.
42 in.
Given: A recreational vehicle campground has a total of 150 RV campsites with electrical power. Twenty-five (25) of the campsites are reserved as tent sites. How many sites are required to have at least one (1) 20- ampere,125-volt receptacle outlet?
150
Determine the minimum size type SO cord permitted to supply a 40 hp,480-volt, 3-phase, continuous-duty, ac wound rotor motor when ran from the motor controller and where installed in an area with an ambient temperature of 86 degrees F.
3 AWG
FLC of motor = 52 amperes x 125% = 65 amperes
Size 3 AWG SO cord with an ampacity of 70 amperes should
be selected from Column A of Table 400.5(A)(1).
Fill in the blank:
Where a 30 hp, 240-volt, 3-phase synchronous motor has a power factor of 90 percent, as per the NEC® the full-load running current of the motor is _________.
69.3 amperes
63 amperes x 1.1 (power factor) = 69.3 amperes
Fill in the blank:
When applying service load calculations, each unit of electric vehicle equipment (EVSE) shall be calculated at either _________ or the nameplate rating of the equipment, whichever is larger.
7200 watts (volt-amperes)
Without considering exceptions, what are the requirements for the branch circuit supplying battery-equipped emergency luminaires during installation?
be on the same branch-circuit serving the normal lighting in the area.
In an industrial establishment, what is the maximum length of 200 ampere rated busway that may be tapped to a 600-ampere rated busway without providing additional overcurrent protection?
50 feet
Fill in the blank:
Size 4/0 AWG, 75 deg. C aluminum secondary conductors of a 3-phase delta-wye transformer, shall be protected at no more than _________.
200 amperes
Size 4/0 AWG AL conductors rated @ 75 deg. C ampacity = 180 amperes Next standard size OCP is rated at 200
amperes.
NOTE: Sec. 240.4(F) requires secondary OCP on delta-wye transformers.
Fill in the blank:
For trade size 3/4 in. MI cable, the radius of the inner edge of the bends shall be no less than _________ times the external diameter of the cable.
five
Fill in the blank:
Where an exposed flat cable assembly, Type FC, is installed less than _________ above the floor or fixed working platform, it shall be protected by a cover identified for the use.
8 feet
Fill in the blank:
The minimum burial depth for conduit or cables installed under an airport runway, concourse or tarmac is _________.
1½ feet
Determine the initial rating or setting of overload protection required for a 480 volt, 3-phase, 15 hp, continuous-duty motor given the following related information:
- Design C
- temperature rise - 40 deg. C
- service factor - 1.15
- actual nameplate rating - 18 amperes
22.5 amperes
FLA of motor = 18 amps x 125% = 22.5 amperes
Assume where the overload protection you have selected on the abovemotor is not sufficient to start the motor and trips, therefore, modification of this value is necessary, determine the maximum rating or setting of overload protection permitted.
25.2 amperes
FLA of motor = 18 amps x 140% = 25.2 amperes
Where a 50 kVA transformer with a 480-volt, 3 phase primary and a 208Y/120-volt, 3-phase secondary is to be installed and overcurrent protection is required on both the primary and secondary side of the transformer; determine the maximum size overcurrent protection device permitted for the primary side.
150 amperes
What is the demand load, in VA, for the general-use receptacles in an office building that has a total of 150 general-use, 125-volt, 20-ampere,single-phase receptacle outlets installed?
18,500 VA
150 receptacles x 180 VA = 27,000 VA
1st. 10,000 VA @ 100%
(remainder) 17,000 VA @ 50%
= 10,000 VA
= 8,500 VA
TOTAL DEMAND = 18,500 VA
Determine the maximum number of size 12 AWG conductors permitted to be housed in a 3½ in. deep, 3-gang metal masonry box that contains three(3)switches.
21
[masonry box] 9 (Size 12 AWG conductors permitted per gang) - 2 conductors per gang (switch)
7 wires per box x 3 gang = 21 conductors
Fill in the blank:
A horizontal raceway entering a dust-ignition proof enclosure from one that is not, need not have a seal-off if it is at least _________ in length.
10 feet
Fill in the blank:
Where abandoned communications cables are identified for future use with a tag, the tag shall be _________.
of sufficient durability to withstand the environment
Fill in the blank:
All 125-volt, 15- and 20-ampere receptacles located within _________ of the inside walls of a storable pool, storable spa, or storable hot tub shall be protected by a ground-fault circuit interrupter.
20 feet
