Conductors and Sizing
Phase and grounded conductors sized _____ AWG and larger are permitted to be connected in parallel
1/0
What is the minimum size THHN conductor required for a 150A circuit breaker or fuse for a nonmotor circuit? Be sure to comply with the requirements of 110.14(C)(1)(b).
1/0 AWG
What size ungrounded conductors are required for a 250A feeder paralleled in two raceways?<br>
1/0 AWG
A raceway contains eight current-carrying conductors. What size conductor is required to feed a 21A noncontinuous lighting load in a dry location? The overcurrent device is rated 30A.
10 THHN
What size THHN conductor is required to feed a 16A noncontinuous load when the conductors are in an ambient temperature of 100 degree F in a dry location? The circuit is protected with a 20A overcurrent device.
12 AWG
Overcurrent devices for PV systems shall be rated to carry not less than _____ percent of the maximum currents calculated in 690.8(A).
125
What size feeder overcurrent device is required for a 100A continuous load?<br>
125A
What is the ampacity of each 1/0 THHN conductor when there are four current-carrying conductors installed in a raceway in a dry location?
136A
The smallest size conductor permitted for branch circuits, feeders, and services for residential, commercial, and industrial locations is _____.<br>
14 AWG copper 12 AWG aluminum
What size conductor is required to supply a 190A noncontinuous load in a dry location? The terminals are rated 75 degree C.
3/0 AWG
What is the minimum size THHN conductor permitted to terminate on a 70A circuit breaker or fuse if the circuit breaker and equipment terminals are listed for 60 degree C conductor sizing?
4 AWG
What size conductor is required for a 70A breaker that supplies a 70A noncontinuous load where the terminals are rated 75 degree C?
4 AWG
Conductor sizes are expressed in American Wire Gage (AWG) from 40 AWG through 4/0 AWG. Conductors larger than _____ are expressed in circular mils
4/0 AWG
The overcurrent device ratings in photovoltaic systems operated at temperatures greater than _____, shall comply with the manufacturer’s temperature correction factors.<br>
40 degrees C
Overcurrent devices must be designed and rated to clear fault current and must have a short-circuit interrupting rating sufficient for the available fault levels. If the minimum interruption rating isn't marked on the overcurrent device, according to the NEC the minimum for circuit breakers is _____ and _____ for fuses.
5,000A, 10,000A
If an 800A service has a calculated load of 750A, what size 75 degree C conductors are required for the service ungrounded conductors if the conductors are paralleled in two raceways?
500 kcmils
What is the ampacity of an 8 THHN conductor when installed in a walk-in cooler (dry location) if the ambient temperature is 50 degree F?
57A
The PV output circuit current is equal to the sum of parallel PV source circuit maximum currents as calculated in _____.<br>
690.8(A)(1)
What is the minimum size THHN conductor that is permitted to terminate on a 50A circuit breaker or fuse if the circuit breaker and equipment terminals are listed for 75 degree C conductor sizing?
8 AWG
All parallel equipment grounding conductors are required to be a minimum 1/0 AWG.
False
In general, THHN (90 degree C) conductor ampacities can't be used when sizing conductors. When more than three current-carrying conductors are bundled together, or if the ambient temperature is greater than 86 degree F, the allowable conductor ampacity must be decreased. THHN provides a greater ampacity for conductor adjustment purposes.
True
One of the purposes of conductor overcurrent protection is to protect the conductors against excessive or dangerous heat.
True
Terminals for equipment rated over 100A and pressure connector terminals for conductors larger than 1 AWG must have the conductor sized according to the 75 degree C temperature rating, as listed in Table 310.15(B)(16).
True
The ampacity of a conductor can be different along the length of the conductor. The higher calculated ampacity can be used if the length of the lower ampacity is no more than 10 ft, or no more than 10 percent of the length of the higher ampacity circuit conductors, whichever is less.<br>
True
The maximum overcurrent device size for 14 AWG is 15A, 12 AWG is 20A, and 10 AWG is 30A. This is a general rule, but it doesn't apply to motors or air conditioners according to 240.4(G).
True
To ensure that currents are evenly distributed between parallel conductors, each conductor within a parallel set must be installed in the same type of raceway (metallic or nonmetallic) and must be the same length, material, circular mils, insulation type, and must terminate in the same method.<br>
True
When equipment grounding conductors are installed in parallel, each raceway must have a full-size equipment grounding conductor sized according to the overcurrent device rating of that circuit.<br>
True
For one- and two-family dwellings, the maximum PV system voltage is _____V.
accessible to an unqualified person
Feeder tap conductors not over 25 ft are permitted, providing the _____.
ampacity of the tap conductors isn’t less than one-third the rating of the overcurrent device protecting the feeder conductors being tapped tap conductors terminate in a single circuit breaker or set of fuses that limit the load to the ampacity of the tap conductors tap conductors are suitably protected from physical damage
The temperature rating of a conductor is the maximum operating temperature the conductor insulation can withstand (without serious damage) over a prolonged period of time. The _____ provide guidance for adjusting conductor ampacities for different conditions.<br>
conductor allowable ampacities ambient temperature correction factors over three current-carrying conductors adjustment factors
Currents of photovoltaic systems are to be considered _____
continuous
Overcurrent devices for PV source circuits must be readily accessible.
false
THHN can be described as _____.<b
thermoplastic insulation with a nylon outer cover having a maximum operating temperature of 90°C
What size equipment grounding conductor is required in each raceway for an 800A, 500 kcmil feeder paralleled in two raceways?<br>
1/0 AWG
What size THHN/THWN conductor is required for an air-conditioning unit if the nameplate requires a conductor ampacity of 34A? The terminals of all the equipment and circuit breakers are rated 75°C and the raceway is installed outdoors in a wet location.<br>
10 AWG
The maximum PV inverter output circuit current is equal to the _____ output current rating.<br>
continuous
If the ampacity of a conductor doesn't correspond with the standard ampere rating of a fuse or circuit breaker, the next size up overcurrent device is permitted. This applies only if the conductors supply multioutlet receptacles for portable cord-and-plug-connected loads.
false
The ampacities listed in Table 310.15(B)(16) apply only when the ambient temperature is 40 degree C and there are no more than two current-carrying conductors bundled together. If the ambient temperature isn't 40 degree C, or there are more than two current-carrying conductors in a raceway, the allowable ampacities must be adjusted to reflect the ampacity under the conditions of use.
false
For PV systems, one source for lowest-expected ambient temperature is the Extreme Annual Mean Minimum Design Dry Bulb Temperature found in the ASHRAE Handbook & Fundamentals.
listed
The _____ of a dc photovoltaic source circuit or output circuit, must be calculated as the sum of the rated open-circuit voltage of the series-connected photovoltaic modules multiplied by the correction factor provided in Table 690.7. <br>
maximum photovoltaic system voltage
The PV source circuit current is calculated by multiplying the sum of the parallel module nameplate short-circuit current ratings (Isc) by 125 percent.<br>
true
The neutral conductor that carries only the unbalanced current from a 3-wire delta circuit, or 4-wire, three-phase wye circuit, is considered a current-carrying conductor for the purpose of applying the adjustment factors of Table 310.15(B)(3)(a).<br>
false
Outside transformer secondary conductors can be of unlimited length without overcurrent protection at the point they receive their supply if _____.
the conductors are suitably protected from physical damage the conductors terminate at a single circuit breaker or a single set of fuses that limits the load to the ampacity of the conductors
Equipment terminals rated 100A or less (receptacles, switches, circuit breakers, fuses, and so on) and pressure connector terminals for 14 AWG through 1 AWG conductors must have the conductor sized according to the 60°C temperature rating, as listed in Table 310.15(B)(16).<br>
true
The neutral conductor of a 3-wire wye circuit from a 4-wire, three-phase, wye system isn't considered a current-carrying conductor for the purpose of applying bundle adjustment factors.
false
The neutral conductor of a balanced 4-wire, three-phase wye circuit, that's at least 50 percent loaded with nonlinear loads (electric-discharge lighting, electronic ballasts, dimmers, controls, computers, laboratory test equipment, medical test equipment, recording studio equipment, and so forth) isn't considered a current-carrying conductor for the purpose of applying bundle adjustment factors.
false
Terminals are presumed to be rated 60 degree C for equipment 100A or less and 75 degree C for equipment terminals rated over 100A unless the terminal temperature rating is specified. Regardless of the conductor ampacity, conductors must be sized no smaller than required by the terminal temperature rating.
true
