When the corrected ampacity of a 10 AWG copper conductor is 12.86 amps, the
maximum size circuit breaker permitted to protect the conductors is ___. - answer15
According to 240.4(D)(7), the largest circuit breaker that can be used to protect a circuit
that uses 10 AWG conductors has a rating of ___ A. - answer30
A 240-volt load, such as a window unit air conditioner, would require breaker ___ to be
installed in the panelboard. - answerb
Generally, circuit breakers must be ___. - answer readily accessible
What is the maximum voltage between circuit conductors when using plug fuses? -
answer125
Refer to Figure 204.5. The conductors at Point I are ___. - answertaps
Where installed in a 3-pole, 600-volt fused safety switch, the minimum number of fuses
required to protect a 120-volt, 1-ph, 2-wire branch circuit is ___. - answer1
The secondary of a 300 KVA, 480 - 240-volt Δ-Δ transformer is delivering 100 amps to
3Ø loads. Based on this load, the smallest permitted primary and secondary conductors
are installed.
Refer to Scenario 223.51. The maximum rating of the primary OCPD is ___ A. -
answer100
The secondary of a 300 KVA transformer delivers power to a 180-amp, 3Ø load. This is
a 480 — 240 volt Δ-Δ transformer. Primary and secondary conductors are the minimum
size required to serve the load.
Refer to Scenario 220.53. The secondary OCPD can have a rating no greater than ___
amps. - answer200
Section 240.21(C)(6) in the NEC® is the "25 foot rule." This section requires that the
secondary conductors be 25 feet or shorter in length and ___.
I. have an ampacity that is ≥ [(Pri OCPD ÷ 3) × (Epri line ÷ Esec line)]
II. have an ampacity that is ≥ the rating of the circuit breaker or fuses at the end
III. be installed in a raceway or otherwise protected from physical damage - answerI, II,
& III
, Circuit breakers shall be marked with a voltage rating not less than the nominal system
voltage that is indicative of their capability to interrupt fault currents ___.
I. between phases
II. from phase to ground
III. between the neutral and ground - answerI & II only
Handles or levers of circuit breakers, and similar parts which may move suddenly in
such a way that persons in the vicinity are likely to be injured by being struck by them,
shall be ___.
I. concealed
II. isolated
III. guarded - answerII or III only
If a fuse label is not marked with a fuse interrupting rating, the fuse size has ___. -
answeran interrupting rating of 10,000 amps
A conductor has a computed ampacity of 75 amps. What is the maximum standard
ampere rating of the overcurrent protection device the NEC® permits to protect this
circuit? This is not a motor circuit or part of a multioutlet branch circuit supplying
receptacles. - answer80 amperes
If the allowable current rating of a busway is 1400 amps, what is the maximum
allowable rating of the overcurrent protection device that may be used to protect the
busway? - answer1200 amps
The use of the term SPD is becoming quite common and is addressed in NEC® Article
___. - answer242
Unless specifically listed for them, a surge-protected device is not permitted on a(n) ___
system. - answerimpedance-grounded
If installed, a surge protective device shall be connected to each ___ conductor. -
answerungrounded
When ___ touch together, this is a ground fault.
I. two ungrounded circuit conductors
II. an ungrounded and a grounded circuit conductor
III. an ungrounded circuit conductor and the metal conduit - answerIII only
One conduit is run from Panel LA to a pull box as shown in Figure 205.13. The 250-amp
breaker has 250 kcmil circuit conductors connected to it, and 500 kcmil circuit
conductors are connected to the 400-amp breaker. Only one grounding conductor is
required in this conduit for all contained circuits. The smallest EGC permitted to be
installed in the conduit between the panel and the pull box is ___ AWG.
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