IEC COMPREHENSIVE EXAM 2026 QUESTIONS
WITH ANSWERS GRADED A+
◉ 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.
Answer: 30
◉ A 240-volt load, such as a window unit air conditioner, would require
breaker ___ to be installed in the panelboard. Answer: b
◉ Generally, circuit breakers must be ___. Answer: readily accessible
◉ What is the maximum voltage between circuit conductors when using
plug fuses? Answer: 125
◉ Refer to Figure 204.5. The conductors at Point I are ___. Answer: taps
◉ 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 ___. Answer: 1
, ◉ 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. Answer: 100
◉ 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. Answer: 200
◉ 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 Answer: I, II, & III
WITH ANSWERS GRADED A+
◉ 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.
Answer: 30
◉ A 240-volt load, such as a window unit air conditioner, would require
breaker ___ to be installed in the panelboard. Answer: b
◉ Generally, circuit breakers must be ___. Answer: readily accessible
◉ What is the maximum voltage between circuit conductors when using
plug fuses? Answer: 125
◉ Refer to Figure 204.5. The conductors at Point I are ___. Answer: taps
◉ 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 ___. Answer: 1
, ◉ 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. Answer: 100
◉ 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. Answer: 200
◉ 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 Answer: I, II, & III
