6 questions · 3% of the Calculations exam
Exam tip
Use Table 310.16(B)(1) to determine the minimum wire size for control circuits based on voltage and current.
Why B is correct
The correct answer is 12 AWG because NEC 2026 Table 310.16(B)(1) specifies a 12 AWG wire for a 277V control circuit.
Exam tip
Always refer to NEC 250.122(A) for the minimum grounding conductor size for disconnecting means.
Why B is correct
The correct answer is 8 AWG because NEC 2026 250.122(A) requires a grounding conductor of at least 8 AWG for a 30A disconnecting means.
Exam tip
Remember that control circuits are covered under Article 240.
Why C is correct
The correct answer is Article 240 because it covers the installation of services, feeders, and branch circuits, which includes control circuits for security systems.
Exam tip
NEC 110.14(A) provides the requirements for the number of poles in disconnecting means based on the circuit rating.
Why B is correct
The correct answer is 2 poles because NEC 2026 110.14(A) requires a 2-pole disconnecting means for 50A circuits.
Exam tip
Use Table 310.16(B)(1) to determine the minimum wire size for control circuits based on voltage and current.
Why C is correct
The correct answer is 10 AWG because NEC 2026 Table 310.16(B)(1) specifies a 10 AWG wire for a 480V control circuit.
Exam tip
Always check for the grounding pole requirement in addition to the number of poles for the circuit rating.
Why D is correct
The correct answer is 4 poles because NEC 2026 requires a 3-pole disconnecting means for 100A circuits, and an additional pole for grounding.
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