17 questions · 27% of the Calculations exam
Exam tip
Be familiar with the specific grounding conductor requirements for different voltage systems.
Why B is correct
According to 250.66(C), the minimum grounding electrode conductor size for a 480-volt, 3-phase, 4-wire system is 3/0 AWG. The other options are not the minimum required size.
Exam tip
Be aware of the specific requirements for grounding electrode conductor sizes based on the type of service and voltage.
Why A is correct
According to 2026 NFPA 70 NEC, a 120/208-volt, 3-phase, 4-wire service requires a minimum grounding electrode conductor size of 1/0 AWG. Options B, C, and D are incorrect as they are larger sizes suitable for different voltage and current requirements.
Exam tip
Check the specific requirements for raceway sizes based on the type of cable being used.
Why B is correct
According to 2026 NFPA 70 NEC, armored cable requires a raceway with a minimum size of 3/4 inch for 14 AWG to 10 AWG conductors. Options A, C, and D are incorrect as they are either too small or too large for the specified cable size.
Exam tip
Remember the maximum lengths for NM cable runs without junction boxes.
Why C is correct
According to 2026 NFPA 70 NEC, the maximum length of NM cable without a junction box is 75 feet. Options A, B, and D are incorrect as they exceed the allowed length.
Exam tip
Understand the spacing requirements for raceways in different installation conditions.
Why B is correct
According to 300.4(A), the maximum spacing allowed between raceways in a concealed location is 2 inches. The other options exceed the maximum allowed spacing.
Exam tip
Be aware of the grounding electrode conductor requirements based on the service entrance conductor rating.
Why A is correct
According to 2026 NFPA 70 NEC, a service entrance conductor with a rating of 600 amperes requires a grounding electrode conductor of at least 3/0 AWG. Option B is incorrect as it is too large. Options C and D are incorrect as they are sizes suitable for different conductor ratings.
Exam tip
Understand the limitations on the length of branch circuits in concealed locations.
Why C is correct
According to 324.16(A), the maximum length of a branch circuit that can be run in a concealed location is 200 feet. The other options exceed the maximum allowed length.
Exam tip
Ensure that the service disconnecting means is appropriately sized for the load requirements.
Why C is correct
According to 230.71(A), the minimum size of the service disconnecting means required is 200 A. The other options are not the minimum required size.
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