Services & separately derived systems: New Hampshire Journeyman Electrician Practice Questions

According to the NEC, how many services may a building generally be supplied by?

Section 230.2 limits a building to one service unless one of the listed special conditions applies (fire pumps, large loads, different characteristics and similar). Exceptions are ignored here.

According to the NEC, may branch-circuit conductors be installed in the same raceway as service conductors?

Section 230.7 keeps other conductors out of service raceways and service cables (grounding conductors and bonding jumpers are allowed). Service conductors are unprotected on the line side, so other circuits are kept apart.

According to the NEC, overhead service conductors run beside a window that opens must keep what minimum clearance from it?

Section 230.9(A) requires 3 ft of clearance from windows designed to open, doors, porches, balconies, ladders, stairs and similar locations. Conductors above the top of a window are exempt.

According to the NEC, a service drop limited to 150 V to ground that passes over a sidewalk accessible only to pedestrians needs at least what clearance above the finished grade?

Section 230.24(B) lists 10 ft over finished grade, sidewalks and pedestrian-only areas for service drops limited to 150 V to ground.

According to the NEC, what is the minimum clearance of 120/240 V overhead service conductors over a residential driveway?

Section 230.24(B) requires 12 ft over residential property and driveways (and commercial areas without truck traffic) for conductors at 300 V or less to ground.

According to the NEC, overhead service conductors over a public street or a parking area with truck traffic need at least what clearance?

Section 230.24(B) sets 18 ft over public streets, alleys, roads, parking areas subject to truck traffic and similar areas.

According to the NEC, the point of attachment of a service drop to a building must be at least how high above finished grade?

Section 230.26 requires the point of attachment to be at least 10 ft above finished grade, and high enough to give the clearances in 230.24.

According to the NEC, what is the smallest copper conductor generally permitted for overhead service conductors?

Section 230.23 sets a minimum of 8 AWG copper (6 AWG aluminum) for overhead service conductors, apart from small limited loads covered by an exception.

According to the NEC, what is the minimum size of aluminum underground service conductors (ignore exceptions)?

Section 230.31 sets a minimum of 8 AWG copper or 6 AWG aluminum or copper-clad aluminum for underground service conductors.

According to the NEC, where should a service head generally be located?

Section 230.54 places the service head above the point of attachment (within 24 in of it only where that is impractical) so water does not run into the raceway.

According to the NEC, why are drip loops formed on service-entrance conductors where they leave the service head?

Section 230.54 requires drip loops and connections below the level of the service head so rain runs off the loop instead of into the raceway.

According to the NEC, service-entrance cable run on the outside of a building must be supported at intervals of no more than:

Section 230.51(A) requires SE cable to be secured within 12 in of the service head, gooseneck or raceway connection and at intervals of no more than 30 in.

According to the NEC, what may be attached to a service mast that supports service-drop conductors?

Section 230.28 allows only power service-drop or overhead service conductors to be attached to a service mast. Communications drops need their own support.

According to the NEC, which wiring method is NOT permitted for service-entrance conductors?

Section 230.43 lists the wiring methods allowed for service-entrance conductors, including RMC, IMC, EMT, PVC and Type SE cable. Type NM is not on the list.

According to the NEC, where a service raceway enters a building from an underground distribution system, what is required?

Section 230.8 (referring to 300.5(G)) requires underground service raceways to be sealed or plugged so moisture and gases cannot travel into the building.