PC Electrical System Design & Installation 3 — Questions and Answers
Question 1: Under NEC 230.70, where must the service disconnecting means be installed?
- At the utility transformer
- Outside the building only
- At a readily accessible location nearest the point of service entrance (Correct answer)
- In the main electrical room regardless of location
Correct answer: At a readily accessible location nearest the point of service entrance
NEC 230.70(A)(1) requires the service disconnecting means to be installed at a readily accessible location either outside or inside nearest the point of entrance.
Question 2: What is the minimum burial depth for a rigid metal conduit (RMC) installed under a residential driveway?
- 6 inches
- 12 inches (Correct answer)
- 18 inches
- 24 inches
Correct answer: 12 inches
Per NEC Table 300.5, RMC installed under a residential driveway requires a minimum cover of 12 inches.
Question 3: When derating conductors in a conduit due to more than 3 current-carrying conductors, which table is used?
- Table 310.15(B)(1)
- Table 310.15(C)(1) (Correct answer)
- Table 310.15(B)(16)
- Table 300.5
Correct answer: Table 310.15(C)(1)
NEC Table 310.15(C)(1) provides the adjustment factors for more than 3 current-carrying conductors in a raceway or cable.
Question 4: A kitchen in a dwelling unit requires at minimum how many small appliance branch circuits per the NEC?
- One 20A circuit
- Two 20A circuits (Correct answer)
- Three 20A circuits
- One 15A and one 20A circuit
Correct answer: Two 20A circuits
NEC 210.11(C)(1) requires at least two 20-ampere small appliance branch circuits for receptacle outlets in the kitchen.
Question 5: What is the maximum number of disconnects permitted per service entrance under NEC 230.71?
- 2
- 4
- 6 (Correct answer)
- 8
Correct answer: 6
NEC 230.71(A) permits a maximum of six switches or sets of circuit breakers to serve as the service disconnecting means.
Question 6: Which conductor insulation type is rated for use in wet locations AND has a 90°C temperature rating?
- THHN
- TW
- THWN-2 (Correct answer)
- THW
Correct answer: THWN-2
THWN-2 (Thermoplastic, Heat resistant, Water resistant, Nylon jacket, 2) is rated for wet locations at 90°C.
Question 7: When bonding a metal water piping system in a commercial building, the bonding jumper must be connected to which point?
- Any metal pipe anywhere in the building
- The water meter
- The nearest hot water heater
- The metal water service pipe on the street side of the water meter (Correct answer)
Correct answer: The metal water service pipe on the street side of the water meter
Per NEC 250.104(A), the bonding jumper must connect to the metal water piping on the supply side (street side) of the water meter to ensure a continuous bond.
PC Electrical System Design & Installation 3
Under NEC 230.70, where must the service disconnecting means be installed?