NECA Electrical Systems & Equipment 3 — Questions and Answers
Question 1: Which insulation type is rated for use in wet locations and direct burial?
- USE-2 (Correct answer)
- THHN
- TW
- FEP
Correct answer: USE-2
USE-2 (Underground Service Entrance) cable is rated for wet locations, direct burial, and use as service entrance conductors.
Question 2: A panelboard rated 42 circuits maximum currently has 40 breakers installed. How many single-pole spaces remain?
- 2 (Correct answer)
- 0
- 4
- 42
Correct answer: 2
42 maximum minus 40 installed leaves 2 available single-pole circuit spaces.
Question 3: What type of grounding electrode is the MOST preferred by the NEC when available?
- Metal underground water pipe (Correct answer)
- Ground rod
- Concrete-encased electrode
- Ground ring
Correct answer: Metal underground water pipe
The NEC lists metal underground water pipe first in the grounding electrode hierarchy because it provides excellent earth contact over a large area.
Question 4: What is the minimum depth for installing rigid metal conduit (RMC) under a concrete slab that is not subject to vehicular traffic?
- 0 inches (none required) (Correct answer)
- 6 inches
- 12 inches
- 18 inches
Correct answer: 0 inches (none required)
RMC installed under a concrete slab with no vehicular traffic requires no minimum cover per NEC Table 300.5.
Question 5: What does a power factor of 0.8 lagging indicate about an electrical load?
- The load is inductive and current lags voltage by 36.87° (Correct answer)
- The load is capacitive and current leads voltage
- The load is purely resistive
- The load has 80% efficiency
Correct answer: The load is inductive and current lags voltage by 36.87°
A lagging power factor indicates an inductive load where current lags behind the voltage waveform.
Question 6: Which NEC article covers the installation of electric motors and their associated controls?
- Article 430 (Correct answer)
- Article 410
- Article 440
- Article 450
Correct answer: Article 430
NEC Article 430 covers motors, motor circuits, and controllers including wiring, protection, and control requirements.
Question 7: When sizing a feeder for a non-continuous load of 80A and a continuous load of 60A, what is the minimum conductor ampacity required?
- 155A (Correct answer)
- 140A
- 120A
- 175A
Correct answer: 155A
Continuous loads are multiplied by 125%, so: 80A + (60A × 1.25) = 80 + 75 = 155A minimum ampacity.
NECA Electrical Systems & Equipment 3
Which insulation type is rated for use in wet locations and direct burial?