EETC Wiring & Installation Techniques 4 — Questions and Answers
Question 1: When installing a subpanel in a detached garage, the grounding electrode conductor must be connected to:
- The main panel ground bus only
- A grounding electrode at the detached structure (Correct answer)
- Any convenient water pipe
- The neutral bus in the main panel
Correct answer: A grounding electrode at the detached structure
NEC 250.32 requires a separate grounding electrode system at each detached structure supplied by a feeder or branch circuit.
Question 2: What is the maximum number of quarter-bends (90° bends) allowed in a single conduit run between pull points?
- 2 bends (180° total)
- 4 bends (360° total) (Correct answer)
- 3 bends (270° total)
- 6 bends (540° total)
Correct answer: 4 bends (360° total)
NEC 358.26 (and other conduit articles) limit the total bends between pull points to 360 degrees (equivalent to four 90° bends) to allow conductor pulling.
Question 3: When splicing conductors in a junction box, what is required for all splices?
- Wire nuts approved for the wire gauge (Correct answer)
- Electrical tape only
- Soldering the connection
- Crimping only with no insulation
Correct answer: Wire nuts approved for the wire gauge
NEC 110.14 requires splices to be made with listed devices (such as wire nuts rated for the conductor sizes) and must be accessible.
Question 4: A 240V, 30-amp dryer circuit requires conductors sized at minimum:
- 12 AWG
- 10 AWG (Correct answer)
- 8 AWG
- 6 AWG
Correct answer: 10 AWG
A 30-amp circuit requires 10 AWG copper conductors, as 12 AWG is only rated for 20 amps.
Question 5: When installing recessed lighting in an insulated ceiling, the fixture must be:
- Any standard recessed fixture
- Rated IC (Insulation Contact) (Correct answer)
- Installed with a 3-inch air gap from insulation
- Covered with a vapor barrier only
Correct answer: Rated IC (Insulation Contact)
NEC 410.116 requires recessed fixtures installed where insulation will contact them to be marked 'IC' (Insulation Contact) rated.
Question 6: The purpose of a 'pigtail' connection at a device is to:
- Extend wire reach to distant panels
- Ensure the circuit continues if the device fails or is removed (Correct answer)
- Increase the wire gauge at the connection
- Create a strain relief for the device
Correct answer: Ensure the circuit continues if the device fails or is removed
Pigtailing ensures the circuit remains complete even if the device is removed, unlike a pass-through connection that breaks the circuit.
Question 7: When sizing a conduit for a pull, the largest conductor's diameter is used to calculate the:
- Total fill percentage only
- Minimum conduit diameter and total fill percentage (Correct answer)
- Number of conductors only
- Wire insulation thickness
Correct answer: Minimum conduit diameter and total fill percentage
Both the largest single conductor diameter (for jam ratio) and total cross-sectional area fill percentage must be checked when sizing conduit.
EETC Wiring & Installation Techniques 4
When installing a subpanel in a detached garage, the grounding electrode conductor must be connected to: