CEA Wiring Methods & Installation Practices 3 — Questions and Answers
Question 1: What is the minimum wire fill percentage allowed in a conduit according to NEC Chapter 9 for three or more conductors?
- 20%
- 31% (Correct answer)
- 40%
- 53%
Correct answer: 31%
For three or more conductors, NEC Chapter 9 allows a maximum conduit fill of 40%, but the standard fill for three or more conductors is 40% not to exceed.
Question 2: Which type of conduit fitting is required when connecting RMC to an enclosure to maintain a grounding path?
- Standard locknut only
- Insulated bushing
- Bonding locknut or bonding bushing (Correct answer)
- Set-screw connector
Correct answer: Bonding locknut or bonding bushing
A bonding locknut or bonding bushing is required where a reliable grounding path must be maintained at RMC enclosure connections.
Question 3: What is the maximum spacing between supports for 1-inch EMT installed horizontally?
- 6 feet
- 8 feet
- 10 feet (Correct answer)
- 12 feet
Correct answer: 10 feet
EMT 1 inch and larger must be supported at intervals not exceeding 10 feet when installed horizontally.
Question 4: Underground feeder cable (Type UF) used as interior wiring must comply with which wiring method requirements?
- No interior restrictions apply to UF cable
- UF cable is prohibited inside buildings entirely
- UF cable used inside must comply with NM cable rules (Correct answer)
- UF cable must be installed in conduit when inside
Correct answer: UF cable used inside must comply with NM cable rules
When Type UF cable is used inside a building, it must be installed in the same manner as Type NM cable per NEC requirements.
Question 5: Where must expansion fittings be installed in a PVC conduit run?
- Every 50 feet regardless of temperature
- Where the conduit crosses building expansion joints or where thermal expansion exceeds conduit's flexibility (Correct answer)
- Only at the ends of the conduit run
- Expansion fittings are optional for PVC conduit
Correct answer: Where the conduit crosses building expansion joints or where thermal expansion exceeds conduit's flexibility
Expansion fittings must be installed where conduit crosses building expansion joints or where significant thermal expansion would stress the conduit system.
Question 6: Type MC cable used in wet locations must have which type of jacket?
- PVC outer jacket only
- Lead sheath or PVC jacket listed for wet locations (Correct answer)
- Aluminum armor with no jacket
- Standard MC cable is approved for all wet locations
Correct answer: Lead sheath or PVC jacket listed for wet locations
Type MC cable in wet locations must have a corrosion-resistant jacket, such as a PVC outer jacket listed for wet locations or a lead sheath.
Question 7: What is the purpose of an anti-short bushing (red devil) in armored cable installations?
- To provide a watertight seal at the box connection
- To protect conductor insulation from the cut armor's sharp edges (Correct answer)
- To bond the armor to the grounding system
- To increase the pull strength of the cable
Correct answer: To protect conductor insulation from the cut armor's sharp edges
Anti-short bushings (also called red devils or anti-short connectors) are installed inside AC cable armor to protect conductor insulation from sharp metal edges.
CEA Wiring Methods & Installation Practices 3
What is the minimum wire fill percentage allowed in a conduit according to NEC Chapter 9 for three or more conductors?