Installation concerns
What this domain tests
Installation concerns test whether you can turn code rules into a safe, inspectable installation. Expect conductor and raceway selection, box fill, support and protection, grounding and bonding, overcurrent protection, working clearances, and proper use of listed equipment.
Core rules
- Start with 110.3(B): use listed and labeled equipment and follow manufacturer instructions. A code-compliant wiring method installed with the wrong connector or in a way the listing forbids is still a violation.
- Maintain 110.26 working clearances and protect conductors where 300.4 requires it, such as near framing edges.
- Size conductors from 310.16, then apply termination limits, ambient correction, and conductor adjustment for bundled current-carrying conductors.
- Keep grounding and bonding continuous and correctly sized; never use the equipment grounding conductor as a neutral.
- Use GFCI and AFCI protection where the branch-circuit article requires it, and verify the device is listed for the application.
Worked example
A 120-volt, 20-ampere circuit uses 12 AWG copper THHN in EMT. The terminals are rated 75°C, there are three current-carrying conductors in the raceway, and the ambient is 30°C. From the 90°C column, 12 AWG THHN is 30 amperes, but the 75°C termination limit is 25 amperes. Three current-carrying conductors require no adjustment, and 30°C ambient requires no correction. The usable ampacity is 25 amperes, so a 20-ampere overcurrent device protects the circuit.
Traps
Using the 90°C ampacity without the termination check, forgetting adjustment when conductors are bundled, mixing neutral and grounding functions, and ignoring listing instructions for connectors and supports.