Journeyman Electrician Exam (NEC)Wiring Methods and MaterialsMedium
A journeyman electrician is installing a new 240-volt, 30-amp circuit for a water heater in a dwelling unit. The circuit will be run through a 1/2-inch EMT conduit. What is the maximum number of 10 AWG THHN copper conductors permitted in this conduit?
- A4
- B5
- C3
- D6
Show answer & explanationAnswer & explanation
Correct answer: B. 5
According to NEC Chapter 9, Table C.1 (for EMT) and referencing 10 AWG THHN conductors, a 1/2-inch EMT conduit is permitted to contain a maximum of 5 such conductors. This ensures proper heat dissipation and ease of pulling.
Why the other options are wrong
- A. 4 is too few; 1/2-inch EMT can hold more 10 AWG THHN.
- C. 3 is too few; 1/2-inch EMT can hold more 10 AWG THHN.
- D. 6 is too many for 1/2-inch EMT with 10 AWG THHN conductors.
Conduit Fill (Specific Conductors)
The maximum number of specific conductor types and sizes permitted within a given conduit trade size, ensuring that the conduit is not overfilled, which could lead to overheating and difficulty in pulling wires.
- Based on conductor insulation type and size.
- Found in NEC Chapter 9, Tables C.1 through C.12(A).
- Prevents overheating and facilitates installation.
Memory trick: Fill the pipe right, don't cram, use the 'C' tables for the count.