CSLB C-10 Electrical ContractorWiring Methods and MaterialsEasy
A residential garage requires a connection for an electric vehicle charging station. The charging station will be located 25 feet from the main service panel, and the circuit will supply a 40A continuous load. The installation will use 8 AWG THHN copper conductors. What is the minimum size EMT conduit required for three 8 AWG THHN conductors, assuming no more than 40% fill?
- A1/2 inch EMT
- B1 inch EMT
- C1 1/4 inch EMT
- D3/4 inch EMT
Show answer & explanationAnswer & explanation
Correct answer: D. 3/4 inch EMT
According to NEC Annex C, Table C.1, three 8 AWG THHN conductors require a minimum of 3/4 inch EMT conduit to comply with the 40% fill limitation. This ensures adequate space for conductor installation and heat dissipation.
Why the other options are wrong
- A. 1/2 inch EMT is too small for three 8 AWG THHN conductors.
- B. 1 inch EMT is larger than necessary for three 8 AWG THHN conductors.
- C. 1 1/4 inch EMT is significantly larger than required for three 8 AWG THHN conductors.
Conduit Fill (Annex C)
NEC Annex C tables provide pre-calculated conduit fill percentages for common conductor types and sizes, simplifying conduit sizing.
- Annex C tables are used when all conductors in a raceway are of the same type and size.
- These tables automatically account for the 40% fill limit for three or more conductors.
- Using Annex C can save time compared to manual calculations based on conductor and conduit cross-sectional areas.
Memory trick: Conduit's size, for wires' ride, Annex C's guide, no need to hide.