Master Electrician Exam (NEC)General Electrical KnowledgeMedium
A master electrician is installing a new 200A, 208Y/120V service for a commercial building. According to NEC 250.24(C)(1), what is the minimum size required for the grounded (neutral) conductor for this service?
- ANo. 4 AWG copper
- BNo. 2 AWG copper
- CNo. 6 AWG copper
- DNo. 1/0 AWG copper
Show answer & explanationAnswer & explanation
Correct answer: B. No. 2 AWG copper
NEC 250.24(C)(1) requires the grounded conductor to be sized not smaller than specified in Table 250.102(C)(1) and not smaller than the required grounding electrode conductor. For a 200A service, Table 250.102(C)(1) specifies a minimum of No. 2 AWG copper for service conductors up to 200A.
Why the other options are wrong
- A. This is too small for a 200A service grounded conductor.
- C. This is too small for a 200A service grounded conductor.
- D. While larger, this is not the minimum required size and would be oversized.
Service Grounded Conductor Sizing
The grounded (neutral) conductor for a service must be sized to carry the maximum unbalanced current and not be smaller than required by NEC Table 250.102(C)(1) based on the service entrance conductor size.
- Must carry unbalanced load current.
- Minimum size determined by NEC Table 250.102(C)(1).
- Cannot be smaller than required for the grounding electrode conductor.
Memory trick: Neutral needs to be 'Balanced and Bonded' to meet Code.