A maintenance technician is replacing a damaged flexible cord on a portable 277-volt industrial lighting fixture. The cord has three conductors and a bare equipment grounding conductor. Which of the following color combinations is permitted for the insulated circuit conductors?
- ABlack, Red, Blue
- BBlack, White, Green
- CPurple, Gray, Pink
- DBrown, Orange, Yellow
Show answer & explanationAnswer & explanation
Correct answer: A. Black, Red, Blue
For multi-conductor flexible cords, the NEC does not mandate specific phase colors, but common practice and good workmanship dictate using standard phase colors for 3-phase systems or common hot colors for 277V. Black, Red, Blue is a standard color code for phases in 3-phase delta or wye systems, and is commonly used for 277V circuits (which are typically phases of a 480/277V wye system). White is reserved for grounded conductors, and Green for grounding conductors.
Why the other options are wrong
- B. White is for grounded (neutral) conductors, not typically for 277V ungrounded conductors, and Green is for grounding.
- C. Purple, Gray, Pink are not standard color codes for ungrounded circuit conductors in the NEC or common practice.
- D. Brown, Orange, Yellow is a common color code for 480V delta ungrounded conductors, but Black, Red, Blue is also common and typically for 277V. Yellow is not a standard phase color for 277V.
Flexible Cord Conductor Identification
Identification of conductors within flexible cords, typically by color, to distinguish between ungrounded (hot), grounded (neutral), and equipment grounding conductors.
- Grounded conductor (neutral) is white or gray.
- Equipment grounding conductor is green or green with yellow stripes, or bare.
- Ungrounded (hot) conductors have other colors; Black, Red, Blue is common for phases.
Memory trick: Colors tell the story: Green for ground, White for neutral, 'Black-Red-Blue' for power's true.