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Electrician Red Seal · Question

A 3-phase, 4-wire, 120/208 V wye-connected system supplies a balanced non-linear load. Under which condition must the neutral conductor be counted as a current-carrying conductor for ampacity correction purposes?

CEC Rule 4-004(1)(d) states that the neutral conductor must be counted as a current-carrying conductor where a major portion of the load consists of non-linear

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Question: A 3-phase, 4-wire, 120/208 V wye-connected system supplies a balanced non-linear load. Under which condition must the neutral conductor be counted as a current-carrying conductor for ampacity correction purposes?

Answer options:

  • It is never counted
  • Only when the load is more than 50% of the circuit ampacity ✅ Always, when non-linear loads are present
  • Only if the load is unbalanced by more than 10%

Correct answer: Always, when non-linear loads are present

Explanation: CEC Rule 4-004(1)(d) states that the neutral conductor must be counted as a current-carrying conductor where a major portion of the load consists of non-linear loads. Harmonics on these systems can cause significant neutral current, even when the phase currents are balanced.

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