Why is a 125% factor used for continuous loads?

• A. To reduce energy loss in high-current circuits.
• B. To comply with labeling requirements.
• C. To ensure conductors and OCPDs are sized to carry continuous loads without overheating.
• D. To allow smaller wiring sizes for intermittent loads.

Answer: (C)

The main idea is that heat builds up when a load runs for a long time. Because continuous operation keeps current flowing for extended periods, conductors and insulation have to tolerate that sustained heating. The 125% factor provides a safety margin so the wire’s ampacity and the protective device’s rating are enough to carry the load without the insulation overheating. In practice, you multiply the continuous current by 1.25 to size the conductors and choose a protective device rated at least that higher value, ensuring safe operation over the whole duration of the load being on. This isn’t about energy loss, labeling, or making wires smaller for intermittent use; it’s specifically about preventing overheating from continuous operation.