For a feeder supplying continuous loads, the minimum conductor size must have an allowable ampacity of at least what percentage of the continuous load plus the noncontinuous load?

In electrical code standards, specifically as outlined in the National Electrical Code (NEC), when calculating the minimum conductor size for feeders that supply continuous loads, the allowable ampacity of conductors must be sufficient to handle both the continuous and non-continuous loads. Continuous loads are defined as loads that will be applied for three hours or more, and they require special consideration due to their sustained demand on the electrical system.

The NEC specifies that when dealing with continuous loads, the conductors must be sized to have an ampacity rating of at least 125% of the continuous load, in addition to the full value of any non-continuous loads. The rationale behind this requirement is to prevent overheating and ensure the safe operation of the electrical system over extended periods. By increasing the conductor size to accommodate this higher percentage of the continuous loads, the risk of thermal failure and potential fire hazards can be significantly reduced.

In this case, the correct percentage to ensure safety and compliance when calculating the minimum conductor size for feeders supplying continuous loads is indeed 125%. This ensures that the conductors can handle the maximum expected load without overheating, thereby promoting reliability and safety in electrical installations.