Final answer:
The minimum ampacity of the feeder wires carrying a non-continuous 55-ampere load must be at least 55 amperes, as per the National Electrical Code.
Step-by-step explanation:
When a single feeder carries the full non-continuous load of a service calculated at 55 amperes, the ampacity of the feeder wires must be at least equal to the load they are carrying. According to the National Electrical Code (NEC), conductors must be sized to carry at least the load that they serve. Since continuous loads are defined as those operating for three hours or more, and the question specifies a non-continuous load, we can use the 100% capacity rule. Therefore, the minimum ampacity of the feeder wires should be 55 amperes. In practice, electricians often use a higher ampacity for increased safety and to account for potential future load increases.