If by distribution panel you mean main distribution panel then the only time you need a main breaker is when you have more than six handles. A distribution box, also known as a distribution board, electrical panel, or breaker box, is an enclosure that houses electrical components responsible for distributing electricity throughout a building. It receives power from the main electrical supply and divides it into separate circuits, each. Longer answer: Nothing ever requires a main breaker in any panel of any description. There are rules that say that all conductors must be protected against overcurrent, and other similar rules about panels, and still other rules about transformer secondary windings. Make sure the breaker matches what it protects. This stops fires and helps everything work right. Follow electrical codes like NEC for safety. Use UL/CE-certified parts and record installation details for future inspections.
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