If the panel is rated (also called "listed and labeled” by NEC) to be installed without a door, then one is not needed. A distribution box is the heart of any electrical system. 26 requires electrical equipment (including electrical panels) to be located to provide required working clearances about the equipment. For. Cut sheets of the circuit breaker and fusible switch distribution panels and panelboards with construction, fuse and circuit breaker amperage and poles, interrupting ratings, and quantities clearly listed, and with bus amperage, voltage, phase and wires, integrated equipment ratings and all. Door delivery may be provided to boxes located at or near the door of a business or residential delivery point, or through a door slot, with prior approval from the local Postmaster, only if the box or mail slot can be efficiently, safely, and conveniently served by the carrier.
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