The internal layout should be partitioned by functions such as power, control, communication, and terminals, while reserving space for wiring, heat dissipation, maintenance, and future expansion. Common structures include full mounting plates, DIN rails, terminal block mounting areas, partitions, and wire ducts. Components requiring frequent operation or replacement should be positioned for easy observation and maintenance once the door is opened.

Component layout must also account for cable bending radius, terminal crimping space, door clearance, and grounding paths. Heat-generating devices, transformers, power modules, or other high-temperature components should not sit directly against sealed doors or sensitive parts. If fans, filters, heat sinks, or AC units are required, cutouts and servicing methods should be confirmed during enclosure design.