Correct wiring inside the small power distribution unit is very important to ensure the safety and reliability of power distribution. The following are some common internal wiring considerations for small power distribution unites:

Main circuit breaker: Install the main circuit breaker on the top of the small power distribution unit to cut off the entire power supply. It's usually the largest breaker and should be easily accessible.

Power Input: Connect the main power cable to the main circuit breaker, making sure it is properly connected to the power source.

Branch circuit breakers: Branch circuit breakers are installed inside small power distribution unites for connection to individual circuits or equipment before power is distributed. Each branch circuit breaker shall be clearly identified as to the circuit to which it is connected.

Wire arrangement: Wires should be connected according to the prescribed color code, for example, black for hot wire, white for neutral wire, and green/yellow for ground wire.

Overload and short-circuit protection: Every circuit should be equipped with an overload protector and a short-circuit protector to prevent damage if the current exceeds the rating or if the circuit fails.

Tightening and Insulation: Make sure that all wire terminals are firmly tightened and not loose, and exposed parts should be covered with appropriate insulating sleeves or insulating tape.

Grounding: Always make sure the ground wire is properly connected and connect the ground wire to a metal part for safety.

Identification: Use labels or signs to identify each circuit and breaker so they can be easily identified when required.

Most importantly, all wiring work inside small power distribution unites should be carried out by qualified electricians or professionals in compliance with applicable electrical safety regulations and building regulations. Incorrect wiring may cause serious problems such as electric shock, fire or power failure.