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Wiring Diagram of Dual Power Explosion-Proof Distribution Box

The installation and maintenance of dual power source explosion-proof distribution boxes often involve intricate wiring processes. Special care is needed, especially when extending connection lines, as improper practices can lead to damaged power lines, mainboard components, fuses, and communication failures. Here, we share the standard procedures and precautions for wiring these
distribution boxes:
A dual power source explosion-proof distribution box contains a dual power switch device, essential for ensuring continuous operation of exhaust fans:

1. In case of failure in one power source, the system automatically switches to the alternate source, maintaining uninterrupted operation of the fan.

2. Typically, dual power source switching is achieved using two contactors, controlled by an intermediate or time relay. This setup manages the two main circuits, enabling the transition between power sources.

physical wiring diagram of dual power explosion proof distribution box
Dual Power Source Explosion-Proof Distribution Box Wiring Diagram

Wiring Method:

1. Simply connect the two power sources to two separate air switches on the power input side and connect the load to the output side of the AC contactors.

2. Before starting the wiring, inspect the distribution box’s exterior, verify the correctness of the wiring, and check the insulation, conductivity, and grounding of all components.

3. After inspection, use a three-phase 5-ampere switch as a test power source and conduct a live simulation test on the distribution box to ensure it meets requirements post-installation.

overall dual power explosion proof distribution box circuit diagram
Overall Dual Power Source Explosion-Proof Distribution Box Circuit Diagram

4. When connecting the power sources, designate the priority source. Connect the primary source to the side without time delay and the backup source to the delayed side.

5. If there’s no connection under the AC contactor, align the same phase of both power sources to ensure uninterrupted power supply from either source.

circuit diagram of dual power explosion proof distribution box
Dual Power Source Explosion-Proof Distribution Box Circuit Diagram

6. After connections, test the power source switching:
Power each source separately, turning the switch to primary, backup, and automatic positions. Check the contactor’s switching, phase synchronization, and contact connections.


1. Although explosion-proof distribution boxes generally have protective structures, safety must always be a priority during operations.

2. If checking load conditions, ensure to apply the rated load for testing.

3. Inspections of live equipment must comply with safety procedures to guarantee secure execution.

These wiring methods and precautions should be studied carefully, followed strictly to standard practices, and executed with precision.



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