Introduction: AJB, DC Combiner Box and AC PV Box — Why Are There Different Names?

Depending on the country, project specification, or supplier, terms such as Array Junction Box (AJB), DC Combiner Box, DC Distribution Box, AC PV Box, and AC Distribution Box may be used differently.

Generally, DC Combiner Boxes are used on the PV DC side, while AC PV Boxes / AC Distribution Boxes are used on the AC side after the inverter. Therefore, always confirm the actual system position, electrical function, and configuration rather than relying on the product name alone.

2.3 DC Surge Protection

A DC SPD helps limit transient overvoltages caused by lightning-related events and switching disturbances. The SPD should be compatible with the actual PV system voltage and should be coordinated with the grounding and protection design.

2.4 DC Isolator

A DC isolator allows the DC circuit to be separated for maintenance or emergency shutdown. Its voltage and current ratings must match the actual DC operating conditions of the system.

2.5 Cable Glands and Connectors

Cable-entry components should maintain the required enclosure protection after installation. Check cable size range, voltage and current ratings, UV resistance, sealing performance and material compatibility.

3. How to Determine the Correct AJB Configuration

The required number of inputs, outputs and protection components depends on the PV system design. Before requesting a quotation, EPCs and buyers should provide as much of the following information as possible:

• Number of PV strings
• Number of modules per string
• Module Voc and Isc
• Maximum DC system voltage
• Required DC output current
• Inverter type and input arrangement
• Required fuse ratings
• SPD requirements
• DC isolator requirements
• Cable size and cable-entry method
• Installation environment and project location
• Required quantity and delivery schedule

An experienced manufacturer should review these parameters before confirming the final AJB configuration, rather than simply offering a standard enclosure.

4. What to Check When Choosing an AJB Manufacturer

5. Sample Approval Is Only the Beginning

For project procurement, a good sample does not automatically guarantee a good bulk shipment. A reliable production process should connect specification, sample approval, production, inspection and shipment.

• Confirm the electrical and mechanical specification.
• Approve the sample and record the approved configuration.
• Use the same approved components and wiring arrangement during production.
• Perform in-process and final inspections.
• Verify labels, quantity, packaging and product condition before shipment.

6. Why Customization Capability Matters

Solar projects are rarely identical. Different inverter architectures, string counts, cable sizes and protection requirements can lead to different AJB configurations.

• 8-input, 12-input, 16-input or other configurations
• Different fuse ratings
• Different SPD and isolator arrangements
• Customized cable-entry and connector solutions
• Customized enclosure dimensions
• Customized labeling and internal wiring
• Project-specific drawings and documentation

7. Documents to Request Before Ordering

• Product datasheet
• Electrical schematic
• Bill of materials (BOM)
• Major component datasheets
• Enclosure specifications
• Relevant test reports and certificates
• Inspection records
• Installation instructions
• Packing information

8. AJB Supplier Evaluation Checklist

9. Final Thoughts

Choosing a reliable AJB manufacturer requires more than comparing quotations. The right supplier should understand the PV DC-side application, select compatible components, control production quality and provide technical support throughout the project.

For EPC contractors, distributors and solar project developers, the most important factors are manufacturing capability, electrical design, component selection, enclosure protection, testing, customization, documentation and production consistency.

A reliable AJB should not simply meet a specification on paper. It should be manufactured consistently, tested properly and configured according to the actual requirements of the PV system.

Looking for a Customized AJB Solution?

Send us your PV system requirements, single-line diagram or basic string information. Our team can review the configuration and recommend a suitable AJB solution for your project.

Feel  free to contact NewSun PV for AJB, DC combiner box , AC PV box configuration review, customized drawings and quotation.