Unipolar junction box HiSmart NV821778 125A, single-string DC combiner for PV systems

Unipolar junction box HiSmart NV821778 125A is a single-string DC combiner designed for photovoltaic installations. Rated for 125 A, the junction box provides a protected connection point for PV string outputs and simplifies wiring in electrical panels. It is intended for mounting on a DIN rail and offers a transparent cover for quick visual inspection of the cable connections. The housing is made of flame-retardant PA (nylon) and the brass-plated terminals ensure durable, corrosion-resistant electrical contact.

Advantages

The HiSmart NV821778 combines a compact, DIN-rail mountable design with a transparent cover that enables visual verification of reliable cable connections. Brass-plated terminals provide good conductivity and corrosion resistance while the PA nylon body meets V0 UL94 flame-retardant requirements. The product supports a wide voltage range suitable for DC PV systems and provides organized cable entry options for multiple conductor sizes.

Suitable for

• Single-string DC combiner for photovoltaic (PV) strings
• DIN‑rail mounting inside electrical distribution panels
• Rooftop and ground-mounted solar arrays requiring string connection and cable management
• Integration with inverters and DC protective devices

Key specifications

• Nominal current: 125 A
• Voltage rating: AC/DC 690–1000 V
• Connected cable cross-sections: 1×(10–35 mm²) or 7×(2.5–16 mm²)
• Installation: DIN‑rail mounting
• Terminals: brass plated
• Body material: PA (nylon), flame retardant, UL94 V0
• Dimensions: 30 × 76.5 × 45.5 mm

How to use

Mount the junction box on a standard DIN rail inside the electrical panel. Route the PV string conductors into the designated entry points and secure them under the brass‑plated terminals according to the specified cross-sectional ranges. Tighten terminal fastenings to the torque recommended by the installation standards applicable in your region. Close the transparent cover to protect the connections while allowing visual inspection of the terminations.

Recommendations

Verify compatibility with system voltage and current requirements before installation. Use appropriate cable sizes within the stated ranges and follow local electrical codes and safety practices. For reliable performance, ensure terminals are properly tightened and periodically inspect connections through the transparent cover.