Combiner Box Application Case for Austrian 1.1MW Hillside Farm Project

Project Background
Located in an agricultural area on the slopes of Austria, local farmers aim to reduce electricity costs through photovoltaic power generation and align with the EU's "Fit for 55" initiative (aim for 45% renewable energy by 2030). The project has a total capacity of 1.1MW and will install 2,750 400W monocrystalline solar panels, each connected in series with 22 panels. The panels operate at approximately 10.15A and 26.67V, and are equipped with 63 18kW inverters.

Customer Pain Points and Requirements
1. Requires more flexible power scheduling: Distributed sites require more independent circuits.
2. Requires high outdoor protection: Located at an altitude of 1,200 meters, the enclosure must be temperature-resistant (-25°C to 60°C), dustproof and waterproof (IP65), and designed for an outdoor lifespan of at least 15 years.
3. Limited budget: A low-cost combiner box with TUV certification is required.
4. Circuit Control: Requires complete circuit disconnection with no residual current.

Solution: 92 2-input, 2-output PV combiner boxes

1. Calculate the required rated voltage and current for the combiner box

Input voltage per string: 26.67V * 22 ≈ 587V. Input current per string: 10.15A
Output voltage per string: 587V. Output current per string: 10.15A

Core Configuration and Electrical Performance

Product Model: LQX-C2/2DC1000V
Input Adaptor: Equipped with a 15A DC 1000V fuse. Maximum input current per circuit is 10.15A (designed for 1.25 times the string short-circuit current: 10.15A * 1.25 = 12.6875A). This fast-blow fuse has a breaking capacity of 33kA and provides overload and short-circuit protection. If a PV string fails, the fuse will quickly open, preventing the fault from spreading and affecting other strings. The T2 surge protector is equipped with a 20kA/40kA 1000V DC DC lightning protection module. It features a multi-stage lightning protection design with a response time of ≤25ns. When struck by lightning or a surge, it rapidly discharges the surge current to the ground, protecting the combiner box and subsequent equipment from damage. The lightning protection module also features a degradation indicator, facilitating timely replacement.

Output Configuration: A 32A 1200V DC disconnect switch completely disconnects the circuit during inspection or maintenance, effectively preventing arcing and providing superior disconnection performance compared to a circuit breaker.

PC ABS waterproof junction box: Made of PC ABS material and equipped with two waterproof strips, the box boasts an IP65 rating and a UL94V-0 flame retardancy rating. It is suitable for use in environments ranging from -25°C to 60°C. The transparent panel features a darkened finish to minimize UV ​​damage to components.

3. Protective Design

Case Material: PC ABS (UV resistant for ≥10 years), (passed a 720-hour salt spray test and withstands corrosion from Austrian winter snowmelt).

Protection Rating: IP65 (dustproof and waterproof), UL94V-0 (flame retardant).

Dark, transparent window: facilitates component inspection while effectively reducing UV damage.

4. Optimized Installation

Quick Installation: Complete internal wiring and MC4 connectors for quick plug-and-play installation.

Cable Management: Input cable (PV1-F 4mm²), output cable (PV1-F 6mm²). 5. Certification and Compliance

Certifications: TUV, CE, CB, UKCA, IEC, ISO, IEC, IP65, and other certifications.

Compliance: Conforms to IEC60947-3, IEC60947-2, IEC61643-31, and IEC60269-6 standards.

IV. Project Highlights

1. Flexible Adaptability: The compact combiner box is more suitable for decentralized site management.

2. Weatherproof and Reliable: IP65 protection and high- and low-temperature-resistant materials ensure stable project operation.

3. Cost Control: An economical enclosure meets user needs while reducing costs.

4. Construction-Friendly: The pre-wired cables in the combiner box are equipped with MC4 connectors for plug-and-play installation. The quick installation design enabled the combiner box to be deployed 10 days ahead of schedule (originally planned for 6 weeks, actual 5 weeks), saving €8,000 in construction costs.

V. Project Achievements
1. Power Generation Efficiency: First-year power generation reached 712,300 kWh (8.2% above design value).
2. Ecological Benefits: The project reduced CO₂ emissions by 386 tons annually (equivalent to planting 20,000 fir trees).