1. Where the combiner box sits in a PV system (String → Combiner → Inverter)
Current path:String (DC) → combiner box (combining + protection + monitoring) → inverter (DC to AC) → grid connection. The combiner box combines 6–16 string inputs (10–15A each) into a single main circuit (100–250A), reducing DC cable runs; it also provides per-string fuse protection, DC surge protection, and string monitoring. It is typically installed beside the module array,outdoors, in full sun, with a temperature range of -30 to +70°C.
2. How to Determine DC Input Count (Round Up the Number of Strings)
| Inverter inputs | Total strings | Recommended combiner box | Inputs per box |
|---|---|---|---|
| 1 MPPT | ≤ 8 strings | 1 × 8-input unit | 8 |
| 2 MPPT | 9–16 strings | 2 × 8-input units or 1 × 16-input unit | 8/16 |
| Multiple inverters | > 16 strings | Configure by inverter zone | 8–16 |
Input count selection principles:MPPT-zoned string combining(strings on the same MPPT go into the same combiner box) to prevent MPPT mismatch from mixed connections.
3. Fuse Configuration (gPV dedicated)
- gPV solar-specific fuses are mandatory: DC 1000V/1500V breaking capacity is fundamentally different from standard AC fuses; substituting an AC part is a major hazard.
- Rated current: Select at roughly string Isc × 1.5 (typical string Isc 10–13A → choose 15A/20A);
- Install on both positive and negative poles: one on PV+ and one on PV- (DC has no zero crossing, arc extinction is difficult, bipolar protection required);
- Voltage matching: for 1000V or 1500V systems, fuse rated voltage ≥ system voltage.
4. DC Surge Protection Configuration (Type 2 SPD)
Select DC-side SPDs according to GB/T 18802.31 :Type 2(In 20kA / Imax 40kA class),Up ≤ 4kV(protection level must be below the inverter DC input withstand voltage); for 1000V systems choose 1000V DC rated, for 1500V systems choose the corresponding rating. Upstream of the SPD, install aDC-specific backup protection(gPV fuse); when the SPD degrades, a remote signaling contact reports to monitoring.
5. Enclosure & Protection: Fabrication Scope (IP65 outdoor)
Zhejiang Golden Unicorn undertakesPV combiner box enclosure fabrication: 304 stainless steel (coastal / high humidity) / 316 (chemical, offshore platform) / powder-coated galvanized sheet (standard) enclosures, IP65, UV resistant, -30 to +70°C; holes cut to drawing (cable gland entries for incoming/outgoing waterproof connections), thermal management structure, monitoring module mounting positions. Fuse holders, DC SPDs, smart monitoring modules and blocking diodes are supplied by our partner; customer-supplied materials are also accepted. Port of departure (Hangzhou).
FAQ FAQ
What is the monitoring module in a combiner box for?
It collects current/voltage for each string and uploads via RS485, enablingremote detection of string mismatch, shading or faults, essential for O&M at large plants; recommended as an option for commercial and industrial plants.
Can AC fuses be used on the DC side?
No. DC arcs have no zero crossing, and AC fuses lack sufficient arc-extinction capability; you must use gPV solar-specific DC fuses.
Can 1000V and 1500V system combiner boxes be used interchangeably?
No. In 1500V systems, fuses, SPDs and terminal creepage distances are all designed for higher voltage; using 1000V components will cause breakdown.
Can Zhejiang Golden Unicorn supply a complete combiner box?
Golden Unicorn handlesenclosure fabrication scope: Enclosure, hole cutting, sealing and thermal management structure are done by us; electrical components such as fuses, SPDs and monitoring are supplied by our partner or installed from customer-supplied materials.
Related pages:Technical notes · Products · Industries · Resource center · FAQ · Get a quote