1. Where the combiner box sits in a PV system The transfer station on the DC side
Current path in a PV power system:Solar panels (DC) → combiner box (combining + monitoring) → inverter (DC to AC) → AC distribution cabinet (distribution) → transformer (step-up) → grid connection.
The job of the combiner box is tocombine the small DC currents from dozens of solar panel strings (5–15A each) into 1–4 high-current circuits (100–500A each), ready for connection to the inverter. A 1MW PV plant typically uses 4–8 combiner boxes, each managing 8–16 strings.
2. The 4 core functions of a combiner box Combining + protection + monitoring + surge protection
- Combining: combine multiple string currents (5–15A each) into 1–4 main circuits (100–500A each), reducing cable usage
- Protection: each circuit is fitted with a fuse or circuit breaker, so a short circuit trips only that circuit and does not affect the others
- Monitoring: monitor current / voltage / power on each circuit and upload the data to a SCADA system
- Surge protection: DC-side SPDs discharge induced lightning surges and switching surges
Combiner boxMust operate outdoors(installed next to the solar panel array), IP65 minimum, rated for -30°C to +70°C. Zhejiang Golden Unicorn buildscombiner box enclosures, MOQ 1 unit, 15–25 days.
3. The 6 Core Components of a Solar Combiner Box One table sorts it out
| Component | Function | Typical configuration |
|---|---|---|
| DC fuse | Short-circuit protection per string | 15A / 1000V DC, 1 per string |
| DC circuit breaker | Total output disconnection | 250A / 1000V DC, 1 unit |
| DC SPD surge protector | Surge protection | Type 2,40kA,Up ≤ 4kV |
| Smart monitoring module | Collects current / voltage per string | 8/12/16 strings, RS485 / Modbus |
| Blocking diode | Prevents reverse current | 1 per string (optional) |
| Enclosure | IP65 outdoor, corrosion-resistant | 304 stainless steel / powder-coated cold-rolled steel |
Zhejiang Golden Unicorn combiner box enclosures304 stainless steel as standard(suitable for coastal / high-humidity sites); 316 available at extra cost (chemical / offshore platform).
4. Solar Combiner Box vs DC Distribution Cabinet: What's the Difference? Don't buy the wrong one
| Item | Solar combiner box | DC distribution cabinet |
|---|---|---|
| Voltage | DC 600–1500V | DC 24/48/110/220V |
| Current | 5–15A per string → 100–500A total | A few A to several hundred A |
| Protection | IP65 outdoor + UV resistant | Mainly IP30–54 indoor |
| Monitoring | Smart monitoring as standard | Optional |
| Typical applications | Solar PV plants | Telecom / DC power supply panels / EV charging stations |
The biggest difference is voltage.: A combiner box ishigh-voltage DC(from 1000V up), and the components must beDC-rated(AC components cannot be used directly). A DC distribution cabinet islow-voltage DC(≤ 220V).
5. How to Select a Combiner Box: Capacity + Surge Protection + Monitoring 3 core parameters
When selecting a combiner box, check 3 core parameters:
- Capacity (number of input strings × current per string): 8 / 12 / 16 strings are common, 10–15A per string. Example: a 12-string combiner box, total current ≤ 180A
- Surge protection level: Type 2 SPD, In ≥ 20kA, Imax ≥ 40kA. For coastal or high-lightning areas, Type 1 + Type 2 in series is recommended
- Monitoring method: RS485 / Modbus RTU is standard; 4G / Ethernet optional; cloud platform upload is a plus
Zhejiang Golden Unicorn suppliescombiner box enclosures and assemblies(components included), MOQ 1 unit, 15–25 days. If UL, TUV or CGC certification is required,it can be provided by a partner with the relevant qualifications, and the specific certification scope is subject to the partner's certificate.
6. Factory Photos: 4 Shots of Combiner Box Enclosure Fabrication (shop floor photos)
FAQ FAQ
Does a combiner box have to be IP65?
Outdoor units must be IP65(mandatory under GB/T 34933-2017); indoor units can drop to IP54. Zhejiang Golden Unicorn defaults to IP65 outdoor, 304 stainless steel enclosure.
Should a combiner box include smart monitoring?
Recommended. For plants above 1MW, smart monitoring is a must — it pinpoints the faulty string and doubles O&M efficiency.For residential plants below 5kW, it can be omitted(poor cost-performance).
Which is better: a combiner box or string inverters?
Each has its advantages.Combiner box + central inverter: lower cost, suited to large ground-mounted plants; string inverters (one per string): higher reliability, suited to rooftops and complex mountainous terrain. Zhejiang Golden Unicorn handles both.
How is lightning protection handled in a solar combiner box?
A DC-side SPD is mandatory(surge protective device). Specify Type 2 (40kA), Up ≤ 4kV. In high-lightning or coastal areas, add Type 1 (100kA). Golden Unicorn combiner boxesship with a Type 2 SPD as standard; Type 1 + Type 2 in series is available at additional cost.
Can Golden Unicorn supply a complete solar combiner box?
We build the enclosure and complete the assembly(enclosure + installed components + wiring). Certification (UL / TUV / CGC) is issued by our partner; Golden Unicorn cancoordinate the process. MOQ 1 unit, 15–25 days.
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