Solar array junction boxes for 1000 V and 1500 V DC systems
An array junction box (AJB) — also called a string combiner box or solar DCDB — is the first protection point of a PV plant. It collects the DC output of several module strings, protects each string with a gPV fuse, diverts lightning and switching surges through a DC surge protection device, and lets the O&M team isolate the array from the inverter with a DC load-break switch. Accu-Panels Energy supplies standard and customised AJBs from 2-in/1-out to 24-in/1-out for 1000 V and 1500 V DC, built in IP65 / IP66 enclosures at its Ahmedabad works for rooftop, ground-mount and MW-scale plants in India, Africa and the Middle East.
Array junction box specifications
| Parameter | Accu-Panels range |
|---|---|
| Maximum system voltage | 1000 V DC or 1500 V DC |
| Configurations | 2/1, 4/1, 6/1, 8/1, 12/1, 16/1, 20/1, 24/1 strings in / outputs out; dual-output for 2-MPPT inverters |
| String fuses | gPV 10 A / 15 A / 20 A / 25 A / 32 A, 10 × 38 mm, IEC 60269-6, in touch-safe holders on positive and negative |
| Surge protection | Type 2 DC SPD (Type 1+2 optional) per IEC 61643-31, with remote-indication contact |
| DC isolator | DC-rated load-break switch 32 A to 630 A, IEC 60947-3, door-interlocked handle |
| Output | Busbar or terminal output up to 630 A, cable up to 300 sq. mm |
| Enclosure | IP65 / IP66; glass-fibre reinforced polyester (SMC), polycarbonate or 1.6 mm CRCA with C5 coating; UV-stabilised; −10 °C to +60 °C |
| Cable entry | MC4 connectors or IP68 cable glands, bottom entry |
| Monitoring (optional) | String-current monitoring unit, RS-485 / Modbus RTU, SPD status, door-open and temperature inputs |
| Standards | IEC 61439-1/2, IEC 60947-3, IEC 60269-6, IEC 61643-31, IEC 60529 |
Why string protection matters
When one string in a parallel group is shaded or faulted, the healthy strings can drive reverse current into it. A correctly rated gPV fuse (typically 1.5 to 2 times the module short-circuit current, Isc) clears that fault before the module or cable is damaged. The SPD limits induced surges from nearby lightning to a level the inverter can withstand, and the DC isolator provides the safe working point every O&M procedure needs. Fuse, SPD and isolator ratings are selected from your module datasheet and string layout.
Applications
- Industrial and commercial rooftop plants from 50 kW upward
- Ground-mount and utility-scale plants with central inverters (1000 / 1500 V DC)
- Solar pumps, carports and off-grid installations
- Combined with solar ACDB and DCDB panels, AC combiner boxes and 800 V LT panels for complete plant electrical packages
Frequently asked questions
How many strings should one AJB combine?
It depends on the inverter input rating and cable economics; 8 to 16 strings per box is common on large plants. We optimise box count against DC cable length for each layout.
How is the string fuse rated?
Between 1.5 and 2 times the module Isc from the datasheet, and never above the module’s maximum series fuse rating.
Polyester or metal enclosure?
SMC polyester is lighter, non-conductive and corrosion-free for open-field mounting; CRCA with C5 coating suits large combiner boxes and rooftop plant rooms.
Can the AJB be monitored?
Yes. String monitoring units report per-string current and SPD status over Modbus RTU / RS-485 to the plant SCADA.
What documents are supplied?
GA drawing, wiring diagram, bill of materials, routine test certificate and warranty certificate with every batch.
Share your module datasheet and string layout with our solar team for AJB sizing and a quotation.
