By Wesley KE
A request for a 16-string PV combiner box is incomplete without the voltage, input and output current, circuit arrangement and protection scope. This guide helps solar EPC buyers and electrical engineers prepare an RFQ for Middle Eastern and South American projects. It focuses on the DC side of the PV system; an AC grid connection box is a different enquiry.
Provide a single-line diagram showing strings, DC inputs and outputs, inverter MPPT allocation, isolation, surge protection and earthing. Clarify whether the box actually parallels strings or preserves separate paths to different inverter inputs. Do not infer the output arrangement from a string-count label.
IEC 62548-1 addresses PV array design, including DC wiring, protection, switching and earthing. Specify the applicable edition and project requirements, and ask the responsible designer to confirm the arrangement. The public standard summary is a scope reference, not evidence that a particular box meets all of its requirements. IEC PV array design scope
Ask the designer to supply the maximum calculated array open-circuit voltage for the project conditions, the module data and the inverter limits. A nominal system label or a normal operating voltage does not replace that check. SMA planning guidance explains the need to keep string voltage within the permitted inverter and module limits. SMA PV generator planning guidance
Request the rated voltage of the complete offered assembly and the relevant ratings of fuses, disconnecting devices, SPDs, connectors and wiring. Do not establish a 1500 V assembly rating from one component. The Junray PV DC combiner page describes DC 1000 V applications; any different project voltage needs explicit technical confirmation.
Record the design current for each input and for every output or MPPT path. Include module short-circuit data, the project design calculation and any relevant reverse-current or backfeed requirements. The designer should provide the applicable factors and limits rather than procurement selecting a fuse from a catalogue label alone.
Published supplier datasheets illustrate why separate fields matter: Phoenix Contact lists per-string current, total current per MPPT and short-circuit rating as distinct data. Its values apply to its own product and must not be transferred to a Junray box. Use that separation when preparing the comparison schedule. Example of separately stated current fields
| Current-related field | Buyer / designer input | Supplier response |
|---|---|---|
| Each string input | Design current and module data | Input terminal, cable and device rating |
| Each output / MPPT path | Topology and required output current | Output conductor and switching arrangement |
| Fault and reverse-current duty | Project calculation and protection requirements | Relevant device and assembly evidence |
| Published current option | Ask whether the figure means input, output or another duty | Define the current designation on the datasheet |
List the required string fuse arrangement, output switching or circuit breaker, DC surge protection, earthing and isolation boundary. Ask the supplier to identify the actual devices, DC ratings, pole arrangement and circuit diagram. Protection requirements depend on the PV arrangement and cannot be inferred from the number of strings alone.
Keep the design review separate from an operating instruction. Isolation and maintenance procedures must be defined for the completed PV installation by qualified personnel; this RFQ checklist does not authorize disconnecting live PV connectors or working on energized circuits.
For Middle Eastern sites, provide maximum ambient temperature, direct solar exposure, dust or sand conditions, altitude and the mounting location. For South American sites, include the actual location, humidity, altitude and coastal exposure where relevant. Ask for the offered thermal limits and enclosure provisions instead of assuming regional suitability.
The Junray product page lists circuit options of 4, 6, 8, 12, 16 and 24, with PC+ABS and IP65 listed for the enclosure. Confirm the actual assembly, cable entries, UV conditions and corrosion provisions. An IP rating does not by itself establish salt-spray performance.
If monitoring is required, identify measured currents, voltage, temperature, device-status signals, alarms, auxiliary power and the receiving system. The listed intelligent option includes RS485/Modbus-RTU; confirm the signal list, register map and commissioning boundary for the quotation. Standard and intelligent versions should be quoted as different scopes.
Send the completed RFQ through Send Inquiry, email or WhatsApp. Review the photovoltaic equipment range; if the enquiry concerns the AC inverter-to-grid interface, use the PV AC grid connection box page instead.
| RFQ line | Required information | Evidence to request |
|---|---|---|
| System | Destination country, SLD, inverter model and MPPT arrangement | Proposed DC circuit diagram |
| Voltage | Maximum design voltage and relevant module/inverter limits | Complete assembly and component ratings |
| Inputs and outputs | String count, current per input and current per output path | Clearly labelled input/output data |
| Protection | Fuses, output switching, SPD and earthing requirements | Device schedule and coordination response |
| Environment | Temperature, UV, dust, altitude, humidity and mounting | Operating limits and enclosure details |
| Monitoring | Signals, communications and auxiliary supply | Signal list, register map and functional scope |
| Commercial | Quantity, drawings, inspection records and delivery request | Included scope, exclusions and deviations |
No. Input count, current per string, output topology and the rating of each output path must be confirmed separately using the project diagram and the offered assembly datasheet.
No. Request the complete assembly voltage and the relevant ratings and arrangement of all selected components. A single SPD, connector or switching-device marking is not a substitute for the assembly specification.
