How to Select a Solar String Combiner Box

Define the circuit arrangement

Document strings per output and MPPT assignment. Combine only compatible circuits permitted by the inverter instructions. Check whether the inverter already provides combining and protection before adding external equipment.

Confirm voltage and current limits

Calculate cold-weather maximum open-circuit voltage and maximum circuit current using module data and applicable design factors. Assess reverse-current exposure, module maximum series fuse rating, DC fuse voltage and interrupting capacity. Use PV-rated switching and surge protection for the circuit design.

Check field conditions and monitoring

Specify enclosure protection for dust and moisture, temperature, UV exposure, glands, conductor sizes, earthing and service access. If monitoring is required, separately specify measured channels, interfaces, auxiliary supply and logger compatibility.

A practical procurement example

A design with twelve strings is not automatically a twelve-input common-output box. If the inverter needs three separate groups of four strings, the approved MPPT arrangement determines the output topology. Submit the string schedule and inverter datasheet for confirmation.

Frequently asked questions

Should all inverter MPPT inputs be combined?

No. Maintain the inverter input arrangement specified by its manufacturer. Combining separate MPPT circuits can impair tracking and exceed input limits.

Are the examples a GEESYS product specification?

No. Worked examples explain selection principles. Use the selected product datasheet and approved project design for actual ratings and installation requirements.

Related GEESYS products

• Solar Dc String Combiner Boxes