Modbus TCP
SunSpec Model 403 — String Combiner (Current)
SunSpec
Overview
SunSpec Model 403 is the standard information model for a DC string combiner in a photovoltaic system, covering current-based monitoring across all connected PV strings. The template reads total DC output current, cumulative amp-hour yield, DC bus voltage, combiner temperature, maximum rated current, and the number of active strings, alongside combiner-level and vendor-specific event bitfields. Per-string scale factor registers enable precise decoding of individual string data in the repeating block. Using Modbus TCP, this template gives installers and asset managers a vendor-neutral view of combiner health and string-level production directly inside the ModbusCloud portal.
Use cases
- Monitor total DC output current from all strings to verify expected combiner yield against irradiance data.
- Track cumulative amp-hour production over time to compare seasonal performance across multiple PV arrays.
- Alert on combiner event flag changes to detect faults such as overcurrent or string disconnection events quickly.
