Three trackers give flexibility, not unlimited mixing
Multiple MPPT trackers can separate roof orientations, module groups or string conditions that would otherwise create mismatch. Each tracker still has its own voltage and current limits, and the inverter’s total DC limits continue to apply.
Build every string from cold-weather Voc first
Use the exact module temperature coefficient and the site design minimum temperature to calculate maximum open-circuit voltage. Keep the resulting string below the inverter’s absolute DC limit with the manufacturer-required margin.
Then verify the operating window
Expected hot-weather Vmp must remain within the MPPT operating range. A string that is safe at cold Voc can still operate poorly if its working voltage drops below the tracker’s useful range in hot conditions.
Check current per input and per tracker
High-current modern modules can make parallel-string current the limiting factor before voltage is a problem. Confirm module Imp/Isc, connector ratings, individual input current and the tracker-level limit.
Use the Fronius Verto 17.5 as an example
The source-reviewed Fronius Verto 17.5 has three MPPT trackers, a 150–870V MPPT range and a manufacturer-listed maximum PV generator size of 26.3kWp. Those figures create a design envelope; they are not a substitute for string calculations and local grid-code configuration.
Document the final allocation
Record which array/string is connected to each tracker, the module revision, design temperatures, calculated Voc/Vmp and current. Review the cold-weather string-voltage guide and module-current guide before commissioning.