The day the system is commissioned is the day the warranty folder should already hold paper. Serial numbers, the string voltages the installer measured, photographs of the labels, the inverter settings, and the as-built one-line if one exists are the minimum. Years later, a fault code or a dull string is compared with that day. Without the file, everyone is guessing whether the array was born this way.
Serials and labels while they are still readable
Photograph the inverter nameplate, the battery nameplate if there is a battery, and the module labels you can reach safely from the method the crew is already using. Write the serials into a list as well as the photos. A portal login that dies with an old email address should not be the only copy. Safety placards and shutdown labels belong in the same set. They weather, and a later technician needs the words that were there when the system was new.
Pacific Northwest National Laboratory's operations guide says a log of service, inverter alarms, conditions that cut performance, and downtime helps identify recurring warranty issues. Commissioning is the first page of that log: Pacific Northwest National Laboratory. The checks that belong before anyone mounts an array are a different list, in what to check before a rooftop solar installation.
Voltages the installer measured
Record string voltage as measured, string by string, with the time of day and a few words for the sky. Label each number as operating voltage or open-circuit voltage. Those are different measurements. A single unmarked volt reading cannot be compared next winter. The design voltage from the proposal is not a substitute for the meter. If the crew measured only one string and said the others match, ask them to write the others down anyway.
Cold open-circuit voltage is a design check against the inverter's maximum input, done from the module sheet and the coldest conditions the design uses. Keep that calculation if the designer produced it, and do not file the commissioned operating voltage in its place. Mixing the two numbers is how a later reader thinks the array has drifted when the labels were simply different tests.
Settings, and the drawing that matches the building
Photograph the charge voltages, the battery type, any current limit, the grid-code or utility profile, and an export limit if one is set. A later firmware update can replace those screens. What to do before someone changes them is in what to photograph before inverter settings change. The as-built one-line, if the job produced one, shows how the array, the disconnects, and the service actually landed. A sales drawing from the first visit is not an as-built. AC and DC disconnects should be identifiable on that drawing and on the labels.
Two copies, and a place you will still have
Keep a copy the owner controls and a copy the installer controls. A portal screenshot is a bonus, not the archive. When a claim starts, the folder you want is the one in what to save for a solar warranty claim. When a fault shows up, the maintenance visit starts from the same papers. What an owner may inspect later, and what stays with a qualified person, is in how to maintain a solar inverter.
Write the commissioning date on the folder. Warranties that run from installation, from delivery, or from energization do not share a clock. The contract says which. The date in the folder is what you will be asked for when the argument starts.
