Combiner Box Commissioning Test Checklist

Pre-energise safety

Define the work and test boundary before starting. Isolate every supply that can energize the section and verify absence of voltage at the work location using the approved procedure. An output disconnect in the OFF position does not make the PV inputs safe: illuminated strings can still produce voltage.

Keep internal inspection and dead-circuit testing separate from measurements on isolated but potentially energized strings. A qualified team should agree the instrument ratings, calibration, test object and acceptance criteria.

Insulation, withstand and continuity test boundaries

Insulation resistance testing, dielectric withstand testing and protective-conductor continuity testing serve different purposes. Do not use a factory dielectric-withstand value as a field insulation-resistance setting. Select the setting and acceptance threshold for the actual test object, applicable procedure and connected equipment.

Insulation resistance: document the selected test voltage, test points, duration and acceptance threshold from the applicable commissioning procedure.

Dielectric withstand: perform only when explicitly required by the applicable procedure, with its separate equipment, limits and precautions.

Protective-conductor continuity: use the specified low-resistance test method and record the result between the required bonding points before energization.

Before an insulation test, identify SPDs, monitoring electronics and other connected components. Isolate them as their instructions require and record every temporary disconnection. A universal insulation threshold or factory withstand setting cannot substitute for the approved field procedure.

Per-string open-circuit voltage

Before paralleling strings, use suitably rated instruments and the approved PV voltage-testing method to record each isolated string voltage and polarity. Compare the result with the expected module count, temperature and configuration. Stop and investigate unexpected readings.

Parallel strings share a bus voltage; their voltages are not added. A string upstream of an open fuse can still show normal open-circuit voltage, so this measurement does not by itself prove fuse continuity or current-delivery capability.

Polarity and reverse-check

Verify the polarity of each identified input before connecting it to the common bus. Record test points and the string connection state. A reversed connection can create a fault path; it does not merely cancel the current of a correct string.

A zero-voltage reading is not proof of correct polarity. Unexpected voltage or identification requires investigation before staged energization. Internal corrective work requires the defined isolation and absence-of-voltage procedure.

Breaker and SPD status

Verify the exact switching and protection devices against the approved schedule, including any required pole arrangement. Follow the switch instructions for inspection and operation; an isolating device does not automatically provide overcurrent protection.

Inspect SPD indications and the protective-conductor connection using the relevant procedure. Do not inject a simulated surge into an in-service combiner. Restore any SPD or electronics disconnected for testing and confirm the final configuration.

Torque verification

Use the installation or assembly instruction for the exact terminal and conductor. Identify the specified tool, torque and verification method. Do not apply a generic setting or assume that every terminal should be tightened again without checking its procedure.

Record the terminal reference, instruction revision and inspection outcome. Rework a nonconforming termination only after isolation and confirmation of the safe work boundary.

Sealing and labelling

Check mounting, cable-entry seals, unused entries, gasket condition, conductor labels and the as-built schedule. Confirm that the installed parts and entry arrangement match the enclosure configuration reviewed for ingress protection.

Resolve damaged seals, unidentified strings and missing safety markings before release. An enclosure nameplate alone does not prove that the completed installation preserves its protection rating.

Sign-off

Before energization, discharge tested circuits where required, restore all disconnected devices and inspect every temporary test connection. Compare the restoration record with the final drawings so a test isolation is not left in place.

Retain measured results, instrument details, device schedule, termination records and responsible approval. Follow the approved staged-energization plan only after the required checks pass.