Commercial Rooftop Solar Commissioning & Handover Checklist in Bangladesh: IEC 62446 Tests, Acceptance Limits & Documents

Direct answer: Commissioning is the formal set of inspections and electrical tests that prove a commercial rooftop solar plant was built as designed, is safe to energise, and performs as modelled — before the client signs acceptance. For grid-connected PV, IEC 62446-1 defines the minimum regime: visual inspection, protective-conductor continuity, DC polarity, string open-circuit voltage and current, insulation resistance, functional tests of switching and protection, and a documented test report. Skipping any of these turns a warranty claim into an argument, because nobody can prove what the plant delivered on day one.

Why commissioning is not a formality

A commercial rooftop plant is a 25-year asset assembled from hundreds of field-made connections. A single reversed string, a loose MC4 connector, or a nicked DC cable can hide behind a normal-looking inverter display for months while it quietly costs production — or, in the worst case, creates an arc fault. Commissioning catches those defects while the installer is still on site and contractually obliged to fix them. It also creates the performance baseline that every later performance-monitoring KPI is judged against: without a day-one performance ratio (PR), a 10% shortfall in year three is a debate, not a claim.

For factory and commercial owners in Bangladesh there is a second reason. Utility interconnection, net-metering approval, and insurer or lender sign-off all depend on documented evidence that the plant complies with the approved design and applicable standards. A commissioning report is that evidence. Treat a handover without one the way you would treat a factory handover without a completion certificate: do not accept it.

Category 1 and Category 2: what IEC 62446-1 requires

IEC 62446-1 divides commissioning into two categories. Category 1 applies to every grid-connected PV system and is the minimum for acceptance. Category 2 adds advanced diagnostics for larger or more complex plants, and is strongly recommended for commercial rooftops above roughly 100 kW, or wherever the owner wants a defensible performance baseline.

Category 1 — required for all systems:

• Visual inspection of modules, mounting, cabling, labelling, and protection devices
• Continuity of protective conductors and bonding
• DC polarity verification for every string
• String open-circuit voltage (Voc) and string current (short-circuit or operating) measurements
• Insulation resistance of DC circuits
• Functional tests of switching, control, and protective devices, including inverter start-up and anti-islanding behaviour

Category 2 — recommended for commercial plants:

• I-V curve tracing for each string or array, with irradiance and temperature recorded
• Infrared (thermal) inspection of modules, combiner boxes, and connections
• A performance assessment against the design model, including an initial PR estimate

Category 2 diagnostics never replace Category 1 tests. An infrared scan can find a hot connector, but it cannot prove insulation integrity; an I-V curve can reveal a degraded string, but it cannot prove polarity was checked. Insist on both layers for a commercial plant.

The electrical tests, with acceptance limits

Every result should be recorded per string, with the test instrument, test conditions, and the expected value shown beside the measured value. A report that lists only system totals is not a commissioning report.

Voc and current readings must be corrected for the conditions on the day. A Voc measured at 40 °C on a Dhaka rooftop in April will legitimately read below the 25 °C datasheet value, because module voltage falls as temperature rises; a competent report shows the correction, not just the raw number. The same applies to current: it must be read against the plane-of-array irradiance at the time of the test, not against a clear-sky guess. If a string deviates beyond the limits above, the cause must be found and fixed before acceptance — a swapped connector, a shaded module, or a faulty bypass diode are all common, fixable causes.

Inverter, protection, and grid-side checks

The AC side deserves the same discipline as the DC side. Verify AC voltage and frequency at the point of interconnection, check that protection settings match the utility's requirements, and confirm that the anti-islanding function actually trips on a simulated grid loss. Record the inverter firmware version and the protection settings themselves — a future firmware update can change behaviour, and the commissioning record is the only way to know what changed.

Check the items that cause fires, not just the items that cause faults. Our fire-safety guide explains why loose or mismatched DC connectors are the leading ignition source on commercial rooftops: torque marks, correct connector pairing, and cable routing away from sharp edges and standing water should all be visually verified and photographed during commissioning, not assumed from the installer's word. The same visit should confirm surge protection devices are correctly installed and that earthing electrodes and bonding are complete, tying into the lightning and surge protection design for the site.

Performance baseline: prove day-one output

On commissioning day, record a clean performance snapshot: plane-of-array irradiance, module temperature, AC output, and the resulting PR, calculated on the method your performance-monitoring guide will use every month afterwards. Take the snapshot at a stable irradiance, ideally above 600 W/m², and state the conditions in the report. This single page is what converts a later underperformance dispute into a measurement: if PR falls 8% in year two with no change in soiling or shading, the baseline proves something degraded, and the warranty process can start from evidence rather than opinion.

The handover pack: documents you must receive

Do not sign acceptance until the following pack is in your hands, in both paper and digital form:

1. Commissioning test report — all Category 1 results per string, plus Category 2 I-V curves and infrared images where agreed.
2. As-built drawings — final layout, string schedule, cable routes, and single-line diagram, reflecting what was actually installed.
3. Equipment datasheets and warranties — modules, inverters, and batteries, with serial numbers matched to the installed positions.
4. Protection settings record — inverter and protection relay settings, firmware versions, and utility approval correspondence.
5. O&M manual — cleaning schedule, inspection intervals, alarm meanings, and the contact route for warranty claims.
6. Monitoring access — live login credentials for the plant monitoring portal, with the owner as administrator, not the installer.
7. Training record — a short session for the facility team covering shutdown procedure, isolator locations, and what to do on a fault alarm.

Bangladesh-specific points to confirm

Three local items routinely delay handover and should be closed before acceptance, not after. First, the utility inspection and bi-directional meter installation for net-metering plants: confirm the meter is installed, the export register is recording, and the readings match the inverter's own export counter. Second, structural and fire-safety compliance for the roof: the mounting design should match the structural assessment for the building, and roof penetrations should be sealed and photographed. Third, cable and protection sizing: verify the installed DC cable sizes match the DC cable sizing calculation in the design, because undersized cable is invisible once trunking is closed and costs 1–3% of annual yield every year.

Common commissioning failures — and what to do about them

• One string reading low on current: check for a shaded or soiled module, a failed bypass diode, or a mismatched string length before accepting any explanation about clouds.
• Insulation resistance below limit: isolate sections string by string to find the fault; a wet combiner box or damaged cable insulation is the usual cause, and it must be repaired, not noted and left.
• Inverter tripping on grid voltage: verify the protection window matches the local utility's actual voltage range; nuisance tripping that is accepted at handover becomes lost production for 25 years.
• Missing string labels or drawings: refuse acceptance until labelling matches the string schedule — an unlabelled combiner box makes every future fault call slower and more expensive.

Owner's acceptance checklist

1. Every Category 1 test passed and recorded per string.
2. Category 2 I-V curves and infrared scan completed for plants above 100 kW.
3. Day-one PR baseline recorded with irradiance and temperature.
4. Handover pack received complete, with monitoring access in the owner's name.
5. Utility meter and net-metering export verified against the inverter.
6. Punch list of defects closed, with re-test results attached.
7. Facility team trained on shutdown and fault response.

A plant that passes this checklist is not merely installed — it is proven. That proof is worth more than any brochure efficiency figure, because it is the only efficiency figure measured on your roof, on your building, under your sky.

FAQs

Can commissioning be done on a cloudy day?

Partly. Continuity, polarity, insulation resistance, and functional tests do not need sun. Voc and current measurements, however, must be interpreted against measured irradiance, and a meaningful PR baseline needs stable, reasonably strong sun. If the weather does not allow it, complete the sun-independent tests, record the weather constraint honestly, and schedule the performance tests for a clear window — do not sign a performance baseline taken under cloud.

Who should perform commissioning — the installer or an independent engineer?

The installer performs the tests, but for commercial plants the owner should require independent witnessing or a third-party verification of at least the Category 1 results and the performance baseline. Self-certification by the party being paid on acceptance is a conflict of interest; an independent witness costs a fraction of one year of lost production.

What happens if a test fails at handover?

The defect goes on a punch list, the installer repairs it, and the affected test is repeated and re-recorded. Acceptance — and final payment milestones tied to it — should wait until the punch list is closed. Accepting a plant with known test failures converts the installer's defect into the owner's maintenance problem.

How does commissioning relate to the module and inverter warranties?

Warranties are usually conditional on correct installation, and the commissioning report is the evidence of correct installation. If a module degrades prematurely, the manufacturer will ask for the commissioning I-V curves and the string records; without them, a claim can be refused on the grounds that the defect cannot be distinguished from an installation fault. Keep the report for the full warranty period.

Sources: IEC 62446-1 (grid-connected PV commissioning, Category 1 and Category 2 tests and documentation); IEC 61724 (PV system performance monitoring); IEC 62116 (anti-islanding test procedure); Fluke/PES guidance on IEC 62446-1 interpretation for field engineers.