Free Solar String Test & PV Commissioning Template (Excel)

Free Solar String Commissioning Template

String map, string test with temperature-corrected Voc and irradiance-corrected Isc, insulation resistance, inverter startup checklist, and racking torque log. Every string gets a PASS or FAIL with the reason.

✓String map: inverter, MPPT, combiner, modules, location

✓Expected Voc = modules × Voc × temperature correction

✓Voc and Isc % deviation vs. your tolerance

✓Isc corrected for irradiance, per-row override

✓Polarity, insulation resistance, IV curve reference

✓Max string Voc at record low vs. equipment rating

✓Inverter startup checklist + racking torque log

Solar String Commissioning

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What's inside the workbook

Pre-formatted, print-ready, with embedded Field PM branding. Works in Excel, Google Sheets, and Numbers.

String Map

Every source circuit: string ID, inverter, MPPT input, combiner/input, modules per string, module model and Wp, block/row/table, home-run cable. kWdc totals.

String Test

Datasheet inputs, expected vs. measured Voc and Isc with % deviation, polarity, IR to ground, IV file, overall PASS/FAIL, plus the cold-weather max-Voc check.

Inverter Startup

Pre-energization, DC and AC verification, startup and functional, monitoring, and documentation checks with pass/fail counts and status.

Racking Torque Log

Specified torque from the racking manufacturer vs. verified, deviation, UNDER/OVER flags, torque stripe, wrench calibration.

Instructions

How to fill each tab, with the math and code references.

Stop re-typing the same form on every job.

Field PM has this exact form built in — crews fill it out from a phone, the data flows into the project record, and you get a clean PDF for the GC or owner with one click. No re-typing, no lost paperwork, no missed signatures.

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Frequently asked questions

How do you calculate expected string Voc for a test?

Expected Voc = modules in the string × module Voc at STC × (1 + β/100 × (module temperature − 25 °C)), where β is the module's temperature coefficient of Voc in %/°C from the datasheet (a negative number). On a hot afternoon expected Voc is well below the nameplate sum, so comparing measured voltage to the uncorrected STC value makes good strings look low. The template does the correction per row and shows the % deviation.

What tolerance should a string Voc test pass at?

It comes from your commissioning plan or owner spec. Many plans accept a few percent from the temperature-corrected expected value and also compare strings to each other under the same conditions. A string low by about one module's worth usually has a missing or shorted module or a failed bypass diode. The tolerance is an input in the template.

Why measure irradiance with Isc?

Short-circuit current scales almost directly with irradiance, so an Isc reading means nothing without the plane-of-array irradiance taken at the same moment. The template corrects expected Isc for irradiance (G/1000) and temperature (the Isc coefficient) and lets each row carry its own irradiance reading when clouds move through.

Is this an IEC 62446-1 test report?

It records the same core measurements IEC 62446-1 calls for in its Category 1 test sequence (polarity, string Voc, string current, and insulation resistance) plus IV-curve references, inverter startup, and racking torque. It is our own layout, not a reproduction of the standard's forms; check your contract for any required report format.

Where do racking torque values come from?

From the racking or tracker manufacturer's installation manual for each connection and fastener. The template does not include any. The example values are placeholders. You enter the specified torque and an acceptance band, and the log flags UNDER or OVER readings, unmarked fasteners, and wrenches past their calibration date.

Test every string against what it should read

PV string commissioning proves each source circuit is wired, polarized, and performing before it's energized: polarity, open-circuit voltage, short-circuit current, and insulation resistance, compared with what the modules should produce under the conditions at the time of test.

This free template gives solar EPCs and electrical contractors a connected workbook: a string map, a string test sheet that does the temperature and irradiance correction for you, an inverter startup checklist, and a racking torque log. Check the design side with our PV voltage temperature correction reference.

On large sites, Field PM puts the same checklists and test records on every crew's phone and rolls them up by block and inverter, so commissioning status is always current.

PV string commissioning that holds up at turnover

Commissioning a PV array is repetitive work with little margin for error. Every source circuit gets its polarity checked, its open-circuit voltage compared with what it should be, its current checked against irradiance, and its insulation tested before it's closed into a combiner or inverter. Do it for 400 strings on a hot afternoon with clouds moving through and the paperwork is where things fall apart. The free workbook above keeps it in four connected tabs: String Map → String Test → Inverter Startup → Racking Torque Log.

1. The string map comes first

Before anyone lifts a meter, map every source circuit: string ID, inverter, MPPT input, combiner and input number (or "Direct" for string inverters), modules per string, module model and wattage, block/row/table, and home-run cable ID. The String Test tab looks up modules per string from this map by string ID, so the expected voltage uses the actual count on the drawings, not an assumed one. The summary totals strings, modules, and kWdc and shows the min/max modules per string. Mixed string lengths on one MPPT are a design question to settle before energizing.

2. Expected Voc: correct for temperature or chase ghosts

Module Voc is rated at STC: 25 °C cell temperature. Real module temperatures on a sunny day run 40–60 °C, and voltage drops as temperature rises. The correction uses the datasheet coefficient:

Expected Voc = modules × module Voc(STC) × (1 + β/100 × (T_module − 25))
% deviation = (measured − expected) ÷ expected, checked against your tolerance

With β = −0.27 %/°C and a 45 °C module, a 26-module string of 49.6 V modules should read about 1,220 V, not the 1,290 V nameplate sum. Measure module temperature on the back of a module in the string's row. The template lets any row override the global temperature if conditions shift through the day.

What the deviations tell you: a string low by roughly one module's Voc (≈ 4%) usually has a missing jumper, a shorted module, or a failed bypass diode. Strings reading high are often a count error on the map. A string that sits far from its neighbors in the same conditions is worth an IV curve before it's energized.

3. Isc and irradiance

Short-circuit current tracks irradiance almost one-for-one, so the template corrects expected Isc by G/1000 and the small positive Isc temperature coefficient. Record plane-of-array irradiance from a reference cell at the moment you read Isc. When a cloud edge passes, record the new irradiance on that row rather than failing the string. If many strings read low together, suspect irradiance or soiling first.

4. Polarity, insulation resistance, and IV curves

Polarity gets checked before any string is landed in a combiner or inverter. A reversed string forces an overall FAIL. Insulation resistance is recorded positive-to-ground and negative-to-ground at the test voltage your spec or IEC 62446-1 sets for the system voltage; the minimum is an input. Record the IV-curve file name so each string's curve can be pulled up later. Steps in the curve point to shading or bypass diodes, and a low fill factor points to series resistance.

5. The cold-weather voltage check

The String Test tab also runs the design-side check the AHJ will ask about: maximum string Voc at the site's record low temperature, using the manufacturer temperature-coefficient method in NEC 690.7(A) (verify against the edition your AHJ adopted), compared with the lowest maximum-voltage rating among the inverter, combiners, disconnects, and cable. Commissioning is the last chance to catch a string built one module too long. See our PV voltage temperature correction reference for the method and the NEC table alternative.

6. Inverter startup and racking torque

The Inverter Startup tab walks pre-energization terminations and labeling, DC and AC verification, startup and functional checks (grid profile per the interconnection agreement, anti-islanding, rapid shutdown where required), communications, and documentation. The status reads COMPLETE only with no fails and no blanks. The inverter manufacturer's startup procedure governs where it differs.

The Racking Torque Log records specified torque from the racking or tracker manual, the verified reading, torque stripe, and the wrench used with its calibration due date. It flags UNDER and OVER against your acceptance band. A cluster of UNDER readings on one crew or one wrench means expanding the sample, not re-torquing one bolt.

From spreadsheet to commissioning record

A workbook works for a rooftop or a single inverter block. On a utility-scale site the hard part is keeping hundreds of strings, dozens of inverters, and several crews on one current record. Field PM's QA/QC module puts checklists, hold points, test records, and photos on the crew's phone, and QA/QC workflows sequence sign-offs so an inverter can't be marked ready before its strings are. Start a free 30-day trial. No credit card required.

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PV voltage temperature correction: NEC 690.7 method explained
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