A complete guide to the ITC Part 2 form for Irish solar PV installers — its relationship to EN 62446, required module and inverter fields, on-site vs STC measurements, DC test results, electrical certificates, and how to get it right.
The ITC Part 2 — Inspection, Test & Commissioning Certificate is a SEAI technical document that confirms a solar PV system has been correctly installed and commissioned in accordance with the relevant Irish and European standards. It is one of three core compliance documents required for every SEAI residential Solar PV grant claim, alongside the Declaration of Works Part 1 and the NC6 Microgeneration Notification submitted to ESB Networks.
The ITC is the most technically detailed of the three forms. Where the DOW confirms the scope and cost of the installation, the ITC records the actual measured test results from the commissioning process. It is signed by the commissioning engineer (typically the installer) and provides the technical audit trail that SEAI uses to verify that the system meets ET 101 and EN 62446 requirements.
The ITC Part 2 is structured around EN 62446-1 (BS EN 62446-1:2016 in the UK/Ireland context), the European standard for documentation, commissioning tests, and inspection criteria for solar PV systems. EN 62446 specifies what must be measured, recorded, and signed off at commissioning.
The key EN 62446 requirements that feed directly into the ITC form are:
These measurements must be taken on the day of commissioning and recorded on the ITC. They cannot be fabricated or estimated — SEAI audits occasionally involve site visits where inspectors may check that recorded values are plausible.
The model numbers entered here must match the hardware actually installed. If you enter a different model than what's on site, the ITC is invalid. SEAI has rejected grant claims where ITC model numbers did not match installation photos.
One of the most misunderstood aspects of the ITC is the distinction between on-site measured values and STC values from the datasheet.
STC (Standard Test Conditions) values — Voc, Isc, Vmp, Imp — are measured by the manufacturer at 1000 W/m² irradiance, 25°C cell temperature, and AM1.5 spectrum. These are the values on the panel datasheet. They represent ideal laboratory conditions.
On-site measurements are taken in actual ambient conditions on the day of commissioning. The irradiance will almost certainly not be 1000 W/m², and the cell temperature will likely not be 25°C. As a result:
The ITC requires you to record both the STC values (from the datasheet) and the measured values at commissioning. The form includes columns for each. The ratio of measured to STC values should be reasonable given the ambient conditions at the time. An Isc measurement that is 95% of STC Isc on a cloudy November afternoon in Galway is implausible and will raise flags.
Best practice: record the ambient temperature and your estimated irradiance (from a pyranometer or irradiance meter) at the time of testing, even if the ITC form doesn't explicitly require it. This context supports your measurements if they are ever queried.
The DC test results are the core technical content of the ITC. You need to record:
Resistance measurement (in ohms) of the earthing conductor from the array frame to the main earthing terminal. Should be very low — typically less than 0.5 Ω for standard domestic installations.
A simple pass/fail confirmation that each string has correct polarity (positive terminal is positive, negative is negative) at the inverter DC input. A crossed polarity will prevent the inverter starting and can damage it — this is one of the most important checks.
For each string, record the open-circuit voltage measured at the inverter input with the inverter disconnected. Compare against the STC Voc multiplied by the number of panels per string, adjusted for temperature.
For a 12-panel string (Voc STC = 39.5 V per panel): STC string Voc = 474 V. On a cold January day at 5°C, cell temperature might be 8°C, so expect: 474 × (1 + (−17 × 0.0026)) ≈ 495 V. A measurement of 492 V is plausible; a measurement of 420 V (unexpectedly low) or 550 V (impossibly high) would indicate an error.
For each string, record the short-circuit current measured using a clamp meter or DC current meter. This is proportional to irradiance. On a sunny day at 800 W/m² irradiance, expect approximately 80% of STC Isc per panel.
DC insulation resistance between the live conductors and earth, measured using a 500 V or 1000 V DC insulation resistance tester. EN 62446 requires a minimum value of 1 MΩ — most well-installed systems exceed 100 MΩ. Record the actual measured value, not just "pass".
The ITC Part 2 often references or must be accompanied by:
If you are acting as both the solar installer and the electrical contractor (as a qualified electrician), you may complete both. If you subcontract the electrical work, ensure the subcontractor provides the ETCI certificate promptly — you cannot complete the ITC without confirming the electrical installation is certified.
The ITC requires specific hardware data — panel Voc STC, Isc STC, inverter MPPT range, rated AC output — that comes from manufacturer datasheets. With Circaidian, this data is automatically matched from your Scoops (or other survey platform) report against our hardware library.
When you upload a Scoops PDF, we:
You then add your on-site measured values (Voc, Isc, insulation resistance) through our review screen before generating the final ITC PDF. The result: no manual transcription of technical data from datasheets, no mismatched models, no STC fields left blank.
See how the full pipeline works → Automate all three forms (NC6, DOW, ITC) →
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