PV system commissioning: thermography after installation secures your warranty

The commissioning inspection directly after a PV system is installed is one of the most effective yet most frequently neglected measures in the lifecycle of a system. It documents the initial condition, uncovers installation errors while the warranty is still running and protects the operator in later disputes with the installer. This guide explains why a standards-compliant commissioning thermographic inspection is indispensable and what it involves.

Why a commissioning inspection?

A new PV system can show errors directly after installation that are not detectable with the naked eye. Incorrectly connected strings, overheated connectors from poor crimp quality, microcracks in modules from improper transport or installation – none of this is visible during normal operation, but it all produces clear signals in the thermogram.

The commissioning inspection has three decisive functions: first, it uncovers defects while the installer is still under warranty obligation. Second, it documents the initial condition of the system – this is the reference for all subsequent inspections and decisive if a defect occurs later and the question of its cause arises. Third, it protects the operator legally: a standards-compliant acceptance report is the strongest documentation for warranty claims.

The right moment

The commissioning inspection should take place within the first 4–8 weeks after commissioning – early enough to still be able to assign installation errors to the installer, but not on the first day as the system first needs to "settle in". Defective connectors and poorly clamped cables only show their thermal signal after some hours of operation under load.

One should by no means wait until shortly before the 5-year warranty period expires. By then the system may already have produced considerable yield losses through undetected errors – and proving that the defect was already present at handover becomes harder the more time passes.

What the acceptance inspection involves

A complete commissioning inspection to IEC TS 62446-3 covers four areas. The Drone thermography surveys all modules systematically and checks for hotspots, microcracks, bypass diode faults and PID patterns. The hand thermography of BOS components inspects inverters, DC junction boxes and connectors for overheating. The Visual check documents mechanical anomalies, damage and installation deficiencies. The normkonforme Bericht classifies all findings, identifies the system position of every defective module and includes recommended actions.

Typical installation errors that thermography uncovers

Schlechte MC4-Steckverbindungen: The most frequent finding at commissioning inspections. Poorly crimped or contaminated connectors create increased contact resistance – visible in the thermogram as a warm spot. At high load currents such connectors can lead to arc discharges and fires.

Verpolte Strings: Incorrectly connected strings operate in the wrong direction and are heavily loaded in operation. The thermogram shows completely overheated rows of modules as a clear signal.

Montageschäden: Through careless handling during transport or installation microcracks can develop in modules. These are invisible to the naked eye but produce characteristic heat patterns in the IR image.

Shadowing-Fehler: If the system planning has not correctly accounted for shading, partial shading leads to hotspots that could have been avoided. The acceptance inspection documents such planning errors.

Fehlerhaft konfigurierte Wechselrichter: Incorrect string assignments or incorrectly configured MPP trackers lead to suboptimal operation visible in the thermogram as uneven load distribution.

Gewährleistung sichern

Under the German Civil Code the client of a PV installation has 5 years of warranty rights against the installer. For a successful warranty claim the operator must prove that the defect was already present at handover. A standards-compliant acceptance report immediately after installation is the strongest evidence for this.

Without acceptance documentation a proof problem arises: was the hotspot already there at installation, or did it develop later through external influence? With a dated IEC report from the first weeks after commissioning the causality is clearly documented.

For systems with manufacturer warranty on the modules: many module manufacturers require a standards-compliant thermographic certificate for warranty claims. A commissioning report to IEC TS 62446-3 meets this requirement.

Abnahme vs. Routineinspektion

The commissioning inspection differs from the routine inspection in its objective and report format. At acceptance the key question is: "Has the installer delivered defect-free work?" At routine inspection: "What condition is the system in and is action needed?" The acceptance report therefore contains an explicit assessment of installation quality and lists all findings attributable to installation errors.

What the acceptance report must contain

A legally relevant acceptance report to IEC TS 62446-3 contains: geo-referenced thermograms of all modules, complete measurement conditions log (irradiance, wind, module temperature), classification of all anomalies by priority, site plan of the system with findings marked and an expert assessment of installation quality. For Premium acceptances with legal usability we recommend the Premium package with expert opinion.

Kosten einer Abnahmeinspektion

The costs for a commissioning inspection are identical to the regular inspection costs – they depend on system size and chosen package. For acceptances with warranty relevance we recommend the Complete or Premium package. Specific guide prices are available immediately in the price calculator on the homepage kalkulierbar.

Frequently asked questions