Main image: One block is heating up relative to the rest of the cells – this indicates a faulty panel and that one of the cells that are connected in series has failed, dropping the performance of the panel. This panel needs to be replaced.

Recent observations of urban-domestic and SME offices, sporting row upon row of solar panels, show evidence of the increasing trend to switch from traditional sources of energy to alternative/clean energy, such as solar energy.

Solar panels are made up of cells joined together in series and relayed to a control box. When connected in series, the panel is as good as the weakest cell – if one of these cells fails, it affects the overall performance of the entire panel. 

Installation considerations

The case history in this article is of a rooftop installation situated on the Old Mutual Building in Johannesburg, Gauteng. In Image 1, the panels are located too close to the concrete roof surface and are affected by radiated heat. This is evidenced by quite a few cells failing along the bottom of the panels. There is no more than 15cm clearance between the roof and the bottom edge of the panels, and for this installation to be successful and give better performance, the panels must be raised, allowing for better ventilation and less heat build-up at the bottom.

A rooftop panel installation at the Old Mutual Building in central Johannesburg, Gauteng. The initial inspection shows where the hot spots are. Using a Fluke TiS60+ thermal imager, the technician identifies and pinpoints faulty panels. The ideal thermal imager has a high resolution (minimum 320 x 240) and good thermal sensitivity, to detect and highlight subtle differences in the cells.

Fluke’s IRR1-Sol Solar irradiance metre measures the panel performance and temperature and is engineered to align solar panels for optimum performance. 

Panel inspections

Ideal conditions for inspecting solar panels are clear, sunny skies for optimum readings. Faulty cells would be much warmer because overcast conditions do not produce maximum performance.

Access to panels

Access is needed to the panels to scan it. The Fluke 401 or TiS60 imagers suit this application if the installations are spaced for maintenance technicians to walk along the series and scan the panels individually. Manually tested, the Ti’s pictures are saved with the time and date and tagged with voice memo recordings of the panels’ location. The photos are then downloaded for the technician to know where the problem panel is. If walk access is not possible, drone technology is needed.

Panel lifetime

Solar panels degrade their output performance over time and they have a finite lifecycle, thus regular maintenance is absolutely necessary.

Devices to test and troubleshoot solar installations

  • Fluke 393FC Clamp metre/troubleshooting tool measures the load and voltage levels.
  • Fluke 1775 PQ Logger measures the power inverter efficiency, power output and power quality of solar systems.
  • Fluke BT520 measures and tests the batteries in solar applications and identifies the weakest battery in the string, allowing owners to choose to replace only one particular battery if needed.

For more information, contact Comtest:
Tel: +27 11 595 1821

Knowledge is power! Sign up for our newsletter:  Subscribe to our free magazine on or join other discussions on, and

Subscribe to our Community👇

Stay Inspired, Stay Educated, Stay Informed

By subscribing you agree to receive our promotional marketing materials. You may unsubscribe at any time.

We keep your data private.