A correctly installed photovoltaic system is a source of pride for its owner. For this reason, it is essential to sign a solid contract with the installer that clearly defines warranty and guarantee conditions. If you plan to carry out the installation yourself, make sure you are familiar with the 5 most common installation mistakes. This can save you a lot of problems!

 

Not using washers under anodized terminals

Many people hesitate to invest in photovoltaics because they fear storms. The truth is that solar panels do not attract lightning. Lightning strikes not devices under voltage, but those that are simply elevated.

Grounding photovoltaic modules reduces both the risk and the potential damage of a lightning strike. However, aluminum, which makes up PV module frames and profiles, has an insulating surface layer. This is especially true for anodized terminals, also known as the black ones. To penetrate this layer and properly ground the system, grounding washers are used.

In the illustration: a grounding washer placed under the end terminal.

 

Besides protecting against electrical discharges, these washers also enhance surge protection.

 

The best practice is to use grounding washers or special grounding terminals.

The video below demonstrates attaching a photovoltaic module to the profile. Notice the small spiked metal plate placed under the module – this is the grounding washer.

 

 

Inadequate protection of wires against UV light

Photovoltaic cables must be UV-protected to withstand exposure for 25-30 years. This can be achieved using protective conduits and UV-resistant cable connectors.

The best practice: professional solar cables do not need to be fully run inside conduits. To optimise costs, conduits can be used only where direct sunlight may affect them, including between modules. Always use UV-resistant connectors.

 

Walking on the modules

Walking or kneeling on photovoltaic modules does not crack the glass, but it can cause microcracks in the cells.

This is shown in the video below:

Microcracks are invisible and initially slightly reduce module efficiency. Over time, however, they can develop into hot spots, which may degrade the backsheet, crack the glass, cause cell corrosion, or trigger bypass diode disconnection. In extreme cases, this can result in an electrical arc to the casing, posing a serious safety risk.

Best practice – photovoltaic modules can withstand hurricane-force winds and heavy snow, but do not walk on them. Surprising, but true.

 

Using connectors from different manufacturers in one installation

Using connectors from different manufacturers, even if considered compatible (but not certified or guaranteed like Altamira connectors), is common but risky.

Illustration: left – real view of connectors from different manufacturers; right – thermographic image. One connector is overheating, indicating resistance, power loss, and a safety hazard. Source: PVEL and Heliovolta – The Ultimate Safety Guide for Solar PV Connectors

The problem is that (apparently) compatible connectors physically fit together, making their use seem safe. However, over time this can cause overheating. In the thermal image, one connector reaches 141.1°C, which can damage the system and may void warranties.

The best practice is to use connectors from the same manufacturer throughout the project. If modules come without connectors and use 4mm² wire, cheaper alternatives can be considered.

Important: using connectors from different manufacturers is not inherently wrong. The risk comes from mixing them within a single installation.

 

Incorrect joining of profiles

Aluminium profiles support the PV installation. Since profiles have limited length, they often need to be joined using profile connectors.

Profiles must be joined correctly, as shown in the illustration below:

1. Do not connect profiles under the last module.
2. Profiles must not end flush with the end terminal; maintain a safety gap of at least 2.5 cm.
3. Do not join profiles with a terminal between modules.
4. Example of proper aluminium profile joining.

Best practice – use professional connectors. Avoid joining profiles under the last module or at module breaks.

 

No protection against birds

A ventilation gap between the roof and PV modules ensures proper cooling, which is essential for efficiency and longevity. The gap is usually about 15 cm, but some birds may nest there. Twigs and debris can scratch the underside of modules, causing hot spots or even short circuits, posing a risk to the system, people, and birds.

 

Best practice – use at least one of the bird deterrent products:

• Spikes – physically block the space under modules without obstructing ventilation.
• Sound deterrents – emit predator bird sounds when birds are nearby.
• Holographic tape – rustles in the wind and shines in the sun to deter birds.
• Bird gels – repel birds with an unpleasant scent.

 

5 Most Common Mistakes in Photovoltaic Installation and How to Avoid Them

A correctly installed photovoltaic system is a source of pride for its owner. Unfortunately, many people make mistakes that can significantly reduce the system’s efficiency and safety. Check out the most common PV installation mistakes and how to avoid them to ensure your investment runs smoothly for years.

• Not using washers under anodized terminals – Grounding modules reduces the risk and harm of lightning strikes. Use grounding washers or special grounding terminals.
• Inadequate UV protection for wires – Cables must be UV-protected for 25-30 years. Use protective conduits and UV-resistant connectors.
• Walking on the modules – Causes microcracks that may lead to hot spots and damage. Avoid walking or kneeling on modules.
• Using “compatible” connectors – Mixing connectors from different manufacturers can cause resistance, power loss, and safety risks. Use connectors from the same manufacturer.
• Incorrect joining of profiles – Profiles must be joined correctly to ensure stability. Do not join profiles under the last module or at module breaks.
• No protection against birds – Maintain a ventilation gap and use spikes, sound deterrents, holographic tape, or bird gels to prevent nesting.

 

Following these recommendations increases the safety of your installation. A well-executed photovoltaic system can operate for 30-40 years, which we wholeheartedly wish for you!