As Zestec’s funded solar PPA projects near completion our technical team prepares a punch list; a list of any issues that need to be resolved before handover. Whilst the majority of installers deliver top-quality installations, over the years we have seen a whole range of standards.

In this article, we highlight the top 5 most common issues we encounter. Invariably, these issues are considered low priority by installers and are commonly overlooked but are important to get right on funded and Capex projects alike.

Health warning: This is an unashamedly technical article, so just check the headlines if that is not your bag! Additionally, the points made below reflect our understanding of current good industry practice, but don’t take our word for it; read and form your own view of the industry standards and regulations.

1. Module clamping zones

All module manufacturers specify a zone along the module frame where clamps should be positioned. It varies according to the manufacturer and yet plenty of roofers are not aware of this requirement or chose to ignore it when the rail placement makes conforming difficult. Whilst it’s hard to argue that a clamp placed a few mm outside the required zone presents a significant mechanical risk, it does run the risk of invalidating the module warranty. When shipping faulty modules back under warranty it is all too easy for manufacturers to cry foul after measuring the clamp positions from marks left on the frame. In an extreme case, we have seen incorrectly placed clamps fail, leading to modules being blown off a roof – a particularly frightening prospect in a commercial/industrial setting. Avoid these issues or extensive re-work by reading and adhering to the module manufacturers’ installation guide.

2. Cable management

For us, cable management offers an insight into the overall workmanship on a PV installation. This is not just a question of neatness; when cables are left lying on the roof, exposed to sharp edges, grouped together in great bundles, or bent around tight corners the long-term performance of those cables and the overall installation is compromised. As we have learned, locating cable faults or damp connectors on large rooftop arrays with poor string ID (more on that below) is tedious and costly. To avoid this, we expect to see cables neatly arranged in cable trays with sharp edges avoided or protected and minimum bend radii respected. In general, whatever cable management method is employed it should ensure the risk of damage arising from mechanical stress is minimised for the lifetime of the installation.

3. Labelling

Adequate identification and warning labelling of components is not only a requirement of the regulations but it also assists greatly with O&M activities. In particular, adding string cable ID at inverter level and array level is a quick job during the installation; tracing back unidentified string cables to locate a fault on the roof in the future is anything but. All labelling should last the lifetime of the system – biro on white insulation tape is not going to cut it, particularly when fit for purpose cable ID kits are widely available, cheap, and easy to use.

4. Earthing arrangements

In addition to normal AC earthing and bonding requirements, you must also consider the earthing, bonding and lightning protection of the array frame. At a minimum, a functional earth will be required in all situations and when this cannot be achieved via the building substructure, an alternative earth must be installed. On the AC side, you should check your inverter installation guide – as many require a secondary earth, and even when this is optional, we consider it sensible to fit the secondary earth.

5. Inverter positioning

Inverters installed at a high level represent an Operation and Maintenance nightmare. If the system design relies on inverter integrated DC isolation then it is questionable whether a high-level inverter provides a safe and readily accessible means of emergency DC isolation. Whilst generally IP65 rated, most inverter manufacturers specify that their units should not be installed externally if directly exposed to the elements and sunlight. Most often these situations arise because the client prefers to have the equipment installed “out of the way” – which is understandable, but if a suitable low-level internal space cannot be agreed then consider an appropriate external, well ventilated GRP enclosure for the inverter and ancillary components.

Installing the inverter and switchgear on a sheet of OSB or plywood may be a convenient installation solution, but unless it is a fire rate board, it will not adequately prevent the spread of fire and in most cases will contravene inverter manufacturer guidance – again risking the warranty.

In summary, none of the points above is difficult to get right and they all help set a good quality installation apart from the rest. At Zestec, we work closely with our partners to consistently achieve good industry practice, as we know this is the level required to ensure a PV system delivers for our PPA clients and our investors not just on day one, but over the long term.

If you’re interested in working with Zestec on PPA projects or are investigating funding options for your own solar installation, then please contact us at or call 01202 862760.