We were asked to install a photovoltaic array on the roof of the listed building occupied by The Chartered Society of Physiotherapists. The array had to be carefully positioned to avoid a number of building services and other objects on the roof and also to minimise the impact of shading on the output of the array.

We installed 24 Yingli YL250c-30 modules in three rows, each with 8 modules. These are connected in two separate strings to SolarEdge SE3000 inverters and each module has its own Powerbox to optimise its output. This technology is better at handling shading, unlike a single central inverter for which shading on a single module would reduce the output of all the modules in the string.

The client was also concerned that the system should not pose a fire risk. The SolarEdge technology incorporates safety features which will nullify the array voltage in the event of a fault, protecting firefighters and the possibility of electric arcing.

To avoid roof penetrations we used a Schuco flat roof mounting system ballasted with concrete paving slabs. The ballast weight was calculated using BRE wind load methodology. The roofing felt is protected from the frames using 10mm thick rubber matting.