St Simon Stock Catholic School, Sports Hall, Maidstone, Kent.

The installation is based on one Hercules 85 Air Source Heat Pump (ASHP) connected to a 1,200-litre buffer tank, storing water at an average temperature of 70°C. The ASHP system is hydraulically separated from the existing Low Temperature Hot Water (LTHW) building heating circuit via a plate heat exchanger.

The LTHW system operates at a 55°C flow temperature and 45°C return temperature. From the buffer tank, the system also supplies a new 500-litre hot water storage tank, which maintains a minimum temperature of 60°C to ensure a constant supply of domestic hot water ready for immediate use.

The heat pump operates between 2:00am and 6:00am, taking advantage of off-peak electricity tariffs to pre-heat the buffer tank ahead of the heating schedule commencing at 7:00am. The hot water storage tank remains available to provide instant hot water throughout the day.

System Performance

During the previous winter, the Hercules 85 ASHP performed exceptionally well, maintaining internal space temperatures comfortably even during sub-zero conditions as low as -4°C, without any operational issues.

Impressed by the system’s reliability and efficiency, the Board of Governors approved the installation of an additional six Hercules 85 units across the campus to further extend the benefits of low-carbon heating and improved energy efficiency.