As schools come under increasing pressure to make the most of their resources, the extra £260m announced in the spring budget to improve school buildings presents the ideal opportunity for institutions to invest in modern and more energy efficient heating equipment. However, when replacing outdated systems, swapping like-for-like may not be the best option, and boiler cascades should be considered, especially by large schools with a high demand for heating.
With heating accounting for up to 60 per cent of total energy use in a typical school building, it’s unsurprising then that energy saving has become a key driver for many business managers in educational establishments. Replacing equipment that is reaching the end of its life naturally presents an opportunity to become more energy efficient. Even systems that appear to be performing adequately may have a high-energy cost so it is always worth reviewing boiler performance.
It should never be assumed that a like-for-like replacement in terms of boiler capacity will offer the best solution. Boilers have often been specified without considering the building’s heat gains from people, lighting and equipment. Even if such heat gains were taken into account when the original system was sized, changes in use, occupancy, and amount and type of heat-emitting equipment such as ICT facilities may have occurred over time.
Therefore, it is important to size a replacement installation based on current building requirements, rather than rely on the size of the boiler originally specified. At the same time, the system also needs to be flexible enough to respond swiftly, accurately and efficiently to changes in output demand. To err on the side of caution, it has long been recognised that there has been a tendency to oversize boilers, which adds to capital cost and reduces seasonal efficiency. However, a more intuitive, rather than an oversized system, delivers better performance and energy savings. This is where boiler cascades can offer a suitable solution, in particular in a large school with fluctuating requirements and high demand at peak times.
Cascade systems comprise multiple linked boilers, which can respond more efficiently to changing heat loads and offer more flexibility to match the exact heat requirements of a building. Individual boiler modulation ensures flexibility by enabling each boiler to adjust its operating capacity in line with demand, but the system can also turn down its capability when only one boiler is needed. For example, the Potterton Sirius Two wall-hung condensing boiler has a modulation range of 9:1; for every additional boiler added to the system, the modulation range improves by a multiple of nine. With three linked boilers, a modulation range of 27:1 can be achieved, delivering impressive efficiencies plus low flue-gas emissions.
Cascade systems marry the best in modern heating technology with controls that ensure the boilers operate at maximum efficiency, respond rapidly to changes in usage patterns, and extend the operating life and reliability of the equipment. These compact, modular systems can offer distinct logistical advantages compared to conventional system designs. When new plant needs to fit into a space that was designed around the old boiler, these systems make it easier to install and fit the required equipment into a restricted space, thereby saving installation time and costs. Furthermore, when it comes to service and maintenance, a cascade system allows engineers to work on each individual boiler, whilst the remaining boilers on the cascade stay switched on – reducing disruption to pupils and staff.
Old Swinford Hospital School in the Black Country, West Midlands, needed to upgrade their heating system to meet the growing demands of the campus. Wall hung and floor standing Potterton Commercial 70kW Sirius boilers replaced their old and inefficient twin boilers. The school now has a more responsive heating system which has delivered significant savings; despite increased output, the school is currently paying less for energy than five years ago.
By installing a cascade system, the age-old tendency to oversize boilers can be avoided. Schools and colleges can improve their ability to meet heating demands whilst reducing their emissions and energy bill, ultimately releasing funds for curricular resources or facilities.