Commercial Heating

On specification - On Time - On Budget

Sherborne Girls School Aldhelmsted East – Commercial Heating

Sector: Commercial Heating

Project: Central Heating System

Timeline: 6 Weeks

Location: Sherborne Dorset

Completed: August 2018

  • Project Description:
    • Replace existing heating and hot water systems supplying Aldhelmsted East, Sherborne.
    • High efficient A rated Condensing boilers and high recovery calorifiers to be Installed.
  • Work Completed:
    • Remove 2 x Ideal Harrier 280 KW Boilers
    • Erect Boiler Frames in 2 Plant Rooms
    • Two pods of 3 Worcester Bosch GB 162 100 KW Boilers
    • Flue Cascade Kit to line the existing chimneys following CCTV survey
    • Install 2 x Joule High Gain Cylinders
    • Upgrade pipework, low energy pumps and digital controls

Multi-boiler cascade system

Having been initially contacted to survey the Commercial Heating at Sherborne Girls School, Bosch Engineers, in conjunction with The Local Boiler Company, designed a system which would not only maximise heating efficiency, but would also safeguard the heating for the residents of Aldhelmsted East. This design was subsequently finalised by Steve Devoto and thanks to a bi-directional interconnector between the two cascades of 3 100kW GB162 gas-fired condensing boilers, any future interruption, or failure to, one cascade will automatically result in heat being diverted from the opposite boiler system.

The versatility of the GB162 proved a perfect solution for the replacement of the Girls School existing heating system. Further to this, we know that the support offered by Bosch post installation is something the Sherborne Girls School can rely on.

Charlie Carling, Commercial Heating Engineer at The Local Boiler Company.

The advantage of using a cascaded boiler system to generate heat and hot water is the reliance upon multiple boilers essentially sharing the workload across each boiler within the system. Each 300Kw GB162 cascade is capable of modulating to as little as 20kW in line with demand and allows each individual boiler within the cascade to contribute equally to the overall base load. By sharing the load across the cascade, the lifespan of each boiler is maximised to its full potential.

As the combined total output of the two new boiler cascades stands at 600Kw, the new installation has successfully reduced the overall installed capacity of the heating system by a third, which is due to the 95% efficiency levels of the GB162, coupled with the high degree of flexibility and system resilience.


With compact dimensions and a lift weight of just 70kg, the GB162 boilers proved to be ideal for the limited access plant rooms.

Whilst the collaborative arrangement between the two boiler cascade systems provides a versatile solution to the building’s heating requirements, the stainless steel flue arrangements had to be carefully surveyed by sending a camera down the flue to measure the circumference to allow a new flue liner to be run through the existing chimney structure. Phased completion of the installation work over the summer months also meant that the heating was not interrupted.