Sector: Education
Building: Boarding school refurbishment
Products: Powerstock glass lined calorifier
Application: Space heating, 210kW; indirect fired DHW

The work was carried out as part of a planned upgrade for one of Canford School’s 24 plant rooms. Wessex Building Services, a mechanical and electrical contractor also based in Dorset, replaced four Hamworthy Purewell Classic atmospheric boilers with three Purewell VariHeat pre mix condensing modular boilers, plus provision for a fourth in the summer when that area of the school is likely to be extended.

The three Purewell VariHeat 70kW condensing boilers and a Powerstock PS300 high performance calorifier are providing the heating and hot water for the school’s biology block. With 635 pupils attending Canford school, the system is very much in demand during term time.

Purewell VariHeat boilers are commonly used in refurbishments projects because they have a greater tolerance of older heating systems, due to their robust cast iron heat exchanger, which is fitted with a down firing pre-mix modulating burner for close load matching.

Designed as a replacement for cast iron atmospheric boilers, such as the now obsolete Purewell Classic, the Purewell VariHeat condensing modular boiler fits on the same footprint but offers up to 50% more output and superior control capability. The boilers are able to link easily with the school’s Building Management System (BMS) and, unlike its predecessor, are fully compliant with the efficiency requirements of the Energy-related Products Directive. 

Ainsley Downer from Wessex Building Services has worked with Hamworthy products for many years and commented;

“We have a great working relationship with Hamworthy; they provide technical support on the phone and knowledgeable sales managers in the field. The Purewell VariHeat boilers are a fantastic, robust product that we have installed in lots of our projects. Together with the flue system from Hamworthy’s partner Midtherm creates a great package”.

Commissioning of the products was carried out by one of Hamworthy’s approved service engineers to ensure the products are set up to the manufacturer’s recommendations for gaining maximum efficiency and minimising the environmental impact. Ainsley went on to say;

“The service engineer who carried out the commissioning has been with Hamworthy for many years; this depth of understanding and experience enables him to set the product working to its full potential so that Canford School can benefit from the most efficient system possible.”

The Purewell VariHeat’s cast iron heat exchanger is complemented by an integral secondary condensing heat exchanger to provide exceptional seasonal efficiencies up to 108% net. The boiler range consists of 5 condensing models with outputs from 70kW to 180kW, and 4 non-condensing models, 65kW to 125kW.

High efficiency gas fired boilers are commonly used with Powerstock calorifiers as the prime energy source for the indirect heating and storage of hot water. There are 7 models in the Powerstock calorifier range with continuous outputs from 501 up to 1635 litres/hour and storage capacities are from 160 litres to 958 litres.


To see how much your school could save on gas bills by upgrading boilers and water heaters, get in touch with us.