With the aim of reducing carbon emissions and improving efficiencies, NHS Surrey embarked on a programme of upgrade to their heating and hot water systems across more than twenty sites. Many of the boilers and water heaters were coming to the end of their economical lifespan it was an ideal time to review their heating and hot water plant.
Gary White, programme manager at Surrey Primary Care Trust (PCT) said, “As well as needing to replace plant that was coming to the end of its life we were looking to lower energy bills and reduce carbon emissions across all sites in line with the NHS Carbon Reduction Strategy for England. The Trust Estates Department wanted to standardise boilers and equipment across the different sites and due to the diverse range of products that Hamworthy Heating offer we were able to choose the most suited boiler and water heater for each application.”
One of the sites, Molesey Hospital, a 20 bed hospital part of the NHS Surrey PCT required a full plant room refurbishment. Southampton based ARB Mechanical Engineering Ltd, the contractors for the project, replaced three gas fired atmospheric boilers with two Purewell VariHeat 70kW gas fired condensing boilers. Two Dorchester DR-FC Evo 30 direct fired condensing water heaters were also installed to provide highly efficient hot water generation.
Hugo Jimenez, Senior Mechanical Designer at MCA Consulting Ltd specified the equipment and commented, “We chose to separate the heating and hot water for this application due to the 24/7 demands placed on the system and the requirement for critical hot water to get to temperature very quickly. The condensing water heaters provide exactly what we needed for this project and the robustness of the Purewell VariHeat boilers means they are more than capable of dealing with the demands faced by the system over a long period of time.”
The three atmospheric on/off boilers that were removed gave a total output of 123kW, with a 3:1 turndown ratio and seasonal efficiencies of 78%. Compare this with the two new fully modulating condensing boilers that provide a total output of 140kW, 7:1 turndown ratio and seasonal efficiencies of 95% and you can clearly see the efficiency improvements and consequential carbon reduction. Take into account the corresponding reduction in service and maintenance costs from lowering the number of boilers plus the fully modulating operation that allows accurate load matching and you have a very attractive proposition for the life of the boiler.
The hot water for the hospital is now provided by two condensing water heaters with a total continuous output of 1,260l/h, thermal efficiencies of 98% – that far exceed the requirements of Part L Building Regulations, low NOx levels and superior controls in a compact unit. Each water heater is fitted with a top-to-bottom recirculation kit for operating during the legionella protection cycle to reduce the likelihood of legionella bacteria forming particularly in this application where occupants are more susceptible to the harmful effects of legionella.