The geothermal system at 1 Kingdom Street was intended to contribute free heating and cooling to the 10-storey atrium, toilets and reception using water circulation from boreholes and water source heat pumps. The system had fallen into disrepair mainly because its operation method was unclear such that the system needed a thorough review and overhaul. To compound these issues, its closed water circuits had developed bacteriological problems due to lack of use and dead legs, and these needed specialist water treatment to resolve them as well as control modifications to prevent reoccurrence.

Focus FM analysed the water circuits in this large system, which are in four stages, determined how their performance could be improved and specified rectification measures to ensure their long-term operation. The initial works replaced failed equipment, installed new filters and removed dead legs from the system. We then rebalanced each circuit to ensure correct flow rates, and prevented energy waste by controlling pump speeds and revising the changeover from heating to cooling set up.

In the final stage, we reviewed and overhauled the system’s control strategy in a clear, open manner so that it will be readily understandable to future users. These modified circulation routes automatically select whether they are heated or cooled dependent on circuit water, room and outdoor temperature and avoiding condensation. We also developed a new control mode that automatically facilitated specific water circulation routines overnight, which ensure bacteria is prevented from developing in each part of every circuit.