Hot water circulates from the central hot water plant through the building via the primary vertical riser pipes and back to the hot water plant. Hot water may be drawn off from the central hot water system through the main floor branch and hot water meters to the units, like any normal system.
If no water is being drawn off, then the circuits after the hot water meters should be kept hot to reduce the time taken for hot water delivery and to reduce water wastage. The H-box is installed which, via the heat exchanger, transfers heat from the primary central heating riser pipes to the secondary circuit and uses a pump to circulate the heated water to the units and back to the H-box via a common return.
In order to achieve the correct flow rates required by the system, an automatic balancing valve is installed on the return lines after each apartment to balance flow rates to a predetermined value in each circuit of the secondary side. The automatic balancing valves are pre-set and supplied as part of the H-box packaged solution.
In the event of hot water being drawn off from a fixture within a unit, the H-box will isolate that particular circulation circuit serving that unit so that all water is being drawn from the central heating system and through the hot water meter and not from the H-Box system.