Legionella growth in DHW circulation systems

A study by the Swedish Energy Agency shows that the domestic hot water system in apartment buildings accounts for 27–81 kWh/m2.year, divided between the heating of DHW and distribution losses (VVC). The heat loss in the VVC system is significant, studies show that these amount to 10-17 kWh/m2. For the 205 million square meters of heated area in Sweden's apartment buildings, this corresponds to 2.5-4.3 TWh/year.

The temperature demand at the faucet is about 40?C, but to counteract the growth of Legionella, the Swedish building code state 50?C as the lowest system temperature, which introduces larger heat losses. This project aims to investigate how Legionella grows at different combinations of flow rate and temperature.

The effects of measures to counteract growth are also examined.

The project will answer what is required to ensure that DHW systems achieve a sufficient risk reduction concerning microbial pathogens, as well as how large the energy-saving potential is.