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Information about Legionella growth by smart control of water heater via Abra

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Introduction

The Legionella bacterium thrives in water with temperatures between 20°C and 50°C and can pose a health hazard if the water heater is not at a sufficiently high temperature. Our smart control solution shuts down the heater for short periods of time to reduce energy consumption during high electricity prices and to prevent the instantaneous power consumption from not exceeding a given level, but the temperature must be maintained at a level that prevents bacterial growth.
 

Temperature requirements and prevention

To prevent Legionella, the Norwegian Institute of Public Health recommends that water heaters maintain a minimum temperature of 60°C. Above 60°C, Legionella is killed quickly, while water below 50°C provides good conditions for bacterial growth. Our system assumes that the water heater is set correctly and maintains at least 60°C. Although the temperature may drop slightly during short-term shutdowns, this will not allow sufficient time for dangerous bacterial growth, provided that the water is reheated to above 60°C.

 

Security Assessment

To effectively kill Legionella bacteria, the hot water must maintain a temperature of at least 60°C for a sufficient time. According to research, the Legionella bacterium can be killed at 60°C after about 2 minutes of exposure. If the temperature is increased to 70°C, it only takes a few seconds for the bacteria to be eliminated. This means that when the hot water reaches above 60°C again after a short-term shutdown, it is necessary to maintain this temperature for a couple of minutes to ensure that any Legionella that may have grown during cooling is killed.

In the case of short shutdowns, the risk of Legionella is minimal when the temperature quickly returns to at least 60°C, which is sufficient to kill the bacteria. Short-term drops in temperature therefore do not pose a serious health hazard as long as the hot water is regularly heated back to a safe temperature.

 

User's responsibility

The user is responsible for ensuring that the water heater is properly set and maintained. If the water temperature does not reach at least 60°C over time, the user should take measures to adjust the temperature. Regular maintenance is essential to maintain a safe temperature and prevent bacterial growth.

 

References

  • Norwegian Institute of Public Health, "Prevention of legionella infection – a guide", 2021.
  • S. Mathys et al., "Survival and Growth of Legionella pneumophila in Potable Water", Applied and Environmental Microbiology, 2008.

 

 

 

 

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