Situation: The new Drinking Water Ordinance has been implemented. To protect against Legionella you already heat your hot water to at least 60 °C constant temperature. However, after only a short time you find that your water heater takes longer and longer to reach the required water temperature.
The reason: Hard water has formed a calcium layer on the heat exchangers and therefore impedes the heat transfer from the heat exchanger to the water.
Hard water causes the calcification of the heat transfer surfaces when heating up in boilers, instantaneous water heaters and plate heat exchangers.
Calcium acts as a very effective insulator and the larger the calcium deposit, the more it impedes the energy transfer. The lower the efficiency, the more heating energy required to heat up the water.
According to our calculations, with a calcium layer of 2 mm the energy consumption already increases by 10 %.
Private households consume the most energy, even more than transportation and industry. After the energy expenditure of 75 % for room heating, water heating comes in at around 12 %, still ahead of the energy consumption for lighting and household appliances.