Hygienic Hot Water
The conventional method of heating and storing water has certain drawbacks with regard to hygiene and taste. Domestic hot water systems are a potential multiplying ground for Legionella bacteria, which have an ideal growth temperature range of 35-45°C. As a result of this, regulations state that stored hot water must be heated to a temperature of at least 60°C for 10 minutes once a day, to kill the bacteria. In conventional boiler heating systems, these temperatures are easily achieved, but the efficiency of a heat pump is affected by high flow temperatures.
To overcome these hygiene problems without having to run the heat pump at high flow temperatures, we recommend the use of a hygienic hot water module, either fitted inside or outside the cylinder. This compact and very economical fresh water solution accommodates a heat exchanger, a quiet circulation pump and a volume flow sensor for instant heating of your hot domestic water needs.
A thermal store is heated to a temperature of 55°C by the heat pump, and is not used directly. As water is drawn from the hot tap, water from the mains supply is diverted past water from the thermal store via a specially designed, high-performance plate heat exchanger. By keeping domestic water separate from the thermal store, germs from the cylinder are prevented from being introduced into the system, avoiding the hygiene problems of conventional hot water storage systems entirely. The high efficiency of these heat exchangers ensures that water can be heated from, for example 10 to 50°C, in fractions of a second. This system complies with all regulations regarding water hygiene i.e. it provides hygienic drinking water and water for your daily shower with amazing savings on your power bill.
Our hygienic hot water system is designed to take pressure so, if the mains pressure and flow rate input to the system are sufficient, the whole system will be pressurised, hot and cold. This eliminates the need for electric pump showers and/or immersions.
Thermal stores are usually 300-500 litres, but larger sizes are available when greater quantities are needed.
Domestic hot water production is always given priority within the heating system. As soon as the temperature in the hot water thermal store is reduced by 5°C, for example, the flow from the heat pump is diverted from the under-floor heating and the total output is dedicated to restoring the temperature of the thermal store to the set point of 55°C. This gives very fast recovery times. The temperature of a 400ltr thermal store can be raised from 50 to 55°C in around 10 minutes with the full output of a 14.2kW heat pump (a typical domestic set-up). The high thermal mass of an under-floor system means that the floor stores energy for a long period of time, so the space heating is not compromised while the heat pump is dedicated to hot water production.