The design of a hot water service may follow the procedure:
- Determine the demand of hot water from the consumers – quantity and temperature
- Select the type, capacity and heating surface of the calorifier – or heat exchanger
- Select the boiler
- Design the pipe scheme and the size of the pipes
The Demand of Hot Water – quantity and temperature
Hot water is normally supplied to fittings and their consumers at 50 – 60 oC. For canteens and professional kitchen temperatures of 65 oC are often required to satisfy hygienic standards. Hot water should not be stored at temperatures below 60 oC (140 oF) to avoid the risk of legionella contamination.
Where lower temperatures are necessary for safety reasons – as in kindergartens, centers for disabled etc. – the hot water temperature should not exceed 40 – 50 oC. Special care should be taken – like regular disinfection of fittings – to avoid legionalla infections.
Note! Hot water can be stored at higher temperatures and reduced to lower supply temperatures by mixing in cold water in blender valves. Storing the hot water at a higher temperatures increases the system overall capacity and reduces the need of storage volume.
Rinnai – Hot Water System Design Manual provides the basic of hot water system design and schematic of system