Page 26 - Building services book

1.2 Understand hot water supply in building

1.2.1 Explain local hot water system

Hot water is used for washing and cooking.

o
The temperature required is about 45 C.

o
Water is usually generated at a higher temperature (55 C to 65 C) in a vessel and mixed
o
with cold water at mixing taps or mixing valves.

o
It is better to store water at a temperature much higher than body temperature (37 C)
to reduce risk of bacteria growth and other water borne diseases.

Hot water service systems may be divided into two main types:

1. Local systems
2. Central systems

LOCAL HOT WATER SYSTEMS can be further subdivided into instantaneous heaters and
storage heaters:

· Instantaneous - Electric type with output of between 0.02 litre/s and 0.05

litre/s, electrical loading from 3kW to 10kW.

· Storage cylinders -for hot water - 7 to 70 litres capacity, with 3kW electrical heating

elements.