Page 398 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

Hot water
storage
cylinder
Secondary heat
exchanger Hot water outlet

Expansion
Pressure vessel Expansion
Boiler relief vessel Pressure Solar collector
relief

Con
trol system

(System fill points
omitted for clarity)
Mains cold inlet Primary heat exchanger Circulating pump

p Figure 6.31 Working principles of solar thermal hot water

Localised systems

Localised systems are often called single-point or point-of-use
systems. They are designed to serve one outlet at the position where
it is needed and are usually installed where the appliance is some
distance away from the fuelled hot water supply.

Again, these can be divided into two categories:
1 instantaneous-type heaters
2 storage-type heaters.

Instantaneous-type fuelled water heaters

These can either be fuelled by gas or electricity, and are generally
described as inlet controlled. This simply means that the water supply
is controlled at the inlet to the heater. The water is heated as it flows
through the heater and will continue to be heated as long as the
water is flowing. When the control valve is closed, the water flow
stops and the heat source shuts down.
p Figure 6.32 Localised instantaneous hot This type of heater is generally used to supply small quantities of
water heater
hot water such as washbasins and showers. Typical minimum water
HEALTH AND SAFETY pressure is 1 bar. There are many different types of electric shower with varying
You must not attempt outputs from 8.5 kW to 11 kW. The higher the kW output, the better the overall
to install any electrical flow rate at a showering temperature. All electric showers feature a low-
appliance such as showers, pressure heater element cut-off so that the temperature of the water does not
immersion heaters or cause harm if the supply pressure/flow rate is low.
hand wash heaters unless
you are competent to do Storage-type localised water heaters
so and have the correct
qualifications. Remember: This type of heater is often referred to as the displacement type heater, as the
electricity can kill! hot water is displaced from the heater by cold water entering the unit. Typical
storage capacities are between 7 litres and 10 litres (for the over-sink type).
They can be divided into the following categories.
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