Page 424 - 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

malfunctions of any hot water heating appliances that may occur. All systems
must be capable of accommodating thermal expansion and movement within
the pipework. Care should be taken when pressure testing open vented cylinders
to ensure that the maximum pressure that the cylinder can withstand is not
exceeded. If necessary, the cylinder should be disconnected and the pipework
capped before testing commences.

The installation methods for hot water systems are very similar to those for
cold water installations. Care should be taken when installing hot and cold
water pipework side by side so that any cold water installation is not adversely
affected by the hot water pipework.

ACTIVITY
To refresh yourself as to the tools, materials and installation requirements of
pipework within dwellings, check out Chapter 2, Common processes and
techniques, and Chapter 5, Cold water systems.

Installation techniques, such as installing pipework below timber floors, solid
floors, within walls, marking out, cabling plastic pipework and so on, are
discussed at length in Chapter 5, Cold water systems.

Installing storage cylinders and cisterns

Where the storage of large amounts of water is required, such as in hot water storage
cylinders and cold water storage cisterns, care must be taken to ensure that the
substrate, where the component is to be installed, can withstand the weight of the
stored water. Water is heavy! Every litre of water has a mass of 1 kg and, wherever
possible, stored water should be positioned over load-bearing structures and walls.
Where this is not possible, a suitable platform must be built that distributes the
weight evenly to the entire structure or directs the weight to a load-bearing part of
the building. This was discussed briefly in Chapter 5, Cold water systems.

Temperature control of hot water systems
According to BS EN 806, hot water systems must not be allowed to exceed
100°C at any time. A maximum normal operating temperature of 60°C is
required to kill off Legionella bacteria. There are several methods by which we
can maintain and control the temperature of hot water systems and prevent it
from exceeding the maximum temperature specified. A thermostat should be
installed and set to the temperature required. A second thermostat, called a
high-limit thermostat, operates should the maximum temperature be exceeded.
This is known as a second-tier level of temperature control.
● Immersion heaters that have a re-settable double thermostat: one
thermostat can be set between 50°C and 70°C, the other is a re-settable
high-limit thermostat designed to switch off the power to the unit when
the maximum temperature is exceeded. It can be reset manually.
● Immersion heaters with a non-resettable double thermostat: one
thermostat can be set between 50°C and 70°C, the other is a high-limit
thermostat designed to permanently switch off the power to the unit until
the immersion heater is replaced and the fault rectified.

412

9781510416482.indb 412 29/03/19 9:02 PM