Page 375 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

Chapter 6 Hot water systems

control over the hot water storage cylinder via a cylinder thermostat and
a motorised zone valve arrangement, as stated in the Domestic Heating
Compliance Guide. Because the primary flow and return are pumped, the
pipe size, in most cases, can be reduced to 22 mm. This subject will be
covered in greater detail in Chapter 7, Central heating systems.

22 mm vent from primary hot water system connected to the boiler,
the coil in the hot water cylinder and central heating system
22 mm vent from secondary hot water system. To determine the height
of the vent = 150 mm + 40 mm per metre of system height (m)
Feed and expansion cistern
fitted with BS1212 part 2
150 litre storage cistern fitted with BS1212 part 2 float-operated valve float-operated valve
Spherical ball-type
service valve
Spherical ball-type
service valve

15 mm cold feed to
22 mm or 28 mm cold feed to the primary system
secondary hot water system
22 mm or 28 mm full-way
gate valve or lever-type
spherical ball valve
22 mm draw-off to the bath then
reduced to 15 mm to all other services 450 mm

22 mm primary flow
and return pipes from
Central heating the boiler to the coil in
flow and return the cylinder
Heat source. Gas, oil
or solid fuel

p Figure 6.6 Indirect open vented (double feed type) hot water storage system with pumped
primary circulation
 Table 6.4 Criteria of choice for double feed indirect systems
Property size Storage capacity Fuel type Installation cost Fuel efficiency
Suitable for all Varies with occupancy. Can be used with gas, oil, More expensive than Gas and oil appliances
domestic properties. Generally, 210 litres for solid fuel and electricity. direct systems due to must be energy-efficient
four people. Suitable for fully pumped the extra pipework for condensing types.
heating systems. Conforms the feed and expansion Can also be used with
to Doc. L of the Building cistern and associated Economy 7 electricity.
Regulations. pipework.

Indirect cylinders for renewable energy hot water supply
Open vented cylinders have been developed for installation onto renewable
energy hot water supply systems, such as solar, geothermal and ground-source

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