Page 379 - 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

22 mm vent from primary hot water system connected to the boiler,
the coil in the hot water cylinder and central heating system
Feed and expansion cistern
fitted with BS1212 part 2
float-operated valve
Spherical ball-type
service valve

15 mm cold feed to
the primary system

Hot water
draw-off

22 mm draw-off to
the bath then reduced
Mains cold water to 15 mm to all other
to kitchen sink services
connection directly
off the mains
Heat source. Gas, oil
or solid fuel

p Figure 6.12 A combination cylinder open vented hot water storage system

 Table 6.5 Advantages and disadvantages of combination cylinder systems
Advantages Disadvantages
A cheap alternative for hot water systems, Suffers from lack of pressure unless installed
especially suited to flats and small houses at height
Easy to install Not suitable for pumped shower installations
Fully compliant with Doc. L of the Building because of the lack of cold water storage
Regulations

 Table 6.6 Criteria of choice for combination cylinder systems
Property size Storage capacity Fuel type Installation cost Fuel efficiency
Small properties Usually 114 litres Best used with Economy 7 Ideally suited to flats and Economy 7 electricity
and flats. for flats but larger electricity but can be double small houses because of is 100% efficient but
capacities are feed type for use with fully the low installation and the tariffs can be very
available. pumped heating systems. materials costs. expensive.

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