Page 377 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)
P. 377
Chapter 6 Hot water systems
INDUSTRY TIP
On no account must central
heating inhibitors be used
in the primary water if
22 mm vent pipe discharging into the a single feed cylinder is
CWSC and sealed with a grommet
installed as this would cause
contamination of the water if
the air bubbles were to rupture.
22 mm or 28 mm cold feed to
secondary hot water system
22 mm or 28 mm full-way gate valve
or lever-type spherical ball valve
Special heat exchanger uses air bubbles
to separate primary and secondary water
28 mm primary circulation 22 mm draw-off to the bath
pipes connect the heat then reduced to 15 mm to
source to the cylinder all other appliances
Heat source.
Gas boiler/oil boiler
p Figure 6.9 Single feed, self-venting indirect system
Other types of open vented cylinder
Combination centralised open vented hot water storage systems
A combination cylinder has its own cold feed cistern attached on the top of
the cylinder, and factory-fitted cold feed and vent pipes. The connections for
the draw-off and the primary flow and return are usually 1-inch male thread
connections. Isolation of the hot water for maintenance should be via a full-way
gate valve installed on the hot water draw-off pipe.
They are known as ‘Fortic’ cylinders and are available in both direct (immersion
heater only and circulator/boiler types) and double feed indirect types. They
come in a variety of sizes, 115 litres of hot water storage being the most
common with 20–115 litres of cold storage above.
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