Page 395 - 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

Combustion air in
Flue gas outlet
Combustion air in
Pressure
switch

Combustion air in
Automatic
air valve Primary heat exchanger
Spark igniter
Gas burner

Expansion Fully modulating
vessel multifunctional control
Pump
Water-to-water
heat exchanger

Diverter valve

System Pressure relief valve
by-pass

Central heating
flow and return

Cold Hot Gas
water water
inlet outlet
p Figure 6.28 Combination boiler

Thermal stores

Sometimes called water-jacketed tube heaters, thermal stores work by passing
mains cold water through two heat exchangers that are encased in a large
storage vessel of primary hot water fed from a boiler. They are very similar
to an indirect system but work in reverse.

Optional F & E cistern Isolation valve
built into the unit
Adjustable
thermostatic
mixing valve
Boiler

Heat exchanger

Expansion
chamber
To hot taps
Pump on
primary return To cold taps
Central heating Heat exchanger
pump
Heating flow
Heating return
Mains cold water inlet

p Figure 6.29 Thermal store

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