Page 469 - 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 7 Central heating systems

Flue damper
Flue

Heating flow
Air

Refuelling door

Water jacket

Heating return

Air
Ash Ash door

p Figure 7.28 Batch fed boiler

Gas central heating boilers KEY POINT

Gas central heating boilers are the most popular of all central heating appliances. The different types of
Over the years there have been many different types, from large multi-sectional commercially available
cast iron domestic boilers to small, low water content condensing types. Both gas are dealt with in
natural gas (those that burn a methane-based gas) and LPG (those that burn Chapter 10, Domestic
propane) types are available. fuel systems.
Central heating boilers can be categorised as:

l traditional boilers (non-condensing)
l traditional (condensing)
l cast iron heat exchanger
l low water content heat exchanger
l combination boilers
l condensing boilers (system and combination boilers).

 Table 7.8 The different kinds of boiler and their flue arrangements

Energy efficient Cast iron heat exchanger Low water content Open vented system Sealed (pressurised) system Open flue Room sealed (natural draught) Room sealed (fan assisted) Wall mounted Freestanding

Traditional boilers û ü ü ü ü ü ü ü ü ü
Condensing boilers ü û ü û ü û û ü ü ü
System boilers ü û ü û ü û û ü ü û
Combination boilers ü û ü û ü û ü ü ü ü

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