Page 492 - The City and Guilds Textbook: Plumbing Book 1 for the Level 3 Apprenticeship (9189), Level 2 Technical Certificate (8202) and Level 2 Diploma (6035)

The City & Guilds Textbook: Plumbing Book 1

Buffer tanks

A buffer tank is basically an extremely well-insulated vessel that holds hot
water for circulation around the heating system. The primary role of a buffer
tank is to maintain a minimum volume of hot water in the heating circuit when
demand for the heating is low. They are usually used with renewable heat
sources such as ground or air source heat pumps. However, they can also be
used in conjunction with gas/oil/wood pellet boilers and solar heating where
the Sun heats the water during the day, which is then used at night to heat the
dwelling when it is required.

Once the water is heated, it acts like a battery, releasing hot water into the
system when the demand for heating is low.

Heating circuit 2 Heating circuit 3

Heating circuit 1 Heating circuit 4

Heating zones controlled
4 Modular boilers by a 2 part zone valve, By-pass controlled by a three-port
a room thermostat and motorised valve
a time-clock
Expansion relief pipe By-pass
Shunt pump
Twin pump sets with non-return
Pressurisation Flow header valves
unit Expansion Expansion Hot water calorifier
vessel vessel Buffer
vessel Return header

Mains cold water
p Figure 7.53 Installation of a buffer tank

Expansion joints
Expansion joints are used in long runs of straight pipework where excessive
expansion would damage the pipework. The expansion is taken up within the
joint, thereby protecting the pipework from distortion and damage. They can
either be prefabricated loops of pipework or manufactured bellows that expand
and contract as the pipes heat up and cool down.

KEY TERM Corrosion protection
Air infiltration: a process Corrosion is probably the biggest problem that takes place within central
where air can get into a
system and cause air locks heating systems and it commonly occurs in two forms:
and corrosion. 1 the formation of red oxide sludge (rust) because of constant air infiltration

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