Page 518 - 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

2 INSTALL CENTRAL HEATING

KEY POINT SYSTEMS AND COMPONENTS

The installation of In this part of the chapter, we will consider the materials we can use to install
pipework within domestic domestic central heating systems and the installation methods for both new-
dwellings is covered in build properties and existing installations.
detail in Chapter 5, Cold
water systems.
Effects of expansion and contraction

l Pipework expansion: if pipework expansion is not catered for during the
installation phase, it can create ticking and creaking noises. To prevent this,
INDUSTRY TIP any notches in joists should be deep enough to allow free movement of the
pipework and any drilled holes should be large enough so that the pipework
A radiator bleed key is a does not rub against them. Notches should be lined with hair felt to act as
useful tool for bleeding air noise suppression.
from radiator air valves. l Expansion in open vented systems (cistern): the water in an open

vented system expands into the feed and expansion cistern and up the
vent pipe. When the water in the system gets hot, the expansion of
water raises the water level in the cistern. It is therefore important that
the feed and expansion cistern is large enough to accommodate the
expanded water.
l Expansion in sealed systems (expansion vessel): the water in a sealed
system expands into the vessel. It is therefore important that the expansion
vessel is large enough to accommodate the expanded water without opening
the pressure relief/expansion valve, as this would release the pressure to
0 bar and prevent the system from working correctly.

Connecting to existing systems

l One pipe: one-pipe circuits are a continuous loop with the heat emitters/
radiators taken from the loop (see the section on the one-pipe circuit at the
beginning of this chapter, page 439). Any extensions or new circuits should
follow the one-pipe layout to prevent the new circuit from taking most of
the heat flow. Swept tees should be used to encourage water flow around
the new circuit.
l Two pipe: two-pipe systems are the easiest to extend. New circuits can
be taken from existing circuits provided there are no more than three heat
emitters on the run of pipework. Ideally, new circuits should be taken from
the main heating flow and return pipes. If the system is a modern installation
that has been zoned with two-port motorised zone valves, care should be
taken to ensure that the new heat emitter is taken from the correct circuit,
i.e. living space heat emitters should be taken from the lounge/dining circuit
and sleeping space heat emitters should be taken from the bedroom circuit.
l Manifold (microbore): when connecting extra circuits to a microbore
system, the circuit must be connected to the flow and return manifolds.
On no account must the circuit be connected to an existing circuit via tee
pieces. Microbore pipework is only capable of carrying a heat load up to
3 kW per circuit.
506

9781510416482.indb 506 29/03/19 9:04 PM