Installation manual

28 ©ESP Ltd. Sept 2008
The purpose of this guide is to provide useful information on Unvented Hot
Water Storage Systems and their benefits, the features and functions of the
typical controls used.
Unvented Hot Water Storage Systems are subject to the legal requirements of
Building Regulation G3 and can only be installed by an “approved installer” in
strict accordance with the relevant manufacturer‟s Instruction Manual, Building
Regulation G3 and the current Water Byelaws.
Reputedly devised by an Englishman as far back as 1861, Unvented Systems
are commonplace throughout Europe, South Africa, North America and Aus-
tralia, although the UK remains one of the last bastions of the traditional low
pressure vented system. However, times are changing. The demands from dis-
cerning householders for increased performance, sophisticated continental-style
taps and showers and pleasing aesthetic looks, has seen a growing trend to-
wards the installation of Unvented Systems in the UK, which will continue to
rise at an increasing rate.
How the Unvented System Works
The basic difference between the high pressure Unvented Systems and a tradi-
tional low pressure vented system is that we no longer require the cold water
storage cistern, open vent pipe or cold feed pipe.
Instead, the unvented unit is fed direct from the mains cold water supply via
an inlet control group preset to the relevant manufacturers specified pressures.
Hot water drawn from the unit is then replenished from the mains supply.
As water expands when heated and, as the name implies, there is no vent pipe
(or cold feed pipe), the expanded water within the system is accommodated
by either an external expansion vessel or, in the case of bubble-top units, an
internal air bubble within the unit which is generated when the system is com-
missioned.
To maximise the benefits of the Unvented System, a sealed heating system, if
applicable, can also be installed providing the boiler used is compatible.
UNVENTED HOT WATER STORAGE SYSTEMS AND CONTROLS