Unvented Design - andrews MAXXflo EVO Series Installation And Maintenance Manual

4.4 UNVENTED DESIGN

When using the Heater on an unvented hot water storage system, the Unvented System Kit, part number
7726954, available from the manufacturer must be fi tted. When used in an unvented system, the Heater will
supply hot water at a maximum of 6 bar or at the pressure available at the mains feed if this is lower. During con-
ditions of no-fl ow, system pressure may rise to a maximum of 8 bar, whilst the burner is operating. When testing
the system, it is recommended that a maximum test pressure
For the hot water supply, a 24 litre expansion vessel is suitable for the stored volume of all models and an
average pipework system. For systems with larger pipe volumes or additional storage, expansion vessels with
greater capacity are available. Assemble the components of the unvented system kit as shown below
When assembling the Pressure Reducing Valve and Double Non-Return Valve, ensure that the
fl ow arrows marked on the
the heater.
The relief valves fi tted to this heater must not be used for any other purpose. No fi tting should be installed be-
tween the expansion valve and the cylinder. The cold water for services may be drawn from the 22mm com-
pression port up stream of the Pressure Reducing Valve. The water pressure at this point will be similar to that
available at the hot water outlet of the water heater. If higher fl ow rates are required for the cold water services, a
suitable tee fi tting should be fi tted to the pipework, upstream of the Pressure Reducing Valve.
All fi ttings and materials supplying water to the storage vessel must be suitable for use with drinking water and
listed in the current Water Research Centre "Materials and Fittings Directory". Installation of unvented hot storage
water systems must comply with Part G of Schedule 1 of the Building Regulations.
Expansion vessel Expansion vessel
(24 litre) (24 litre)
Through fl ow valve Through fl ow valve
One piece inlet control One piece inlet control
(6 bar pressure reducing (6 bar pressure reducing
valve, check valve & 8 bar valve, check valve & 8 bar
pressure relief valve) pressure relief valve)
(supplied with heater) (supplied with heater)
Installation
Unvented Systems should only be fi tted by an Approved Installer
components are pointing in the direction of fl ow, that is towards
7726954 Unvented kit
Cold Cold
water water
feed feed
Tundish Tundish
To drain To drain
of 9 bar is used.
23
HWS HWS
Temperature & pressure relief valve Temperature & pressure relief valve
(Factory fi tted) (Factory fi tted)
10 bar 95˚ ˚ C 10 bar
MAXXfl o EVO