User guide

11
HOT
COLD
Combined outlet PRV
with internal non-return valves
- Expansion vessel required.
Cold takeoff after PRV
- Expansion pressure taken up by
unvented cylinder expansion vessel.
Reduced
pressure to
unvented
cylinder
High
Inlet
Pressure
Reduced
pressure to
cold inlet of
shower
Reduced
pressure to
unvented
cylinder
High
Inlet
Pressure
Reduced
pressure to
cold inlet of
shower
Expansion
Vessel
Safety devices
not shown
for clarity
2. Unvented mains pressure showers
The shower can be installed with an unvented, stored hot water cylinder. Only
a "competent person" as defined by the Building Regulations may fit this type
of system.
For packages with no cold water take off after the appliance reducing valve, it
will be necessary to fit an additional drop tight pressure reducing valve when
the mains pressure is over 5 bar. The drop tight pressure reducing valve must
be set at the same value as the unvented package pressure reducing valve.
Note! An expansion vessel MUST be fitted (and regularly maintained) if any
form of backflow prevention device is fitted, e.g. non-return valve, PRV. This
will ensure that excess expansion or pulse pressures do not damage the product
or the plumbing system.
Figure 2