Dual control thermostatic mixer
4
Service
valves
Balanced cold mains supply
Cold mains supply
Mixer
Expansion
vessel
Pressure
reducing valve
Stop tap
Unvented
hot water
storage unit
Safety devices
not shown
Pipework to
fixed head
Fig.3
(
diagrammatic view – not to scale)
Pipework to
fixed head
CH flow
Cold
mains
supply
Hot water
CH return
Service
valves
Mixer
valve
Stop
tap
Expansion
vessel
Pressure
reducing valve
Combination
boiler
Fig.2
(
diagrammatic view – not to scale)
TYPICAL SUITABLE INSTALLATIONS
a) Instantaneous gas-heated systems,
e.g. combination boilers (fig.2)
The shower control MUST be installed with a
multipoint gas water heater or combination
boiler of a fully modulating design (i.e.
to maintain relatively stable hot water
temperatures).
A drop tight pressure reducing valve MUST
be fitted if the supply pressures exceed 5 bar
running.
An expansion vessel (shown in
fig.2
) MUST
be fitted, and regularly maintained, to ensure
the shower mixer is not damaged by excess
pressures. This may already be installed within
the boiler (check with manufacturer) and is in
addition to the normally larger central heating
expansion vessel.
The layout and sizing of pipework MUST be
such that nominally equal inlet supply pressures
are achieved and the effects of other draw-offs
are minimised. The hot supply temperature
MUST remain a minimum of 10°C hotter than
the required blend temperature for optimum
performance.
b) Unvented mains pressure systems
(fig.3)
The shower control can be installed with an
unvented, stored hot water cylinder.
For systems 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 additional expansion vessel
(fig.3)
may be required if a second pressure reducing
valve is installed. This does not apply to
packages with a cold take off after the pressure
reducing valve to the cylinder.
The layout and sizing of pipework MUST be
such that nominally equal inlet supply pressures
are achieved and the effects of other draw-offs
are minimised.
