Combi HP thermostatic mixer shower

Fig.2 diagrammatic view (not to scale)

Shower

mixer valve

Combination

boiler

Service

valves

 

Hot water

CH flow

 

Expansion

 

vessel

 

Cold

Stop tap

CH return

mains

Pressure

 

supply

 

T00221

reducing valve

 

 

 

TYPICALypical suitableSUITABLEinstallationsINSTALLATIONS

a)Instantaneous gas-heated showers, 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. where the water draw-off rate indirectly controls the gas flow to the burner). A drop tight pressure reducing valve must be fitted if the supply pressures exceed 5 bar maintained.

An expansion vessel (shown in fig.2) must be fitted, and regularly maintained, to make sure the unit 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 the best performance.

Fig.3 diagrammatic view (not to scale)

Stop valve

 

 

Riser

 

 

 

 

 

 

 

Cold water Cold supply

rail

 

 

cistern

 

 

 

 

 

Alternative

 

 

 

 

 

supply

 

 

 

 

 

(must be

 

 

 

 

 

below

 

 

Mixer

 

vent pipe tee)

 

 

 

 

 

Valve

 

Gate

 

 

 

Hot

 

 

 

valve

 

 

 

supply

 

 

Cold

 

 

 

 

 

 

 

 

 

water

 

 

 

 

 

mains

 

 

 

 

 

supply

 

 

 

 

 

 

 

Hot water

Service

 

Service

 

 

valve

 

valve

 

 

cylinder

 

 

 

 

 

Pump

 

 

 

 

 

 

 

 

 

 

Ring main

Drain

 

 

Isolating switch

valve

Other

 

 

or pull cord

 

 

 

 

switch (both

draw-offs

 

 

fused at 3A)

Draw-off must point

 

 

down to avoid airlock

 

 

T00222

 

issues

 

 

 

b)Pump assisted gravity fed systems

(fig.3)

The pump MUST be fed from a cold water cistern and hot water cylinder providing nominally equal pressures. The pump must be capable of maintaining a minimum running pressure of 1 bar.

c)Unvented mains pressure showers

(fig.4)

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.4) may be required if a second pressure reducing valve is installed. This does not apply to