HP COMBI 2180206H manual Instantaneous gas-heated showers, e.g. combination boilers

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