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 |
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Cold | Stop tap | CH return |
mains | Pressure |
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supply |
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T00221 | reducing valve |
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TYPICALypical suitableSUITABLEinstallationsINSTALLATIONS
a)Instantaneous
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
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
Fig.3 diagrammatic view (not to scale)
Stop valve |
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| Riser | ||
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| Cold water Cold supply | rail | ||
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| cistern |
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| Alternative |
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| supply |
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| (must be |
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| below |
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| Mixer |
| vent pipe tee) |
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| Valve | ||
| Gate |
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| Hot |
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| valve |
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| supply |
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Cold |
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water |
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mains |
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supply |
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| Hot water | Service |
| Service |
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| valve |
| valve | |
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| cylinder |
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| Pump | |
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| Ring main |
Drain |
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| Isolating switch | ||
valve | Other |
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| or pull cord | |
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| switch (both | |
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| fused at 3A) | |||
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down to avoid airlock |
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T00222 |
| issues |
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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