Working principle of the appliance
18 Instruction manual GWV
2
gis
2.5 Safety of the instal-
lation
As well as the standard safeties in the appliance (2.4 "Protection for the
appliance"), it must also be protected by an inlet combination and a pressure-
reducing valve. A P-valve is also used.
2.5.1 Unvented installation
With unvented installation, an expansion valve and expansion vessel prevent
excessive pressure in appliance. This prevents damage being caused to the
enamelled coating (in the appliance) or to the heat exchanger. A non-return
valve prevents excessive pressure build-up in the water supply system. This
valve also prevents water from flowing backwards from the storage tank into the
cold water supply system. The pressure-reducing valve protects the installation
against excessively high water supply pressures (> 8 bar). These components
are fitted (3.6 "Water connections, Vented") to the cold water pipe.
2.5.2 Vented installation
With a vented installation, excess pressure is taken up by the open water tank.
The height of the head tank determines the working pressure in the appliance,
which may not exceed 8 bar. The appliance must also be fitted with a vent pipe
from the hot water pipe, which opens into the cold water tank.
Normally, the vent pipe should discharge into a separate discharge
channel/drain or otherwise to the open cold water head tank. The appliance
should also be fitted with a stop valve (3.6.2 "Hot water side") on the hot water
side.
2.5.3 Inlet combination and pressure-reducing valve
An excessively high pressure in the storage tank can damage the enamelled
layer. An inlet combination and pressure-reducing valve prevents this. The inlet
combination acts as a stop valve, non-return valve and overflow valve. If the
water supply pressure is too high (> 8 bar), a pressure-reducing valve must be
used. Both components must be fitted in the cold water supply (3.6 "Water
connections, Vented").
2.5.4 P-valve
The appliance has a P-valve (33) as standard. A P-valve (Pressure Relief Valve)
monitors the pressure in the installation. If the pressure gets too high (> 10 bar),
the valve will open. The water can now flow out of the installation. Because the
installation is under water supply pressure, cold water will automatically flow into
the storage tank. The valve remains open until the unsafe situation (< 10 bar)
has been resolved.
