Safety of the installation
Instruction manual DR-RS
15
gis
2.5
Safety of the instal-
lation
2.5.1
Unvented installation
With an unvented installation, an expension valve and expansion vessel prevent
excessive pressure in the water heather. This prevents damage of the water
heater. A non-return valve prevents excessive pressure in the water supply
system. This valve also prevents water from flowing backwards from the heater
into the cold water supply system. The pressure reducing regulates the water
supply pressure to a normal operating pressure of 3.5 bar. The components are
fitted to the cold water pipe. See paragraph
2.5.2
Vented installation
With a vented installation, excess pressure is taken up by the open water tank.
The level of the water determines the working pressure which may not exceed
8 bar.The installation must also be fitted with an open vent from the hot water
pipe. Ideally the vent pipe should be linked to a separate tundish/drain or else
to the cold water storage tank. A safety valve should also be fitted to the water
heather. See paragraph
.
2.5.3
Temparature and Pressure valve (T&P valve)
A T&P valve is mandatory in an 'unvented' installation.
A T&P valve monitors the water pressure in the water heater and the water
temperature at the top of it. If the pressure in the water heater becomes
excessive (> 7 bar) or the water temperature is too high (>97°C), the valve will
open. The hot water will immediately flow out of the heater. Because the water
heater is under water supply pressure, cold water will automatically flow into it.
The valve remains open until the unsafe situation has been averted. A
connecting point for a T&P valve is standard on the water heater. See paragraph
2.6
Indicators and
Alarms
2.6.1
Volt Free Contacts
Volt free contacts are supplied as standard to give remote indication/alarm of
'normal run' and 'lockout'. The 'lockout' indication includes shut down due to
operation of the safety thermostat, loss of flame and failure to ignite.
2.7
Options
The heaters can be supplied with the following additional variations, either
ready fitted or for site fitting:
2.7.1
LPG
The heaters can be supplied adjusted for use on propane or butane, see section
3.12. It is most important that the heater is correctly adjusted for the gas to be
fired.
2.7.2
Unvented Supply
The heaters can be supplied with a purpose designed and sized unvented kit
comprising pressure reducing valve, non-return valve, expansion vessel,
expansion relief valve and pressure/temperature relief valve, to enable the
heater to be coupled directly to the mains water. For details see 2.5.1, 2.5.3 and
3.6.
