unvented hot water cylinders
installation and maintenance instructions
Page 9 / 17
COMMISSIONING
FILLING
First you must ensure that the pressure in the expansion vessel is the same as the setting of the pressure reducing valve i.e. 3
bar (45PSI). The valve is of the Schrader car tyre type. Check all the connections for water tightness including any factory made
connections such as the immersion heater and the temperature and pressure relief valve. Prior to filling, open the hot tap
furthest away from the cylinder to expel air. Open the cold main isolation valve and allow the unit to fill.
Once the cylinder as been fully commissioned should be heated to its normal operating temperature. Draw off secondary hot
water to each outlet and allow hot water to flow from each outlet for at least 30 seconds to remove any flux residue from the
pipe work within the secondary hot water system. Then fully drain the cylinder and re-filled to ensure that all flux residues is
removed from the system.
DIRECT UNITS
After both filling with water and purging of sterilisation liquid, switch on the power to the immersion heaters and allow the unit
to start to heat. The immersion heater is supplied preset at 55°C. Turning fully to + sets to approx 65°C.
INDIRECT UNITS
Fill the primary circuit according to the boiler manufacturers’ commissioning instructions. Ensure the lever on the two port valve
is set to the filling position. When full, move the lever back. Switch the programmer to Domestic Hot Water (DHW) and allow
the unit to start to heat. Adjust the dial of the dual thermostat to between 30°C and 70°C as required.
STORAGE TEMPERATURE
60-65°C is the recommended storage temperature for both direct and indirect cylinders. In hard water areas consideration
should be given to reducing this to 50-55°C. In many healthcare applications the guidance on Legionella control and safe water
delivery temperatures will require storing the water at 60-65°C, distributing at 50- 55°C and using thermostatic mixing valves to
control the final temperature. For details consult the NHS Estates Guidance on safe hot water temperatures.
SAFETY VALVE CHECKS
Any sign of water coming from either the expansion relief valve or the temperature/pressure relief valve during heat-up
indicates a problem. Next hold both of these safety valves fully open, allowing as much water as possible to flow through the
tundish. Check that your discharge pipework is free from debris and is carrying the water away to waste efficiently. Release the
valves and check that they reseat properly.
Completion of the Benchmark checklist on pages 15 – 16 MUST be adhered to by the installer.
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