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unvented hot water cylinders
installation and maintenance instructions
Page 4 / 20
GENERAL INSTALLATION
CONNECTING TO THE CYLINDER
All of the pipework connections on the cylinder are 22mm compression and supplied complete with gland nuts and olives, in the
Accessory Kit box. Only connect 22mm Table X copper tube to these connections. Cut the tube with a pipe cutter and ensure no
sharp edges or burrs protrude. Slide both gland nut and olive onto the tube and push tube fully home into the connection,
ensuring the tube end fully bottoms on the connection recess. Smear the outer wall of the olive with plumbing paste and
tighten gland nut correctly.
Upon filling / commissioning, ensure all connections are completely watertight.
Note: No control or isolation valve should be fitted between the expansion relief valve and the storage cylinder. The relief valve
connections should not be used for any other purpose.
COLD MAINS PIPEWORK
Run the cold main through the building to the place where is to be installed. Take care not to run the cold pipe near hot water
or heating pipe work so that the heat pick‐up is minimized. Identify the cold water supply pipe and fit an isolating valve (not
supplied). A 22mm BS1010 stopcock can typically be used but a 22mm quarter turn full bore valve would be better as it does
not restrict the flow as much. Do not use "screwdriver slot" or similar valves. Make the connection to the cold feed of the
cylinder and incorporate a drain valve. Position the inlet control just ABOVE the Temperature & Pressure Relief Valve (TPRV)
mounted on the side of the cylinder. This ensures that the cylinder does not have to be drained down in order to service the
inlet control set. Ensure that the arrow points in the direction of the water flow. Select a suitable position for the expansion
vessel. Mount it to the wall using the bracket provided. Use the flexible hose provided to connect to the inlet control group.
BALANCED COLD CONNECTION
If there are to be showers, bidets or monobloc taps in the installation then a balanced cold supply is necessary. There is a 22mm
balanced connection on the inlet control set.
HOT WATER PIPEWORK
Run the first part of the hot water distribution pipework in 22mm. This can be reduced to 15mm and 10mm as appropriate for
the type of tap etc. Your aim should be to reduce the volume of the hot draw‐off pipework to a practical minimum so that the
time taken for the hot water is as quick as possible. Do not use monobloc mixer tap or showers if the balanced cold connection
is not provided. Outlets of this type can back pressurize the unit and result in discharge. Select a suitable position for the
expansion vessel. Mount it to the wall using the bracket provided and connect to the inlet control set with the flexible hose
provided. Ensure that the top of the vessel is accessible for servicing.
PRIMARY COIL CONNECTIONS
Connect the primary connections (Indirect only) using the compression connections provided. The primary circuit must be
positively pumped. Gravity circulation is not suitable. Either primary connection may be used as the primary flow. Reheat times
are identical either way. The primary circuit can be open vented or sealed, with up to a maximum pressure of 3.5 bar. If you seal
the primary circuit an additional expansion vessel and safety valve is required. The boiler may be Gas, Electric or Oil but must be
under effective thermostatic control. Uncontrolled heat sources such as some AGA's, back boilers, solid fuel stoves, etc. are NOT
SUITABLE. Please contact our Technical department for guidance. Connect the two port zone valve (indirect only) into the
primary flow pipework. The direction of flow arrow should be towards the primary flow connection. On twin coil solar cylinders
we have provided an extra thermostat boss should you wish to use it. Again a two port zone valve should be fitted (supplied).
SECONDARY CIRCULATION
Can be used with secondary circulation. An appropriate WRAS approved bronze circulator should be used in conjunction with a
non‐return valve to prevent backflow. On large secondary circulation systems it may be necessary to incorporate an extra
expansion vessel into the circuit to accommodate the increased system water volume. Secondary circulation should be avoided
on Direct electrically heated units being used on off‐peak electricity tariffs.
A secondary return boss is fitted as standard on 200L, 250L and 300L units. On smaller sizes, tee into the cold feed pipe above
the drain.
IMMERSION HEATERS
Only immersion heaters with a thermal cutout may be used. To help ensure this, the immersion heaters have a special 1¾"
thread. They are rated at 3 kW at 240 V and are of a low noise Incoloy construction. They have both a thermostat and a high
limit cutout. Please order the correct replacement from BIASI; fitting non‐approved immersions may affect your guarantee.
When fitting, ensure the 'O' ring is positioned correctly on the head of the immersion heater and lubricate before fitting. Fit it
by hand until almost home then tighten gently as the 'O' rings will seal easily. The electrical supply to each immersion heater
2
must be fused at 13A via a double pole isolating switch to BS 3456. The cable must be 2.5mm
heat resistant (85°C HOFR)
sheathed flex complying to BS 6141:1981 Table 8. Do not operate the immersion heater/s until the unit is full of water. Do not
operate the immersion heater/s if any sterilisation liquid is in the cylinder as this will cause premature failure. Fit the immersion
thermostat (indirect units only) into the thermostat pocket. Complete the wiring – use the appropriate wiring diagrams.
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