1. To obtain the best performance from your OSO unvented system it is advisable to feed the unit
with an uninterrupted supply.
2. Before connecting to the multibloc, flush the cold supply pipework of all flux and debris.
3. Locate the water heater in a suitable position to facilitate the installation of the cold water supply,
discharge fittings and pipework. Also take into account access to the immersion heaters and the
commissioning valve.
4. Fit the combined male elbow drain cock to cold supply point (13), so that the compression fitting
is vertical.
5. Fit the blanking plug (12) to the secondary return fitting. If secondary return is to be used - see point 16.
6. Fit both 1/2’’ male solar sensor pockets to the Solar Sensor bosses (19).
7. Fit the female outlet of the tee piece to the temperature and pressure relief valve (5) with the
horizontal connection facing right at approx. 45°.
8. Fit the tundish (6) to the tee piece using a short length of 15mm copper tube.
9. Fit the length of copper tube 22mm specified in Table 2 to the cold feed elbow (see 4 above) to
include a T piece for expansion vessel flexible hose.
10. Fit the pressure reducing valve (3) to the top of the copper tube (see 8 above), so that the black
knob is facing right.
11. Connect the flexible hose to the 1/2’’ outlet of the expansion valve (4) and the horizontal outlet
of the tee piece (see 6 above). Discard compression nut & ring.
12. If a balanced mains pressure cold water supply is required to a
shower or bidet (over rim type
only)
, remove the blanking cap from the pressure reducing valve (3) and connect to the shower
or bidet cold supply.
Using the balanced cold connection to feed bath taps can reduce the
flow available to the unvented cylinder. (Major shower manufacturers advise fitting a mini
expansion vessel in the pipework to accommodate thermal expansion and prevent
tightening of shower controls)
13. Connect the cold supply to the Multibloc (3).
14. Fit the expansion vessel to the wall close to the water heater using the enclosed mounting bracket.
Connect the expansion vessel hose to the T piece in the cold feed pipe to the cylinder.
Hot water supply
15. Connect the hot water supply pipe to the outlet (9). Ensure connection is water tight.
Secondary return (optional)
16. Connect secondary return if required to fitting according to diagram on page 16.
Discharge pipe
17. Connect the discharge pipe from the tundish (6). This must have a continuous fall and be fitted
in accordance with The Building Regulations (see page 16).
Boiler Primaries
Primary flow & return and motorised valve
18. The boiler primary flow and return connections should be made to the upper coil connections
unit. The motorized valve can be connected to either the primary flow or return pipe. The primary flow
and return fittings are 3/4’’ BSP female. The valve has 22mm x copper connections. The direction of
primary flow in the boiler coil is bottom to top.
19. For electrical connection of the motorised valve and immersion heater, please read Electrical
Installation Instructions. (Pages 7 - 11)
Solar Primaries
20. The Solar flow and return connections should be made to the lower coil connections.
Temperature control from the Solar circuit is achieved using a differential solar controller. This
controller must be wired in series through the thermal cut-out on the OSO thermostat (see figure
4 pages 9 & 11). If Solar Panels are to be installed at a later date then connect the boiler primaries to
the lower coil. The driection of solar primary flow in the solar coil is top to bottom.
21. If the solar primary circuit contains a mechanical shut-off device, ensure that a non return valve
in the circuit prevents thermal syphoning if the circulation is stopped. Should a mechanical shutoff
device not be present, one should be fitted and wired in series to the thermal cut-out. Care
should be taken to ensure the device is suitable for temperatures and fluids that may be present
in a solar-thermal system.
22. Temperature sensors for the cylinder provided with the differential controller should be inserted
into the pockets provided (see pt 5 above).
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COLD WATER SUPPLY
