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Thermostat connection
When connecting cables to thermostats, use spade or ring connectors as shown in diagram. Ensure that
connector is less than 10mm in outer dimension and fits inside the shoulders of the thermostat and is not
tightened onto the top of the shoulders.
Immersion heaters
The immersion heater is designed as an auxiliary heater as an emergency back-up.
Wiring instructions for the immersion heater is located on the reverse side of the electrical box lid. Follow
the wiring instructions connecting the live, neutral and earth as indicated. The electrical connection to
the immersion heater must conform to current IEE wiring regulations. The unit must be permanently
connected to the electrical supply through a double-pole linked switch with a minimum break capacity of
13 amps. All internal wiring is factory mounted. The immersion heater has a working thermostat adjustable
between 40°C - 70°C. A safety cut-out is also incorporated within the thermostat and will operate at 85°C
± 3°C. Should this happen, press the reset button.
Important: Before resetting the safety cut-out or altering the thermostat setting, isolate electrical
supply to the unit prior to removal of the lid. Ensure the lid to the electrical box is replaced
correctly and the retaining screw is fitted.
Motorised valve
To comply with regulations governing the installation of indirect unvented cylinders, a motorised valve must
be fitted in the primary flow or return. Your OSO unit has been supplied with a two port motorised valve,
which will act as a positive energy cut-out should the safety cut-out operate.
The motorised valve will also control the temperature of the domestic stored water via the cylinder
thermostat, which is located in the electrical box. The unit should be installed on an “S” or “Y” plan system.
Please follow the instructions carefully.
All electrical connections must conform to current IEE
wiring regulations. The working thermostat is adjustable between 40°C - 70°C. A safety cut-out is also
incorporated within the thermostat and will operate at 85°C ± 3°C. Should the safety cut-out be brought
into operation, the motorised valve will operate and close down the primary flow to the cylinder. To reset
the safety cut-out and the motorised valve the reset button must be pressed in (see fig.4 page 8).
ELECTRICAL INSTALLATION
RESET
RE
SET
M2
1
2
3
4
70
40
60
50
POWER SUPPLY CABLE
SAFETY
CUT-OUT
RESET
BUTTON
WORKING
THERMOSTAT
TEMP.
ADJUSTMENT
SCREW
SPADE OR RING
CONNECTOR
LESS THAN
10 mm
OSO Hotwater (UK) Limited can not be held
responsible if alternative wiring plans are used.
Important: Before resetting the safety cut-out or
altering the thermostat setting isolate electrical
supply to the unit before removal of the lid.
