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4. ELECTRICAL INSTALLATION
4.1 Thermostat connection
The power supply cable to the upper electrical
box (23) is fed through the cable fastener fitted
to the box cover. The power cable to the lower
electrical box (24) is fed up from the bottom of
the product, see illustration on previous page.
Use supplied cable fastener. All wiring must be
fitted by authorized electrician, who must ensure
suitable cable quality is used.
When connecting cables to thermostats, use
spade connectors as shown in diagram. Ensure
that connector is less than 10 mm in outer di-
mension and fits inside the shoulders of the ther-
mostat and is not tightened onto the top of the
shoulders.
4.2 Immersion heaters
All units are fitted with an immersion heater
which is located behind the bottom electrical
box cover. Wiring instructions for the immersion
heater is located on the reverse side of the elec-
trical box lid.
Follow the wiring instructions connecting the
live, neutral and earth as indicated. A dedicated
permanent supply complying with current IEE
regulations should be used, and each circuit
must be protected by a suitable MCB and double
pole isolating switch with a contact separation of
at least 3 mm in both poles. All cables should
comply with BS6141 table 8 HOFR 85c.
All internal wiring is factory mounted. The im-
mersion heater has a working thermostat adjust-
able between 40°C - 70°C. A safety cut-out is also
incorporated within the thermostat and will op-
erate 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. En-
sure the lid to the electrical box is replaced cor-
rectly and the retaining screw is fitted.
4.2.1 Temperature sensor installation
A temperature sensor bracket (22) is factory fit-
ted to the upper electrical box, see illustration
on previous page. Ensure the sensor has proper
contact with the inner vessel when fitting.
4.3 Motorized valve
To comply with regulations governing the in-
stallation of indirect unvented cylinders, a mo-
torised 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 elec-
trical box. The unit should be installed on an “S”
or “Y” plan system.
Please follow the instructions carefully. All elec-
trical 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.2 above).
OSO Hotwater (UK) Limited can not be responsi-
ble 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.
4.4 Electrical spare parts
Part for
Description
Part No.
Indirect Immersion heater
71214
Indirect Upper thermostat
80030
Indirect Lower thermostat
80020
MAX
10 mm
Element
Reset button
Safety
cut-out
Working
thermostat
Temperature
adjustment
screw
RESET
RE
SET
M2
1
2
3
4
THERM-O-DISC
40°C
70°C
60°C
50°C
1
2
Power
supply
