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4. ELECTRICAL INSTALLATION
4.1 Thermostat connection
When connecting cables to thermostats, use
spade or ring connectors as shown in diagram.
Ensure that connector is less than 10 mm in outer
dimension and fits inside the shoulders of the
thermostat and is not tightened onto the top of
the shoulders.
4.2 Immersion heaters
All units are fitted with immersion heaters
which are located behind the electrical box
covers. 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. A dedi-
cated permanent supply complying with current
IEE regulations should be used, and each circuit
must be protected by a suitable fuse 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
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.
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 safe-
ty 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 cur-
rent IEE wiring regulations. The working ther-
mostat 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 op-
eration, 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 respon-
sible if alternative wiring plans are used.
Important: Before resetting the safety cut-out
or altering the thermostat setting isolate electri-
cal supply to the unit before removal of the lid.
MAX
10 mm
Reset button
Safety
cut-out
Working
thermostat
Temperature
70°C
adjustment
screw
Element
4.4 Electrical spare parts
Part for
Description
Indirect Immersion heater
Indirect Upper thermostat
Indirect Lower thermostat
1
3
2
4
1
THERM-O-DISC
2
40°C
60°C
50°C
Power
supply
Part No.
70628
80030
80020
11
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