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3.6 Primary Flow and Return and Motorised valve
3.6.1 The heat pump/boiler primary flow and return connections should be made connections 1 & 2. 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 direction of primary flow in the coil is bottom to top. The maximum operating temperature of the primary
flow would typically be 82°C.
3.6.2 For electrical connection of the motorised valve and immersion heater, please read Electrical Installation
Instructions. (Page 5).
4. Commissioning and filling up
4.1 Commissioning
4.1.1 Check all connections for tightness.
4.1.2 Open hot water tap furthest away from the PAW cylinder. Open the mains stop cock to fill the water heater. When
water flows evenly from tap, allow to run for a few minutes to flush through any dirt, swarf or residue, then close the tap.
Open successive hot taps to purge any remaining air.
4.1.3 Check all water connections for leaks and rectify if necessary.
Manually operate Expansion relief valve 4 (see page 3) to ensure free water flow through discharge pipe by turning knob
counter-clockwise. To close continue to turn counter-clockwise until the valve shuts.
Manually operate Temperature and Pressure Relief Valve 5 (see page 3) to ensure free water flow through discharge
pipe.
5. Draining & flushing out the system
5.1 Draining
Switch off the electrical power (Important to avoid damage to element). Isolate heat pump/boiler from cylinder. Turn off
the cold water supply valve. Open hot water tap. Open drain 12 (see page 3) at base of cylinder.
The unit will drain. Draining process may be speeded up by opening the temperature and pressure relief valve. An
internal ø18 mm hose can be applied to lead the water to a gully, sink or similar.
5.2 System flushing
This will not be necessary under normal circumstances as the line strainer will prevent ingress of foreign materials,
however if flushing is required, run at least 50 litres of water from the cylinder at the highest possible flow rate. Close
the taps and follow draining procedure (above).
6. Electrical installation
6.1 Immersion heater Thermostat
The immersion heater is designed as an auxiliary heater as an emergency back-up. Power to immersion heaters
should not be switched on until the unit is filled with water. All units are fitted with one 1.5 kW @230V immersion heater
which is located behind the electrical box. Alternative thermostats should not be used, regulations require immersion
heaters on unvented cylinders to be connected with a thermal cut-out. Follow the wiring instructions below connect-
ing the live, neutral and earth as indicated. The unit must be permanently connected to the electrical supply and each
circuit must be protected by a suitable fuse and double pole isolating switch, compliancy to IEE regulations.
The immersion heater has a working thermostat adjustable between 18°C - 70°C (+/- 5°C). A safety cut-out is also
incorporated within the thermostat and will operate at 87°C (± 5°C). Should this happen, check reasons for thermal
cut-out button being released and when satisfied press the reset button.
- all wiring must conform to current IEE regulations
OSO Hotwater AS 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.
Ensure the lid to the electrical box is replaced.
5
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