Safety And Servicing - OSO DGC 200 Installation Manual

7. Safety and Servicing

Maintenance must be carried out by a competent person.
7.1 Safety Cut-out
The safety cut-out operates if:
1. Wiring is incorrect.
2. The immersion heater thermostat or cylinder thermostat fails.
3. Thermostat is set too high.
4. Remember before resetting the safety cut-out or altering the thermostat setting, isolate electrical supply to the unit prior
to removal of the electrical box lid.
5. Reduce thermostat setting and press the reset button. After adjustments are completed, ensure the lid to the electrical
box is replaced.
6. If still out of operation, contact installer.
7.2 Intermittent or slow discharge from tundish
1. Turn off the electrical supply to the immersion heaters.
2. Turn off cold water supply valve.
3. Open a hot tap.
4. Turn the knob on the Temperature and Pressure Relief Valve (5) to the left and hold in this position for thirty seconds.
5. Attach a foot pump with a schraeder (car type) valve to the expansion vessel.
6. Pump up to 3 bar
7. Open cold water supply valve.
8. When water flows through open tap, close tap
9. Turn on electrical supply to the immersion heaters.
7.3 Continuous very hot water discharge from tundish
This indicates a malfunction of a thermal cut-out, operating thermostat or the combined temperature and pressure relief
valve. Turn off the electrical supply to the immersion heater and also isolate an indirect unit from the Heat Pump. Contact the
installer or competent engineer.
7.4 Expansion vessel maintenance
The expansion vessels do not require annual maintenance and should not be tampered with unless an intermittent or slow
discharge from the tundish occurs when water is being heated. In this situation, maintenance must be carried out by
competent person and the precharge pressure must be restored to the original value. An annual visual inspection is
recommended. Important: To check the precharge the expansion vessel must be completely empty of water. If the precharge
pressure is different from the value shown on the label it must be restored to the original value.
Do not remove expansion vessel without depressurising the cylinder and draining 10 litres of water from the drain valve at
the base of the cylinder.
7.5 Guarantee
Cylinder should be serviced annually and the log book should be updated in order to validate guarantee. The log book and
service records act as guarantee document. For terms of guarantee please see the log book on page 15.
7.6 Servicing Procedure:
7.6.1 Expansion relief valve
Ensure that expansion relief valve works by manually opening to discharge water to tundish.
7.6.2 Pressure reducing valve
Isolate the cold water supply and open a ground floor cold tap. Unscrew the pressure reducing cartridge. Clean the filter
mesh and the cartridge under running water. Replace cartridge ensuring that strainer is correctly located and reassemble the
unit.
7.6.3 Expansion relief cartridge
Isolate the cold supply and open a ground floor cold tap. unscrew blue expansion relief headwork from valve body. Clean
valve seat face and seating - do not scratch or damage either seat face or seating. Refit in reverse order. Do not overtighten.
7.6.4 Temperature and Pressure relief valve
Ensure that Temperature & Pressure Relief valve works by manually opening to discharge water to tundish.
7.6.5 Internal inspection
The immersion heater can be removed to provide visual inspection access to the cylinder.
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