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9.3 Refrigerant charge
Do not inject refrigerant liquid into the LP side of the circuit. Be very
careful, and charge the circuit properly. If the charge is insufficient,
the efficiency of the unit will be lower than expected. (In the worst of
cases the LP transducer may stop the unit.)
In the presence of an excess charge, the condensing pressure will
rise (in the worst of cases, the HP pressure switch may be activated,
resulting in the stop of the equipment), and the consumption will
increase as well.
It is strictly forbidden to use the compressor as a vacuum pump to
drain the plant.
Fill the refrigeration circuit after it has been drained for maintenance
purposes (leaks, replacement of the compressor etc.). The amount
of the charge is indicated on the plate affixed to the unit.
Before refilling, it is important to drain and de-hydrate the circuit, thus
obtaining a minimum abs. pressure value of 50 Pa.
Inject the refrigerant fluid before removing the vacuum, then fill the
circuit up to 90% of the total gas requirement (in liquid form). The
appliance must be filled through the filling valve on the liquid line, on
the outlet side of the condenser.
It is recommended to connect the refrigerant cylinder to the filling
valve on the liquid line, and to arrange it in such a way as to inject
only liquid refrigerant.
9.4 Compressor
Compressors are delivered with the necessary charge of lubricating
oil. During normal operation, this charge is sufficient for the whole
life of the unit, providing that the efficiency of the refrigeration circuit
is satisfactory and if it has not been overhauled.
If the compressor needs to be replaced (following a mechanical
failure or if burnt), contact one of authorised Service Centers.
Compressors use polyester oil. During maintenance operations
on the compressor, or if you have to open the refrigerant circuit in
any point, remember that this type of oil is highly hygroscopic, and
accordingly it is important that it is not left exposed to the weather for
prolonged periods, as this would require the replacement of the oil.
9.5 Condenser
Check at regular intervals that the water side of the heat exchanger
is perfectly clean. To do this, measure the pressure drop, water side
(see Section 8) or measure the temperature of the liquid leaving
and entering the heat exchanger, and compare it to the condensing
temperature.
To obtain an effective heat exchange, the difference between the
temperature of the leaving water and the saturated condensing
temperature must be in the 3 - 5°C range. A greater difference
would indicate a low efficiency of the heat exchanger (i.e. the heat
exchanger is dirty).
In this case, the heat exchanger must be subjected to chemical
cleaning, an operation that shall be carried out by authorised
engineers.
For other maintenance operations (extraordinary overhauling,
replacement of the heat exchanger etc.), contact an authorised
Service Centre.
9.6 Dehydrating filter
The refrigeration circuits are provided with dehydrating filters.
The filter clogging is marked by the presence of air bubbles in the
sight glass, or by the difference between the temperatures measured
downstream from and upstream of the drying filter. If, once the
cartridge has been cleaned, there are still some air bubbles, the
appliance has lost a part of the refrigerant charge in one or more
points, that must be identified and serviced.
9.7 Sight glass
The sight glass is used for inspecting the refrigerant flow and the
humidity % of the refrigerant. The presence of bubbles indicates that
the dehydrating filter is clogged or the charge insufficient.
A colour indicator is positioned inside the sight glass. If you compare
the colour of the indicator to the scale on the ring of the sight glass,
you can calculate the percentage of humidity of the refrigerant. If it
is excessive, replace the filter’s cartridge, operate the appliance for
1 day and then check the humidity % again. When the humidity % is
within the pre-determined range, no other operations are required. If
the humidity % is still too high, replace the dehydrating filter again,
start the unit and operate it for another day.
9 - Maintenance (continued)
