59 © STULZ SpA . – all rights reserved EN/39B/06.2018
SAL
Sight glass and filter dryer
Bubbles in the sight glass indicate that the charge is insufficient or that the filter dryer is clogged. A
pollution of the filter dryer, whose origin task is to clear the refrigerant from impurities and humidity,
can be detected by a temperature difference upstream and downstream the filter dryer.
With too much humidity in the circuit, the expansion valve can freeze. In addition to this, the POE oil
in the compressor, which comes in touch with the refrigerant, takes up humidity and loses its ability
to lubricate. In this case the refrigerant must be completely evacuated and recharged according to
the evacuation instruction described in paragraph "Extraordinary maintenance".
8.2.3. General cleaning
The metal casing of the unit can be cleaned using a liquid detergent as long as this liquid is
compatible with: PVC, polyethylene, silicone and polyester coating. Be careful not to wet the
electrical connections inside the unit.
ATTENTION
Use of an unsuitable detergent might cause damage to the unit. Do not use either acid or caustic
substances or solvents to clean any part of the unit.
Remove dust with a vacuum cleaner. Clean the internal parts with a liquid detergent and compressed
air not greater than 4 bar, with the unit suitably earthed.
8.3. Extraordinary maintenance
The extraordinary maintenance operations are done every time is necessary to substitute or repair a
component activated by an electrical motor or a component of the refrigerant circuit, as for example
the thermostatic valve, the evaporator, the condenser, the compressor.
Refrigerant charge
An insufficient charge causes the formation of bubbles in the sight glass or in extreme cases
the stop of compressor due to protection against low pressure. An operation with an insufficient
refrigerant quantity over a longer period leads to a reduction of cooling capacity and to high
superheating temperatures, which have a disadvantageous effect on the compressor lifetime.
ATTENTION
When refrigerant charge is more than 3kg, control of refrigerant leakages is obligatory,
according to European Regulation 517/2014 (F-gas). Certified personnel and companies
(according to Reg. 303/2008) provides regular leak testing (according to Reg. 1516/2007
and Reg. 1497/2007) and maintain records of maintenance activities in a dedicated log book.
If a leak is detected:
• Let out the refrigerant in a collecting device down to a pressure of 1 bara;
• Connect a vacuum pump via a pressure gauge station on the high and low pressure side;
• Extract the refrigerant by the vacuum pump (not by the compressor!) to approx. 0 bara;
• Dispose the refrigerant according to the national regulations;
• Fill the circuit with nitrogen to 1 bara;
• Repair the leak;
• The circuit has to be run dry by several (at least 3) fillings and extractions of nitrogen. When
necessary change the filter dryer;
• Fill with R407C.
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