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Technical description
11.4 Refrigerating compressor
The employed refrigerating compressors are constructed by leading manufacturers. The hermetically sealed construction
is absolutely gastight. The integrated safeguard protects the compressor against overheating and excess current. The
protection is automatically reset as soon as the nominal conditions are reached again.
11.5 Condenser
The condenser is the component in which the gas coming from the compressor is cooled down, condensed and liquefied.
Under no circumstances must the temperature of the ambient air exceed the nominal values. It is also important that the
condenser unit is kept free from dust and other impurities.
11.6 Aftercooler
The aftercooler is the element where the incoming hot air undergoes the cooling stage. Mechanically, it is formed by a
copper tubing circuit (with the compressed air flowing inside) immersed in an aluminium blades package. The cooling
operation occurs via a high efficiency axial ventilator which, in applying pressure on the air contained within the dryer,
forces it into the blades package. In models DRYPOINT RA HT 20-50 NA the aftercooler is combined with the dryer's
condenser, thus forming just one heat exchanger battery, cooled by just one high efficiency axial fan.
It is mandatory that the temperature of the ambient air will not exceed the nominal values of the dryer. It is important
TO KEEP THE UNIT FREE FROM DUST AND OTHER IMPURITIES taken in by the fan.
11.7 Pre-Filter (1 micron)
Positioned at the outlet of the aftercooler, it assures a good air cleanliness level, in addition to the complete removal of
the water condensed in the aftercooler. REPLACE THE FILTERING ELEMENT (CARTRIDGE) AT LEAST EVERY 12
MONTHS.
11.8 Filter dryer
Despite controlled vacuuming, traces of moisture can accumulate in the refrigeration cycle. The filter dryer serves to
absorb this moisture and to bond it.
11.9 Capillary tube
The capillary tube is a copper tube with a reduced diameter which is located between the condenser and the evaporator,
serving as a restrictor to reduce the pressure of the refrigerant. The pressure reduction serves to reach an optimum
temperature inside of the evaporator. The lower the outlet pressure at the capillary tube, the lower the evaporation
temperature.
The length and the inner diameter of the capillary tube are exactly dimensioned to ensure the performance of the dryer.
Settings or maintenance works are not required.
11.10 Aluminium heat exchanger
The heat exchanger module consists of an air/air heat exchanger, an air/refrigerant heat exchanger, and of a high-
performance separator. The compressed air flows top-down through the heat exchanger. The large cross-sections of the
flow passages cause low flow rates and low compressed-air losses. In the air/air heat exchanger, the heat exchange is
effected in a reverse current. This guarantees maximum heat transfer. The heat transfer in the air/refrigerant heat
exchanger also takes place in a reverse current. This allows full evaporation of the refrigerant. The high-performance
separator ensures almost complete separation of the condensate. Maintenance of the high-performance separator is not
required.
11.11 Hot-gas bypass valve
At partial load, the valve directly returns a part of the hot gas to the suction line of the refrigerating compressor. The
evaporation temperature and the evaporation pressure remain constant.
ADJUSTMENT
The hot gas by-pass valve is adjusted during the manufacturing testing phase.
As a rule no adjustment is required; anyway if it is necessary the operation must
be carried out by an experienced refrigerating engineer.
WARNING
the use of ¼" Schrader service valves must be justified by a real malfunction of
the refrigerating system. Each time a pressure gauge is connected, a part of
refrigerant is exhausted.
Without compressed air flow through the dryer, rotate the adjusting screw
(position A on the drawing) until the following value is reached:
Hot gas setting (R134.a):
•
temperature 33°F (+1 / -0 °F) [0.5°C (+0.5 / -0 °K)]
•
pressure 29 psig (+1.45 / -0 psi) [2.0 barg (+0.1 / -0 bar)]
Hot gas setting (R407C) :
•
temperature 33°F (+1 / -0 °F) [0.5 °C (+0.5 / -0 °K)]
•
pressure 75.4 psig (+1.5 / -0 psi) [5.2 barg (+0.1 / -0 bar)]
22
DRYPOINT® RA HT 20-350 NA UL
A
4 mm
5/32 in.
-
+
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