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Technical description
11 Technical description
11.1 Control panel
The control panel explained below is the only dryer user interface.
1
0
1
A
Main switch
1
ON-OFF switch
11.2 Functional description
Operating principle – All dryer models described in this manual function according to the same principle. The hot and
moisture-loaded air is led into an air/air heat exchanger. Afterwards, the air flows through an evaporator, which is also
known as an air/refrigerant heat exchanger. The air temperature is reduced to approximately 36°F (2°C), so that water
vapour condenses to liquid. The continuously accumulating condensate is collected in the separator to be discharged
via the condensate drain. Subsequently, the cold and dry air is led through the air/air heat exchanger, so that it is
reheated to up to 46°F (8°C) below the inlet temperature when leaving the dryer.
Refrigeration cycle – The refrigerant is conducted through the compressor and reaches a condenser under high
pressure. There, cooling-down takes place, making the refrigerant condense to a liquid state which is under high
pressure. The liquid is pressed through a capillary tube where the resulting pressure drop ensures that the refrigerant
evaporates at a defined temperature. The liquid refrigerant which is under low pressure is led into the heat exchanger,
where it expands. The cold resulting from the expansion serves to cool down the compressed air in the heat exchanger.
During this process, the refrigerant evaporates. The low-pressure gas is resupplied to the compressor, where it is
compressed again.
Operation in cycling mode (Energy Saving, ESS=YES – see section 11.12.7) – The DMC51 electronic controller
constantly monitors the temperature of the DewPoint. In low load conditions, the temperature of the DewPoint tends to
fall close to the freezing point, at this point the DMC51 controls the switching off of the compressor.
The compressor will be started again when the DewPoint temperature rises above a target value. To avoid an
excessive number of cycles, DMC51 keeps the compressor on for a minimum time (about 6 minutes) within which, if
necessary, will activate a solenoid valve EVH that enables the operation of the hot gas by-pass valve. In this way the
compressor cannot make more than 10 cycles per hour. The solenoid valve EVL and the check valve CHV (where
installed) help to extend the off time of the compressor and avoid the immediate balancing of high and low pressures of
the refrigerant circuit. The solenoid valve EVL is activated before the compressor to balance the pressures and is kept
active for the entire time during which the compressor is on.
With these dryers, the energy consumption will be adjusted closely proportional to the thermal load applied to the dryer
itself, allowing considerable energy savings in the majority of applications.
Operation in hot gas by-pass mode (NO Energy Saving, ESS=NO – see section 11.12.7) – The DMC51 electronic
controller constantly keep activated the compressor, the solenoid valve EVH and the solenoid valve EVL. In cases of a
reduced compressed-air load, the excess refrigerant is bypassed automatically to the compressor via the hot gas
bypass valve.
20
K
reset
Set
K
T4
T3
2
T2
3
T1
2
Electronic control unit DMC51
3
Air and refrigerant-gas flow chart
DRYPOINT® RA CT 200-500 NA 3PH
A
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