FRIULAIR ACT ES 20-500, User Maintenance Manual And Spare Parts

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Technical description
20 – EN ACT ES 20 – 500
7.2 Operation
Operating principle - The dryer models described in this manual operate all on the same principle. The hot
moisture laden air enters an air to air heat exchanger. The air then goes through the evaporator, also known
as the air to refrigerant heat exchanger. The temperature of the air is reduced to approximately 36°F (2°C),
causing water vapor to condense to liquid. The liquid is continuously coalesced and collected in the
separator for removal by the condensate drain. The cool moisture free air then passes back through the air
to air heat exchanger to be reheated to within 46°F (8°C) of the incoming air temperature as it exits the
dryer.
Refrigerant circuit - Refrigerant gas is cycled through the compressor and exits at high pressure to a
condenser where heat is removed causing the refrigerant to condense to a high-pressure liquid state. The
liquid is forced through a capillary tube where the resulting pressure drop allows the refrigerant to boil off at
a predetermined temperature. Low-pressure liquid refrigerant enters the heat exchanger where heat from
the incoming air is transferred causing the refrigerant to boil; the resulting phase change produces a low
pressure, low temperature gas. The low-pressure gas is returned to the compressor, where it is re-
compressed and begins the cycle again.
Operation in eco (cycling) mode (Energy Saving, ESS=YES – see section 7.12.7) – 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 7.12.7) – 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