2920 1351 01
8
Instruction book
1.4 Automatic regulation system (Fig. 2)
Expansion valve (13) maintains the evaporating temperature
between 1 and -1°C (34 and 30°F); these are the approximate
limit temperatures at zero and maximum air load respectively.
At partial or no load, the excess cooling capacity is transferred
in liquid separator (7). The condenser pressure must be kept
as constant as possible to obtain stable operation of expansion
valve (13). Therefore, on air-cooled dryers, fan control switch
(S3) stops and starts cooling fan (M2). On water-cooled dryers,
the temperature is controlled by an automatic regulating valve
on the water circuit. The switch or regulating valve ensures
proper operation at low air load and/or low ambient temperature.
1.5 Electrical system
These dryers are three-phase units.
The refrigerant compressors are equipped with a crankcase
heater. When voltage is supplied, the heater is energized. It
keeps the oil in the crankcase warm to prevent condensing of
refrigerant in the compressor housing, which could result in
serious damage of the compressor at restart (liquid knock).
On air-cooled dryers, fan control switch (S3-Fig. 4b) will start
fan motor (M2-Fig. 4b) via contactor (K2-Fig. 3) as soon as
the condenser pressure reaches the upper set point of the switch
and will stop the fan motor when the condenser pressure
decreases to its lower set point.
High pressure shut-down switch (S2-Figs. 4b and 5b) stops the
compressor motor when the pressure in the refrigerant circuit
reaches the upper set point of the switch. The compressor motor
will automatically restart when the pressure drops to the lower
set point.
The motors have a built-in thermic protection. If the compressor
motor stops without apparent reason, it will most probably be
the thermic protection which has tripped. In such case, the
compressor will restart when the motor windings have cooled
down, which may take up to 2 hours.
An electronic dewpoint indicator with display and alarm
functions is installed on the instrument panel (Fig. 10). Display
(3-Fig. 12) shows the pressure dewpoint temperature. The set
point value, i.e. the pressure dewpoint temperature at which
the alarm indicator lamp (H3-Fig. 10) lights up, can be checked
by pressing key (5-Fig. 12); the value will blink for 5 seconds
on the display. The differential value (dT), i.e. the temperature
difference between alarm on and alarm off, can be checked by
pressing key (4-Fig. 12); the value will blink on the display for
approx. 5 seconds.
Altering the set point value (indicated "L1"):
- Press key (5); the current value blinks on the display.
- Press the up (1) or down (2) key until the desired value is
reached.
- To store the new value, press key (5) or wait a few seconds.
Altering the differential value (indicated "HY1"):
- Press key (4); the current value blinks on the display.
- Press the up (1) or down (2) key until the desired value is
reached.
- Press key (5) or wait a few seconds to store the new value.
If the temperature increases above the preset value, alarm
indicator lamp (H3-Fig. 10) will light up.
An automatic interval drain 1) may be connected between
condensate trap (4-Fig. 2) and manual drain valve (6-Fig. 2) to
flush the trap regularly. The interval time and opening time
can be adjusted.
2 INSTALLATION
2.1 Dimension drawings (Figs. 6)
See pages 9 up to 12
1) Optional equipment.
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