Pub. No. 2200772355 — October 2006
9
CONTROLS
FIGURE 11 — COMMAND AND CONTROL PANEL
OPERATION
See Figure 12. The gaseous refrigerant coming from the
evaporator (4) is drawn by the refrigeration compressor
(1) and is pumped into the condenser (2). This allows its
condensation, with the help of the fan (3). The condensed
refrigerant passes through the dewatering filter (8), it
expands through the capillary tube (7) and goes back to
the evaporator, where it produces the refrigerating effect.
Due to the heat exchange with the compressed air which
passes through the evaporator against the stream, the
refrigerant evaporates and goes back to the compressor
for a new cycle.
The circuit is equipped with a bypass system for the
refrigerant. This intervenes to adjust the available
refrigerating capacity to the actual cooling load. This is
achieved by injecting hot gas under the control of the
valve (9). This valve keeps the refrigerant pressure
constant in the evaporator and therefore keeps the dew
point from decreasing below 32 °F (0 °C) in order to
prevent the condensate from freezing inside the
evaporator. The dryer runs completely automatically; it is
calibrated at the factory for a dew point of 39 °F (4 °C)
±2 °F (1 °C) and therefore no further calibrations are
required.
FIGURE 12 — DRYER FLOW DIAGRAM
1
3
2
4
1.
Refrigerant suction pressure
gauge
2.
Stop - ON/OFF switch
3.
Operation indicating lamp
4.
Compressor overload alarm light
AIR OUTLET
AIR INLET
CONDENSATE
AUTO DRAIN
1.
Refrigerant compressor
2.
Condenser
3.
Motor fan
4.
Evaporator
5.
Separator
6.
Particle strainer
7.
Expansion capillary tube
8.
Refrigerant filter dryer
9.
Hot gas bypass valve
10. Air-to-air heat exchanger
11. Refrigerant suction pressure gauge
12. Fan control pressure switch (Only
QPNC 25 to QPNC 50)
13. Condensate auto drain
