SRL Service Manual
Revision 00
July 2007
Page 19 of 56
3.2.5 Expansion
Device
The expansion device reduces the pressure (and therefore temperature) of the
refrigerant and regulates it’s flow into the Air-to-Refrigerant Heat Exchanger.
All models use a capillary tube expansion device. The capillary tube is a copper
tube of precise length and diameter that provides a specific pressure drop and
choked flow rate. For details on each model, refer to Section. 2.3.
3.2.6 Refrigerant
The refrigerant is the medium used to transfer energy. By changing pressure and temperature and
changing from a liquid to a gaseous state it effectively transforms the input energy (i.e. compressor
electrical energy) to output energy (i.e. cooling of the air). All models feature R407C refrigerant.
R407C is classified as an environmentally friendly refrigerant, and offers an ODP (Ozone Depletion
Potential) of zero. As a consequence R407C has no planned phase-out date and can be used without
restrictions. It also offers a very low GWP (Global Warming Potential) level. R407C furthermore
features a high COP (Coefficient of Performance), thereby ensuring that the dryer’s power
consumption is kept to a minimum.
3.2.7 High Pressure Switch
Settings: On: 406 psig (28 barg), Off: 305 psig (21 barg).
Shuts down the dryer in the event of overpressure of the refrigerant system.
Installed at the compressor outlet. When it trips, the display will show the HP (High
Pressure) alarm, and the remote alarm contacts will be activated.
On all models the switch automatically resets when the pressure goes back below
305 psig (21 barg).
See Section 10 for details on troubleshooting an HP (High Pressure) alarm.
3.2.8 Low Pressure Switch
Settings: On: 21.7 psig (1.5 barg), Off: 36.2 psig (2.5 barg).
Al models have a Low Pressure Switch to shut down the dryer in the event of low
pressure at the compressor inlet, as this indicates a refrigerant temperature below
freezing. If the pressure goes below the set point for more than 2 minutes, the
microprocessor will shut down the dryer and go into alarm. The display will show the
LP (Low Pressure) alarm, and the remote alarm contacts will be activated.
The switch automatically resets when the pressure returns above 36.2 psig.
See Section 10 for details on troubleshooting an LP (Low Pressure) alarm.
