55
Purge Refrigeration System Diagnostic Procedure
Caution:
Do not attempt to measure system discharge or liquid line pres sure, it could
result in the loss of your refrigerant charge.
Operation of the purge unit's refrigeration system can be diagnosed by taking temperature
measurements at various points in the refrigeration circuit (refer to Figure 6 on page 19.).
With the purge condensing unit operating, the constant pressure expansion valve (CPEV) will
maintain a constant low side pressure in the purge refrigeration system, even with a slight
variation in refrigerant charge.
Measuring suction pressure is not recommended, nor is it a good indication of proper
refrigerant charge. The only reliable method for determining if the system has a proper
charge is by measuring surface temperatures at various points of the refrigerant circuit.
Condensing temperature (Point 2 in Figure 6 on page 19.) can be determined by measuring
the condenser surface temperature at the 2nd or 3rd condenser tube U -bend from the top on
the side opposite the discharge gas inlet.
NOTE:
Use an accurate (±1° F) temperature meter to take temperature mea surements.
Attach the temperature sensor tightly to the surface of the tubing at the appropriate
point and insulate. When attaching the sensor to points 4 and 5, be extremely careful
not to disturb temperature sensors TS1 and TS2.
With the purge condensing unit running, read surface temperatures at points 2 and 3 in Figure
6 on page 19. The difference between these two temperatures is the sub -cooling. With a
proper refrigerant charge normal sub-cooling should range between 5°F and 15°F.
A sub cooling less than 5°F indicates a refrigerant undercharge.
A sub-cooling greater than 15°F indicates a refrigerant overcharge.
NOTE:
The purge unit's refrigeration system must contain a proper charge of refrigerant
before any further diagnosis can be made. (Refer to page 10)
Evaporator Pressure CPEV
The function of the constant pressure expansion valve is to regulate and maintain constant
evaporating pressure within the purge tank cooling coil under varying load conditions. Proper
operation of the expansion valve can be determined by checking the temperature at point 4 in
Figure 6 on page 19. An optimum constant operating temperature of 5°F should be measured
at this point. However, temperature between 0°F and +10°F is acceptable.
Temperature Sensor TS1
Sensor TS1 can be checked for proper operation by measuring the surface temperature at
point 5 in Figure 6 on page 19. Place display in the "SENSORS" mode and continuously
monitor both the temperature at point 5 and "Compressor Suction Temperature." After
sufficient air has entered the purge tank, the temperature at point 6 will drop. Also, the
Summary of Contents for Redi-Purge PRG-113-C3
Page 2: ...2 Revised Technically as of October 11 2013 1994 REDI CONTROLS INC GREENWOOD INDIANA...
Page 4: ...4...
Page 67: ...67...