Trane PRGD series, Installation, Operation And Maintenance Manual

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30 PRGD-SVX01F-EN
Table 2. Troubleshooting a purge system (continued)
Diagnostic or Problem
Cause Solution
Restriction in exhaust lines.
Check carbon tank for restriction, check solenoid valves for restriction,
check outlet tubing from the carbon tank to the chiller vent line.
Carbon Regeneration
Temperature Diagnostic
Procedure
If a Carbon Regeneration Temperature Setpoint Not
Satisfied diagnostic is generated, follow this
procedure:
1. Close the regeneration solenoid valve and turn off
the heater.
2. Reset the calculated carbon capacity to 100 percent.
3. Turn the purge refrigeration circuit on and allow the
carbon tank to cool for 4 hours or until the carbon
temperature reaches 100°F (37.8°C), whichever
comes first.
If the carbon tank temperature does not decrease more
than 25°F (13.8°C) in the first hour after this procedure,
the controller initiates a latching diagnostic, Carbon
Regeneration Temperature Limit Exceeded. The
purpose of this diagnostic is to identify a failed heater
relay or temperature sensor. This diagnostic disables
the purge system and opens the exhaust solenoid
valve.
If a Carbon Regeneration Temperature Limit Exceeded
diagnostic is generated, follow this procedure:
1. Open the exhaust solenoid for 5 minutes and then
close it.
2. Run the refrigeration circuit for 15 minutes.
Operating the refrigeration circuit during the carbon
cool-down cycle allows time for any gas that may
have remained in the carbon tank to accumulate in
the purge tank.
3. While the refrigeration circuit is running, enable
pump-outs. If enough gas has accumulated in the
purge tank, a pump-out cycle is activated following
completion of the cool-down cycle.
Purge Refrigeration Circuit
Diagnostic Procedures
You can troubleshoot the refrigeration circuit by taking
surface temperature measurements and using them to
diagnose specific problems, as explained in this
section.
Taking Surface Temperature
Measurements
While the purge condensing unit is running, take
temperature readings with an accurate (±1°F [±0.55°C])
surface-mounted thermocouple-type temperature
probe that has a range of -40°F (-40.0°C) to 200°F (93.3°
C). The locations to be measured are shown in Figure
6, p. 16 . The temperatures that you should expect to
find under typical operating conditions are given in the
same figure.
1. To ensure accurate measurements, remove any ice
that may exist on measuring surfaces before
attaching the probe.
2. Fasten the sensor of the probe tightly against the
tubing surface and insulate around the sensor for
accurate results.
3. To measure the temperature at Location 1, move
aside a small portion of the insulation covering the
tubing between the expansion valve and the purge
tank.
4. To read the purge refrigerant compressor suction
temperature, view the purge component screen of
the Tracer® AdaptiView™ display. Then confirm
that reading by measuring the temperature with a
surface-mounted thermocouple at Location 2.
5. To measure the compressor discharge temperature,
mount the probe on the surface at Location 3.
6. To measure the condenser temperature
(Location 4), remove the sheet metal cover from the
side of the condenser and measure the surface
temperature of the second or third from the top
condenser tubing U-bend on the side of the coil
opposite the discharge gas inlet.
7. To measure the liquid line temperature, measure
the tubing between the purge condenser and the
expansion valve (Location 5).
Determining the Refrigerant
Charge Level
To operate correctly, the purge refrigeration system
must have a proper charge level of R-404A. The charge
level should be determined before any other
refrigeration circuit components are evaluated.
1. Take the surface temperature measurements for
Locations 1–5 as described in “Taking Surface
Temperature Measurements,” p. 30 .
2. Calculate the difference between Locations 4 and 5.
3. The difference is the sub-cooling value. If the
system is properly charged with R-404A, the sub-
cooling value should be between 8°F (4.4°C) and 15°
F (8.3°C).
a. A sub-cooling of less than 5°F (2.8°C) indicates a
possible refrigerant undercharge and a possible
leak.
b. A sub-cooling value greater than 20°F (11.0°C)
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