T -304
5--3
04/08
5.5 PUMPING THE SYSTEM DOWN OR REMOV-
ING THE REFRIGERANT CHARGE
NOTE
Toavoiddamagetotheearth’sozonelayer ,use
arefrigerantrecoverysystemwheneverremov-
ing refrigerant.
5.5.1 System Pump Down For Low Side Repair
To service or replace the filter--drier, pump the
refrigerant to the condenser and receiver as follows:
a. Remove evaporator and condenser covers.
b. Install manifold gauge/hose set. (Refer to Section
5.4.1).
c. Frontseat the filter--drier inlet servicevalve by turning
clockwise. It will be necessary to install a jumper
across the low pressure switch (LPS) contacts at the
compressor in order to reach 0 PSIG.
d. Start the system and run in cooling. Stop the unit
when suction reaches 10 ”/hg (25.4 cm/hg) vacuum.
e. Frontseat filter/drier outlet servicevalveto traprefrig-
erant inthehighsideofthe systembetween thecom-
pressor andthe filter--drierinlet valve. Wait 5minutes
to verify that system remains in a vacuum.
f. Service or replace filter--drier.
g. Leak check connections after replacing filter--drier.
Refer to paragraph 5.6.
h. Usingrefrigeranthosesdesignedforvacuumservice,
evacuateanddehydratethefilter--drierbyconnecting
a vacuum pump to center connection of manifold
gauge set. Evacuate system to 500 microns. Close
off pump valve, isolate vacuum gauge and stop
pump. Wait 5 minutes to verify that vacuum holds.
i. Read Micron Gauge again to verify that the pressure
did not rise more than 500 microns within that 5--min-
ute timeframe.
If the Micron Gauge rises more than 500 microns (to
excedeagaugereadingof500+500=1000microns)at
the end of 5 minutes, either a leak is present or an
unacceptable level of moisture remains in the circuit. If
the gauge reads a gain of less than 500 microns during
the5--minute wait, the circuit is acceptablytight and dry.
j. Once vacuum is maintained, rechargesystem by ad-
mitting vapor from the refrigerant cylinder.
k. Remove manifold gauges. Backseat both filter drier
service valves.
5.5.2 Removing Entire System Charge
To remove the entire refrigerant charge, do the
following:
a. Connect a manifold gauge set to the system as
showninFigure5--2.
b. Connect a reclaimer tothe center manifold gaugeset
connection.
c. Recover refrigerant in accordance with reclaimer
manufacturers instructions.
D
S
7.
2.
3.
4.
5.
6.
To Compressor
1.
Figure 5--2 In--Line Service Connections
1. Discharge Service
Port
2. Suction Service
Port
3. Manifold Gauge
Set
4. Vacuum Pump
5. Reclaimer
6. Refrigerant Cylinder
7. Thermistor Vacuum
Gauge
5.6 REFRIGERANT LEAK CHECK
A refrigerant leak check should always be performed
after the system has been opened to replace or repair a
component.
To check for leaks in the refrigeration system, perform
the following procedure:
NOTE
It must be emphasized that only the correct re-
frigerant should be used to pressurize the sys-
tem. Use of any other refrigerant will contami-
nate the system, and require additional
evacuation.
a. Ensure filter drier service and solenoid valves are
open.
1. Filter drier service valves should be back seated.
b. If system is without refrigerant, charge system with
refrigerant vapor to build up pressure between 20 to
30 psig (1.36 to 2.04 bar).
c. Add sufficient nitrogen to raise system pressure to
150 to 200 psig (10.21 to 13.61 bar).
d. Check for leaks. The recommended procedure for
findingleaksin asystem iswithanelectronicleakde-
tector. Testing joints with soapsuds is satisfactory
only for locating large leaks.
e. Remove test gas and replace filter--drier.
f. Evacuate and dehydrate the system. (Refer to para-
graph 5.7.)
g. Charge the unit. (Refer to paragraph 5.8.)
5.7 EVACUATION AND DEHYDRATION
5.7.1 General
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