6--4
T-334
c. The area between the suction modulating valve and
evaporator expansion valve may not be open to the
access valves. To ensure evacuation of this area,
check that the suction modulating valve is more than
10% open at controller function code Cd01. If re-
quired, the suction modulating valve may be opened
by use of the controller function code Cd41 valve
override control. If power is not available to open the
valve, the area may be evacuated by connecting an
additional hose at the low side access valve.
d. Test the evacuation setup for leaks by backseating
the unit service valves and drawing a deep vacuum
with the vacuum pump and gauge valves open. Shut
off the pump and check to see if the vacuum holds.
Repair leaks if necessary.
e. Midseat the refrigerant system service valves.
f. Open the vacuum pump and electronic vacuum
gauge valves, if they are not already open. Start the
vacuum pump. Evacuate unit until the electronic vac-
uum gauge indicates 2000 microns. Close the elec-
tronic vacuum gauge and vacuum pump valves. Shut
off the vacuum pump. Wait a few minutes to be sure
the vacuum holds.
g. Break the vacuum with clean dry refrigerant 134a gas.
Raise system pressure to roughly 0.2 kg/cm
2
(2 psig),
monitoring it with the compound gauge.
h. Remove refrigerant using a refrigerant recovery sys-
tem.
i. Repeat steps f.and g. one time.
j. Remove the copper tubing and change the filter drier.
Evacuate unit to 500 microns. Close the electronic
vacuum gauge and vacuum pump valves. Shut off the
vacuum pump. Wait five minutes to see if vacuum
holds. This procedure checks for residual moisture
and/or leaks.
k. With a vacuum still in the unit, the refrigerant charge
may be drawn into the system from a refrigerant con-
tainer on weight scales.
Procedure - Partial System
a. If refrigerant charge has been removed from the low
side only, evacuate the low side by connecting the
evacuation set-up at the compressor suction valve,
economizer service connection valves and the liquid
service valve except leave the service valves front-
seated until evacuation is completed.
b. Once evacuation has been completed and the pump
has been isolated, fully backseat the service valves to
isolate the service connections and then continue
with checking and, if required, adding refrigerant in
accordance with normal procedures.
6.3.5 Refrigerant Charge
Checking the Refrigerant Charge
NOTE
To avoid damage to the earth’s ozone layer, use
a refrigerant recovery system whenever remov-
ing refrigerant. When working with refrigerants
you must comply with all local government envi-
ronmental laws. In the U.S.A., refer to EPA Sec-
tion 608.
a. Connect the gauge manifold to the compressor dis-
charge and suction service valves. For units operat-
ing on a water cooled condenser, change over to air
cooled operation.
b. Bring the container temperature to approximately 0C
(32F) or below. Then set the controller set point to
-25C (-13F) to ensure that the suction modulation
valve is fully open. (Position of the suction modulating
valve may be checked at controller function code
Cd01.)
c. Partially block the condenser coil inlet air. Increase the
area blocked until the compressor discharge pressure
is raised to approximately 13 kg/cm
2
(185 psig).
d. On units equipped with a receiver, the level should be
between the glasses. On units equipped with a water-
cooled condenser, the level should be at the center of
the glass. If the refrigerant level is not correct, contin-
ue with the following paragraphs to add or remove re-
frigerant as required.
Adding Refrigerant to System (Full Charge)
a. Evacuate unit and leave in deep vacuum. (Refer to
paragraph 6.3.4.)
b. Place cylinder of R-134a on scale and connect charg-
ing line from cylinder to liquid line valve. Purge charg-
ing line at liquid line valve and then note weight of cyl-
inder and refrigerant.
c. Open liquid valve on cylinder. Open liquid line valve
half-way and allow the liquid refrigerant to flow into
the unit until the correct weight of refrigerant (refer to
paragraph 2.2) has been added as indicated by
scales.
NOTE
It may be necessary to finish charging unit
through suction service valve in gas form, due
to pressure rise in high side of the system.
d. Backseat manual liquid line valve (to close off gauge
port). Close liquid valve on cylinder.
e. Start unit in cooling mode. Run for approximately
10 minutes and check the refrigerant charge.
Adding Refrigerant to System (Partial Charge)
a. Examine the unit refrigerant system for any evidence
of leaks. Repair as necessary. (Refer to paragraph
6.3.3.).
b. Maintain the conditions outlined in paragraph 6.3.5.
c. Fully backseat the suction service valve and remove
the service port cap.
d. Connect charging line between suction service valve
port and cylinder of refrigerant R-134a. Open VAPOR
valve.
e. Partially frontseat (turn clockwise) the suction service
valve and slowly add charge until the refrigerant
appears at the proper level. Be careful not to frontseat
the suction valve fully, if the compressor is operated in
a vacuum, internal damage may result.
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