CRR-20 & CRR-40, September 1999
Refrigeration Maintenance and Service Operations
Low Side Pump Down
6-7
8.
Connect the charging hose to a source of nitrogen. Adjust
the pressure regulator to 1380 kPa, 13.80 bar, 200 psig.
See “Using Pressurized Nitrogen” in this manual chapter.
CAUTION: Nitrogen (N2 ) is under 15,170 kPa,
151.70 bar, 2200 psig pressure in a full cylinder
at 21 C (70 F). DO NOT use oxygen, acetylene or
any other type of pressurized gas in the system.
9.
Pressurize the system with nitrogen to 1380 kPa, 13.80
bar, 200 psig.
10. Close the supply valve on the nitrogen bottle.
11. Use an electronic leak tester to inspect all joints and con-
nections. (Use a soap solution as an alternative test com-
ponent.)
NOTE: If system leakage is indicated, loosen
supply line hose fittings to release pressure.
Repair leakage condition.
12. If system repair is necessary, recheck system after repairs
are completed.
Low Side Pump Down
1.
Install the gauge manifold on the compressor.
2.
Set the controller setpoint temperature well below the
return air temperature and operate the unit in the Cool
mode until the temperature stabilizes (at least 5 minutes).
3.
Close the receiver tank outlet valve. Allow the unit to
operate until it reaches -15 to -40 kPa, -0.15 to -0.40 bar, 5
to 11 in. vacuum on the suction pressure gauge (3-5 min-
utes). Then shut the unit down manually with the On/Off
switch.
CAUTION: Never open the low side to the atmos-
phere while it is in a vacuum. Air and moisture
will be drawn in and contaminate the refrigerant
system.
4.
To place the unit back in service, open the receiver tank
outlet valve and turn the On/Off switch ON.
Refrigerant Charge
The refrigerant charge should be checked during pretrip and
routine maintenance inspections. A low charge of refrigerant
will cause the container temperature to rise due to the lack of
liquid refrigerant at the expansion valve even though the unit
is operating in a cooling mode. The refrigerant charge can be
checked by inspecting the receiver tank sight glass.
NOTE: See “Receiver Tank Sight Glass” under Unit
Instruments in the Operating Instructions chapter for
information about checking the moisture indicator in
the sight glass.
Unit Refrigerant Charge:
• Standard receiver: 4.9 kg (10.8 lb) of R-134a.
• Water-cooled condenser-receiver: 5.45 kg (12.0 lb) of R-
134a.
Checking the Refrigerant Charge
1.
Inspect the receiver tank sight glasses with the unit operat-
ing in COOL.
2.
a.
Standard Receiver Tank:
• If the balls FLOAT in the sight glass at any time,
R-134a charge is OK.
• If the balls DO NOT FLOAT, R-134a charge may
be low.
b.
Water-cooled Condenser-receiver Tank with two
sight glasses (Before 8/99):
• If the BOTTOM sight glass balls FLOAT, the R-
134a charge level is OK.
• If the BOTTOM sight glass balls DO NOT FLOAT,
R-134a charge level may be low. Go to step 3.
Standard Receiver Tank
1. Sight Glass: Refrigerant charge is OK if ball
FLOATS at any time
2. Service Fitting
3. Fusible Plug
Содержание CRR-20
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