Carrier 69NT40--541--200 TO 299, Операция и обслуживание

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6-3 T--317
The refrigeration unit is now ready for repair, and/or
component replacement.
8. Pressurize the system with nitrogen and R-134a,
and leak test the entire system.
9. Connect the vacuum pump to the center hose on
the manifold gauge set, and thoroughly evacuate
the system to 500 microns.
10. Charge the system with the correct weight (refer to
unit model plate, see Figure 2-1 for location) of
refrigerant R-134a using an accurate weight scale.
11. Run test the unit.
When it is determined that the unit is performing
normally, the unit should be sealed to its original
hermetic state as explained below.
12. Use the process tube pinch-off tool to seal the tubes
before the 3/8 inch flare assembly (one tube at a
time, if necessary).
13. Vent the line to the gauge set and tighten. Check for
refrigerant leaks after the pinch-off tool, monitor the
gauge set for a pressure rise. If there is a pressure
rise, tighten the pinch-off tool until there is no
pressure rise at the gauge set.
14. Leave the pinch-off tool in place, and remove the
fittings from the liquid line or suction line process
tube.
WARNING
Do not remove the pinch-off tool from the
process
tubes until the following
procedures are completed.
15. Using the tubing cutter, cut-off the excess tubing as
close to the pinch-off tool as possible.
16. Use an oxyacetylene torch to braze the exposed
end of the process tubes.
17. Remove the pinch-off tool and leak test the process
tubes at the brazed end.
18. Install both baffle plates, then connect the tube
clamp to the baffle plate on the liquid line process
tube.
6.5 REFRIGERANT LEAK CHECKING
WARNING
Never use air or gases containing oxygen
for leak testing or operating refrigerant
compressors. Pressurized mixtures of air
or gases containing oxygen can lead to ex-
plosion.
a. The recommended procedure for finding leaks in a
system is with a R-134a electronic leak detector.
Testing joints with soapsuds is satisfactory only for
locating large leaks.
b. If the system is without refrigerant, charge the system
with refrigerant 134a to build up pressure between 2.1
to 3.5 kg/cm
@
(30 to 50 psig). Remove refrigerant cyl-
inder and leak-check all connections.
NOTE
Only refrigerant 134a should be used to pres-
surize the system. Any other gas or vapor will
contaminate the system, which will require
additional purging and evacuation of the sys-
tem.
c. If required, remove refrigerant using a refrigerant
recovery system and repair any leaks.
d. Evacuate and dehydrate the unit. (Refer to paragraph
6.6.)
e. Charge unit per paragraph 6.7.
6.6 EVACUATION AND DEHYDRATION
6.6.1 General
Moisture is the deadly enemy of refrigeration systems.
The presence of moisture in a refrigeration system can
have many undesirable effects. The most common are
copper plating, acid sludge formation, “freezing-up” of
metering devices by free water, and formation of acids,
resulting in metal corrosion.
6.6.2 Preparation
a. Evacuate and dehydrate only after pressure leak test.
(Refer to paragraph 6.5.)
b. Essential tools to properly evacuate and dehydrate
any system include a vacuum pump (8 m 3 /hr = 5 cfm
volume displacement) and an electronic vacuum
gauge. (The pump is available from Carrier Trans-
icold, P/N 07-00176-11.)
c. If possible, keep the ambient temperature above
15.6
_
C (60
_
F) to speed evaporation of moisture. If
the ambient temperature is lower than 15.6
_
C
(60
_
F), ice might form before moisture removal is
complete. Heat lamps or alternate sources of heat
may be used to raise the system temperature.
d. Additional time may be saved during a complete sys-
tem pump down by replacing the filter-drier with a
section of copper tubing and the appropriate fittings.
Installation of a new drier may be performed during
the charging procedure.
6.6.3 Procedure - Complete system
a. Remove all refrigerant using a refrigerant recovery
system.