Carrier 69NT40-541-300, Операция и обслуживание, Страница: 92 / 152

6 − 4 T − 318
e. 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.
f. Break the vacuum with clean dry refrigerant 134a
gas. Raise system pressure to approximately
0.2kg/cm (2psig), monitoring it with the compound
gauge.
g. Remove refrigerant using a refrigerant recovery
system.
h. Repeat steps e.and f. one time.
i. 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.
j. With a vacuum still in the unit, the refrigerant charge
may be drawn into the system from a refrigerant con-
tainer on weight scales. Continue to paragraph 6.7.
6.6.4 Procedure - Partial System
a. If the refrigerant charge has been removed from the
compressor for service, evacuate only the compres-
sor by connecting the evacuation set-up at the com-
pressor service valves. Follow evacuation proce-
dures of the preceding paragraph except leave
compressor service valves frontseated until evacua-
tion is completed.
b. If refrigerant charge has been removed from the low
side only, evacuate the low side by connecting the
evacuation set-up at the compressor service valves
and liquid service valve except leave the service
valves frontseated until evacuation is completed.
c. 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.
6.7 REFRIGERANT CHARGE
WARNING
EXPLOSION HAZARD: Failure to follow this
WARNING can result in death, serious
personal injury and / or property damage.
Never use air or gas mixtures containing
oxygen (O
2
) for leak testing or operating the
product.
Charge Only With R
− 134a: Refrigerant must
conform to AHRI Standard 700
specification.
6.7.1 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., refer to EPA
section 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
1.7 ° C (35 ° F) or -17.8 ° C (0 ° F). Set the controller set
point to -25 ° C (-13 ° F) to ensure that the suction mod-
ulation valve is at maximum allowed open position.
c. Partially block the condenser coil inlet air. Increase
the area blocked until compressor discharge pres-
sure is raised to approximately 12kg/cm (175psig).
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.
6.7.2 Adding Refrigerant to System (Full Charge)
a. Evacuate unit and leave in deep vacuum (refer to
paragraph 6.6).
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 (refer
to section paragraph 6.7.3).
d. Backseat manual liquid line valve (to close off gauge
port). Close liquid valve on cylinder.
e. Start unit in cooling mode. Run approximately
10 minutes and check the refrigerant charge.
6.7.3 Adding Refrigerant to System (Partial
Charge)
a. Examine the unit refrigerant system for any evidence
of leaks. Repair as necessary (refer to paragraph
6.5).
b. Maintain the conditions outlined in paragraph 6.7.1
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.