Carrier 69NT40-541-505, Operation And Service Manual, Page: 96 / 143

T-368 7–4
Figure 7.4 Refrigeration System Service Connec-
tions
1. Discharge Service Valve
2. Compressor
3. Suction Service Valve
4. Receiver or Water Cooled Condenser
5. Liquid Service Valve
6. Vacuum Pump
7. Low Side Hose
8. Center Hose
9. High Side Hose
10. Electronic Vacuum Gauge
11. Manifold Gauge Set
12. Refrigerant Cylinder
13. Reclaimer
- - - - -
7.6.3 Complete System
a. Remove all refrigerant using a refrigerant recov-
ery system.
b. The recommended method to evacuate and
dehydrate the system is to connect three evacu-
ation hoses (see
Figure 7.4 ) to the vacuum
pump and refrigeration unit. Be sure the service
hoses are suited for evacuation purposes.
c. Test the evacuation setup for leaks by backseat-
ing 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.
d. Midseat the refrigerant system service valves.
e. Open the vacuum pump and electronic vacuum
gauge valves, if they are not already open. Start
the vacuum pump. Evacuate unit until the elec-
tronic vacuum gauge indicates 2000 microns.
Close the electronic 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 approxi-
mately 0.2kg/cm
2
(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 container on weight scales. Continue
to
Section 7.7 .
7.6.4 Procedure - Partial System
a. If the refrigerant charge has been removed from
the compressor for service, evacuate only the
compressor by connecting the evacuation set-
up at the compressor service valves. Follow
evacuation procedures of the preceding para-
graph except leave compressor service valves
frontseated until evacuation is completed.
b. If refrigerant charge has been removed from the
low side only, evacuate the low side by connect-
ing the evacuation set-up at the compressor ser-
vice 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 ser-
vice valves to isolate the service connections
and then continue with checking and, if required,
adding refrigerant in accordance with normal
procedures.
7.7 REFRIGERANT CHARGE
WARNING
!
EXPLOSION HAZARD: Failure to follow
this WARNING can result in death, seri-
ous 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 spec-
ification.
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