Adding Refrigerant To System; Checking Refrigerant Charge; Adding Full Charge; Adding Partial Charge - Carrier 68G5-105 Series Operation & Service Manual

4.7 ADDING REFRIGERANT TO SYSTEM

4.7.1 Checking Refrigerant Charge

a. Connect an accurate high pressure gauge to the
discharge service port at the compressor. (See
Figure 4-4)
b. The condenser coil should be clean and free of any
debris.
c. Coach engine operating at high idle (800--1000RPM).
d. The compressor should be fully loaded (six cylinder
operation).
e. Unit must be operating in the cool mode until the
discharge pressure has stabilized (3 to 5 minutes)
and the interior temperature is between 70 and 80_F
(21.1 and 26.7_C).
f. Discharge pressure at least 150 psig (10.21 BAR)
and stable for R-134a systems (It may be necessary
to partially block condenser airflow to raise discharge
pressure).
g. Observe the Liquid Line Sight Glass and use the
following chart to determine the condition of the
refrigerant charge:
Table 4-1. Checking Refrigerant Charge
Sight Glass
Observation
Liquid present
Clear of all bubbles
Liquid present
Occasional bubbles
present
Liquid present
Many bubbles present
h. If the conditions in steps b. thru f. are met and there is
still doubt about the refrigerant charge level use
Table 4-2:
Table 4-2. Checking Refrigerant Charge
Condenser Inlet Air
Temperature
_ _ _ _ F _ _ _ _ C
60 16
65 18
70 21
75 24
80 27
85 29
90 32
95 35
i. With an accurate temperature gauge, measure the
condenser inlet air temperature.
NOTE
Do not use a temperature gun as it measures
surface temperature and not air temperature.
T-312
Condition
Good/Possible over
charge -- Continue to step
i.
Good
Possible under charge --
Continue to step i.
Discharge Pressure
Range
PSIG BAR
110--135 7.48--9.19
120--145 8.16--9.87
130--155 8.85--10.55
140--165 9.53--11.23
150--175 10.21--11.91
160--186 10.89--12.66
175--200 11.91--13.61
190--212 12.93--14.42
1. If the actual discharge pressure is higher than the
discharge pressure range, the system may be over
charged.
2. If the actual discharge pressure is lower than the
discharge pressure range, the system may be under
charged.
3. If the actual discharge pressure is in the discharge
pressure range, the system charge is adequate.
Many system related problems will effect
system pressures. Use Table 3-5 General
System Troubleshooting Procedures to
determine other possible causes before
adding or removing refrigerant.

4.7.2 Adding Full Charge

a. Evacuate and dehydrate system. (Refer to paragraph
4.6.)
b. Place appropriate refrigerant cylinder on scales and
connect charging hose from container to filter-drier
inlet valve. Remove air from hoses.
c. Note weight of refrigerant and container.
d. Open liquid valve on refrigerant container. Midseat
filter-drier inlet valve and allow refrigerant to flow into
the unit. Refer to paragraph 1.3 for correct charge.
e. When drum weight (scale) indicates that the correct
charge has been added, close liquid line valve on
drum and backseat the filter-drier inlet valve.

4.7.3 Adding Partial Charge

Refrigerant charge is critical, when adding
charge to the unit do not add any more
charge to the system after bubbles have
been eliminated from the sight glass.
a. Start the vehicle engine and allow the system to
stabilize. (Refer to 4.7.1a. to f.)
b. Connect charging hose from appropriate refrigerant
cylinder vapor valve to compressor suction service
valve.
c. Open cylinder valve and add vapor charge. Under the
above conditions, the system is properly charged
when the condenser sight glass is clear with
occasional bubbles showing. Add or remove
refrigerant until the proper charge is obtained.
d. Backseat suction service valve. Close vapor valve on
refrigerant drum. Replace all valve caps.

4.8 CHECKING FOR NONCONDENSIBLES

To check for noncondensibles, proceed as follows:
a. Stabilize system to equalize pressure between the
suction and discharge side of the system. The engine
needs to be off for several hours.
b. Measure temperature at any of the copper tubing in
the condenser.
c. Check pressure at the compressor discharge service
valve.
d. Determine saturation pressure as it corresponds to
the condenser
Temperature-Pressure Chart, Table 4-6.
4-6
NOTE
NOTE
temperature using the