Adding Refrigerant To System; Adding Full Charge; Adding Partial Charge; Checking For Noncondensibles - Carrier GR-45 Operation And Service

g. Remove refrigerant using a refrigerant recovery sys-
tem.
h. Start vacuum pump and open all valves. Dehydrate
unit to 500 microns Hg vacuum.
i. Close off pump valve, and stop pump. Wait five min-
utes to see if vacuum holds.
j. Charge system. Refer to paragraph 4.8.2

4.8 ADDING REFRIGERANT TO SYSTEM

4.8.1 Checking Refrigerant Charge
The following conditions must be met to accurately
check the refrigerant charge.
a. Coach engine operating at high idle.
b. Unit operating in cool mode for 15 minutes.
c. Head pressure at least 150 psig (10.21 bar). (It may be
necessary to block condenser air flow to raise head
pressure.)
d. Under the above conditions, the system is properly
charged when the refrigerant liquid level is at 1/2 to
3/4 of the lower receiver sight glass. If it is not at the
proper level, add or remove refrigerant to bring it to
the proper level. Refrigerant level should not appear
in the upper sight glass, as this would indicate an
overcharge.

4.8.2 Adding Full Charge

a. Install manifold gauge set at the compressor suction
service valve and service port above the discharge
line check valve. See figure Figure 4-6.
b. Evacuate and dehydrate system. (Refer to paragraph
4.7)
c. Place appropriate refrigerant cylinder on scales. Pre-
pare to charge liquid refrigerant by connect charging
hose from container to center connection on gage
manifold . Purge air from hoses.
d. Note weight of refrigerant and cylinder.
e. Open cylinder valve, backseat discharge valve on
gauge manifold and allow liquid refrigerant to flow
into the high side of the system
f. When correct charge has been added, refer to para-
graph 1.3, close cylinder valve and frontseat man-
ifold discharge valve. At this point, the high side of
the system has been charged but the low side is still in
a vacuum because the liquid line solenoid is normally
closed.
g. Prepare the cylinder as required to allow vapor charg-
ing. Backseat the manifold suction valve and charge
vapor to build 20 to 30 psig (1.36 to 2.04 bar) pres-
sure on the manifold suction gauge. Close cylinder
valve and frontseat suction manifold set.
h. Check charge level in accordance with the procedures
of paragraph 4.8.1.

4.8.3 Adding Partial Charge

a. Install manifold gauge set at the compressor suction
service valve and service port above the discharge
line check valve. See figure Figure 4-6.
b. Place appropriate refrigerant cylinder on scales. Pre-
pare to charge vapor refrigerant by connecting charg-
ing hose from container to center connection on
gauge manifold . Purge air from hoses.
c. Run unit in cool mode for 15 minutes. With suction
service valve midseated open cylinder valve and add
vapor charge until refrigerant level appears in the
lower receiver sight glass. Under the above condi-
tions, the system is properly charged when the refrig-
erant liquid level is at 1/2 to 3/4 of the lower receiver
sight glass. If it is not at the proper level, add or re-
move refrigerant to bring it to the proper level. Re-
frigerant level should not appear in the upper sight
glass, as this would indicate an overcharge.
d. Backseat suction service valve. Close vapor valve on
refrigerant drum and note weight. Remove manifold
gauge set and replace all valve caps.

4.9 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.
b. Check temperature at the condenser and receiver.
c. Check pressure at the compressor discharge service
valve.
d. Check saturation pressure as it corresponds to the
condenser/receiver temperature using the Tempera-
ture-Pressure Chart, Table 4-4.
e. If gauge reading is 3 psig (0.20 bar) or more than the
saturation pressure in step d, noncondensibles are
present.
f. Remove refrigerant using a refrigerant recovery sys-
tem.
g. Evacuate and dehydrate the system. (Refer to para-
graph 4.7.)
h. Charge the unit. (Refer to paragraph 4.8.2.)
4.10 CHECKING AND REPLACING HIGH PRES-
SURE SWITCH
DO NOT USE A NITROGEN CYLINDER
WITHOUT A PRESSURE REGULATOR
DO NOT USE OXYGEN IN OR NEAR A
REFRIGERATION SYSTEM AS AN EX-
PLOSION MAY OCCUR.
a. Disconnect wiring and remove switch from unit. All
units are equipped with a schrader valve at the high
pressure switch connection.
b. Connect switch to a cylinder of dry nitrogen. (See
Figure 4-7.)
4-5
WARNING
WARNING
T-295