Adding Partial Charge; Checking For Noncondensibles; Checking And Replacing High Pressure Cutout Switch; Checking High Pressure Switch - Carrier CAPRI-280 Operation And Service Manual

c. Note weight of refrigerant and cylinder.
d. Open liquid valve on refrigerant container. Midseat
filter-drier inlet valve and allow refrigerant to flow
into the unit. Correct charge will be found in section
1.3.
e. When cylinder 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

a. Start the vehicle engine and allow unit to stabilize.
b. Place appropriate refrigerant cylinder on scales and
connect charging hose from container vapor valve to
compressor suction service valve.
c. Run unit in cool mode for 15 minutes. With suction
service valve midseated, remove air from hose at
refrigerant cylinder. Open cylinder valve and add
vapor charge until refrigerant level appears in the
lower receiver sight glass. Under the above
conditions, the system will be properly charged when
the lower receiver sight glass appears full of
refrigerant. Add or remove refrigerant until the
proper level is obtained. Refrigerant level should not
appear in the upper sight glass, as this would indicate
and overcharge.
d. Backseat suction service valve. Close vapor valve on
refrigerant drum and note weight. 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.
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-Pressure Chart, Table 4-4.
e. If gauge reading is 3 psig (21 kPa) or more than the
calculated P/T pressure in step d, noncondensibles
are present.
f. Remove refrigerant using a refrigerant recovery
system.
g. Evacuate and dehydrate the system. (Refer to
section 4.6.)
h. Charge the unit. (Refer to section 4.7.)
T-283
temperature using
4.9 CHECKING AND REPLACING HIGH
PRESSURE CUTOUT SWITCH
4.9.1

Checking High Pressure Switch

!
DO NOT USE A NITROGEN CYLINDER
WITHOUT A PRESSURE REGULATOR.
DO NOT USE OXYGEN IN OR NEAR A
REFRIGERATION SYSTEM OR AS AN
EXPLOSION MAY OCCUR.
a. Remove switch from unit. All units are equipped
with schrader valves at the high pressure switch
connection.
b. Connect an ohmmeter across switch terminals. If the
switch is good, the ohmmeter will indicate no
resistance, indicating that the contacts are closed.
c. Connect switch to a cylinder of dry nitrogen. (See
Figure 4-4.).
1
2
3
Figure 4-3. Checking High Pressure Switch
d. Set nitrogen pressure regulator higher than cutout
point on switch being tested. (See section 1.3.)
e. Open cylinder valve. Slowly open the regulator valve
to increase the pressure until it reaches cutout point.
The switch should open, which is indicated by an
infinite reading on an ohmmeter (no continuity).
f. Close cylinder valve and release pressure through the
bleed-off valve. As pressure drops to cut-in point, the
the
switch contacts should close, indicating no resistance
on the ohmmeter.
g. Replace switch if it does not function as outlined
above. (Refer to section 4.9.2.)
4.9.2

Replacing High Pressure Switch

a. The high pressure switch is equipped with schrader
valve to allow removal and installation without
pumping the unit down.
b. Disconnect wiring from defective switch.
c. Install new cutout switch.
d. Check switch operation. (Refer to section 4.9.1.)
4-4
WARNING
4
1. Cylinder Valve
5
and Gauge
2. Pressure Regulator
3. Nitrogen Cylinder
4. Pressure Gauge
(0 to 400 psig =
6
0 to 2.8 mPa)
5. Bleed-Off Valve
6. 1/4 inch Connection
!