4-10
T-312
guage. The second unloader should energize (check
for magnetism at the unloader coil) increasing suction
pressure by 3 to 5 psig.
f. Slowly open the suction valve until the suction guage
reads 28 psig. The first unloader should de--energize
decreasing suction pressure by 3 to 5 psig to show it
is operating properly.
g. Back seat the suction service valve, remove the
guage(s) to resume normal operation.
4.12.4 Compressor Oil Level
NOTE
The compressor should be fully loaded (six
cylinder operation); the unit should be fully
charged and the compressor crankcase
should be warm to the touch.
a. Start the unit and allow the system to stabilize.
b. Check the oil sight glass on the compressor to ensure
that no foaming of oil is present after 20 minutes of
operation. If oil is foaming excessively after 20
minutes of operation, check the refrigerant system for
flood-back of liquid refrigerant. Correct this situation
before proceeding.
c. Check the level of oil in oil level sight glass
immediately after shutting down the compressor. The
lowest level visible should be at the bottom of the
sightglass and the highest level should be at the
middle of the sight glass. (See Figure 4-9)
4.12.5 Adding Oil with Compressor in System
Two methods for adding oil are: the oil pump method
and closed system method.
NOTE
Special care must be taken when working
with POE oil that is used with HFC
refrigerants such as R--134a, as POE oil is
very hygroscopic. (POE oil will easily absorb
water.) Do not leave POE oil containers
open to the atmosphere.
4.12.5.1. Oil Pump Method
a. One compressor oil pump that may be purchased is a
Robinair part no. 14388. This oil pump adapts to one
U.S. gallon
(3.785 liters)
metal refrigeration oil
container and pumps 2-1/2 ounces
(72.5 milliliters)
per stroke when connected to the suction service
valve port. Also, there is no need to remove pump
from can after each use.
b. When the compressor is in operation, the pump
check valve prevents the loss of refrigerant while
allowing servicemen to develop sufficient pressure to
overcome the operating suction pressure to add oil,
as necessary.
c. Backseat suction service valve and connect oil
charging hose to port. Crack open the service valve
and remove air from the oil hose at the oil pump. Add
oil as necessary.
NOTE
Allow time (at least 60 seconds) for the oil
to flow thru to the crankcase and show on
the sightglass.
4.12.5.2. Closed System Method
a. Install manifold gauge set. (See Figure 4-3)
b. Unplug the suction pressure transducer (SPT).
c. Frontseat the compressor suction service valve by
turning clockwise.
d. Start the unit and run in cooling until 10 ”/hg (25.4
cm/hg) of vacuum is reached. Shut the system down
and tag out system power source.
e. Frontseat the compressor discharge service valve
and wait 5 minutes to verify vacuum is maintained.
f. Remove the crankcase oil fill plug on the side of the
crankcase.
g. Replace the crankcase oil fill plug with a Carrier
Service Parts no. OTBO889 fitting. This fitting has a
1/4 inch flare access port with a shrader valve.
h. Using refrigerant hoses designed for vacuum service,
connect a vacuum pump to center connection of
manifold gauge set.
CAUTION
Care Must Be Taken To Ensure That The
Manifold Common Connection Remains
Immersed In Oil At All Times Or Air And
Moisture Will Be Drawn Into The System.
i. Connect a refrigerant hose with a shrader depressor
to the fitting described in step g. above, put the other
end of the hose in a fresh oil container.
j. Evacuate the compressor and observe the oil level in
the compressor crankcase. When the desired oil
level is reached, disconnect the hose from the fitting.
k. Reinstall the crankcase oil fill plug.
l. Using refrigerant hoses designed for vacuum service,
connect a vacuum pump to center connection of
manifold gauge set.
Evacuate system to 500
microns. Close off pump valve, isolate vacuum gauge
and stop pump. Wait 5 minutes to verify that vacuum
holds.
m.Once vacuum is maintained, backseat compressor
service valves and disconnect manifold gauge set.
n. Reconnect the suction pressure transducer(SPT).
4.12.6 Adding Oil to Service Replacement
Compressor
Service replacement compressors may or may not be
shipped with oil.
If the replacement compressor is shipped without oil,
add oil through the oil fill plug. (See Figure 4-9)
4.12.7 Removing Oil from the Compressor:
a. If the lowest oil level observed in paragraph 4.12.4,
step c., is above middle of the sight glass on
compressor crankcase, oil must be removed from the
compressor by performing the following procedure. If
lowest oil level visible is below bottom of the
sightglass, oil must be added to the compressor by
following the procedure in paragraph 4.12.5.
