Refrigeration Maintenance
131
To check compressor oil level with an
ambient air temperature above 50 F (10 C):
Install a gauge manifold on the compressor.
Operate the unit on cool with a 20 psig (138 kPa)
minimum suction pressure and a 185 psig
(1275 kPa) minimum discharge pressure for 15
minutes or more.
After the unit has maintained the above conditions
for 15 minutes, observe the oil level. The oil
should be 1/4 to 1/2 up in the sight glass.
To check compressor oil level with an
ambient air temperature below 50 F (10 C):
Run the unit through a complete defrost cycle.
After completing the defrost cycle, run the unit on
cool for ten minutes. Observe the oil level. The oil
should be 1/4 to 1/2 up in the sight glass.
If the box is empty, you can run the unit on the
heat cycle instead of the defrost cycle.
NOTE: Use refrigeration compressor oil ONLY.
Polyol Ester P/N 203-513 is required for
R-404A.
To add compressor oil pump down the compressor
and equalize the pressure to slightly positive.
Disconnect the compressor oil filter return line
from the top of the compressor and add the oil.
Reattach the oil filter return line to the
compressor. Evacuate the compressor before
opening the service valves.
High Pressure Cutout Switch
(HPCO)
The HPCO is located on the compressor discharge
manifold. If the discharge pressure rises above
470 psig (3241 kPa), the HPCO opens the HPCO
circuit to the run relay and stops the unit. To test
the HPCO, rework a gauge manifold as shown in
Figure 212 “High Pressure Cutout Manifold” and
use the following procedure.
1. Connect the gauge manifold to the compressor
discharge service valve with a heavy duty,
black jacketed thick wall #HCA 144 hose with
a 900 psig (6204 kPa) working pressure
rating.
2. Use the Service Test Mode to run the unit in
high speed cool.
3. Raise the discharge pressure of the
compressor by blocking the condenser coil air
flow by covering the condenser grilles with
pieces of cardboard. This should increase the
discharge pressure enough to cause the HPCO
to cut out.
4. If the HPCO does not open to de-energize the
run relay and stop the unit, it must be
replaced.
1.
Relief Valve (66-6543)
2.
O-Ring (33-1015)
3.
Adapter Tee Weather Head No. 552X3
Figure 212: High Pressure Cutout Manifold
CAUTION: If the discharge pressure
reaches 477 psig (3289 kPa), shut the unit
off immediately. Do not allow the
discharge pressure to exceed 477 psig
(3289 kPa).
