Refrigeration Service Operations
154
Use the following procedure to change the
compressor oil filter.
1. Pump down the low side and equalize the
pressure to slightly positive.
2. Front seat the discharge and suction service
valves. Recover the remaining refrigerant
from the compressor.
3. Disconnect the oil lines from the compressor
oil filter. Hold the oil filter with back-up
wrench on the hex behind the ORS fitting.
4. Remove the clamp and the compressor oil
filter.
5. Coat the new O-rings with clean compressor
oil and place them in the ORS fittings on the
ends of the new compressor oil filter.
6. Fasten the new compressor oil filter in place
with the clamp.
7. Attach and tighten the oil lines to the
compressor oil filter. Hold the oil filter with a
back-up wrench on the hex behind the ORS
fitting.
8. Evacuate the compressor and filter to a
maximum of 500 microns to remove trapped
air.
9. Open the service valves, operate the system,
and check the compressor oil filter for leaks.
Checking Compressor Oil
Pressure
The oil pressure at the oil pressure access port
varies with the suction pressure in the compressor.
Therefore, we need to calculate the “net oil
pressure” to determine the actual compressor oil
pressure. The net oil pressure is the pressure at the
oil pressure access port minus the suction pressure
below the throttling valve. Use the following
procedure to check the compressor oil pressure.
1. Attach a suitable oil pressure gauge to the oil
pressure access port on the compressor oil
filter.
2. Attach the low pressure gauge of a gauge
manifold to the fitting on the side of the
throttling valve (or suction valve adapter).
This fitting allows you to monitor the suction
pressure in the compressor below the
throttling valve.
3. Start the unit and note the pressure at the oil
pressure access port and the suction pressure
below the throttling valve.
4. Subtract the suction pressure below the
throttling valve from the pressure at the oil
pressure access port to get the net oil pressure.
5. The net oil pressure should be at least 20 psig
(138 kPa). If the net oil pressure is low, first
check the compressor oil level, then check the
compressor oil pump and relief valve.
1.
Oil Pressure Access Port
2.
Inlet Fitting
3.
Outlet Fitting
Figure 241: Compressor Oil Filter
2
1
3
AEA718
Pressure at Oil Pressure Access Port
– Suction Pressure Below Throttling Valve
= Net Oil Pressure
