10 PFS 155C - 315C OM 135
Filter-Dryers
Change the filter-dryer every scheduled service maintenance of the unit, or when any one of the
following conditions occur:
• Excessive pressure drop is read across the filter-dryer (The maximum recommended pressure drop
across the filter-dryer is shown in Table 2.
Table 2, Filter-dryer pressure drop
Maximum recommended pressure
drop
Percent Circuit Loading PSIG (kPa)
100 10 (69)
75 8 (55.2)
50 5 (34.5)
25 4 (27.6)
• When bubbles occur in the sightglass with normal subcooling
• A partially clogged filter causes a trip on the no liquid run sensor.
• Moisture indicating liquid line sightglass indicates excess moisture.
Pump-down
Note: Pump-down the unit before changing filter-dryer cores, replacing solenoid valves (except
solenoid valve coils), or to change expansion valve.
Unit condensers are sized to hold the entire refrigerant charge. Use method (A) or (B) below to pump-
down the unit.
A. Unit pump-down using the compressor.
1. Go to MicroTech menu number 16.
2. Select “Manual Pump-down”
3. Choose “YES”.
B. Unit Pump-down using a refrigerant transfer pump.
1. Stop the unit by opening the remote start / stop input.
CAUTION
Do not close any liquid line shutoff valves while unit is in operation. Liquid injection and
suction injection must be available at all times.
2. Close all liquid line shutoff valves at the condenser liquid line outlets.
3. When the compressor shuts off, close the discharge line ball valve in each compressor
circuit.
4. Connect a refrigerant transfer pump between the service valve on the evaporator and the
service valve on the top of condenser. Pump all remaining refrigerant out of evaporator,
compressors, and liquid line.
5. Complete pump-down according to EPA refrigerant guidelines before opening the circuit.
6. Servicing of the components may now continue.
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