Applicable Systems
Copeland Scroll Compressor (CoreSense/Comfort Alert)
Symptoms
The CoreSense/Comfort Alert module LED flashes 4 times, indicating a Pressure Switch Trip. The oil pressure safety switch or discharge pressure switch has tripped, shutting down the compressor to prevent mechanical damage from low lubrication or excessive discharge pressure.
Possible Causes
- Oil pressure too low due to low oil charge or faulty oil pump
- Discharge pressure too high due to condenser fan failure or dirty condenser coil
- Oil pressure switch itself faulty, tripping at normal oil pressure
- System has a refrigerant overcharge causing excessive discharge pressure
- Expansion valve or capillary tube restricted causing abnormal pressure ratios
Troubleshooting Steps
- Step 1: Check the discharge pressure gauge against the system design pressure
Discharge pressure is within the normal operating range for the ambient condition - Step 2: Check the oil level sight glass on the compressor crankcase (if equipped)
Oil level is between the 1/3 and 2/3 marks on the sight glass - Step 3: Verify the condenser fan is running and the condenser coil is clean
Fan operates at full speed; coil fins are clean and unobstructed - Step 4: Check the oil pressure switch setting and wiring
Switch opens at the correct pressure threshold (typically 7-10 psi below normal) - Step 5: If oil level is low, check for oil in the system and add oil as needed
Oil level returns to the normal range in the sight glass
How to Reset
To reset: 1) Fix the pressure or oil issue. 2) Press the manual reset button on the oil pressure safety switch (if equipped). 3) The module will clear the alert after the reset. Caution: Do not bypass the oil pressure safety switch; low oil pressure will destroy the compressor bearings within minutes.
Common Replacement Parts
- 022-0010: Copeland oil pressure switch (Match the pressure setting to the compressor model specification)
Frequently Asked Questions
- Q: What is the oil pressure safety switch?
The oil pressure safety switch monitors the difference between oil pump discharge pressure and crankcase (suction) pressure. If the net oil pressure drops below a safe threshold, the switch opens and shuts down the compressor to prevent bearing damage.
- Q: How can I tell if the discharge pressure is too high?
Compare the discharge pressure to the pressure-temperature chart for the refrigerant being used. If the actual pressure is significantly higher than the saturated pressure at the condensing temperature, there may be air in the system, an overcharge, or condenser airflow problems.
Source: Copeland Application Engineering Bulletin AE4-1303, CoreSense Diagnostics
Category: Refrigeration