Applicable Systems
Copeland Scroll Compressor (CoreSense/Comfort Alert)
Symptoms
The CoreSense/Comfort Alert module LED flashes 2 times, indicating a Phase Reversal fault. The compressor may be running backward, which can cause low compression, high current, and potential mechanical damage.
Possible Causes
- Two of the three-phase power leads are swapped at the terminal block
- Utility power phase rotation changed after maintenance or reconnection
- Motor starter or contactor rewired incorrectly after replacement
- Phase rotation changed after generator switch-over
Troubleshooting Steps
- Step 1: Check the phase rotation at the compressor terminals with a phase rotation tester
Phase rotation is A-B-C (clockwise) matching the compressor nameplate - Step 2: If reversed, swap any two of the three power leads at the terminal block
Phase rotation tester confirms correct A-B-C rotation - Step 3: Verify the compressor is now running in the correct direction by checking discharge pressure
Discharge pressure rises to normal operating range - Step 4: Check suction and discharge temperatures to confirm proper compression
Discharge temperature is higher than suction by the expected amount - Step 5: If alarm persists after correcting rotation, check the module wiring to the contactor
Module control wiring is correct and contactor coil energizes properly
How to Reset
To reset: 1) Swap two phase leads to correct the rotation. 2) The module will auto-reset. 3) If manual reset is required, press the reset button on the module. Caution: Running a scroll compressor backward for extended periods can damage the scroll mechanism.
Frequently Asked Questions
- Q: How do I know if the compressor is running backward?
A scroll compressor running backward will have low discharge pressure, high suction pressure, and may make an unusual humming sound. The CoreSense module detects this via the phase rotation and flashes Alert Code 2.
- Q: Why would the phase rotation change?
Phase rotation can change if the utility company reconfigures their lines, if a motor starter is replaced with different wiring, or if a backup generator with different rotation is switched in. Always check phase rotation after any electrical service work.
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Source: Copeland Application Engineering Bulletin AE4-1303, CoreSense Diagnostics
Category: Refrigeration
Published: 2026-09-26
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