Carel AL014

What does Carel AL014 mean?

AL014 on the Carel FLSTDmSCHE screw chiller controller means the discharge pressure probe S3 on EVD Circuit 1 — the pressure transducer monitoring the high side of Compressor 1 — is broken or disconnected. Without discharge pressure feedback, the EVD driver cannot protect the compressor from high-pressure events, so the controller shuts down Compressor 1 in a controlled sequence. AL014 resets automatically once a valid probe signal is restored.

Symptoms

• AL014 displayed on pCO5 terminal with Compressor 1 in controlled shutdown
• EVD Driver 1 discharge pressure reading absent or out of range
• Circuit 2 may continue operating normally if its probe is intact

Common causes

• Discharge pressure transducer on Circuit 1 has failed — signal output below 4 mA or outside ratiometric range
• Wiring break or loose terminal on the S3 probe cable between the high-pressure side and EVD Driver 1
• Refrigerant or oil contamination of the pressure transducer port damaging the sensing element
• Connector corrosion at the EVD driver S3 input terminal

Diagnostic steps

1. 01

   Locate the Circuit 1 discharge pressure transducer

   Refer to the chiller wiring diagram to identify the S3 discharge pressure transducer on Circuit 1's high side and trace the cable back to EVD Driver 1's S3 input terminals.

2. 02

   Inspect wiring and terminal connections

   Power down EVD Driver 1 and inspect the S3 cable for wiring breaks, loose screws, and connector corrosion. Pay particular attention to the cable near the hot high-pressure line where heat damage is common.

3. 03

   Measure transducer output

   Reconnect power and measure the S3 transducer output with a multimeter. For a 4–20 mA transducer at standstill, expect approximately 4 mA at minimum pressure. No output or output below 3.5 mA confirms transducer failure.

4. 04

   Replace the discharge pressure transducer

   If the transducer has failed, replace it with a CAREL-compatible unit of the correct pressure range and signal type. The system must be recovered before removing a transducer from a live refrigerant circuit.

5. 05

   Verify alarm auto-reset and compressor restart

   After probe replacement and signal verification, AL014 should clear automatically within 10 seconds. Confirm Compressor 1 restarts and discharge pressure reads correctly on the pCO5 display.

When to call a professional

Discharge pressure transducer replacement on the high side of a live refrigerant circuit requires EPA 608 certification for refrigerant recovery, and proper nitrogen pressure testing after reinstallation. A licensed refrigeration mechanic must perform this work. If the discharge pressure values after repair indicate the circuit has been operating in an unsafe pressure range, a full refrigerant system audit is warranted.