Safe stop activated by HP (High Pressure) switch trip

What does #68 mean?

The system has initiated a safe stop due to the High Pressure (HP) switch tripping. This indicates that the system's internal pressure has exceeded its safe operating limits, triggering a protective shutdown to prevent damage to the compressor or other components within the refrigeration circuit. The system will not operate until this condition is cleared.

• Blocked or restricted discharge line (e.g., clogged condenser, closed manual valve V10) causing a rapid pressure increase in the system.
• Cooling fan failure or insufficient airflow across the condenser, leading to inadequate heat rejection and elevated pressure.
• Overcharge of refrigerant or process fluid beyond system design limits, resulting in higher operating pressures.
• High Pressure (HP) switch (e.g., PS-2) malfunction or incorrect calibration, tripping prematurely at normal operating pressures.
• Contamination or non-condensable gases within the system, increasing overall system pressure beyond safe limits.

Click steps to track your progress.

1. 1

   Verify the reading of the discharge pressure transducer (e.g., PT-1) against a calibrated mechanical pressure gauge at the high-pressure side.

2. 2

   Inspect the condenser coils for dirt, debris, or obstructions blocking airflow; clean as necessary using appropriate methods.

3. 3

   Check the operation of the condenser fan motor(s) (e.g., M2) and verify correct rotation and airflow volume.

4. 4

   Measure the opening/closing pressure of the High Pressure (HP) switch (e.g., PS-2) using a controlled pressure source and verify its setting (if adjustable).

5. 5

   Check for any closed manual isolation valves (e.g., V10) or damper positions in the discharge piping that could restrict flow.