Alarm 20 — Safety Switch Input Open

What does 20 mean?

This alarm is displayed when an optional safety switch (like a blower overload, loss of phase protector, or supply duct high pressure limit switch) connected to the unit controller is open. This indicates a safety condition has been met, shutting down the unit.

• Activated safety switch (e.g., blower overload tripped).
• Loss of phase power to the motor.
• High pressure in the supply duct.
• Wiring issue with the safety switch.
• Safety switch is not enabled in configuration.

Click steps to track your progress.

1. 1

   Identify which safety switch has been activated.

2. 2

   Reset any tripped overload relays or high-pressure switches.

3. 3

   Check for wiring faults to the safety switch input.

4. 4

   Ensure the safety switch monitoring is correctly enabled in SETUP > INSTALL > CONFIGURATION ID 2, Position 5.

5. 5

   If the condition persists, investigate the underlying cause of the safety switch activation.