Pt (Pt1, Pt2) PID Feedback Signal Loss fault in Toshiba drive
Pt (Pt1, Pt2) PID Feedback Signal Loss fault in Toshiba drive
Description In PID control mode (typically used for maintaining constant pressure in plumbing or airflow in HVAC), the drive relies on a sensor (transducer) to tell it the current system status. "Pt" indicates that this feedback signal has been lost. Unlike a standard analog input loss, this is specific to the PID loop logic. If the drive cannot see the pressure, it cannot regulate the speed, so it trips to prevent over-pressurizing pipes. Causes
1. Sensor Failure: The pressure transducer or flow meter has failed.
2. Power Supply: The 24VDC power supply feeding the sensor has died or fused.
3. Wiring: The feedback wire connected to the VFD input is broken.
4. Range Mismatch: The sensor is reading a value outside the programmed range (e.g., negative pressure or extremely high pressure interpreted as a fault). Solution Locate the transducer. Measure the voltage supply to it (usually 24VDC). If the sensor has no power, check the VFD's 24V output terminal (often labeled P24). If P24 is dead, the drive's internal supply is blown (often due to a short in field wiring). You may need an external 24V power supply.
If power is present, measure the return signal (4-20mA or 0-10V) while the system is pressurized. If the pipe has pressure but the sensor reads 4mA (or 0V), the sensor is dead.
Also, check the "Feedback Loss Detection" parameters. Sometimes air bubbles in a pipe cause momentary signal drops. Increasing the "Feedback Loss Delay" time (e.g., to 5 seconds) can prevent nuisance tripping caused by air pockets or turbulence.
Description In PID control mode (typically used for maintaining constant pressure in plumbing or airflow in HVAC), the drive relies on a sensor (transducer) to tell it the current system status. "Pt" indicates that this feedback signal has been lost. Unlike a standard analog input loss, this is specific to the PID loop logic. If the drive cannot see the pressure, it cannot regulate the speed, so it trips to prevent over-pressurizing pipes. Causes
1. Sensor Failure: The pressure transducer or flow meter has failed.
2. Power Supply: The 24VDC power supply feeding the sensor has died or fused.
3. Wiring: The feedback wire connected to the VFD input is broken.
4. Range Mismatch: The sensor is reading a value outside the programmed range (e.g., negative pressure or extremely high pressure interpreted as a fault). Solution Locate the transducer. Measure the voltage supply to it (usually 24VDC). If the sensor has no power, check the VFD's 24V output terminal (often labeled P24). If P24 is dead, the drive's internal supply is blown (often due to a short in field wiring). You may need an external 24V power supply.
If power is present, measure the return signal (4-20mA or 0-10V) while the system is pressurized. If the pipe has pressure but the sensor reads 4mA (or 0V), the sensor is dead.
Also, check the "Feedback Loss Detection" parameters. Sometimes air bubbles in a pipe cause momentary signal drops. Increasing the "Feedback Loss Delay" time (e.g., to 5 seconds) can prevent nuisance tripping caused by air pockets or turbulence.
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