Condenser Temperature Sensor Failure

Issue:

Condenser Temperature Sensor Failure

Resolution:

• This diagnostic occurs when there is not a valid signal on the condenser temperature sensor input on the SCM (1U49) used on 20-30 ton units or the MCM (1U49) used on 40-60 ton units.  
• The sensor has to be in the range of 55° F to 209° F (approximately 500,000 to 700 ohms).  
• All IntelliPak chiller units ship with the condenser temperature sensor(s) as standard, located on the U-bend midway up on the condenser coil.  
  • 20-30 ton units only have one refrigeration circuit and one sensor.  
  • 40-130 ton units have two refrigeration circuits with a sensor on each circuit.  
• This is an automatic reset diagnostic.  The diagnostic will clear when the module measures a valid resistance.

Here are the steps for Intellipak Air-Cooled Chiller

Step #1 Wiring Error

• Verify the wiring between the Condenser Sensor and the SCM or MCM (1U49).  
• Refer to unit schematics for wire numbers and connections.  
• If the wiring checks good, proceed to the next step.

Step #1 Wiring Error

• Verify the wiring between the Condenser Sensor and the SCM or MCM (1U49).  
• Refer to unit schematics for wire numbers and connections.  
• If the wiring checks good, proceed to the next step.

Step #2 Sensor Checkout

• Disconnect the sensor wires from the SCM/MCM (1U49).  
• Check the resistance reading of the sensor and wiring at the plug connector.  
• Compare the resistance reading to the above chart.  
• If the values are not correct, double check for wire errors.  
• Replace sensor if none are found. 
• If the values are correct, proceed to the next step.
   

Step #2 Sensor Checkout

• Disconnect the sensor wires from the SCM/MCM (1U49).  
• Check the resistance reading of the sensor and wiring at the plug connector.  
• Compare the resistance reading to the above chart.  
• If the values are not correct, double check for wire errors.  
• Replace sensor if none are found.  
• If the values are correct, proceed to the next step.
   

Step #3 SCM/MCM Checkout

• Connect a known resistance in the valid range to condenser sensor input to the SCM/MCM (1U49) directly.  
• Using the Human Interface (1U65) check the status of the appropriate Condenser Temperature Sensor. 
• If the diagnostic clears and the correct temperature is displayed, recheck wiring and sensor.  
• If the Human Interface does not display the correct value with the resistor connected to the board, replace the SCM/MCM (1U49).

Step #3 SCM/MCM Checkout

• Connect a known resistance in the valid range to condenser sensor input to the SCM/MCM (1U49) directly. 
• Using the Human Interface (1U65) check the status of the appropriate Condenser Temperature Sensor. 
• If the diagnostic clears and the correct temperature is displayed, recheck wiring and sensor. 
• If the Human Interface does not display the correct value with the resistor connected to the board, replace the SCM/MCM (1U49).

Facts:

• Intellipak Air-Cooled Chiller 20-60