Liquid Pressure Sensor Failure

Issue:

Liquid Pressure Sensor Failure

Resolution:

• This diagnostic occurs when there is not a valid signal on the liquid pressure sensor input on the SSM (1U91).  
• The sensor has an operational range of 0 to 5 VDC.  
• These sensors would only exist on IntelliPak chiller units with the Superheat/Subcooling option installed and are located on the liquid line of each refrigeration circuit (designated as 4U92 for circuit 1 and 4U94 for circuit 2).  
• This is an information only diagnostic and will clear automatically when the module measures a valid voltage.  
• This diagnostic will not affect the operation of the unit.

Here are the steps for Intellipak Air-Cooled Chiller

Step #1 Sensor Calibration Setting

• Verify the calibration setting in the pressure transducer device characteristics located in the Setup Menu.  
• For Liquid Pressure Sensors, the settings should be:  0 PSIG = 0.118 VDC & 400 PSIG = 4.847 VDC.
   
• The Ckt1 Liquid Line Pressure Transducer setup screen appears only if the Superheat/Subcooling        option is installed. This screen allows the user to adjust the voltage to pressure calibration setpoints at 0  PSIG (0.000 - 4.000 VDC) and 100 PSIG (1.000 - 5.000 VDC).

• The Ckt2 Liquid Line Pressure Transducer  setup screen appears only on 40-60 Ton units with the Superheat/Subcooling option installed. This screen allows the user to adjust the voltage to pressure calibration setpoints at 0 PSIG (0.000 - 4.000 VDC) and 100 PSIG  (1.000 - 5.000 VDC).

Step #2 Wiring Error

• Verify the wiring between the Liquid Pressure Sensor and the SSM (1U91).  
• Refer to unit schematics for wire numbers and connections.  
• If the wiring checks good, proceed to the next step.

Step #3 Sensor Checkout

• The sensors used to determine liquid pressure are 3 wire pressure transducers.  
• These transducers require an operating supply voltage of 4.5 ? 5.5 VDC.  Verify the supply voltage from the SSM (1U91). 
• If the voltage is not in this range, disconnect the plug connector from the SSM (1U91) and verify proper supply voltage.  
• If supply voltage is not present, replace the SSM (1U91).  
• Once supply voltage has been confirmed, re-connect the plug connector and check the output voltage of the pressure transducer.  
• Convert this voltage to a pressure based on the linear scale 0 PSIG (@ 0.118 VDC) to 400 PSIG (@4.847 VDC).  
• If the output is not correct versus an actual pressure gauge reading, replace the pressure transducer.  
• If the output is not correct versus the HI display of liquid pressure, replace the SSM (1U91).

Facts:

• Intellipak Air-Cooled Chiller 20-60