Unit HI Communications Failure CGAF

Issue:

Unit HI Communications Failure

Resolution:

• This diagnostic means that the unit mounted Human Interface (HI , 1U65) is not communicating with Cold Generator Module (CGM,  1U48).  The cause for this can be as follows:
  
  a) wiring error
  b) defective HI
  c) defective module other than HI
   
• All the modules share a comm link using twisted wire.  
• The J1 connector on each module is the connection point for this comm link.  
• They all connect to a common point on the 1TB9 terminal strip mounted over the CGM.  
• The comm link is polarity sensitive.

Here are the steps for Intellipak Air-Cooled Chiller

Step #1 Wiring Error

• Verify proper wiring between HI to 1TB9 and CGM to 1TB9.  
• Refer to unit wiring diagram control box door for wire numbers and connection points.  
• Check for good connections and proper polarity.  
• If no errors are found, proceed to Step 2.

Step #2 Defective Human Interface

• There is no way to check the Human Interface other than take it to a known good unit and test it.  
• If the HI does not function in a known good unit, replace it.  
• As a note, a defective HI will not prevent the unit from functioning normally in other aspects.  
• So, if the unit is operating properly, it is a good indication that the HI is defective.   
• If the HI functions in another unit or the unit is not functioning, proceed to Step 3.

Step #3 Module Problems

• If the CGM (1U48) does not have 24 VAC, this diagnostic will be generated.  
• Check for 24 VAC at J2 on the CGM.  
• If 24 VAC is not present, check wiring.  
• Refer to unit schematics on the control box door.   
• If 24 VAC is present at J2, continue below.
• Disconnect unit power.  
• Unplug the J1 and J2 connectors from all modules except the HI and the CGM.  
• Restore power to the unit.  
• If communications are restored, one of the modules has a problem.  
• Plug them back up, one at a time, to find which one is pulling the comm link down.  
• Check that module for wiring errors per the unit schematics. 
• If none are found replace that module.  
• If communications are not restored, continue below.
• Disconnect unit power.  
• Unplug all connectors except J1 and J2 on the CGM. 
• If communications are restored, check module wiring per unit schematics.  
• If communications are not restored, replace CGM.  
• If possible verify defective CGM by exchanging with a CGM from another unit.

Facts:

• Intellipak Air-Cooled Chiller 20-60