CVHE-SB-32A 34
Troubleshooting IPC Communication Diagnostics
1 Check the IPC connections to all modules. Make sure the twisted pair wires that plug into
each modules’ J1 connector are making good contact with the wire. Be sure each connector
is not clamping down on the wire insulation.
2 Verify that the polarity of the IPC link is correct. The twisted pair IPC link is two color twisted
pair wire. Be sure the same color wire is on top for each twisted pair connection.
3 Using a voltmeter set to AC volts, measure the voltage at the J2 connector on each module. It
should read between 20 and 28 VAC. Also check the green connector to make sure it is
securely plugged into the module. Inspect each screw terminal to be sure they are not
clamping down on the wire insulation.
4 Most of the UCP2 modules have 24 VDC and 5 VDC test points on the board. They are
clearly labeled and accessible without removing the sheet metal covers. For the Starter and I/
O modules, the test points are located in the upper left hand corner of the module. For the
other modules, they are located on the upper right hand corner of the module.
Using a voltmeter set to DC volts, measure the 5 volt test point. It should be between 4.75
VDC and 5.25 VDC. Measure the 24 volt test point. It should be between 23 VDC and 25
VDC. Note: The I/O module’s 24 VDC test point will read 0 VDC. If any of the voltage
measurements are not within the acceptable range, replace the module.
5 Verify that a good ground exists between all modules. The CLD requires a dedicated green
wire ground. Verify this is in place, and has a good connection. Paint may need to be scraped
away to insure a good connection.
6 For remote starters only: It is very important that a good ground exists between the starter
panel and the chiller control panel. Use a continuity checker to verify a good ground exists
between the two panels. If there is not a good ground, run a dedicated ground wire between
the starter panel and the control panel.
For a “No Communication, Data Not Valid” message on the Clear Language Dis-
play:
1 Perform the above checkout procedure.
2 If the message still did not go away, unplug all of the IPC connections from the Chiller module
except for the IPC link that goes to the Clear Language Display.
3 Establish communication with only the Chiller module and then plug the other IPC
connections back onto the Chiller module one at a time. If the “No Communication, Data Not
Valid” message suddenly reappears when you plug one of the connections back in, you have
identified the IPC link that is causing the fault. Carefully check that link for a lead to lead short
or a short to ground.
For a “Loss of comm with Stepper” diagnostic:
1 Make sure the wiring to the stepper motor is correct. If the wiring is not correct it will destroy
the power supply on the module, and a loss of comm with Stepper will result.
The Correct stepper wiring follows:
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