Hi
we use 3 Carrier 30XA0402 chillers at our plant.
The plant PLC (GE Rx3i) communicates with the chillers through Modbus RTU (Rx3i PLC is installed with an IC695CM002 Serial card whose port 2 is configured as a Modbus Master). For each chiller there are 8 Modbus exchanges. After a recent power loss, the Modbus comms to Chiller 2 came up with error code 26, which implies "Slave Device Busy". In an attempt to fix this problem, we disabled all the 24 Modbus exchanges for the 3 chillers from the Modbus Master. However, by doing so we now cannot communicate to any of the chillers and we get Modbus error 36, which is means "CRC error on response". When we check the LED's on the CCN mother-board controller and the Modbus translator daughter-board of the chillers the Red LED is flashing with a frequency of 1 Hz, implying both the mother- and daughter-boards are functional. However, the green LED on the daughter-board is always off, indicating a problem with LEN bus connecting the mother to the daughter- board. We believe that when we disabled the Modbus exchanges to the chillers, the mother board controller must have taught there is no need for Modbus communication and somehow disabled the link to the Modbus translator daughter board. If this is the case we need to know how to re-enable the LEN bus link. The mother-board controller is connected to a Carrier Pro-Dialog HMI and we guess there may be a way to restore the LEN Bus link between the boards through Pro-Dialog HMI.

Any assistance on this issue is greatly appreciated.