Communication Problems between Carel C3-05 PCO and ABB AC800f


Thread Starter


Dear all,

Hi, i would like to start by saying i am new, so please bear with me if i sound a bit like a newbie.

Ok! I have a ABB Freelance AC800f controller with a serial Card for Modbus RTU (rs485) Communication and a Carel C3-05 PCO Controller with PCO1004850 Serial Card (rs485) for a DENCO HVAC Unit.

I am using a
- two-wire bus plus shield
- impedance of 120ohms
- only device connected
- length not more than 15ft (AWG 22 twisted and shielded)
- baud rate and address confirmed

no communication between the two controllers. I have done everything over and over again, but i am unable to find the problem. I would really appreciate some assistance in this matter. As there are any known issues between these two particular controllers which are not publicised.

Thank you in advance to those who do reply.