It is depending on the PLC and it's communication possibilities and what you would like to communicate. If you want full control, and if ethernet/wifi is not an option in your PLC, best would be to play around with RS232 port on your PLC(mostly available on many PLC's) as the OpenEVSE has TTL serial communication possibilities. You will need to play around with this, but be careful on voltage levels. Some background articles:
I opened a ticket the last week about this, but I haven't received any answer, so I decided to start a new topic.
I recently purchased a kit and successfully assembled it. I would like to know if it includes PLC communication and if it's possible to add it if it doesn't.
I'd appreciate any help.