System sizing with IRC

When designing a control system that includes communicative zone controllers (Integrated Room Control, IRC), we must ensure that the number of controllers connected to the PLC does not exceed a critical limit. Behind it, it would no longer be possible to operate the controllers in software, the response time on the bus would be unbearably long, or commissioning and servicing would be "just" complicated. Let us now look at some of the restrictions that must be respected. Some limits are "hard", others depend on other factors, such as the number of communicated variables per controller.