To clarify things (since the ‘master’ station on a controller and a ‘master’ controller are two different things), let me call the master station ‘pump station’ instead. A pump station is allowed to be a remote station (i.e. defined as IP address followed by station index). You can have the actual pump relay connected to a remote controller. Then you can have, say, three master controllers, each with a pump station that points to the remote controller. As a concrete example:
– Pump relay is connected to remote controller R (say, with IP address 192.168.0.R, first station)
– On a master controller: define a pump station and set it as a remote station with IP address 192.168.0.R. You can have multiple master controllers.
This way, when you activate a valve on the master controller, it will turn on the pump station, which internally sends an HTTP request to the remote controller to turn on the actual pump.