I have a home that has cat 5 in most rooms. The home is large and i have the Primary router and 3 secondary routers connected via Ethernet and 2 points connected via Wi-Fi. My issue is that a Rainbird Wi-Fi enable sprinkler system for my yard try's to connect to my primary router via Wi-Fi rather than a secondary router connected via Ethernet. I have managed to turn off the Rainbird device several time and finally got it to connect to my secondary router. However after a power outage it reconnect to the primary router via Wi-Fi that has a weaker connection. I have seen posts that say you cannot disconnect the Wi-fi radio on the primary nest router. They also suggest that you setup the primary router on a different Wifi network with a different password, so the devices can not connect to that primary router and must connect to the secondary routers? Is this possible and how can this be done? Or is there a way to connect a particular device to a particular nest point?
WiFi client devices decide which access point to connect to. Some do a (much) better job of this than others. Devices are supposed to scan (listen) for all available access points that are advertising (beaconing) the network name that device is trying to connect to, measure the received signal quality from each, and select the one with the strongest signal. Ideally, they'd repeat this process occasionally (for a fixed device, once every 24 hours would probably be sufficient). But, some manufacturers have taken some shortcuts in this process. They may start listening for access point beacons, and then just connect to the first one they hear, even if it isn't the best signal quality.
I suspect your sprinkler system falls into the latter category. I would also suspect it's connecting to your primary/router unit more often because it's a 2.4GHz device, and that unit has selected a lower 2.4GHz channel than the other units. There is one more possibility, though, and that is that after a network restart, the primary/router unit is the first one to start advertising, so a lot of devices will jump on it and just stay there. This would be the case after a power outage. You might have some luck by power cycling the Rainbird device manually when that happens (but it may still connect to the router, depending on how it's startup scan is implemented).
In answer to your specific questions, no – the primary/router unit WiFi cannot be disabled, and it cannot be on a different WiFi network name / password than the secondary units. As I said above, devices decide which access point to connect to. It sounds like the Rainbird device doesn't have a great WiFi implementation, unfortunately.
I'm wondering how big an issue it is that the Rainbird system isn't connected to a nearby access point, though. I expect it doesn't generate much traffic, so as long as the connection it can get back to the primary/router unit is reliable, it should still work just fine and won't cause issues for other devices.
If it isn't working reliably, I would send some feedback to the Rainbird manufacturer, and then dig out an old WiFi router (or pick up an inexpensive travel router) and set it up in bridge mode with a separate network name + password just for your Rainbird system. It would need to be connected to your Nest WiFi system via Ethernet.
Thank you for your response. I am going to reach out to Rain Bird and ask questions on how their device broadcasts. I am also going to move my secondary nest router on to the ceiling in the middle of of garage after installing a new Cat 5 cable to that area. This way maybe that device might be the first to be connected to the Rain bird sprinkler controller box. If that does not work I will take your advice and get an old Wi-Fi router and bridge it to my primary router. This might also help later when I setup my pool to be Wi-Fi. Just so you know if you need advice on FEIT Light switches, I have been using them for a while now. I have also started using the FEIT motion sensors with the switches. Thanks again.