Trying to figure out if this is possible and haven’t found a clear answer.
I have a V3 hub in my shop plugged into LAN I don’t use the WiFi on it at all, have Unifi for that.
In an addition on my shop I am not getting reliable connection of ZWave devices to the hub. I have no LAN line in the addition. So can I get another V3 hub and connect it to my network by WiFi, add it to the existing shop hub as a secondary group and everything will work?
You can add a second v3 hub in two ways. One way is to add it as an independent hub where you can add additional devices to that hub. You might consider that option if you were reaching the memory or device limits of your current hub. Downside to that is that Routines involving devices on different hubs run in the cloud.
The other option is to add the additional hub as a secondary hub in a hub group. The secondary hub acts as a radio repeater, extending Z-Wave, Zigbee, and Thread meshes while the primary hub handles the message processing. With recent firmware updates, the secondary hub serves as a backup to the primary in the event the primary fails.
Not exactly true now. Some will run locally. 
after one of the hub firmware updates this past summer… it changed.
Why not put a few smart plugs along the way which can act as repeaters to connect those devices back to the main hub? Something like this:
That’s an unusual way of talking about Wi-Fi on a V3 hub. Can you confirm you do indeed have a V3 hub (model number beginning with IM6001-V3P) and not one of the Samsung Wi-Fi Hubs (models ET-WV5xx).
I have to say that completely passed me by.
I can see how it could be for a narrow subset of Rules but I wasn’t aware it had been.
This is the hub that I have: SAMSUNG GP-U999SJVLGDA 3rd Generation SmartThings Hub
I thought about plugs to try and get it to repeat. But all metal lines walls and ceiling and what not, I think it would be more reliable to have a hub in the other room.
Is there a way to know which kind of routines or devices will trigger locally across hubs? Was this update only for the V3?
I have a ST Wifi mesh and a ST Station, and now I’m realizing that the routines across them are cloud. I bought the Station to add matter to my home but if I knew that the routines would be cloud base I would have bought a V3.
Advanced Web App would show whether devices/routines are local or cloud
I am not sure what determines local with multiple hubs. Some users have reported they see Routines that show as local when they have multiple hubs.
I believe Routines will be local when you have multiple hubs in a Hub Group. This is because the secondary hubs work simply as radio repeaters and the message and Routine processing is handled by the primary. It’s similar to the way the ST Wi-Fi hubs work.
When each hub is independent and not in a Hub Group, the notion of having local Routines doesn’t really grok since each hub would either have to process the Routine independently or portions of the Routine would have to exist in each hub and require some coordination mechanism. Hence, it makes sense the Routine executes in the cloud and Routine actions are sent to the hubs from the cloud via API calls.
Unless I’m misunderstanding what you’re saying, there’s no difference between the station and a V3 in this specific regard. Some routines, but not all, Will be local within a shared hub group. But if you have two SmartThings hubs that are not combined in a hub group, routines using some devices from each will be cloud-based.
And things may have changed, but the last time I looked the SmartThings hubs which also work as a Wi-Fi router cannot be included in a hub group anyway. 
Yes I’m aware of that, the intention never was to create a group. I was advices by the ST team to add a new hub to my home because my ST Wifi mesh hub was having symptoms related to low memory (non working routines among others things). I was instructed to not create a hub group because if I did it wouldn’t free up space in the hub memory.
I went with the station because of the price and complementary functions with the wifi mesh (Station has matter and wifi mesh has zvawe) but if I knew must of my routines would become cloud base I would up in for the V3 instead as a stand alone hub which was the second option.
I guess the only solution is to create a bunch of virtual devices and edit most of my +500 routines so one devices doesn’t make the whole routine cloud base.
One question, do you know if the 200 device limit is per hub or per location?
Last I heard it was per location, and it’s a limitation which is imposed by the app.
Hopefully, if that’s changed to someone will post the current information.
All of that said, I don’t think a virtual device approach will make any difference to this. The virtual switch only belongs to one hub, so you can’t use that to stay out of the cloud while integrating with the other hub.
And since your SmartThings Wi-Fi hub doesn’t use matter, there aren’t any workarounds with that.
Off the top of my head, the only way I can think of to get local in the kind of situation you’re describing is to use a hue bridge as an intermediary and use its custom local integration with smartThings. Then you might be able to use a Hue plug connected to that Hue bridge and turned that on and off locally, have that be recognized by both of your SmartThings hubs, and use that to trigger separate routines on each. But I can’t guarantee this will work. You would have to test it to see if you maintain a local option throughout.
Or as I think about it, you might be able to use a Shelly local integration in the same way. But I think you have to connect it once to each SmartThings hub, and I just don’t know if it allows for that. Or possibly a local Homebridge or home assistant connection.
The point is some local third-party intermediary which allows for a separate connection to each SmartThings hub. It would be a lot of work to set up if you have that many routines, though.
i believe the current limit is 300 devices per location.
I have 249 devices at one location and 204 devices at a second location.
v3 or otherwise, Routines with devices that are on separate standalone hubs will be executed in the cloud. Additionally, the v3 is underpowered compared to the Station and the Wi-Fi mesh hubs, so it would not have solved any low memory problems. And, anyone who told you to get another hub, but not create a hub group with your existing hub, has no idea what they are talking about since the Wi-Fi hubs can’t be in hub groups.
Could probably solve the issue of the cloud based Routines if there was an intermediary like Alexa. In hub 1, turn on virtual device on hub 1 which is a proxy for device in hub 2. Then create Alexa routines for the virtual device events that trigger actions on the real devices on hub 2. Not sure how much it will help with his low memory issues however and surely a ton more complex.
That’s a great idea!!! I could what the BYS hue driver in one hub and the official hue driver in the other and they will communicate locally thru the hue bridge!
What I was saying before about the virtual switch is because once one cloud device is involved in the routine the whole thing become cloud base, even as if all other devices in the routine are local, and even if the routine is a type OR routine (correct me if I’m wrong). So using virtual switches I could duplicate devices that will run in the cloud with local virtual switches so the routine will work if it’s not entirely dependent in that cloud device. I’m not sure if I explained myself correctly.
But with the 300 limitation per location it could be very difficult, I recently had troubles with hidden devices that I didn’t use for any routines, that made all my routines dissappear, I’ll be careful adding new devices because I’m around 200, if I add the hue official integration that’s 50 more.
Alexa routines run in their cloud, so I don’t think that’s what the OP is looking for.
That’s why I said you have to pick an intermediary that runs its own routines locally, like Apple home or home assistant.
