So I’ve seen with the new hub update you can change the Zigbee channel , some questions
Thanks
@Kianoosh_Karami who would be able to answer these questions on the Zigbee channel feature? Its so new, I’m positive none of us out here in the community have these answers…
Id also love to get a list of caveats…
I don’t think the firmware update is responsible as only one of my hubs has updated and both seem to allow it.
I think an IDE change has been sneaked in on the quiet and somewhere there is an engineer chortling away waiting to see when anyone notices. The little tinker.
Not only can it be changed but it can be changed to a wide range of channel numbers instead of the handful it selected from previously.
Its actually been there since around the time firmware 32 was released
It only recently started working. Maybe @tpmanley @BroderickCarlin or @nkooistra can answer
As a bit of a warning though, while all devices should reconnect on the new channel it’s possible that the device does not support the channel chosen (ZLL, for example) or the device may have a bug or problem properly following the hub to the new channel. Also note that sleepy devices won’t be made aware of the changed channel until they wake up again and attempt to communicate with their parent. Because of this you may see sleepy devices (motion sensors, open/close, etc.) miss an event or two immediately following a channel switch
You get warned that early ST sensors might need to be paired again. I can also tell you that Aqara sensors need to be too, having spent the last hour or so walking around a sleeping house in the dark pairing a shedload of the things. My IKEA stuff sorted itself out.
Can anyone specify which channels are ZLL and which are ZHA?
Sure. 
The primary ZLL channels are defined to be 11, 15, 20, and 25.
Technically, ZLL devices can operate on the secondary channels as well, but the manufacturer may not have designed them to do so except with a ZHA profile.
The one that most typically causes problems is channel 14.
Zigbee channels start with channel 11.
The ZLL primary channels were selected to give you A choice of one per Wi-Fi band so you could try to limit interference.
https://www.digi.com/resources/documentation/digidocs/90001537/references/r_channels_zigbee.htm
My hub is on channel 20. All zigbee devices working great and quit a few Hue bulbs connected to Hue bridge (which I understand uses ZLL), would there be any advantage to changing to a non ZLL channel?
No, unless you have local interference, particularly with Wi-Fi channel 11. But if everything is working great, you’re actually probably a little better off being on one of the ZLL primary channels.
Thanks for the quick answer. Youre a great help around here!
Something I have found is that only 1/3 of my ST Presence Fobs changed channels and the others will no longer re-pair or pair on any channel. Which is frustrating to say the least …
Update: After much effort I got them all back, but only on the hub that had been updated to 34.9. The other hub, where they were previously, wasn’t interested.
so after 2 months we can say that if we change channel some devices will follow…others not.
right ?
cause 2 years ago i had an issue with a tradfri (ikea) power supply which was impossible to connect it if you wasn’t in a certain zigbee channel (the only way back there was to reset your hub and change the channel in the initial setup) , i don’t remember anymore in which one . But it doesn’t worth the risk for just one device.
Correct. Some devices don’t handle the channel change well. Those that don’t would need to re-pair. But you shouldn’t have to delete anything, just kick the device into pairing mode and do the add nearby device (or whatever they named it now) to make the hub start inclusion.
