How many devices per hub? Zigbee and Zwave network considerations

đź’¬ Lounge
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Okay I am not certain this has been covered in detail, but I know I have seen mention of it, and it makes a little bit of sense.

There is only so much capacity a given device like a hub has. But just how much is that capacity.

I am presently at 79 physical and virtual devices, and am going with more, before I go with less. I.E. Adding Hampton Bay Fan speed / light controllers, 3 virtual devices, to replace 4 smart bulbs and a virtual bulb group, so add 3 subtract 5 I guess...

Anyway I digress...

How many devices is too many on a C7 hub? What is a good means of distributing load between hubs while maintaining a consistent mesh?

My priority for replacing bulbs with switches I would think should be start off with multi bulb, or multi fixture circuits first, THEN go after the single bulb jobs like closets, driveway etc...

I'm not presently seeing issues with performance, but I can see how this could get to be a problem long run.

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The actual Z-Wave max number of devices on a network is 232, but the hub takes the first few nodes for who knows what (and no longer displays those nodes it claims so that they won’t be confusing and won’t accidentally be removed.

That’s not the difficulty. The difficulty is if you have “chatty” devices, such as S0 paired devices or power monitoring plugs. For some reason, power-monitoring plugs are the kiss of death for a C-7’s Z-wave network; they seem to work fine on a C-5.

Another consideration is if you have older Z-Wave non-plus, because they don’t report state changes and have to be polled.

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Sorry for the hijack, just didn't want to start a whole new thread of similar questions.

To add to OP's question, how much of that bandwidth is used to send a command? I've noticed on my small network (20 devices) that if a switch is sent 2 commands at the same time it likely won't process them both. Is this a bandwidth issue or a limitation of the switch? I've over come this with delays which is fine, but I'm mostly just curious.

And how do you know if you have a chatty device? I've noticed in my logs that my zigbee plugs are reporting their on/off status every 5 minutes. This seems unnecessary to me. Is that normal?

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Neither, really. It’s protocol handling time. Sometimes the protocol stack gets wedged if stuff is pumped to it too quickly. Some stuff for handling simultaneous commands to lots of devices will space out the commands.

Get a Z-Wave sniffer, watch the traffic.

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One Aeon HEM v1 might be one too many LOL.. As has been mentioned, power monitoring devices are renowned for sending too many messages. This is often a config issue, but for antiques like that HEM, it's the device too.

Try and reduce Power Monitoring reports to the minimum you need. My favorite example is a Washing Machine... you do not need to a Report for every Watt that gets changed. Typically you'd look at the value when the Washer is idle, then again when it's running and pick a threshold pretty close (20%) to the 2nd higher value. This will tell you that the Washer is On/Running and that's all most people need to know. When the use is well above minimum, it's running, when it's well below minimum, it's stopped. For that use case, there is no need for additional messages. People will often set a small increment and a small time interval.... usually because that's the factory default for those types of device. Most people will want to turn off the timed/periodic report... or at least make it extraordinarily long. :slight_smile:

It's not that power monitoring messages are bad, it's the quantity of them if the defaults are accepted. Hundreds of Contact open/close messages will cause the same congestion... it's just harder to achieve. :slight_smile:

Roughly speaking... look at your logs... let it run for 5 mins and count the number of events, divide into 300 (5 mins) and your result should be X seconds per event

My 4 hubs are running at about 12 seconds per event at the low end and about 3 seconds per event on the burdened hub, average and I have roughly 65 devices per hub.

As you can see, burstiness isn't factored in, which is exactly what power monitoring does:

dev:212 2021-05-04 12:47:07.059 pm info LaundryRoomWasher power is 0.000 W
dev:212 2021-05-04 12:47:06.966 pm info LaundryRoomWasher energy is 4.138 kWh
dev:212 2021-05-04 12:47:06.962 pm info LaundryRoomWasher energyDuration is 37.1 Days 
dev:212 2021-05-04 12:47:06.893 pm info LaundryRoomWasher current is 0.000 A
dev:212 2021-05-04 12:47:06.782 pm info LaundryRoomWasher voltage is 123.879

5 messages, pretty tightly packed. 20 of those in one house would eat a lot of Mesh time, especially if those messages are a the slowest speed of 9.6k/sec. :smiley:

There are also Runtime Stats to assist with these calculations too. I'm just too used to the days before the wonderful stats. :smiley:

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