Have you noticed automation slowdowns or even Z-Wave devices that aren’t firing at all? It is likely that one (or more) devices in your system are demanding too much Z-Wave bandwidth. One of the biggest bandwidth hogs is unnecessary power reporting. Let’s take a look at Z-Wave bandwidth constraints and how you can reduce or eliminate issues caused by power reporting.
The Z-Wave radio in your Hubitat Elevation hub is designed with more than enough bandwidth to handle your day-to-day automations such as turning things on/off, setting levels, getting sensor notifications, etc. But this can be easily overwhelmed by overactive reporting for a few devices--typically from power metering. Unfortunately, many of the devices on the market today default to an unsustainable reporting rate.
If you look at the way a Z-Wave networks with multiple hops functions, it is easy to see how it can be overwhelmed with data. Z-Wave consists of 2 channels, 1 40Kbps and one 100Kbps, which means under optimal conditions and if every packet were timed perfectly you could get up to 100Kbps of data between your devices and the hub. However, every hop you go through reduces this bandwidth in half as it must be re-transmitted on the same frequency so 1 hop ~50Kbps 2 hops ~25Kbps 3 hops ~12.5Kbps.
What happens when your mesh is overloaded with reporting? Because there is no central control of transmit timing, or who can talk, devices re-transmit as packet collisions happen. This degrades your performance even more as your network is having to take double the amount of airtime re-sending the same data. Eventually this can snowball into packet loss as devices will only attempt to re-transmit a limited amount of times before giving up.
So what can you do to prevent this problem? The first stop is to turn off power reporting on your devices unless it is absolutely necessary. You can find this in the device detail page under preferences. If you must use power reporting, adjust the reporting interval to be as infrequently as possible.
We know some of our users employ high-frequency power reporting to graph and track their power usage. If you are doing this and notice slowdowns or poor performance, you may need to switch to wi-fi devices as these tend to offer the best performance for whole-house energy reporting while keeping your Z-Wave bandwidth free for fast, reliable automations.
by @bcopeland - Lead Z-Wave Engineer at Hubitat. This article was previously featured on Hubitat Newsletter.
