this post was submitted on 09 Feb 2024
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I bought Shelly relays. These fit behind existing switches so you can keep the originals. They can tie into Home Assistant.
+1 for shelly or sonoff
How do you deal with grounding? None of them seem to have ground pins which is rather concerning
May I ask why grounding is concerning? Im not expert, but afaik normal wall switches dont use ground wire and ceiling lights may use one. I thought if wall switch is made of plastic there is no need for grounding. Please correct me if Im wrong, I want to learn. I was looking at sonoff zbmini-l2, but didnt buy any yet
Every normal electrical box in every house ive lived in has a white wire, a black wire, and an exposed copper wire. Every switch has always had a green screw that the copper wire goes around. The zigbee adapters all seem to lack a spot for the copper wire, which is meant to help protect electrical equipment and prevent fires during events like power surges and whatnot.
@semperverus
In European countries you only have live wire, never the ground, neutral in newer installations.
The switches don’t need ground as there is no exposed metallic component. Ground is needed where a human could be exposed to live (due to a fault) as it would trigger the breaker.
Every wall switch I’ve seen (in US) has an attachment for a ground wire, except really ancient ones, and every “Romex” style wiring includes a ground wire
My house is an older one with steel junction boxes, so those need to be grounded, but plastic boxes obviously do not.
So, my experience may be limited but I’ve always seen switches grounded and always seen everything support grounding.
As someone further up said, it’s the neutral that is the problem. I don’t know if it’s code or convention, but older wiring tends to use “switch loops” without a neutral, while more modern wiring is “pass through” and does. Even before smart switches, this was needed for things like lighted or programmable switches
Current national electrical code in the US (since the 1980s) is a neutral in every switch box. Before then a switch loop was allowed so you see a lot of older construction with those.
You also see newer construction with those where Uncle Dave™ decided it was easier to only have to run a wire down from the light rather than fish it up through the crawlspace, NEC be damned.
It’s also a matter of saving on the wiring. I may not be (quite) that Uncle Dave, but I really regret a few places I pulled wire for a switch loop without the extra conductor for a neutral.
At the time, I rationalized it was already an improvement over what was there and I had no immediate use for the neutral. I believe the neutral wasn’t required by local code, only recommended, or I would have done it
Of course now I’m cursing my choice, trying to decide whether I need to go back and do it over, or whether I even can practically since it’s a two person job and my buddy retired to Florida. Wiring I pulled many years ago was great for dimmers, more convenient switches, and extra three-ways, but not so great for smart switches
Edit: looks like neutral wasn’t required until NEC 2011
I didn't realize it was that recent of an addition to the NEC. Weve only lived in super old houses where everything was always needing completely redone. I was usually replacing 2 conductor and cloth-jacketed stuff everywhere.
That was around 2012 and I remember the electrician we hired at the time mentioned it being a thing so that makes sense.
There's nothing for a ground pin to be connected to, the case is plastic.
The bigger issue is that a lot of light switches also lack a neutral connection. They have live, and switched live. You can get devices to allow them to scavenge power, but they can also cause led bulbs to glow dimly.
Thats interesting. I would assume ground is important for metal devices since they can shock you but what would be the risk of a plastic device without grounding be?
You don't need to ground your Shelly if the circuit is otherwise properly grounded. The Shelly will fail open if something internal shorts.
Per the rest of the discussion re: hot wire loops to switches with no neutral or ground, just put the Shelly into the upstream junction box. (Wherever the switch wire branches from the circuit. Usually that's where the light is.)
In the UK most lights don't have a live, neutral and earth wires. Which is a pain when looking for smart switches
I've come across Shelly relays as well, they seem like a viable option to me. I'd probably prefer a separated network like Zigbee, but that should be doable. Thanks!
You can do this with Shelly Zwave relays.
That would generally preferable to ZigBee for such a system from an RF perspective.
Aeotec or Zooz usb dongle on your server, every Shelly acts as a signal relay.
You can get zigbee 3.0 relays on aliexpress. I got the GIRIER store ones, but while I've done a test with a bulb and a switch on a board, I haven't gotten them properly installed yet. Seems promising tho.