Wiring Aeon Labs Aeotec Micro Smart Energy Switch G2 (c) into existing 3-way switches

Hello! I’m a new SmartThings user. I’ve already had some great success integrating a thermostat and garage door monitor/opener, and a few other simple things.

I’m pretty comfortable with software, but I’m a novice when it comes to electrical wiring. I’ve had some success with some pretty simple tasks, but I’ve run into some trouble with my latest endeavor.

I want automate a light using a pair of Aeon Aeotec micro switches (DSC18103-ZWUS) with an existing 3-way circuit. Such is to say - there’s already a pair of conventional light switches - one at the top of the stairs and one at the bottom - controlling the light in question. I’d hoped that I could install the Aeon micro switches into the existing switches, but the wiring I’m seeing doesn’t match up with what little instructions Aeon provided.

The box for each of the two existing light switches has three wires (installed circa 1977 I believe) -

  • Black (Live?)
  • White (Neutral?)
  • Red (Traveler?)

I made my best guess as to how this wiring matched up with the incredibly sparse and cryptic documentation from Aeon. See my attempt in the attached photo at the bottom of the post.The good news is nothing burst into flame and no magic smoke escaped. However I never saw any sign of life from the Micro Switch. The LED never illuminated and the little button on the micro switch didn’t cause the light to toggle on/off. I tried this on each of the two light switches, but not both at the same time.

On one hand I recognize that I may be out of my depth here and I might need to hire an electrician. On the other hand, the wiring in place seems relatively straight-forward. I’m hoping that the community may be able to give me a few simple pointers to get this going.

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For a 3-way switch application, you should only need one Micro Switch. Here is some documentation about all of the supported wiring options:


However, I would expect to see 4 wires in a 3-way application… Hot, Neutral, Load, and Traveler

Can you also open up the electrical box where the light fixture is mounted and see what the colors of the wires in there are?

Edit: I’ll just add that wiring the micro switch in a 3-way application is pretty difficult, and may require some changes to the physical wiring in your house. But we’ll do our best to help ya out here!

biggest thing about a 3-way is identifying all of the wires and where they go.

Most likely, one end has power coming in (so, there will be a black/white wire pair that is always hot regardless of the state of the swtches) and the other end feeds to the load (light or whetever is controlled), so there would be a black/white pair that goes to that.

In between, “usually” they run three wires. two of the wires are travellers, one of which will carry power at any given time. The third one carries the neutral (White) wire.

I will warn you. These switches do not work like they are supposed to. You are supposed to be able to toggle the switch based on the presence or absence of current, but when I tried this at my house, it worked when I had the switch outside the box, but when I cut the power to stuff everything back in, it did not work after that.

There is a thread on the board talking about it and I am not the only one with this experience.

If the line comes into the same box that the load goes out and the switches are just a switch loop, the Aeon module should work fine. (I’ve done this with 3-way and single-pole switches.)


After following the bazillion threads on aeon three/x-way switch and dimmer installs, I’m pretty sure I’m the only one to get this working reliably and consistently from the get go. I didn’t follow any of aeon’s suggestions for this, which is probably why it worked in the first place and continues to work now.

They work great if you are running through the three-way as a switch loop. (Out the low-voltage side to the common side of the first three-way, then Red/White/Black between boxes, with Red and Black connecting the traveller wires and white attached to the common screw of the far switch to bring the loop back and then that white wire tied into the other low-voltage switch side.)

But, if you have line on the first box and load on the second box and all you have on the load side is whether or not there is power flowing and you have to run that into the low-voltage (or, I guess, more correctly, the low current side), that seems to be flaky. (at least for me and for others on the board)


Thanks so much for the responses! I had a look at the little junction box immediately adjacent to the (tube florescent) light. Unfortunately there’s more going on in that box besides the wiring for this light, which complicates things. There’s a picture below, for what it’s worth.

Near as I can tell, this is what’s going on:

  • The red wire coming in from the switches connects to a black wire that goes to the light
  • The white wire coming in from the switches connects to a whole bunch of other white wires coming in there, one of which goes to the light
  • The black wire coming in from the switches goes straight through and doesn’t appear to be connected to anything

I neglected to mention that there is, in fact, a second light involved. It is in between the switches. It simply has a white and black wire connecting to the light and what appears to be a ground wire connecting to its box.

It’s still hard to tell. Can you post a better picture of the switch box?

How many separate wire bundles are coming into the junction box?

Do you live in the United States with 110v power?

Also, maybe a picture of the wall showing proximity of the switch box and junction box?

Below is a of picture of the switch box as currently wired (with the conventional switch).

The junction box has four bundles coming into it.

  • One comes from the set of switches I’m trying to upgrade - a black, white and red wire and… you know what I’m just gonna sketch it out. See below.

The ?? is some wire going to some no-longer-attached medical device (at least I think that’s what it was). The orange/green looks is what I believe to be ground wires (uninsulated copper wires)

Yes, in the US with 110v power. The junction box is on the ceiling in the basement, a good 15’ away (and around a few corners from) the first of the two switches.

Switch Box:

Junction Box:

Okay. Getting closer. What I think I can tell here is that only the hot wire is coming from the switch to the light.

If you look at a 3-way switch, there is always a screw that is a different color than the other two. On one end, that screw goes to the line (back to the breaker or fuse) and on the other end, that screw attaches to the load (light or whatever else is being switched on and off.

The two screws that look the same connect between the two switches.

So, the power comes from the breaker to the different colored screw on the first switch. That switch then, depending on its position, sends the current to one screw or the other. flipiing the switch causes the current to be on one wire or the other. Those two wires connect to the same terminals on the other switch, and it works the same way, but it takes the incoming current on one wire or the other and, depending on the position of the switch, moves it to the different colored wire on the switch, which then goes to the load.

So, the first switch sends the current on wire A or wire B and the second switch connects the load to wire A or wire B. If both switches are “pointing” to the same wire, the light is on, if the switches are “pointing” to different wires, the light is off.

So, now we know that the switch you are looking at is the second switch, the one leading to the load. But, it is only sending one wire to the light.

One wire is not enough to make the light work, we also need a return wire. That wire is usually white and is not usually switched, so it just needs to go straight back to the breaker panel. Since it doesn’t need to be switched, sometimes electiricians run a separate wire to the last switch or the light to provide that return. I suspect that in your case, that return wire is in the light box.

Unfortunately, I think you are in the situation where people have had trouble getting this to work. You need to trigger the state of the Aeon switch based on the presence or absence of current.

Additionally, unless there are other wires in that last switch box, you probably do not have the power you need to install it there.

You might be able to put it up in the box where the light is.

Remember how I said that the return wire is probably in the light box? Electircians generally work with what is called 14/2 WG wire. This wire has two 14 gauge wires and a 14 gauge ground wire. The two wires are usually black and white. It would be unlikely that an electrician just ran a single white wire to your lamp. It is much more likely that he ran 14/2 WG to the box. So you should have both a black and white wire in that box. the black wire is likely not used and as long as he did not cut it off in the box, and as long as it actually has been connected to a breaker in your panel, you could use that to power your Aeon switch, put the light as the load on the Aeon switch and connect the wire coming from the switch to the switch side of the Weon switch (you will likely need to use smaller wire to make that connection, because the screw terminals on that side are not big enough to take a 14 gauge wire.

If all of that works out, in theory, everything should work the way you want it to, but people have had issues making that work.

I know this is a lot. Read it and let me know if you have any other questions.


Hi Todd - I just wanted to take a sec and say thanks for taking the time and effort to explain all of this. I haven’t yet had the chance to try any of your suggestions out, so no idea if it’ll work - but either way I really appreciate it. At the very least I’ve learned a lot. I’ll let you know how it works out!

Reading through what you wrote, I’m realizing I made a mistake in my little diagram. The big cable going out to the light (the 14/2 WG wire, as I now know it) does, in fact, have both a black and a white wire (and a ground). The white wire is connected to all the other white wires in the box. Then the black wire is connected to the red wire coming in from the switch, as shown in the diagram.

Here’s a new diagram (of the junction box by the light). It’s much prettier. And more accurate.

Is the mystery medical thing on all the time? Or, is the black wire going to it hot all the time regardless of the switch states?

I suspect that it’s on all the time. That wire just goes to an odd looking socket in a bedroom on the first floor. We suspect (but don’t know) that it was for some piece of medical equipment (ergo the mystery). I’d be pretty surprised if whatever was plugged in there was controlled by the switch for the basement light.

Also, the 14/2 WG wire going out to the right in the diagram goes to a simple lamp-style light that has it’s own little pull switch and is not controlled by the wall switches.

Okay. Perfect.

You can put your aeon micro switch in this box.

Get some 14/2 wire and strip the sheathing off to get some extra black and white wires.

Add a black wire to that bundle that goes to the mystery thing and attach the other end to ACPower L.
Add a white wire to the white bundle and attach the other end to ACPower N.

Then unhook the red to black wire nut. Run the black wire from that bundle and hook it up Load L.
Then, you will need a lower gauge wire to connect one end to the red wire and the other end to one of the Wall Switch screws on the Aeon.

This SHOULD work, but people have had trouble with that. If that works, you should be set.


I did it! What you suggested here didn’t quite work. It controlled the light on that junction box, but not the second light between the switches - which makes sense to me now. However out of all of this I gained enough understanding that I decided to go back and looked at the switch boxes again. Eventually I noticed that one of the two switch boxes had an additional neutral (white) bundle and an additional black bundle running through it that I hadn’t seen the first time around. I ran a wire from these respectively into the ACPower N and ACPower L to power the smart switch, then I ran the red wire that had been going into the old conventional switch and wired that to the Load L. Once I’d done that the smart switch controlled the lights if I used the little button on it. Then I ran a wire from the ‘switch’ port on the smart switch to the spot on the conventional switch where the red wire had been.

Now it all works perfectly. The conventional switches at the top and bottom of the stairs toggle both the lights on and off like they used to, and the smart switch controls them as well. I have to admit this took some experimenting, and some breakers were tripped here and there… but in the end I got what I wanted and learned a ton.

Thank you so much.

Anyone knows is this switch work on 220 Volt ?

The switch it self will work, I do not know if the energy readings will be correct, they may or may not, this could be adjusted in the device handler if necessary.

I can’t find the device spec that tell about operating voltage. do you this device ? Is there any spec information about operating voltage there ?

The US ones have spec of 120vac, however a forum member in UK installed a US version and reported that it worked.

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very helpful, thanks