Rule Triggered by Device Going Offline?

I have a circuit in my workshop with a GFCI that frequently trips. Unfortunately, it has a refrigerator plugged into it.

I realized that I could monitor the circuit using a smart plug (e.g., a Kasa HS110). But although I can set up a Smartthings routine triggered by whether the switch is on or off, I can’t find an option to trigger a routine when a device goes offline.

Any ideas?

For a bunch of technical reasons, capturing the moment when a device goes off-line just isn’t really a good match to the home automation architecture that SmartThings uses. Particularly when it’s from a power cut. (No power means no way to send a message from the device.)

However, One clever workaround which people have used for years is to plug a device into the other socket of the GFCI outlet And set that device up so that it switches to battery power when the power is cut: and then it’s quite easy to get a report from that device to say that it is now on battery power. (If you use an open/close sensor, then typically you will get a report that the sensor has opened, for example.)

Here’s a project report from back in 2016. That explains how one person did it.

Simple way to detect power out

The smartest house used to sell a kit with the parts you need to do this, but it looks like they’ve discontinued it. Most people doing this kind of thing just put it together themselves.

A different approach designed for the new SmartThings architecture introduced in 2023 is in the following project report. This takes advantage of some of the newest architecture designs, but it will require having an always on server device on your system. So that’s a bit more work to set up and will also probably cost more than the “switch to battery” idea. So I would probably tend to recommend the second method only for someone who’s trying to track a device which isn’t as simple as an in wall outlet.

Build automations based on device online/offline status


Thanks - potentially quite helpful.

To be clear, I don’t need a momentary report. Knowing within even an hour would do the trick. It’s just that, because this is in a spot that doesn’t get visited on a daily basis, it’s easily overlooked… leading to a bunch of defrosted food.

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The kit from the Smartest house isn’t available anymore, but the parts for the kit are still available. I put one of this in my garage for the same reason. I want to know if my power is out in my garage, since I have a standalone fridge and freezer out there. I was able to find a copy of the old pdf so I’m including it. Essentially it’s an Ecolink door/window sensor with a Zooz ZAC98 relay and a 12v DC power supply. The main thing that this doesn’t tell you is that your ST’s hub and internet connection need to be on battery backups too, if you don’t have power, it can’t send the alert. If you have a V2 hub, it has a built in battery, but you still need to make sure your internet gateway is covered. I’ve had mine installed for about a year. I’ve had a couple of false positives, but I’d rather have that than a freezer full of defrosted food. Hope this helps


Thanks much. I do already know when power is out generally, both because I work from home and I get multiple notifications from other IoT devices.

Would you be willing to post the rule trigger interface you see for this? And/or the pdf?

Here’s the rule for my power outage routine. Since my garage is not attached to the house and that circuit is on a GFCI breaker, I wouldn’t necessarily know the power is off to the freezer. That’s why I put the device on an outlet on that circuit.


The PDF is in the post right above yours. It just shows the wiring diagram for an open/close sensor which has The right type of dry contacts to be wired to the relay.

When the power on the relay fails (because the GFCI tripped) the battery powered contact sensor will then send the hub a message that it has been opened. So you just use the regular SmartThings app to create a rule for when that contact sensor opens.


This is the Specific relay device being used in the pdf. It has both normally open (NO) and normally closed (NC) dry contacts. It costs under $10 and is a dumb device.

The Z wave battery powered contact sensor shown in that PDF is an older model and may be hard to find now. But you could use any contact sensor with dry contacts. It’s all the same idea. When the power fails on the device which is plugged in, The dry contacts inside the sensor Will cause it to change state. And because it is battery powered, it can still send a message to the hub that the state has changed.

Here’s the FAQ on newer devices with dry contacts. Remember that for your particular use case you need one that is battery powered, not an in-line relay.

FAQ: List of devices with dry contact input from external sources

The easiest to find will probably be the Aeotec, but it does cost somewhat more than most of the others. It should work well for this use case, though


So just like the 2016 project report that I linked to in my first post, these all use the same approach.

A) Get a dumb device that plugs in to the second socket in the outlet that you want to monitor. This is typically a transformer or a relay.

B) Then get a smart battery powered device with dry contacts that you will use to monitor whether the dumb device in A) has power. when the dumb device loses power, The smart device will change state and report to the hub.

C) Then you can just write a very simple routine in the SmartThings app for when the Smart device changes state.

It’s your choice as far as what devices you use for A) and B). It’s a pretty straightforward method. :sunglasses:

Note that none of these set ups allow you to remotely turn the outlet back on after the GFCI trips: you still have to manually do that. But this will allow you to get a notification if the outlet loses power.


I’ve now seen multiple reports that as long as you are in North America and have a SmartThings/Aeotec hub with a Z wave radio, you can get one plug-in device, the Zooz zac38 zwave repeater, and use it with their custom edge driver.

[ST EDGE] Zooz Edge Driver Channel

And when it switches itself from mains power to battery, it will send a message to the hub, and you will be able to use that as the trigger in a routine that you create in the SmartThings app.

So that would be the easiest, but I haven’t seen a specific screenshot of what the routine looks like.

Also, if you have only the station or one of the hubs built into another Samsung device, you can’t use it because it’s a Z wave device. (of course, that’s also true of the Aeotec model that I mentioned.) If you don’t have a Zwave hub, you’ll have to look for something using Zigbee or Matter instead, and probably go back to the two device method.

Also, this would only be good for a situation where you have a two socket wall outlet, you only have one device plugged into it, and you want to be notified when that outlet loses power. Then you can use the other socket for the power monitoring device. If you are trying to monitor power for any other kind of device, this method probably won’t work and you’ll need to take a look at @taustin’s method discussed upthread.

If anyone has the Zac38 can you check and see what the routine options are and post a screenshot? Thanks!