I tried the Aqara sensor in my upright freezer recently after completing a manual defrost and cleanout. As the freezer worked its way down, the sensor reported temp, humidity and battery life, perfectly, but once I hit about -13C or 8F it stopped reporting. Tried numerous locations and could not get it to work. Moved it to a nearby fridge and about 10mins later (after it warmed up?) it started reporting again.
I use Yolink temperature and door sensors.
They work fine in the refrigerator. The temperature sensor reacts extremely quickly.
Itās a bit dicey in the freezer. The sensors do work there, for a bit. But eventually, they go offline, sometimes in just a few days. I think the AA/AAA batteries canāt operate properly at those temperatures. Itās a PITA to replace them, also. Requires tweezers for the temp sensor.
Could you check for cooled air escaping the fridge/freezer using an external IR thermometer pointed at the gap that exists when the doorās open even just a tiny sliver (or wide open)?
This gadget might do it MLX90614 non-contact thermometer ā ESPHome
That says youād need an IĀ²C Bus too
This approach wouldnāt detect a mechanical failure that leads to a loss of cooling, but it could detect cold air coming out a door for however long you want ātoo longā to be before triggering some alarm
This also wouldnāt work if the ambient temperatureās as cold as the applianceās interior. But on the plus side, if thatās the case, your food isnāt going to spoil due to the door being left open, so thatās fine that you wonāt get an alarm about your food spoiling. (Assuming some other technique is in play for polar bear mitigation)
For freezer / fridge temp monitoring, I highly recommend the Switchbot IP65 Indoor Outdoor Hygrometer, available on Amazon. Theyāve been rock-solid.
- Price - about $12
- IP65 water resistance rating (very well sealed)
- Using them here in 2 fridges and 4 freezers, for 18+ months.
- Specs say battery life 2 years, & I believe them. (2x AAA)
- Bluetooth; specs say 394 ft range. Iāve got ESPHome Bluetooth Proxies around the house; I did have to move one BT Proxy closer to one particular fridge/freezer to get solid connection.
- Positioning doesnāt matter within the freezer/fridge.
FYI- I also have a Wi-Fi smart plug on same circuit as fridges / freezers, so when those go offline I know the power is out. (Iāve had a temperamental GFCI circuit that runs two freezers in one of the garages. Supposedly fixed, but I want to know.)
Also FYI, my ESPHome BT Proxy units are very small and unobtrusive. I use āAtomUā microcontrollers from M5Stack, which have a USB-A plug that goes straight into flat wall-hugging USB adapter. So Iāve got several of those around the place.
But my main point is: I personally wouldnāt use anything but the Switchbot IP65 hygrometer / thermometer units for fridge / freezer monitoring (along with ESPHome BT Proxies).
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Thank you.
The Switchbot IP65 Indoor Outdoor Hygrometer are no longer available from Amazon, but can be bought from Switchbot.
Is their hub required? Iāve got a Zooz Z-Wave module, and then there is the Zigby native in my HAS Yellow.
Thanks
Switchbot IP65 Hygrometer uses BLE (Bluetooth Low Energy), not Zigbee or Z-Wave. I believe you can put a Bluetooth USB dongle on the HA Yellow. But even simpler, & more flexible, would be to put a Bluetooth Proxy on your network. Then you can position that device anywhere you want (e.g., near the Switchbot unit), as long as the BT Proxy unit has wifi connectivity to your HA.
My preferred choice for quick/simple BT Proxy is an Atom U microcontroller from M5Stack ($12.50), programmed via a USB cable from your PC to be a BT Proxy, by using the āESPHome Readymade Projectsā web page. Then just plug that Atom U device (which has USB-A connector) into a USB power adapter on the wall. And HA just automatically starts recognizing Bluetooth devices.
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Thank you,
Iāll look into this.
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Apollo TEMP-1 sensor - ESP based and get the long flat cable sensor option.
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I use these for both of my freezers. Mains powered and easy to place sensor because of the flat cable ( I held cable unobtrusively in place using white duct tape)
Have both been flawless so far.
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i did finally find a sensor which is zigbee, uses standard batteries (2xAAA) and does work in my freezer:
ā¦have tested it against my home-built homematic sensor (with BME280 sensor), see graph below, and it works without problem down to -24Ā°C
ā¦the measured values seem to be a bit off against my other sensor, but is working 
ā¦canāt say anything about runtime of the batteries yetā¦
I use the yolink integration with its hub and the yolink 8003 temp humidity sensorsā¦ I have 2 fridge / freezers, each has an 8003 it. The LoRa radios reach the hub with no problems. And even in the freezers, the batteries last about a year.