Refrigerator ZWave Temperature Sensor

I have a fridge which randomly freezes up. I attempted to get a zwave sensor to monitor it remotely. Unfortunately, because it’s basically a Faraday cage, the battery dies very quickly as I assume it’s power is all the way up. Does anyone have a better way of doing this? Maybe a sensor with a small wired remote probe?

Not sure what kind of fridge you have. Some of fridges used i.e. in hospitals and grocery stores might have space for installation of additional temperature probes.

In essence what you need is a sensor with an external probe. Look for sensor which allows to plug a thermocouple. Using such thing you can separate electronics and battery from environment which is under supervision. Not sure if such things are available for zwave, but its worth looking for them.

I have managed to solve that problem with DS18B20 temperature sensor connected to Basic Sonoff switch with Tasmota. It is connected via very slim flat cable attached with white montage tape on the fridge ceiling. It is almost invisible during every day use. No problems with that for a few years.

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I also used flex ribbon cable, to allow connection between a sensor (the waterproof ds18b20 kind) and a ESP8266, which does mqtt over wifi. Not ZWave, but the same connection could be used to get out side the fridge.

Temperature Sensor | Scott Hraban’s Home Automation if you want details on my diy sensor.

The flex ribbon cable goes right under the rubber seal without compromising the seal.



I use a combination of an RTL SDR device (cheap), GitHub - merbanan/rtl_433: Program to decode radio transmissions from devices on the ISM bands (and other frequencies) (it can ouput JSON which is pretty easily readable), and cheap Acurite fridge/freezer sensors. You need to use the Energizer Lithium AA’s in them, normal alkalines or rechargables die pretty quick in a freezer environment. Altogether probably under 50 bucks to get a few freezer/fridge sensors and very cheap to just add more Acurite temp sensors wherever you need one.

Zigbee temperature/humidity sensor (Sonoff SNZB-02 - yellow), TFA Dostmann temperature sensor (433 MHz via SDR - green). Battery of the Zigbee sensor still at 100% (after two months; according to sensor report):

Please do not take this the wrong way . But basically what you are doing is trying to use a software solution to resolve a hardware failure. If your purpose was to monitor your fridge to use some type of DIY thermostat or energy conservation approach what you are doing would make logical sense and perhaps the cheapest way would be to use something like ( then use any zwave or zigbee or what ever type of contact switch to notify you when it crossed thresholds and you could in fact use any simple widget from a openhab perspective.
There are also several thermostat like option that allow you to monitor/use either a serial (RS485type) that you could port all the real temp data out but of course those are much pricier.
I would be more concerned with trouble shooting the fridge to find out why it is freezing up randomly.
Clean condenser coils and other basic activity may be all it needs.
A refrigerator that freezes up is a pretty basic common issue to resolve with a few simple checks.
You will find many great u-tube videos on what to check and how to check it based on your model. Also keep in mind a fridge that freezes up is wasting tons of energy as well.

Thank you all for the suggestions. I’ll go do some research on them to see what’s appropriate for this.

So you’re half right. There’s nothing actually wrong with the fridge day to day. The problem is when one of the kids leaves a door open. The humidity in the air sucks in and the drains freeze up. Then the coils freeze, then the fans freeze, and were hosed.
Unfortunately, we don’t pickup on the caacading failure until a day or two later when the foods already all dead. I’d like to be able to set a temperature threshold with an auditory alert through my sonos speakers so we can hopefully save the food.

understand that failure mode completely. :laughing: I have several of the cheap less then 20 dollar controllers I linked in my last post for some very similar conditions. if what you want to solution is door ajar then perhaps a simple door contact zwave or zigbee is a much better approach no temp monitor nor wires in to fridge just simple door contact on outside at top required door ajar and a simple rule after it is ajar for more then so many seconds. one for fridge side one for freezer easy enough to do and all external.
Now if you want to get really wild and automate you could also add a door auto closer but that takes the fun out of telling the child to go close the refrige door and teaching them to pay more attention to what they are doing. While they wonder how you knew it was open! :upside_down_face:

Yeah I’m definitely adding the door sensors as well. The problem is that even if we catch the doors the fridge may still slowly fail over days so I still need awareness of what’s happening inside. The sensor I have now is based on CR2477 batteries and they maybe last a week.

If it is really freezing up that quickly you may also have a issue with the defrost circuit weak defrost heater or defrost timer that is not quite up to snuff that would make the fridge way more subject to freeze ups. Drains freezing up should not cause the evaporator to freeze up just cause water on the floor and inside bottom of fridge side when the defrost kicks in till it melts and drips out to the drain pan that sits on the condenser and normally evaporates any water that was accumulated.

@jimduchek Would mind sharing more details about your setup. I’ve been looking for a good solution for this, and yours sounds pretty good. I have a regular fridge where I would want to monitor both freezer and fridge compartments, a beverage (beer) fridge, and a chest freezer. So I need a solution that supports 4 sensors.

There’s really no limit to the number of Acurite sensors you can use (I think I’ve got 8 or so going, in various places?) I mean, I’m sure there’s some limit :D. You can actually probably find them at a local big box store as well. Some of them (especially ones that come in kits with a receiver) have switches on the inside for channel, but the SDR receiver will pick them up regardless, they have internal serial #'s that get transmitted as well and that’s what I use to split them

My Jython script that sorta runs it. Honestly this is a little overly complicated, I was kinda playing with some other stuff at the time.

Thanks! Much appreciated.

Can I infer from this that range is not a big issue? I’m interested to know the max distance you have from sensor to SDR antenna, and whether interior walls (i.e. wood studs and drywall) pose a big issue.

So using the SDR, you really don’t need to use the receiver that comes with the set?

Sorry @morph166955 I’m not trying to hijack your thread. :wink:

… and even if you encounter a limit, you can switch to a different sensor - the rtl_433 documentation lists several sensor types manufactured/distributed by Acurite:

[10]  Acurite 896 Rain Gauge
[11]  Acurite 609TXC Temperature and Humidity Sensor
[40]  Acurite 592TXR Temp/Humidity, 592TX Temp, 5n1 Weather Station, 6045 Lightning, 899 Rain, 3N1, Atlas
[41]  Acurite 986 Refrigerator / Freezer Thermometer

It might be cheaper (and more robust) to use a Zigbee approach though:
20 USB for the dongle (e.g., plus 10 USD/sensor.

Which way is right really depends on which additional sensor types you are going to use.

rtl_433 does support MQTT which makes an additional script unnecessary, see Fleet management using openHAB for an worked example.

Ah. Range may be some issue. No idea, I live in an RV. No sensors farther than 20 feet away from the receiver, but that 20 feet seems to be no problem. Occasionally I get dropouts from my ‘outside’ sensor which is probably the furthest one away but it’s also ziptied to the metal frame, which probably doesn’t help the signal. There’s one in a chest freezer that’s about 15 feet away from the receiver (and the freezer has a metal case), which works fine.

rtl_433 does support MQTT which makes an additional script unnecessary, see Fleet management using openHAB for an worked example.

Oh, nice! That’s new, it certainly didn’t 4-5 years ago when I set mine up. That makes it a ton easier.

If range is an issue, consider using Zigbee and a Zigbee repeater (e.g., TRÅDFRI Signalverstärker - IKEA Deutschland) near the refrigerator.

As stated before, 1-wire temperature sendor connected to the Door/Window sensor will have the added advantage of monitoring whether the door is open. Which could then alarm if open for more than a given time.

No worries, I’ll give you a pass lol!

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