Ideas Wanted - Roof Heating Cable

I’m looking for ideas to control the “On/Off” cycle of a roof heating (de-icing) cable. The cable is currently operated by a non-smart control sensor that turns it on when the temperature is near or below freezing and moisture is detected by a sensing cable installed in the gutter and along one edge of the roof. This setup works well when roof and gutter is completely dry. The heating cable remained off until our first snow fall, a week ago. After snow started falling the sensor detected moisture in the gutter and on the roof then turned the heating cable on. The snow’s now gone but the control unit won’t shut off! The gutter is damp which I think is preventing the control unit from shutting off.

The gutter isn’t filled with water, it’s just damp along the bottom. I suspect that until the sensor cable dries completely, the heating cable will remain on. At this time of year, weather here can be very damp. Until it gets much colder, I suspect the sensor will not dry sufficiently to turn off the heating cable.

I see this extended on time as energy wasting and wish to install a TP-Link HS401 extension receptacle ( as additional control over the heating cable. The idea would be to have HA weather control the on/off cycle of the HS401. What I’m unsure of is how to configure the automation.

I thought about using current weather conditions, specifically “Snow”, to activate the HS401. One problem I see with this approach is that current conditions may change from snow to clear, or some other state before all snow on the roof has melted. To overcome this, I thought a timeout condition could be added. Keep the HS401 energized for at least 24 hours following a change in weather conditions – snow to clear for example.

I’ve searched the forms for related ideas. I came across one posting ( but it’s based on temperature so I don’t think it would work in my case. If you have any suggestions or alternative approaches, please let me know.

With appreciation

You could use the heating sensors as designed, then put in an outlet that does power monitoring so you can know when the cable is heating or not and build out automation that only allows it to heat for X hours or have it analyze your weather stations.

The idea being that you don’t have to know if it’s snowing or not at all times, only when you detect if the cable is heating. Outside of that you would have to put your own moisture/temp sensors around (i.e., ESPHome device, Z-Wave leak sensors, etc) to figure out if you need to start/stop the heating element.

You could also use multiple weather extensions to average the temperature or snow conditions and act on it that way. Just a couple thoughts.

I have my version 2 setup at my mother’s house. I have a ESP8266 in the detached garage to detect garage door open and close. I also have a DS18B20 temperature sensor sticking out of the garage eve to get outdoor temperature. I bought an outdoor plastic utility box, installed a Tripp Lite power strip with breaker and on/off switch, and two Sonoff S31 smart outlets. (Because she has two roof heat strips.) I also added a Thermo Cube and small LED light bulb for the box in hopes of keeping it warm (since it’s outside). In HA, I have a boolean variable called “snow on the roof” and expose it so my mother can turn it on or off. When it’s on, automations take care of turning on and off the heat strips between 10-degrees F and 35 degrees F. (I can adjust these if needed.) No it’s not completely automated because a human has to turn it on and off.

In my case the outside outlet that powers this is a 20 amp GFCI. The Sonoff S31 is rated for a 15 amp max load. I had to figure out how much the two strips would draw. The power strip breaker makes me feel better too. The S31’s are flashed with ESPhome. I can also see the power they’re drawing, so if one strip dies I should know it.

I’ve tested this setup but won’t know how it will work in the extreme cold until this coming Winter.

Version 1 used an smart outdoor outlet mounted inside an upside down bucket outside. This failed, I think, because the outlet isn’t rated to operate at temperatures like 0 degrees F. Works great inside the basement but not in the extreme cold.

@CO_4X4, I think this is the way I’ll have to go. Any ideas on what those extensions would be and how they’d be configured in an automation?


Mark, this is an excellent point! I’m able to see the control unit from a bedroom window. This allows me to monitor the units on/off function light. Monitoring current flow is an excellent suggestion. Just because the control unit turned on doesn’t mean the cable is operating. There could be a fault that would go undetected until snow builds up on the roof. Not good!

I think a smart outlet with power monitoring would be a wise addition to my setup.

Ya this post dates 2021 but just in case this situation interest others. I followed the idea of using Canada weather hourly forecast for my location to detect snow as input to an HA automation using sonoff switch supply to roof heating. Which work fairly well. I then added a rain / snow detector hook up to a second sonoff switch (see reference) . I use the switch as an signal input to the hourly forecast heat cable automation.

I installed the double switches in a box with power and exit 120vac stand plugs and supply for the sensor . The added benefit is that same box setup can be re-use for watering system in summer simply by enabling a different automation to control the water valve.

(rain/snow sensor is )