Unknown Heater, roughly 1 minute, roughly 3 times a hour


Runs 3 times a hour on average. Uses about 240 watts of power while running. Only runs for 1 minute each time. (55 seconds to just over a minute). Sense detected it as a Mystery Heater. Frequency of runtimes doesn’t seem to change throughout the day, but the gap between runs changes. Sometimes 10 minutes, sometimes as much as half an hour, but it maintains an average of 3 times an hour all day. All night.

If it is a motor, it has a very low startup current.

Some background:
Gas Water Heater, the rest of appliances are all electric. The AC has a blower that runs for 10 minutes an hour…so not that either.

Any ideas?





I have one of those too, looks almost exactly like that. Although my water heater and furnace are both gas, and my A/C has not run in a couple of days due to the cooler weather. I still haven’t figured out what it is.


I’m glad I’m not alone. It’s really odd. What kind of refrigerator(s) do you have? We have a Samsung refrigerator that has 2 compressors / evaporators… one for the freezer, one for the fridge. I can’t see why it would run for just a minute 3 times an hour like clockwork, but just trying to work it out.


I have three refrigerators (only one of which has been discovered): Kenmore (and it is definitely not this one, as I managed to turn it off while the mystery heat was on and it didn’t go away), Amana in the garage, that one is like 20 years old (it has an icemaker, but it isn’t hooked up or turned on), and a mini fridge. I have tried to rule it out on the other two fridges, but the mystery heat runs in such small increments, it is hard to tell whether my unplugginig something made it go away, or if it just was time to stop normally. Someone on this forum did suggest it might be the icemaker or defroster though. It just isn’t one of those things on the Kenmore (which is my main refrigerator and the only one Sense has found so far).


Thanks for the insight. I also have a Kenmore Fridge w/ Ice Maker as one of the 3. The defrost cycle on any freezer should be in the 18 to 30 minute range. So, that doesn’t fit the “1 minute on” that we have here. I think it is interesting that it has a run time that varies from 55 seconds to roughly 62 seconds. There might be some delay / lag in Sense detecting the device turn on / off… or it might be an “analog” timer that is running this for about a minute. I have literally gone around the house room by room, inside and out, trying to think how any of my devices could fit this profile.

When I get to the point where I’m ready to narrow it down, I’m going to just unplug each refrigerator for 40 minutes or until the next time the “unknown heater” comes back on and rule them out 1 by one. If it isn’t a refrigerator, then I’m going to have to go circuit breaker by circuit breaker ~40 minutes at a time or next time the unknown heater comes back online to rule out that breaker.


Actually, I do have a slight difference. The average run time of my “Heat 5” is 1:27. So I guess mine stays on a tiny bit longer than yours does. However, the usage stats for this month alone say it has been on over 2000 times and averages 204w each time. Do post an update if you figure it out, I’m stumped.


Are you on Septic or Sewer? I have a septic system with a septic pump. From what I read, a lot of those use ~500 watts, but they run for short amounts of time (when using a float / basin system). Not sure why it would run 3 times an hour pretty regularly unless I had a water leak somewhere. Pretty sure I don’t. I have a well pump here and my well would be running a lot more often if that was the case.


Nope, I have city water.


So, it seems that my mystery “Heat 5” must be something to do with the refrigerator in my garage. Sense had discovered the fridge overall, but I wasn’t sure it was actually the garage fridge because it didn’t seem to go off when I would unplug the fridge while Sense said it was on. However, yesterday we unplugged the garage fridge, and since then, we haven’t seen either the “Garage Fridge” device or the mystery “Heat 5”. So, looks like Heat 5 is associated with that refrigerator somehow. I can’t imagine what it would be doing though. I don’t have the icemaker turned on. Maybe something to do with the defroster? But still, why would it run so frequently?


Thanks for the update! I’ll try fridges first when I go to try and narrow this down!


Sump pump?


I’m not familiar with any sump pumps that use 2 amps or 1 amp (120v vs 240v). Also sump pumps have a float. This load is running about 3 times an hour day and night.


Could it be an air circulating fan in the frige? It might come on and not the compressor.


It certainly could be. Would it make sense that an air circulator would come on for almost exactly 1 minute 3 times an hour (average) day and night? I’m not sure why it would vary so much in terms of coming on anywhere from 10 minutes to 30 minutes apart… but the average of about 3 times an hour certainly holds strong.

I really wish Sense would show whether or not a detected device is 120V or 240V. That would certainly help narrow down the search for devices.


Mine was definitely something in the fridge. Unfortunately, when I went to plug the fridge back in, it started tripping the GFCI outlet that it is plugged into. I thought it might be the outlet so I tried it in another GFCI outlet that is within reach, and it trips that one too. Weird, it was working fine before I unplugged it. But on the other hand, I haven’t seen any more of the mystery heat device since it has been unplugged (over a week now).


I agree that would help. What i do to determine 120 vs 240 is, if it a significant enough of a draw, is goto Settings\My Home\Sense Monitor\signals and watch the realtime wattage info for the mains. When it’s 110 you should see only one main increase proportionately, 220 would spike both. It helps to have two instances of the app running to correlate evidence of device turning on/off looking at mains to the timeline readout in the second app.


Thanks. I’ve tried that with mixed success. It would work better if I had two devices to run the app on. I don’t, at this time. The info shouldn’t be that hard to display in the app if they choose to add it.