Another mystery heat

I have two new heat devices that have been detected a couple of weeks ago, but since then I’ve only seen them on once. I can’t imagine what they could be. Do these graphs look familiar?

Heat 3

Heat 6


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maybe a heating element internal to a device. … the second one, with the spike then level.

the first one, i have a mystery heat as well. I thought it was the heating element in the dishwasher, but it’s fired when the dishwasher was off .(decided it must the the defroster in the fridge)… and then was firing repeatedly when I washed dishes yesterday - so now I don’t know again.

please post again if you figure it out.

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That’s the thing it’s so infrequent I have no idea what either of them could be. And the run times are so short I’m not sure it would be a defroster either. Definitely a puzzle.

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Many gas appliances have igniter glowplugs in them that stay lit for the entire duration that the gas is on. They draw around 500 watts.

The first pic looks like my gas oven which draws 500watts whenever gas is on. The last looks like my gas dryer. It’s glowplug only stays on briefly when the gas valve opens.

So look at your gas appliances.

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I’ll bet my mystery heat is my oven. I use the stove all the time, the oven seldom. I did have it on yesterday. I didn’t think about it having a glow plug. the surface burners have an electric igniter that just sparks. I’m a little embarrassed to say I didn’t know the oven was different. I can test that easily when I get in tonight.

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Hmmm. The only gas appliances I have are the water heater and two furnaces. Since neither of these things has come on at all in 3-4 days, I don’t see how it could be one of them, unless there is another component associated with them that is less frequently used.

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I have an LP hot water heater as well, but I don’t believe it has a the same kind of igniter that the dryer does. it sparks, like the stove top so I don’t expect sense to see it.

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a quick test last night proved that mystery heat 3 is indeed my LP oven. avg consumption 309 watts. avg run time 11 minutes. It’s a GE LP conversion. I didn’t find a model number.

Here is the pattern. You can see where I turned it on and left it on almost an hour. Screenshot_2017-12-27-07-07-43

Here is a close up. it doesn’t really spike, just comes on and holds pretty steady. Screenshot_2017-12-27-07-08-01

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You should see power draw every time the oven’s burner comes on. The irregular spacing of your chart kind of says that sense hasnt quite got the pattern learned and it’s missing some pulses… It took several months for it to pick up every burner cycle on my oven.

I also thought that once the oven got hot, it didn’t need to heat up as often… this is all so new. This has been ID’d for awhile, but I literally don’t use the oven maybe once or twice a month.

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I suspect the second may not be a heat source, but a motor, perhaps a fan integral to some appliance that you’ve no direct control over.

The power-on transient is the clue and, perhaps, if it’s an easy starting motor, it’s not triggering the frequency domain parameters that are no doubt used to identify motors.

I’ve had Sense identify my HVAC fan as a heat source.

Us correcting the mis-identification should be slowly tuning the detection process if all is set up as I envisage


Well I figured out what heat 6 is,and it’s apparently my stove. Interesting because the stove had already been detected (well, two burners on it anyway). So before on the particular burner, it would only show up if we had it turned up fairly high. This new heat 6 seems to be associated with having the burner on low. It seems odd but that has to be what it is, and the stove is used infrequently. Still no idea what the other one is though.


So, I’m still trying to track down Heat 3, which runs at such odd intervals, I have no idea what it might be. Here is when I have seen it in the last four weeks:

12/27 between 6 and 7pm
1/1 between 8 and 10pm
1/7 between 2 and 3pm
1/13 between 5 and 6am
1/19 between 4 and 5am
1/25 between 6 and 7am

Anyone have any idea what this could be? The pattern of every six days seems strange, as all my refrigerators, gas furnaces, and gas water heater were all running consistently during that time.

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One process is to ignore the odd (distracting?) pattern of days and times and consider what it could be based on that sample of about 2 mins on / 1 min off and a consumption of about 600W, looking like a resistive only (heat or light) device.

You’re then making the assumption that Sense is only sporadically identifying it so far, which seems reasonable as part of the machine learning process.

It’s also worth looking at the overall power meter display during the time when sense is detecting this - can you see that pattern superimposed on the overall steady power trend or not?

The above thoughts are based on my experience of Sense not consistently detecting my HVAC fan, so far at least.

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A good point.

Also note the longer first draw and then later draws consistent in timing and duration (if you can trust it, it almost looks like it failed to detect a shutoff with the flatline there). Like it’s trying to warm something up. A stove top, one leg of the oven, a toaster oven?

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@Mcraeh, @NJHaley has unwittingly triggered what may be some useful activity between my ears.

The sporadic nature of the power consumption could be due to a very specific fault in an appliance that I have seen before (pre-Sense).

The clue would be if that power consumption is appearing as additional to whatever was the steady usage at that time, especially in those middle of the night time slots. If not, it’s likely sporadic detection. If it is, read on…

Then I’d go looking for a heating appliance, say a coffee machine, that had those characteristics when it was operating and I’d unplug it for a few days when not in use and see if it stops The current is about right, 6 or 7 amps.

The potential fault is a power relay that’s progressively failing in the on state, allowing what’s typically a second thermostat-controlled relay to perhaps intially allow it to heat the water in a reservoir, then cycle to keep it at the desired temperature. So it can’t be a kettle, or a toaster. It certainly could be an espresso machine or …

Actually an example of how useful Sense can be when detection is really mature and we’re able to assume that odd usage data is indeed telling us something is behaving oddly


I’ve certainly been there before. I posted this a while back, but there was a weekend my fridge signal was all wrong. I thought it was a Sense error, but turns out my fridge was long cycling because the radiator fins were blocked up with dog hair.

More recently, our water heater went out and Sense was giving wonky signals. Sense helped pinpoint exactly when it started failing.


Well, that is food for thought. I actually had not considered that Sense might not be accurately reporting the device, which I should have since it does frequently misreport other things. So that is certainly possible. It might be difficult to catch, but I’ll try to get a look at overall power usage next time it comes on (assuming it isn’t in the middle of the night).


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