Vexing "Heat 2" device help?

Hi everyone,

First time poster, but long time reader here. I’ve had my Sense online for ~6 months now and have been presented the challenge to solve what “Heat 2” may be.

Having ruled out various appliances with heating elements, e.g. refrigerators for defrost cycles, etc. I come back to what appears to be a very distinct signature that may look familiar to someone…

While it does not cycle at the same time each day, it does take place daily (or closer to once every 20 hrs or so), and each occurrence takes ~20 minutes (+/- a minute) and averages ~329W.

I’m hoping that the signature looks familiar to someone or if there are any technical people who can decipher what type of device might act this way.

Thanks, in advance, and I hope I can help the community as I continue to detect new devices,

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I’m fairly new here, just got my Sense around Thanksgiving. I don’t think that looks like a heating element, it’s too ‘rough’. A heating element will be smoother as the resistance is a single ‘designed’ value but increases as the element heats up. The resistance increase will follow the temperature, which would be smoothly increasing, not bouncing up and down rapidly.
I would think this is some type of (pump) motor, the rotation being resisted mechanically by the viscosity of what it’s pumping. Tell us more about your home and what mechanical motors (1/2 HP) there might be. Can you catch the device in action and start opening breakers to see which circuit it is on?

Thanks for the input! I admit to being confused by the naming as “Heat 2” given your description that those should generally be smoother. My Sense has picked up our electric oven, coffee maker, etc. all of which exhibit exactly as you’ve described.

To your question on catching the device in action, I’ll definitely continue to do so and report back. Off the top of my head we have a garbage disposal (already discovered device), a hot water recirc pump (generally always on during the day/waking hours), etc.

But we have 2 Carrier Infinity heat pump systems, which are probably registering as a combination of various devices. My initial thinking was some sort of timed defrost cycle. I went outside during one of the 20-minute cycles last week, and there was absolutely no noise or perceptible change in any of the outside equipment.

It’s personally interesting to see the relatively consistent profile given your comments about “the rotation being resisted mechanically by the viscosity of what it’s pumping.” I’m a bit out of my element here, so thanks for giving me those insights to think about.

FWIW, the latest “Heat 2” cycle ran about 9a this morning, so figure it runs for ~20 minutes per ~20 hour interval.

For sure the trace you posted looks rather rugged and is not characteristic of resistive/heat loads/devices. What would be useful, from the community, is some data as to Watts/Duration for typical devices, to limit what is it we need to look into. These multiple ‘heat’ devices (I’ve seen/had my share) that last for several minutes tend to be challenging. I have a fridge + freezer + water dispenser (hot/cold) and each has their own defrost cycle, then there is the heating element of the dishwasher for heated dry cycle. These are the first culprits I’d look into, but one needs an idea of how much current/watts the device draws, and the duration.

That 20 minute duration every roughly 20 hours sounds a lot like my 1 year old fridge’s defrost cycle, but the graph is a little off. My wattage is higher than your ~329w. Here’s more for comparison.

I don’t recommend using the meter view for “device X” when trying to identify it; it’s often not accurate enough (which doesn’t make sense, but trust me). You need to use the whole house meter view for the time period you know device X was on. That view will be a true watt usage graph and will give you a much more accurate view.

Having said that, it does sound like a defrost cycle on a fridge or freezer.

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At risk of asking a dumb question, what benefit does looking at an overall view of the house give me to decipher which of my gadgets is Heat 2 (in this example)?

The reason the whole house view is better is because the “device” meter view isn’t a true view of the actual usage; it’s what Sense thinks the power usage is. You know because the device view shows nothing BUT the device usage, and all other usage is 0w.

Just do some small math and see what the baseline wattage was before device x turns on, then see what the wattage use is after it turns on, then find the difference. This will be the TRUE usage (even though other stuff in the house is on/off). But trust me, the device meter view is not 100% accurate; it’s calculated.


Hey mike13,
I had to look up Carrier Infinity yet got inconclusive results at first glance. I was looking to see if they were a UTC branded mini split inverter heat pump type unit.
Last month when I started using the recently installed mini split heat cycle instead of cooling, I had a heat (2) and later a week or two later, a motor (2) that monitored for some time before I concluded and have since merged into my HVAC data bubble.

Do you by any energy efficient chance have a hybrid heat pump water heater?

Thanks for the clarification. Given the 20 hour cycles, I’ll probably give it a few days as the next scheduled cycle should come on sometime overnight tonight.

Hi fabricgator, thanks for the research! We have the Infinity Greenspeed heat pump, which has a variable-speed compressor that has been a bit of a challenge for Sense to detect. But we only have a standard gas tank water heater.


Update: I pulled the Z-Wave plug from behind my washing machine (used in part to track its energy) and placed it at the kitchen fridge instead. I was able to correlate the jump in power from Heat 2 reported per second (or so) by Sense to the similar jump reported per minute by the Z-Wave switch. I have some charting software running on the home automation server to graph it where the duration matched between the two reports.

So I think that I’ve solved it! Thanks to each of your for your input and ideas, particularly to steer me towards focusing less on the Sense report and more on the likelier devices’ energy themselves (with different means to monitor power).