Single speed HVAC fan detection

I’ve contacted Sense about this twice and both times was told to just wait and Sense should find it, but it isn’t happening.

I have a basic gas furnace, with an exhaust blower and the main circulation blower. When I originally installed Sense, after a few weeks it detected a device that was related to this furnace. We were right inbetween running as AC and Heating, so the exhaust blower may not have been always running along with the circulation fan. Sense saw it as ~800 watts when running.

About 2 months ago, the device stayed the same name, but only started seeing it as 93 watts and I confirmed it was only detecting the exhaust blower that starts a few seconds before the circulation blower while things heat up. The 636 watts of the circulation blower are not detected as part of any device and impact the Unknown number only. It has a distinct jump when starting, and since it runs at a separate time, I don’t understand why Sense hasn’t detected it either as part of the existing device like it did, or as a separate device which would be preferred.

Support just says to wait, but 2 months is long enough as it cycles many times a day and has the same pattern, and it is a standard motor, nothing fancy like multi-speed etc.

Especially frustrating as it was included, then the signature differentiated enough to not be included in the existing device, but never seen as a new device.

Same thing has happened with my Dryer. It found the heating element and motor separately and I identified them as the dryer. Then randomly the dryer heating element was not recognized as the dryer but was visible in the unknown.

So… if its any consolation for you, its not a problem unique to you… however I do not believe the answer is anything other than wait.

I’m closing in on 5 months and my gas furnace hasn’t been detected. I’ve tried killing the furnace when I have unidentified loads, but no furnace elements so far.

I’m about 50 days in and it’s picked up the igniter of my gas furnace.

My blower and vent motors are variable speed so might take a while.

About 4 days after I posted this I happened to check the Settings screen and noticed that I had one more device than I saw before. It was Unnamed Motor which was my circulation blower.

Does your fan run on a hourly timer or only when there is a call for heat?

My HVAC was the very first device detected within 24 hours from install, but 6 weeks in and it has failed to see the blower motor. It may be lost in the initial surge, but has a distinct ramp up and continues to run for a few seconds upwards of a minute after the condenser/compressor shuts off. Anyone else have better luck with their Sense seeing this obvious pattern?

*About a 360w decrease when blower shuts off each time

Sense has lumped my blower and compressor into one device which is fine for the summer. Check the stats for the device and see if the Avg consumption wattage is for just the compressor or if it includes the blower too. It will be interesting to see what happens when the winter comes and the blower runs with the gas furnace without the compressor. Hope it doesn’t mess up my AC device detection. It’s the biggest energy user I have.

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It’s hard to tell what’s going on:

Histogram of my total usage with 630-640w steady before the HVAC kicked on and fluctuating between 3830w and 3930w. You can see the compressor shut off, usage drops by 2900w, the blower continues to run for another minute then usage drops by ~366w to get back to the 630w usage before the HVAC kicked on.

Histogram of the specific HVAC device usage from the device page “Power Meter” showing over 3500w usage for the HVAC itself. Not sure how they got 3500w when usage was already 640w before the HVAC started and total only went up to 3900w. 3500+640 != 3900. Plus this does not show as much fluctuation during operation as the first histogram does nor the 1 minute of blower usage at the end. This could be part of an inaccuracy in the modeling, but don’t see how the numbers are off between the device usage and the total usage.

Your second screen shot show it drops to 400W.

I agree that it may not be picking up the cooling/Evaporator unit fan.

(3500 is about what my crappy 13SEER 4 ton AC uses. Hoping to upgrade to a 2KW model - 18 SEER 3 ton sometime next year. Will also need to insulate the house).

I’m not sure where you see the 400w because the second image drops to 0 as it only shows when the specific device was running. The 366w for the blower is part of the 3530w HVAC usage only it doesn’t show the separate power-off cycles. What I also noted was I had a base usage of 640w before and after the HVAC ran, but total usage only went up to 3900w. 3530+640=4170w To me this means one of two things are going on:

  • coincidentally my base usage dropped at the exact same time the HVAC kicked on and came back up at the exact same time it turned off
  • Sense is lumping some of my base usage into the HVAC device and over calculating the device usage by over 200w

This image.


The 410w was from a different instance. The dates and the time stamps show different days :wink:

After some more investigation I pulled up a separate instance from this morning to make sure it is less likely that scenario number one (pure coincidence) happened. It still appears that Sense is showing my HVAC using more than it should be when looking at the specific device usage. I have combined three images together showing the total usage of my house before, during, and after a cycle of the HVAC:

As you can see my usage starts at 592w, the HVAC kicks on and total usage hovers around 3730, and when it turns off usage drops back down to 581w. Calculating HVAC usage, assuming the base usage stayed in the 580-590w range, shows around 3150-3160w.

Looking at a snapshot of just the HVAC device itself (under Power Meter) Sense is still showing that the HVAC is using over 3500w and not the 3150w that it should be using based on the whole home histogram above. So, it still appears that there is a miscalculation or detection issue somewhere…

Your experience is intriguing. I started looking closely at my AC numbers, but only after I was able to accurately detect the furnace blower on its own, using a feature on my thermostat. My AC detection is a merge between two different autodetected components - a Mystery Motor spike and AC (which I presume to be the compressor, plus steady state furnace blower). I see steady state AC operation at about 3400W with a 4000W flatline and a 600W baseline on the Power Monitor. Sense is placing the steady state operation at about 3350W in the Device drill down.

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Jeff, I’ll say it is a detection issue and sense is combining some of your unknown into the HVAC when it cycles on.

To investigate, have the app open and take a look at your unknown consumption, then manually cycle the HVAC on and see if the unknown watts lowers a little then look at the HVAC to see how much watts it reads in realtime.


Excellent suggestion! I followed through and it did exactly what you said – combined unknown into the device:

The HVAC kicks on, and after it is detected, “Other” completely goes away at first. It comes back up almost immediately, but within seconds, Sense moves wattage from Other into the HVAC device and within another few seconds the Other category has vanished again.

Here’s a video of the issue to see it in real-time:

As a side note – I see that the firmware version is now 1.2.1526. Not sure when this was pushed, but obviously this issue isn’t fixed in the update that I just tested. I did notice that I now have a “Currently Learning” and “Up Next” under device detection; which I didn’t have before.

hmm…mine still shows as “unknown”. Did yours change to “other” after the firmware update?

I’m pretty sure its been Other since install --or as far back I as I proof, which is July 21st :smile:

Someone noticed the same. It was just a naming change.

"Unknown" or "Other" Gray Bubble?

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