Induction motor for HVAC detected

This is all new to me so I’m a bit like a kid in a candy store.

A few days ago Sense detected a device classified as “furnace”. Took me a bit to figure it out since I was thinking it was the primary blower. Turns out what it detected was my induction fan motor that runs prior to initial ignition. Still waiting on quite a few devices but it’s keeping me busy :slight_smile:

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I’m not an HVAC guy, so is there a general guide for what components there are to a gas furnace and the sequence of their operation? I haven’t been able to nail down a single part of mine, and I could use some help to make sure I’m not missing something.

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Well generally on a modern high efficiency furnace the cycle starts with the thermostat calling for heat. The induced draft motor will come on pulling combustion air through the unit and then the gas valve will open and the ignitor will activate to create a flame while the flame sensor tests to ascertain if a stable flame has been established. As the heat exchanger starts to heat up the forced air blower will come on to absorbe the heat and circulate it around the house. Hope that is what you were looking for.


It’s a start, thanks. Are their archetypal patterns that each of these look like? It would be great to have a few examples of each to look at. Hmmm. I’m wondering if we shouldn’t be building a wiki to help each other out with this kind of information.

The induction draft motor and the blower motor will most certainly be identified as separate devices. What the categorization of each of those devices will be may be up for debate. But in a gas forced air heating system the only two major electrical devices are the motors.

I’ve had Sense since July and it has yet to detect my gas furnace, air conditioner or the heat pump in the attached apartment. My other devices is frequently 2,500 watts or more.

I have a question as well. I’m not sure if it should be here or on it’s own thread but here goes…

I have two units, a 2.5 and a 3 ton (tonne?). heat pump w/ “emergency/auxiliary” (electric) heat and the a/c units. The a/c units haven’t run since I’ve had Sense and I haven’t played with turning them on yet. It’s the heat pump vs electric heat that I’m wrangling with. It’s supposed to use the heat pump if the actual temp is within 2 degrees of the setting and the electric heat if it’s more than two degrees off. It’s my understanding that the electric heat uses exponentially more energy that the heat pump, but in trying to correlate with Sense, it seems like my heat pumps are running about 3,000-5,000 watts and the electric heat about 1500-1800. I’ve had the HVAC guys out three times,including supervisor and seniors techs. They’re scratching their heads but can’t find anything wrong.

any ideas?

editing… I’m assuming that Sense differentiates between the heat pump, fan and electric strip since it’s picked out the elements of other devices.

Hey @Becky,

In this case, I’d recommend submitting this to Sense HomeCheck, a free (beta) program we’re running to look into home issues: Introducing Sense HomeCheck.

Thanks Ben, I will if it doesn’t sort itself out over the next month.

Hi, I am new to Sense - still detecting devices. I also have a heat pump system, a Carrier multi-zone Ductless Split system with 2 outdoor condensing units (4 tons each) and 10 indoor splits, so i imagine it will be a complex signal to identify. I am thinking of putting the Sense sensors directly on the heat pump circuit itself to simplify the identification. Is this possible to do?

Is there a heat pump group?


I’ve had Sense (which we fondly call “non-sense”) for many months, and it’s still hot found most of our all-electric home properly. So, getting weird readings from it is exactly what I’d expect.

Regarding heat-pumps, we have a 5 ton (60,000 rated BTU) Climate Master heat pump, which is slightly less than the combination of your two. It provides heating and cooling, depending on what mode we have it set for. Both Sense and my WelServer show the heat pump draw at about 4,900 watts. We also have a boost for when the heat pump needs some extra assistance…fortunately not that often…resistance heating is about the least efficient/most costly heat you can get.

My system draws 4.7 KW when the heat pump is running and 6.3 KW when the booster kicks in. So, that means that I’m getting most of required BTW for something like 1/4 the electricity cost and the remaining BTU at 1x efficiency.

Unit Power Draw Conversion Rated BTU

Heat Pump 4.9 KW 12,000 58,800

Resistance 1.6 KW 3,412 5,459

So, I believe that you are seeing about the correct heat pump draw. The only benefit of the resistance heating is that the response time is quicker, which is why it kicks on only when the temperature is very different, runs for a short time, then turns off again.

I’m surprised your HVAC guys can’t explain what your system is doing, because what you describe matches my understanding of how such systems work. Basically, since a heat pump is about 5x more efficient than electrical resistance heating, the objective is to use the heat pump for the bulk of the load and only trigger the (much smaller) booster heating when absolutely needed.


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Hey @belli ,

Sense’s current sensors by no means be moved! Moving the current sensors from the mains will throw off the system and you’d need to do a data reset to get things working again.

Device detection takes a little time. Some devices will be identified within a few days, others may take a number of weeks, and others may still need algorithms improvements in order to be properly detected. Check out this blog article that someone wrote about their first month experience with Sense: My First Month with Sense - Sense Blog. It should give you a sense of what to expect.

Thank you Andy.

Andy, the confusion is that when the aux heat kicks on, it dropped.

here I found this screen shot.


That’s before it identified many devices, this was turning the device on and watching the overall totals. (it came up because I had my annual HAVC checkup and the service guy tried to ease over some quirky stuff so I pulled my Sense out even though it was new). They replaced one part that didn’t help anything except their own bottom line and reprogrammed one of my thermostats.

It has since identified some if not most of the devices that make up the heating system so I’m watching and waiting. I’ve been keeping a closer eye on it and it seems to be more in line with what you’re saying. The waiting is hard. :slight_smile:

That does seem odd. Usually you would see a (hopefully short) bump up when the booster kicks in, not a drop. You would also see somewhat longer periods with no boost heat at all.
Best of luck sorting it out. Andy

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