Variable Speed Motor Detected

Many have been talking about this and many have been looking for it. I have been puzzled by it for sometime now and just got it figured out. ( Where are you going you say…)

Last summer I got a new device detected and I was sure it was not right. Read all the talk about doing resets and stuff. What do you do when you get a new device found and you are 90 percent sure it is wrong??.. Let it go as I did??? Last summer I got a new device detection of “Light 1”. It showed up as I was monitoring “on”. I know it was wrong, my wife was still in bed and I am here at my computer. Also it showed 47 watts. Not a motion detection light with that low wattage.

Well this fall in Northern Michigan the furnace is starting to cycle more often. “Light 1” was on more often then what I could believe that it was a light. It is our furnace. OK… before you go off the deep end and say no furnace runs and heats the house on 47 watts… read on…

We have a high end Carrier Infinity Furnace. ( ). This is a 98.5 efficient furnace. “Variable-speed, constant airflow ECM blower motor for ultimate comfort and ultra-quiet operation.” Also the combustion motor I would guess is ECM. You can go to the URL and read more if you want.

This morning reading my Sense News…Etc… I always have the app up for my furnace in the corner screen. Set to the screen of operating status, showing percentage of heating. This furnace is so quite you don’t know it is running. Forced hot air with no drafting in the rooms. I have put small streamers on the air vents to see that it is running. ( Please don’t laugh and fall off your chair… )

Let’s look at some data… Format will be Watts of Light 1 and percentage of heat from Carrier app… First number Watts, Second number % Heat. Some may not make sense for one motor my run / draw more and skew the watts a little. I logged the readings about every 15 to 20 seconds.
( 112, 63; 114, 61; 120, 60; 114, 57; 107, 56; 109, 54; 101, 52; 93, 49; 107, 49; 104, 49; 96, 48;
103, 46; 98, 46; 101, 42; 91, 41; 80, 41; 53, 41; 57, 40; 56, 40; 48, 40; 47,40 ) Furnace will run for 10-15 minutes at the 40 percent prior to shutting off.

Renaming Light 1 to furnace.

There you go … Variable speed motor detected… Gerry


My Trane air handler has a variable speed fan, and at least part of it has been detected. I think it only detects the initial startup though, because Sense thinks it only runs for an average of 1 second for 30W, but my Trane thermostat is connected to Nexia and looking at the log of events and comparing it to the mains power meter and the device history in Sense, the two line up.

I live in FL, and it’s crazy how much power I use for the AC, even with a really efficient unit. The last few days, we’ve ended the day at 14 - 18 kWh used. In the summer when the AC runs for about 20 out of 24 hours, we tend to be around 36 - 43 kWh.

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Real fine… At times I watch my ‘bubble’ for the furnace and the wattages goes up and down. With this I am sure that it is locked in on the air circulator fan. It will show from about 60 to 140 watts. I believe that when my furnace comes on it is at 65% on the ‘combustion’ fan and the air circulator is maybe not on at all. After about 10 seconds or so of the combustion air fan running at 65%, it will lower to about 40-50 percent depending on the requirement of the heating cycle. Then the circulating fan will ramp up once the heat exchanger will be building up heat. I believe this is where Sense will show up. I believe that there are 3 items that modulate up and down depending on the heating requirement. The combustion fan, circulating fan and the gas valve.

The furnace is a 100k BTU’s and modulates from 30 percent to 100 percent in 1 percent divisions. It is of 98.5 percent efficiency.