Central A/C separate components

When the heater runs, or when you just run the hvac fan, Sense shows the Furnace Fan at 400+w. The draft inducer fan I guess is in the Other category, it hasn’t found that.

Now it’s finally cooling season, Sense has found AC. But it shows 1400+w for AC and about 2000w lumped in Other. Not sure which is the condensor compressor and which is the condensor fan. And during AC operation the Furnace Fan doesn’t show even though it’s on, I guess it is hiding in Other or AC during AC operation.

You are definitely right - Sense detects individual components for HVAC systems. Sense originally found my Furnace Fan, but not the draft inducer. I eventually put it on a smartplug and saw what the fan detection was missing. Even before I had it on a smartplug the furnace fan was showing up most of the time with my AC as well, but not always.

I think my AC detection picks up both the AC compressor and compressor fan at the same time, about 3000W with a 5000W spike at the start.

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I am happy that its intent is to identify each component individually. But if I have no way to know if “AC” is the compressor or the condensor fan, so it’s not of much help. And I need the other components hiding in “Other” to be identified.

One other challenge I’m seeing with Sense for IDing AC units is premature off-detection when the AC is running for long periods. Here’s a timeline that blends data from my Sense and from my Ecobee from yesterday. We’re in the middle of a NorCal heat wave - 90 degree temps. My upstairs HVAC (using smaller units than I included in the last post) was running all of yesterday from about 9:30AM onward thanks to the Ecobee commands for continuous cooling (Up_Cool column - 3600 secs / hour of cooling in red). AC2 is the Sense reported hourly energy consumption for my upstairs unit (in blue) and FurnaceUp is the Sense/HS110 reported energy consumption for the upstairs furnace fan (in green). By the looks of the power usage it looks like the furnace controller might have inserted some brief fan, and possibly compressor, breaks around 6 or 7 PM. And either Sense got bored (timed-out) or got confused by a brief break at that time and treated it as an off-signature with no subsequent on (the Sense detected power drops to zero, even though the Ecobee is still calling for cooling)

The good news is that I can see exactly what happened with the furnace fan, since it is on an HS110. It looks like the power reduction was more of a dip, than even a brief off.

So I’m guessing that Sense eventually timed out thinking my compressor couldn’t have been on that long. Of course, that’s speculation since I only have Sense’s view to go by.

I might be able to investigate this a little more by looking for extra “Other” showing up after about 6:15 PM.

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This is pretty fascinating.

You can see in the HS110 tracking that 6:15 seems to coincide with the “valley” in that slight ramp-down then ramp-up waveform.

Meanwhile the Sense detection is a clear plateau “threshold”.

So it looks like Sense timed out the detection based on going below that threshold?

Hard to tell what’s going on because the other AC unit and lot of other device are popping on and off. Here are 4pm to midnight time slices of Total Usage, Upstairs Furnace Fan, and Detected AC2.

Oh well, today my central AC is all showing lumped under “Other” and not even using “AC” or “Furnace Fan” at all. I have 4200+ k in “Other” which is all of the AC components plus a few hundred for the regular “Other” stuff.
It is not even consistent from day to day.

I don’t know how long you have had Sense installed, but my experience is that you need a month or two of the cooling season before Sense settles down and get’s reasonably consistent about identifying the compressor.

I just installed Sense in March and it has been a cool spring here so just very recently started using AC. Ok thanks let’s hope it settles then.

Almost 2 months now and no signs of Sense settling on how to recognize my AC consistently. Usually displayed as a mix of AC, AC2, Other but no discernible logic as to why it is different every day. Today it is all completely under Other.

Hmmm. Do your have a single forced air furnace and AC compressor ? Do the start/on of AC or AC1 have any correlation with the startup of your compressor or furnace blower when they do start. Depending on the thermostat and system, the furnace blower can start before and run longer, or even independently from the compressor.

Yes just one condensor outside and one evaporator in the furnace inside.

Compressor, condensor fan, draft inducer fan, furnace blower , cannot correlate them to what shows on Sense, becuase everyday it’s different.

During heating season the furnace blower consistently showed up as what Sense guessed 90% was Furnace, I named it Furnace Fan. But in cooling operation Furnace Fan never ever shows even though the same blower is running.

In some modern central systems, the fan control during heating and during cooling are different. In my mini-duct based system it varies by almost 2:1. The computer control allows setting those parameters, and the installer apparently chose much higher air flow for A/C than for heating.

If yours is similar, Sense would need two devices, one for fan operation during heating and a different one for fan operation during cooling. Sense thinks of a “device” as something with very specific signature and consistent behavior. That’s why lots of today’s variable (depending on load) speed devices cause Sense to give up on them.

@andy, in your system, where does the “intelligence” that adjusts the difference live ? In the thermostat ? In the furnace controller ? I know with my furnaces, there is a jumper on the controller board that controls fan speed,but it is essentially fixed.

My Unico mini-duct blower unit has a microprocessor based control board that talks to my smart TekMar thermostat system. The microprocessor (which has a computer interface for management) adjusts air flow based on inside temp, set point, outside air temp, and of course whether it’s heating or cooling. Our primary heating is geothermal (which also drives the Unico) radiant floor heating. That’s probably also why he scaled down the heating air flow.

I’d never seen such a thing before, but based on its efficiency and comfort level, I’m completely convinced. So far I’ve not messed with the settings, and the user manual is pretty thick.


@kevin1, my 2017 Trane 17 SEER conventional split system also has different values for blower CFM/ton in heating and cooling mode. It’s a 2 stage compressor, so there are ultimately 4 different speeds that the blower will use in steady-state mode, not including ramp up/down profiles, which are also different in heating vs cooling mode.

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