So. I’ve had Sense for about a month. After reading a bunch of blog posts and forum post about the elusive AC I get the impression that my AC will likely never be detected.
I have Carrier Infinity variable speed AC with something like 6 stages.
Anyone reported Sense picking up a variable speed AC system?
On the upside, Sense does support that the stages do have different power draw and is not just a sales gimmick.
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I have a similar Trane system. Variable speed air handler and variable speed compressor. The issue is that Sense is looking for on/off events, and our systems are designed to run at a low power speed for most of the day without turning off. I know it’s something they are working on, but I wouldn’t expect our ACs to be detected, at least not fully.
My system actually has a variable speed compressor and single phase air handler/fan so it does turn on and off. It’s just that it’ll often run between ‘dehumidify’ to stage 1-5 for several hours at different stages without turning off.
Sense did originally confuse the AC fan with my water heat pump but this seems to have improved over the last week.
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Usually these systems have both the air handler and the compressor run at variable speed. In most homes they are both also single phase.
From what I’ve seen, Sense can sometimes detect the high setting of these but that’s it. So people will see it in Sense and it will appear to run for 3 to 5 minutes. That’s the length of time they usually run on high before staging down.
There is a misconception that these are designed to run all the time. That is not actually the case. They do have longer run times because the btu’s Moved and lower speeds just naturally takes longer. But they use less KWH per BTU making it more efficient overall.
Yeah, I guess there may be a variable air handler but the control thermostat only list the fan as on or off. So I’ve noticed at Stage 1, the combined fan/compressor system draws only 600-700w(hard to tell from the monitor) but Stage 5 can be over 2000w.
This system works well to precool a well insulated home when you have solar and time of use rates. Keeps the home cooler than what you’d need but it’ll “waste” non-peak solar and keeps cost down during peak hours when it’ll just use lower energy maintenance modes.
Here’s a simpler detection to ponder in this regard that might help to decrypt what’s going on:
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(Fancy) Oven hood with 4 discrete fan speeds and halogen lights with 5 “electronic” switches on it. It’s not strictly “variable speed” but it is revealing …
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Sense has so far detected the hood as “Heat 1” which is triggered when any of the 4 fan speed switches is activated.
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Looking at the detection PM, Sense does not seem to have missed any of the hood activations … which is usually once a day like clockwork … despite the likelihood that we are switching the fan & lights on at slightly different times. Clearly the light is not part of the detection.
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Regardless of the fan speed selected, the fan is detected BUT it will show the same peak wattage and general ramping despite the fact that the different speeds have dramatically different power usage. Meaning, the “on/off signature” seems to be the same regardless of the fan speed. Makes sense given the electronic switching.
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Notice the l-o-n-g ramp down in the individual signature. This is not a reflection of the actual power so much as an arrival to the “average” plateau. Algorithms at work.
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From May through August the peak wattage according to Sense has dropped from around 270W to 250W.
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Were we using higher fan speeds for some of the time earlier in the year? Or did the supply voltage change? Again, notice the nice averaged plateau of usage.
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I have to install a smartplug on it!
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