Multi Stage AC - Ductless Unit Coaire was running on - ‘low power’ was not one of the known devices…
I have come to learn that variable speed/multi speed devices are an issue, plain and simply because of how things work, so i get that.
I have a post going on about training devices…
Now that I discovered this particular issue, and i’ve come to learn that Device Detection & ongoing monitoring has to do with SHARP ON/OFF more than detecting an ‘electrical signature’ while running, is it safe to assume that there isn’t anything I/WE can do to help SENSE with detecting the lower speed/lower voltage use of such devices?
Without Sense I wasn’t able to even know what the REAL Electrical Consumption of it was, and I was BLOWN AWAY at how little it was using.
What I had been using this 2nd AC for was to cool my office down, and I would have it set to come on, run for a period time, and turn off… which of course was using the higher power levels…
What I would be able to KNOW NOW is if I ran the office AC constantly, and it was using the LOWER POWER over an entire day, vs high power on/off as needed, could lead to significant savings
I have two Mitsubishi mini-split AC units, both hardwired to 240. Sense is smart enough to lump them into other, so I can see that they use just shy of 1,000 watts each, much less than my forced air unit that Sense has identified that uses 3,400 right now. I’ve had my Sense installed since January, so while the regular AC was found in just a couple weeks, I know I’m in the long game for the mini splits. I’m hoping that eventually they will be found.
I haven’t got enough data yet but my intention is to delve deeper along the lines of answering your question:
There are many considerations in running a variable-speed compressor/fan split system but some basic physics probably answers your question best …
Assuming constant occupation and constant heat load and the desire for a constant temperature, it stands to reason that the LOWEST POWER that can keep up with the heat load is ultimately more efficient than a cycling system. All thermostatically controlled systems will cycle around the target temperature and the highest efficiency will come from extending those cycles.
In reality though you typically need to balance occupation, load and thermal mass with the maximum capacity settings of your system. Cooling only the air is something that can happen quickly but if you have a lot of thermal mass and sun-exposed windows warming it or other heat load, it will necessitate either a higher power of cooling or waiting longer (in potential discomfort) for the air to cool the thermal masses.
An interesting aspect of air cooling (the usual manifestation of cooling is, after all, Air Conditioning) is that human thermoregulation for homeostasis is often best achieved starting with the head, hands and feet. Sticking your feet in a bucket of iced water will quickly allow you, or even make you want to, increase the temperature on your thermostat!
I have a reasonably well insulated space with good non-exposed thermal mass (blackout blinds at peak sun!) so running at low power is how I achieve a stable temperature.
One last consideration is efficiency of the entire system. e.g. If you have solar and are losing efficiency by sending power to the grid then during those periods, often of peak solar and so peak heat, it may well be more “efficient” to crank your AC system and do some over-cooling of thermal masses. Generate ice at noon!