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There's a product called Ecostella that's supposed to reduce a home's HVAC power use. According to the website, it does this using two methods:

  1. It runs the furnace fan for a while after heating or cooling is complete.
  2. It turns off the AC compressor "every time your system has run long enough that it is holding all the energy it can." I presume this means the AC compressor will operate intermittently instead of continuously when the thermostat is calling for cooling.

I can understand the benefit of feature 1, but I don't know how significant it is. Regardless, it's something my Ecobee thermostat already does, so I don't need another product to provide it.

What about the second feature? Would that only be useful for oversized air conditioners? Could the cost savings make up for the extra wear on the compressor?

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  • I would be interested in what thoughts the HVAC people here have regarding this product. Also what is the cost? Is it such that you need to stay in your home for 7 to 10 year to recover the investment?
    – RMDman
    Commented Aug 4, 2023 at 18:37
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    @mrog, Yeah, My thoughts are , If I think I will not be in the home long enough to recoup my money, I will not invest in it. I have the tendency to then not care how it works, because it is moot to me.
    – RMDman
    Commented Aug 4, 2023 at 19:08
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    Probably better ways to spend money to save electric cost. Awnings/window film can reduce solar gain in a room, extra attic insulation plus good attic ventilation can help also.
    – crip659
    Commented Aug 4, 2023 at 20:12
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    That's nonsense. There's no free lunch. Worse, turning the A/C compressor on and off at short intervals is called "short cycling" and it's VERY hard on the motor. If you want an efficient A/C, they are all over the market and they also heat. Commented Aug 6, 2023 at 7:36
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    flashing before it exits the coil or not is why you do the superheat or subcooling thing. And that's a one-and-done if it doesn't ever leak.
    – Mazura
    Commented Oct 28, 2023 at 1:55

3 Answers 3

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For method 1, you already have an Ecobee, so there's nothing to be gained.

For method 2, let's think about this. It says:

every time your system has run long enough that it is holding all the energy it can

Really? What does that mean in real life? Imagine yourself standing outside your house talking with an HVAC tech about your A/C, and you ask, "Can't this thing make the house any cooler?" And he answers, "No sir, it's holding all the energy it can!"

I'm rolling on the floor right now. Who says that? Nobody. Nobody in the history of air conditioning has ever said anything about A/C "holding all the energy it can." It's a crock. It's advertising copy.

So let's dissect the ad copy a little deeper. This thing is connected to thermostat wires. What information about the compressor's state can this thing read over the thermostat wires? None. Does it come with pressure and temperature sensors for the condenser and evaporator coils? Nope.

So how can it possibly achieve a cost savings? That's easy. It contains a timer that will cut off your compressor for a few minutes when it has run continuously for a certain time. No compressor, no power consumption except for the blower, and you save money.

But wait, don't you already have a thermostat for that purpose? If the compressor is running, your thermostat is calling for cooling because it's too hot in the house. But this thing doesn't care about your comfort. It will cut off your compressor to save money, as it promises to do. At the expense of your comfort.

So if that's what you want, by all means have it installed for $1000. You can achieve the same thing for free by setting your thermostat a little higher on very hot days when your compressor runs for hours at a time continuously. You'll be a little less comfortable and you'll save a little on electricity.

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After reading they pure marketing material without and supporting data, it is a no go for me.

Your smart thermostat will already run the fan after the compressor stoped. The duration set is based on the OEM data, for how long the heat exchanger stays cooler then room temperature. You have the option to set how long the fan will run (from minutes to hours). The coil will have stored energy (coolant) for about 3-5 minutes before reaching room temperature.

The compressor is strictly controlled by the thermostat.

If it runs continuously (the room newer reaches the set temperature), you either have to small HVAC or your setting is to low for cooling. Start by increasing the temp set point (every 30 minutes) by 1 degree until compressor starts cycling. Cycling should be at 50/50 on/off time, or 70/30. This will save you 30% to 50% in energy, much more than the gadget.

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Seems to be a serious lack of basic knowledge in this thread. Allow me to shed some light on the topic. Once the thermostat reaches set point, your compressor turns off and the fan will run for about 90 seconds per manufacturer specs. What utilities have found via numerous studies that those 90 seconds are sometimes too much and quite often not enough to exhaust the coil. This is why variable fan timing functions such as the one in this ecostella product were created and patented. VFT's ensure you get all the fan you need and none of what you don't AND because you're optimizing the fan and, in most cases, increases air flow, there is ZERO compromise to comfort.

As to the compressor: every coil has a capacity, meaning an amount of energy it can contain. That is why there are different sized systems. During extended run periods, coils can reach their capacity, however if the thermostat hasn't satisfied, the compressor will continue to run, thus consuming energy while not contributing any value to the system. As I understand it, the ecostella product cycles the compressor off during the periods thus eliminating unnecessary run-time...which saves energy.

The entire technology is based on some sort of timing matrix. In other words, we can calculate how much energy is produced depending on how long a compressor runs and therefore how much fan is needed to pull that energy through. I've included a graph from one of the utility studies I found from California. Not sure how to post the full study.

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    Do you work for Ecostella? Based on this, it sounds like you're in their marketing department. How does this device know exactly how long to run the fan to "perfectly" exhaust whatever heat/cool is left in the coil? Where does this "some sort of timing matrix" come from? Your included graph didn't quite make it, and you can simply edit your answer and include links to all the studies you'd like. They'd be interesting reading...
    – FreeMan
    Commented Oct 27, 2023 at 18:23
  • This is priceless! I nominate paragraph 2 of this answer for Advertising Claptrap of the Month Award.
    – MTA
    Commented Oct 27, 2023 at 21:34

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