Re: A research team has managed to coordinate 100 domestic air conditioners to stabilise the power grid in real time, as if they were a flexible power plant.

On 6/14/2025 6:12 PM, KevinJ93 wrote:

E.g., house maintaining 68F for heat and at 1 minute prior to bedtime,
the thermostat notices it is now 67.9F and calls for heat... when
the setpoint will be lowered to 62 a minute later?  (and, the
changing of the setpoint likely causing the heating cycle to be
prematurely aborted:  "Oh, the house is now at 67.93 degrees
and the setpoint is 62 so let's shutdown the plant instead of
waiting for it to attain the OLD setpoint of 68F...")
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Imagine the stresses on the equipment by all this ineffective
cycling (esp the compressor!)
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Ideally, you want to notice how the system behaves and tune
your controls to maximize *it's* ability to satisfy the
user's stated needs while reaping some rewards for the provider
(and, ultimately, for the user by way of reduced capital
investments)

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Many thermostats have had those features for at least the last decade.
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My ten year old Carrier thermostat addresses most of those items. It also has

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Then, how many minutes BEFORE as setpoint change will it ignore the
scheduled change?  Does it look at the response of the interior to
such changes and adapt so the "back off" varies with temperature,
setpoint difference, outdoor temperature and wind speed?  Otherwise,
you're just shifting the point at which it makes an unfortunate
change in control.

 I don't know how many minutes prediction it does but it is supposed to do similar to what you describe. There is very little user control, just to enable or disable the feature.

But the user has created a scenario that the "system" (plant plus field)
can't make much sense of.  If he truly wants the house to be "at least"
68 degrees until "bedtime", then doesn't he really *mean* "68 until bedtime"?
And, NOT "68 until sometime NEAR bedtime".
I.e., at bedtime, the criteria will be "at least 62 degrees".  So, at that
point whether it is 68 or 75 in the house will still satisfy the specified
criteria of 62 degrees.  Why should the thermostat be allowed to bend
the rules and settle for 67.9 just before bedtime?  Wouldn't the user
have said "67.9 is acceptable within N minutes of bedtime??

[The thermostat that I designed for my parents, *40* years ago
does those things.  But, still for a single measurement point
in the house (e.g., my bedroom was always considerably warmer
than the rest of the house; the kitchen always considerably
cooler -- partly because of the house's orientation on the lot
and partly because of the way the heating was plumbed).  But,
the thermostat knew how to get the heat (no central air) *to*
the desired temperature *at* the specified time -- instead of
simply switching setpoints at those times]

 That's what it's supposed to do. You set the times that you want it to be at the target temperature and it is supposed to learn and predict how much in advance to start heating/cooling. I have noticed that it starts operating at different times depending upon the weather/existing house temperature. I do have the room temperature logged by the home automation system and it seems to reach the target temperatures pretty much at the requested times.

We looked at Google's (Nest) offering and found it performed really poorly
(I wanted to know what performance I had to beat).  Likely is overestimates
the indoor thermal mass (or underestimates the plant's heating/cooling
abilities) in order to not annoy users by leaving them "uncomfortable"
while it tries to catch up.

an exterior outside temperature sensor and takes in weather predictions over the internet so that it ramps the temperature appropriately and maintains a comfortable temperature and humidity.

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I do that here -- adding decision criteria as to when the swamp cooler
can be called on to provide cooling (cognizant of a "comfort factor").
If today's OUTDOOR temperature is likely to be more than ~30 degrees
above the desired indoor temperature, then the cooler is ill-advised
as refrigeration will be required once the indoor-outdoor differential
reaches that point.  As I (currently) have to rely on manual action
to vent the house adequately, you don't want to have to tell the
homeowner to close all the windows so the ACbrrr can come online.

I don't rely on "services" for this data.  First, they represent an
input that can be suspect (another attack vector).  But, more importantly,
they don't reflect conditions *here*.  I don't care what the conditions
are at the airport (no one LIVES there!).  And, if I look at the "citizen
weather stations" monitored by weather underground, I see the overnight low was
reported as 79 -- yet I know it to have been 66 on my porch.  The current
temperature is claimed to be 104 (though I see "local" sites reporting 102,
103, 104, 105, 106) yet I see 108.

The compressor protection is commonly built into the compressor control unit so that any command from the thermostat that compromises the compressor safety is ignored until safe.

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The compressor won't usually turn ON until a suitable time has elapsed
to ensure the compressor's pressure has leaked off to a safe starting
point.  But, once commanded on, it will usually turn off as soon as
told to turn off.  Has it done any meaningful work in that short
time?  Or, just cycled out of blind devotion to the control signal?

 There can be significant delay from manually altering the target point (for both enabling and disabling) but as the control input is not visible I don't know whether the thermostat or controller is doing that.

Just wait until the compressor starts.  Then, unplug the thermostat
(so any "protection" has to be entirely within the compressor).
Wanna bet it shuts down immediately?  If the compressor "needed"
to run for some minimum time, then it would ensure that.
You'll likely find the *blower* will continue to run to further
"dissipate" the cooling in the A/N coil (likewise, to cool down
the heat exchanger after heat has been requested).  But, these
are usually just fixed timers that don't care about what is actually
happening in the plant.  As long as they address the "bulk" need,
they are likely considered to be adequate (who cares if the blower
burns a few more watt-hours UNNECESSARILY!?)
[Some of the ductless units have better instrumentation but no idea
if they actually leverage that beyond diagnostic purposes.  I.e., do
they shut down their blowers once they see no additional "benefit"
accruing from their continued use?]