Hidden tech of the Nest Thermostat
scanofthemonth.com
scanofthemonth.com
I did a ton of research on this space, and dove into their source code. Literally all over the world, companies have been working on this problem for decades. How you know when someone is coming home so you can turn on the heat or A/C, or how the utility company can do it for you: all that is very, very well covered. I don't think there's anything fundamentally new about the Nest, and I don't have one in my house.
I actually stayed in someone's house that had two, so it's not as though it's completely foreign to me. I don't think that web-ifying your whole house is ever a good idea and I'm never going to do it. YMMV.
You can set your own schedule with Nest, you don't have to let the AI take over. Mine is fully on my own manual schedule.
Personally I think it's significantly better than what was common ( in the UK ) before, but the tech is dime a dozen, and new houses should probably come with underfloor, and control per room, though most still don't.
If it only takes one of heating or cooling to do this, not both, a standard "dumb" thermostat can of course do this just fine. Just set it to "cool" or "heat" mode and set a temperature. But of course you will need to change modes as the season changes (unless you live somewhere where only one mode is ever needed).
If you want to not have to change modes when the season changes, it gets more complicated, because the simple control system in the standard thermostat is too dumb for that. For example, suppose you set your temperature to 75. The actual temperature rises to 76, above the setpoint, so your A/C comes on. It cools the house to 74 and then the thermostat shuts it off (you have to have some buffer so the A/C doesn't come on again almost immediately). Now the temperature is below the setpoint, so your heat comes on. It heats the house to 76 and then shuts off. Now the temperature is above the setpoint... You can see what's going on.
From a pure design perspective, the right way to solve this problem is an outside temperature sensor (and probably a sun sensor as well since sunlight is a significant heat input to your house), so the system can predict what will happen when both cooling and heating are off. Given reliable sensors, the control algorithm is fairly simple (automatic climate control systems in cars already do it). I have never seen this in a house, though. I'm not sure why.
The linked esphome docs are actually great whether you care about esphome or not - they explain all of this very well and you can tell from the configuration values and samples what kind of logic goes into all of this.
I am perfectly comfortable (and therefore want my system to turn off) after my AC has been running long enough to drop the humidity a bit, even if the temp has only dropped a fraction of a degree. As humid air leaks in, I want the AC back on even if the temp has barely increased a degree. Basically the heat index in my house swings enough to change my comfort and therefore could be a useful trigger, even if the temperature doesn't swing nearly enough to be a useful trigger.
The Nest even has a humidity sensor, but it only gets used in very specific (hardly useful) situations.
I considered writing a Works With Nest app for this. Then that platform disappeared in favor of Works With Google, but I never found the time for either...
You could try wrapping your thermostat in a wet sock.
Actual web-bulb thermometers would either require manually adding water when you want to make a measurement, or have a large tank of water that gets continuously wicked onto a cloth which is wrapped around the thermometer. The general idea is that, if the surrounding air is dry, the water in the cloth will evaporate and cool the thermometer below the temperature of the air itself (the "dry-bulb temperate"). This is just the same evaporative cooling effect that makes sweating and swamp coolers work. If the surrounding air is very wet (humid), very little evaporate cooling will occur, and the wet-bulb temperature will be very close to the dry-bulb temperature.
I'm not sure how well a thermostat that only used the wet-bulb temperature would work. To actually calculate relative humidity, you would need at least a wet-bulb and dry-bulb measurement. But given that relative humidity in most places probably doesn't swing that wildly, I imagine that just finding a comfortable wet-bulb temperate for your thermostat might work okay in practice.
Rigging a wet sock (with constant wicking from a water source) onto my actual wall-mounted Nest Thermostat would never fly, as I said, but I have no qualms about doing this experiment with my Nest Temperature Sensor, being a small and relatively cheap thing that I can easily steal for a while...
According to a psychrometric chart [0] it looks like if the dry-bulb temperature stays locked at 70F, while the RH drops from 60% to 40%, the wet-bulb temperature will drop from 62F to 56F. Or if the dry-bulb temperature stays locked at 80F while the RH drops as before, the wet-bulb temperature will drop from 70F to 64F. That's linear enough for my purposes.
Therefore if my conventional (dry-bulb) set point is 75F in the summer, and I'm most comfortable around 50% RH combined with that 75F, then I'll try a set point of 63F with my Nest using the remote Sensor wrapped in wet cloth!
Apparently I also need continuous airflow over this wet-bulb thermometer. I wonder how much.
[0] https://hvacologist.com/2022/02/21/wet-bulb-temperature-vs-d...
When I get back from a run in August at near heatstroke levels I will almost never cool down if it's not set on the "chilly" side. Conversely, in winter when heatstroke is replaced with near frostbite I am chilled to the core and need much higher heat to ever warm up.
And if you loosen that spec, then, as others have already pointed out, just having two setpoints, a lower one for heating and a higher one for cooling, will be sufficient as long as the difference between them is large enough (probably 2 degrees or more would be enough for many use cases). That would be simpler than adding a PID controller.
Why ? What would be so hard in detecting "every time I don't do anything temperature goes up therefore summer and I need to use AC" ?
> If you want to not have to change modes when the season changes, it gets more complicated, because the simple control system in the standard thermostat is too dumb for that. For example, suppose you set your temperature to 75. The actual temperature rises to 76, above the setpoint, so your A/C comes on. It cools the house to 74 and then the thermostat shuts it off (you have to have some buffer so the A/C doesn't come on again almost immediately). Now the temperature is below the setpoint, so your heat comes on. It heats the house to 76 and then shuts off. Now the temperature is above the setpoint... You can see what's going on.
All would it take is to put a gate "if I used cooling to correct temperature last time, don't use heating for few hours or until it drops to higher difference and vice versa". You're trying to portray it in way more complicated way that it is.
> From a pure design perspective, the right way to solve this problem is an outside temperature sensor (and probably a sun sensor as well since sunlight is a significant heat input to your house), so the system can predict what will happen when both cooling and heating are off. Given reliable sensors, the control algorithm is fairly simple (automatic climate control systems in cars already do it). I have never seen this in a house, though. I'm not sure why.
Too simplistic. Which side of house you monitor, is it in shade or does it show temperature when sun heats up the wall ? Which room is closest to "hot" wall/window?. It would be a lot of work for very little improvement
There's an additional complication for multi-story houses that I didn't mention before. In multi-story houses, when you're cooling, you want most of the ducted airflow to be directed to the upstairs outlets, to take advantage of natural convection (cooler air sinks); similarly, when you're heating, you want most of the ducted airflow to be directed to the downstairs outlets (warmer air rises). That requires adjusting dampers in the ducts, usually just downstream of the output of your HVAC unit. Unless that adjustment can be automated (which would require automatically controlled motors on the dampers, something I haven't seen marketed, though again I'm not sure why), your airflow will be suboptimal for either heating or cooling if the system automatically switches between modes.
A typical suggested application is controlling the airflow to a room using a thermostat to open or close the damper, but they can be hooked up to anything with a switched output.
As an example, this damper has an adjustable bleed rate, with a 2 wire input for switching the state:
https://www.resideo.com/us/en/pro/products/air/forced-air-zo...
(Click the "Install" tab to access installation guides)
E.g., if the thermostat expected a temperature of 75 F at 12 PM but it was actually 78 F, then you know the house received a lot of sunlight and can correct accordingly.
As others have indirectly pointed out, for the range of circumstances a given house is going to encounter, the linearizing assumptions in a standard PID controller are probably sufficient. If tuned properly, the "differential" portion of the PID controller will shut down the heater earlier when it's warmer out and/or there's more solar energy coming through your windows.
In effect, two strips of metal were bonded together forming a coiled "spring." Because each metal had different coefficient of thermal expansion, the spring would expand or contract to different lengths depending on the temperature. Place the electrical contact at the temp where the heater or HVAC should turn on & bam.
No electronics at all, just a temperature-dependent mechanical switch.
I had a problem with the temperature in my house often being wrong, so I bought a smart thermostat. Now I have ten problems.
Seems to be a Google habit. I regularly get "commute traffic reports" several hours before or after I leave home or the office. Of course there's absolutely no way to set the alert schedule yourself.
They define do have something fundamentally new. I think it was exactly what was described in the video - easy installation, intuitive design, and right timing.
"Home automation" is also not a new concept. X10 came out in 1975:
https://en.wikipedia.org/wiki/Home_automation
What Nest had is consumer-friendliness, which I give them full credit for. Not surprising for Tony Fadell, who came out of Apple.
Oh look, now he's into crypto:
https://www.msn.com/en-us/news/technology/man-behind-the-ipo...
Maybe he'll bring his magic to that, too.
https://www.cnet.com/home/smart-home/nest-says-it-has-sold-o...
I was getting quotes for some heating/cooling projects at home and, while discussing the control panels, I expected that Nest would be an option. I was surprised and found it comical when the salesperson claimed that the Nest control panel was not supported. This is an instant non-starter for me.
I go for longer run times and use a CPH of 2, so the thermostat tries to run for 15 minutes followed by 15 minutes off. In mild weather, it is more like 8 minutes on and 20 minutes off. I was skeptical about replacing my Nest with it, but I think it holds the temp more comfortably. Plus you can add wired and/or wireless sensors to various rooms in you house so everything stays more balanced.
Maybe not what you're looking for, but if you're just looking for a 1F degree lag in temperature change, you can also try just increasing the heat stored in your house's thermal mass. For example you could add something with high thermal mass (i.e. concrete) to the place you want higher thermal lag, and position it so it soaks up a lot of solar radiation. That'll buffer out your temperatures.
If you desire 100% local control, it's worth looking at Zigbee and Z-Wave thermostats. Using Home Assistant can give you full local control without requiring a vendor's hub and app.
Not even remotely true. The Nest wires the same as any other thermostat. Prior to the Nest there were plenty of inexpensive to high end devices with simple instructions included .
For what it is worth, I think the Nest has been generally worse than a dumber programmable thermostat, especially after Google took it over. The App only allows a single phone to be connected now which is a problem when both me and my wife want access. There is also no way to run the fans without switching it on heat or cool. The fans can also only run for a maximum of 12 hours before it needs manual intervention to restart. All of which are a problem if you have say a pellet stove providing heat in one part of the house and want to circulate the air to the rest of the house using the furnace fan. On my old thermostat I could even switch the fan to low speed mode when the heat pump wasn't running, which is something the Nest seems to have no concept of. There is an API, but it's all Googlefied and requires a subscription and kind of assumes you're already a full stack Google developer.
But we generally don't use the Nest app much any more, except to use its horrible scheduling interface (horrible because Google's UI for changing the schedule is way too finicky and non-standard).
Everyone in the house uses HomeBridge which has a fantastic Nest plugin. The plugin uses the API you mention. Much faster than opening the Nest app. Less than 1 second to update the temperature and hear the furnace kick on via the iPhone's control center.
The last time I used the Google Home app I couldn't set my fan to continuous but the Nest app still allowed it. Seems wild to me that they don't have this basic stuff nailed down.
My ecobee has connectivity issues over HomeKit and the API requires the cloud (which is annoying for something like home assistant). I’m also convinced it’s intentionally dumb in its scheduling. I always felt I needed to manually update the settings and could never trust it to just maintain temperature.
It does let you manually control the fans and stuff, which is a feature I really liked when I had air filtration built into the HVAC. I would miss it on a Nest I guess. Edit: it seems others are contradicting this claim.
That said, the API doesn’t require a subscription, just a one-time $5 fee (which is likely less than server and ops costs to run the API). And the API seems like a pretty standard rest api based on the docs. Similarly, the ecobee api seems roughly as complicated. The only difference is auth with a Google account or ecobee API key.
I don't think the Nest has any options for local control though, so HomeKit on the Ecobee seems like a win, but I got distracted before I figured out how to do what I want with HomeAssistant.
The Nest does better fan scheduling IMHO, although neither one does anything smart with sequencing multiple units, which is really frustrating.
They seem to have been hit pretty hard by supply chain problems too (most online prices 2x or more than what they were).
What I installed instead (myself) was an Ecobee 3+. I've been very happy with it. I have it set to run the fans 10 minutes of every hour to move air around a little bit. With a previous dumb thermostat, using the fan more often caused a noticeable spike in the electric bill. We live in a 1914 house with multiple levels and minimal air returns so there tends to be variations in temperature (top hot in summer, cool in winter; basement coldest in summer even with vents closed but exposed pipes are full of cold air, etc.) that aren't easily fixable.
Ecobee has started selling security cameras, which I haven't looked into. I really do like the idea of having a best-of-breed thermostat and I hope that Amazon doesn't buy them. I'm a little surprised that they haven't.
Amazon had their own thermostat so they don’t need it. Their own thermostat locks people into Alexa, ecobee doesn’t.
Polar opposite of our experience. We have two Nest thermostats in our home and both my wife and I can connect to and manage each one with our respective phones.
> There is also no way to run the fans without switching it on heat or cool.
Also not our experience. We can run the fans independently of heat/cool. That could be a consequence of your HVAC system opposed to the Nest itself.
It seems to work fine for both me and my wife.
> These leaf springs allowed for the self-configuration of the unit, saving the time and troubleshooting that would have prevented a regular person from tackling installation. And it worked! It was so simple that grandparents were making YouTube videos of themselves installing it.
Did Nest sponsor this article? It's a Google property and they managed to reference another Google property.
YouTube is ubiquitous. It’s not like they referenced someone’s blogger account or something.
I remember my very cold mother calling me because there was a message about a wifi problem and she didn't know she could somehow bypass it and turn up the thermostat.
The Nest gets around the common requirement by cheating - it charges a rechargeable battery by leeching current into the signal wires. If the endpoint is a coil on a relay or solenoid, this usually causes no problem, it often causes no problem if the relay is solid state, but on some equipment that return current will switch on the equipment when it tries to charge its own battery. In other cases it won’t charge at all. Usually it’s quite clear if this happening as the equipment will be cycling even with no call for heat.
(I thought it was a shortage of return but once I eliminated that I cut open the furnace and found the problem)
Those who took hands on classes like these could read the simple instructions with a traditional thermostat or even a Nest and easily install it. They were comfortable with a handful of low voltage wires, some screws, and a simple diagram.
I wonder how the lack of hands on practical teaching in schools has impacted folks comfort with handling these fairly simple tasks.
Many people in my previous social circle would regularly take on personal car repair, plumbing, electrical, pest control, etc jobs based on youtube. Others including myself upskilled or got entirely new jobs with no experience beyond a youtube "apprenticeship".
Also in a normal home, the only things you can damage are yours. Also the repairs are probably cheaper in a normal house.
One model of Nest works fine with two wires, but the cheaper and assumed less power hungry (less features) Nest does not.
But back to your point, I think we should be teaching much more hands-on and life-oriented tasks at the high-school level.
The intention's always good, I think, it just rarely is as nice as the author felt it would be.
If you look at this datasheet for example, pins 10 and 11 in the schematic can be used to detect insertion of the jack: https://www.switchcraft.com/assets/1/6/35RASMT8CHNTRX_CD.pdf
Side note; Not sure I've heard 3.5mm connectors called 1/8" connectors before, though I have heard of the larger 1/4" connectors.
Some googling:
3.5mm jack - 49million results
1/8" jack - 63 million results
3.5mm stereo jack - 19 million results
1/8 stereo jack 5.9 million
1/8" stereo jack - 5.47 million
Evidently, it's a common term! Guess once I decided what I was calling them, that's what I searched for, and what I skimmed technical details for.
Metric dimensions of rifle-cartridges, however, seem to reliably be the land-diameter: 5.56x45, 7.62x51, and 7.62x39 all have eponymous land-diameters.
* Regarding "Jack" In February 1884, C. E. Scribner was issued US Patent 293,198 for a "jack-knife" connector that is the origin of calling the receptacle a "jack". . . . The current form of the switchboard-plug was patented prior to 1902 . . . It is today still used on mainstream musical equipment, especially on electric guitars. [0]
* 3.5mm connector There are at least four different varieties of 3.5 mm plugs and jacks, each with its own purpose and application. . . . TS, TRS, TRRS . . . The letter T stands for Tip, and the R stands for Ring (like a ring on your finger, not like ringing the telephone). . . . a TS plug has two conductors, a TRS has three, a TRRS has four, and a TRRRS has five. . . A TRRS or Tip Ring Ring Sleeve plug has four conductors and is very popular with 3.5mm, and can be used with stereo unbalanced audio with video… or with stereo unbalanced audio plus a mono microphone conductor. . . . Unfortunately, there are two conflicting standards associated with its use with stereo unbalanced audio plus a mono microphone conductor. [1]
0. https://en.wikipedia.org/wiki/Phone_connector_(audio)
1. https://www.provideocoalition.com/ts-trs-trrs-trrrs-combatin...
I still have an old phone (not a smartphone) that uses a 3.5 mm TRRS jack for that purpose and I would not trade it for any Bluetooth gizmo, it works perfectly, you just need to be a bit careful with the cable. But no stress about the earpods running out of juice.
The first time I saw a 3.5 mm was in my 1975 six transistor Japanese little 9V AM radio. It came with one of those weird pinkish earpieces.
I'll keep an eye out for more if you want.
The chat experience was really shockingly good, and I expected it to be pretty bad. There was no wait, the person was knowledgeable, and at the end they emailed me a picture of how to do the wiring.
It is tiny and light-weight though, I'll give them that.
I’ve got some beef with the original design, for example there’s no good reason why they don’t support a local thermocouple versus Wi-Fi local weather, but overall I have to say it’s been a welcome addition to that household. The installation was painless and with a propane furnace I’m certain that it has saved me thousands of dollars over the years.
Get off your skyhigh horse there, dude.