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Thermostats: Cooler than you think!

Thermostats: Cooler than you think!

When you go up to your thermostat to raise
the temperature, what really happens? Obviously the heating system comes on (if
we’re still in heating season) but what did the thermostat do to make that happen? Well, it did one of the three things a typical
thermostat can do. It commanded heat. It could have also told your forced-air furnace
to run the fan. Or, if we’re in the summer months, it can
tell it to run the fan and turn on the air conditioner. That’s it. The typical American thermostat has just 4
wires going to it. A common 24 volt AC feed, a return wire for
heat, another wire for cooling, and another wire for the fan. All the thermostat does is complete a circuit
on one of those three control wires and the heating and cooling system will respond accordingly. It will either heat. Or cool. Or circulate the air. Now, notice that it can’t tell the furnace
how much to heat. It can only tell it HEAT NOW. And then it can tell it to stop. That’s all the control it has. See, the furnace or air conditioner or whatever
you’ve got doesn’t typically have any sense of what’s actually going on. There are some more complicated systems, yes, but
the basic domestic HVAC systems you see all around the US are actually quite dumb. Really, most home appliances are dumber than
you think, but I digress. So, they rely on a thermostat as a sort of
life coach to tell them what to do. Now a lot of you are probably thinking “duh,
I know this, why is Technology Connections talking about thermostats?”. But there are reasons. First is that a number of people have asked
me to explain to someone in their life that setting the thermostat up to 80 degrees does
not make the heat go faster. It just makes the heat run for a long time
as it works to reach that much-higher-than-right-now temperature. If you want to set the thermostat higher,
just set it where you want it. The furnace will run on full blast until it
gets there, then it will shut off. It runs on full blast because that’s the
only degree of blast that a furnace can run. There is no medium blast. Only full. And off. I’m sure there are exceptions even in the domestic environment so be sure to comment about them. It boosts engagement! Anyway, the second reason I’m making a video
on thermostats has to do with the fact that they’re pretty neat. Now, new digital thermostats like this are
pretty boring. It’s basically a small battery-operated computer that closes the contacts of a relay when necessary. Add an LCD, some buttons, and boom. Programmable thermostat. [read with intense apathy]
Then put it on WiFi and connect it to the internet and all sorts of amazing things can happen. So, how can just 4 wires provide the necessary
control to regulate the temperature of your home? To show you, we need a furnace. Perfect! So, unless your heating system is frightfully
ancient, there’s gonna be a control board in there somewhere with some relays, resistors,
and all that fun stuff, as well as a terminal block with a few wires attached to it. These wires are going to the thermostat which,
in this case, is upstairs in the living area. For now, ignore the blue one. We’ll get back to that. So, the control board is providing a 24 volt
A/C feed on this here terminal, labeled R for Red. These other terminals are inputs. The white wire is the input for heat. Yellow does A/C. And green runs the fan. Blue does nothing. Ignore the blue. To make the furnace heat, all we need to do
is jump the red wire to the white wire. Now, the logic board sees 24 volts on the
heat input, and it starts to heat. And when it no longer sees 24 volts on the
white wire, it shuts off. And what jumps those wires together? Why, the thermostat, of course! Thermostats are among the simplest ways to
regulate temperature. And they do it with time. See, suppose you have a furnace that can output
10 kilowatts of heat (that’s roughly 34,000 BTUs per hour). There aren’t many days when you need that
much heat, but it’s there just in case. Suppose on a typical day, you only need an
average of 3 kilowatts of heat. Well, how can you make a dumb furnace do that? It has no mechanism of its own to reduce its
heat output. You can only tell it to be on or off. Well that’s fine. I only need 30% of its total heat output,
so what I’ll do is I’ll have it run for three minutes, then be off for 7. In every 10 minute period it runs for three
minutes, which means it produces 30% of its rated heat, or 3 kilowatts. Simple. Yeah, it is pretty simple. Almost remarkably so. Thermostats are a reactive means of controlling
temperature output. If the current temperature is lower than the
thermostat’s set point, it will command heat from the furnace. After the house has warmed to a certain degree
beyond the set point, it will stop commanding heat. Even though it has only a binary state, either
on or off, it is able to regulate temperature by running the furnace periodically to stay
within a set temperature range. The most interesting thermostats are the super
basic cheap ones. These work using the most rudimentary of technologies,
and yet they are still an effective means of regulating temperature. This is as basic a thermostat as you can get. It just handles heat, and it’s very cheap
feeling and kinda ugly but hey. It works. Inside this you will find a pair of contacts,
one of which is on this groovy spring thing. That spring is a really long bimetallic strip
formed into a coil. A bimetallic strip will bend as its temperature
changes thanks to the slightly different thermal expansion properties of its two laminated
halves. When formed into a coil, a change in ambient
temperature will cause the coil to get tighter or to loosen. Since this end of the coil is free to move
about, the effect is that this end will move either left or right with a change in temperature. This exact sort of thing is what makes those
big ‘ol garden thermometers work, though in that case this end would be fixed and the
center would be free to rotate a pointer needle. Adjusting the set point of this thermostat
adjusts the tension on the coil through rotating its central attachment point. In this case, as the temperature falls, the
spring gets tighter which causes the free end to move to the right. As it gets colder and colder, the free contact
gets closer to the other, and once it gets close enough *click* The contacts are pulled
together with the help of this little magnet. And what are those contacts attached to, you
ask? Why, the red and white wires going to the
board on your furnace. So long as these contacts are touching, it
commands heat from the furnace. Once the ambient air has heated up enough
to cause these contacts to break apart, then the furnace no longer sees 24 volts on the
white wire, so it stops heating. It’s that simple. The reason there’s a magnet is to create
clear start and stop points in order to prevent the furnace from running very frequent, very
short cycles. Without it, imagine what would happen when
the contacts touched. The furnace would switch on, but after heating
just a teeny tiny bit, the contacts would move apart again. Then of course, they’d almost immediately
touch when it cooled just an itty bitty bit. This is no bueno. The magnet prevents this by forcing the contacts
to stay together until the ambient air temperature has risen by at least a degree or so. And as a bonus, once the spring can finally
overcome the magnet’s attraction and the contacts snap apart, it’s now so far to
the left, that it needs to get at least a degree or so colder before they touch again
and command heat. Clever. Additionally, it helps to prevent arcing on
the contacts by ensuring they connect and disconnect as quickly as possible. But what about the green wire? And the yellow one? You might have already spotted that there’s
a suspiciously similar indentation in the plastic to the left of the heating contact. If there were another contact placed there,
then we’d also be able to control an air conditioner. Since the contact moves to the right as it
gets colder, it would work in exactly the same fashion, though in reverse–in this case,
when it gets too warm, the contact snaps to the left, which would put 24 volts on the
yellow wire and start the air conditioner. And of course, once it’s cool enough, it
snaps back to the right and breaks the connection, turning the air conditioner off. Honeywell didn’t really try to hide the
fact that they just sold you a de-featured thermostat. There’s a rather clear Y label for what
would be your air conditioning terminal. Too cheap to make a different mold, eh? When equipped for air conditioning, too, there
would be a mode switch coming out the bottom to disable heating or cooling commands. All that it would do is prevent a cooling
call from happening in heat mode, and vice versa. This prevents a scenario where it cools so
much that it snaps to the right, which turns on the heat, which snaps it to the left, which
turns on the A/C, which snaps it to the right, which turns on the heat, which snaps it to
the left, which turns on the A/C, which snaps it to the right, which turns on the heat,
which snaps it the left… Now that you know that thermostats are really
just shunting a couple of wires together to command the furnace to do something, you’ll
understand why newer digital thermostats need batteries. In the case of this basic digital thermostat,
this relay performs the task of connecting the wires together. The mode switch probably changes the path
of the connection, allowing for one relay to do both heating and cooling. It uses a thermocouple to determine the current
temperature and compares it to the set point, and when it determines that it needs to command
heat, you hear a click. Then, and only then, is there an actual complete
circuit going through the thermostat. While there is 24 volts potential on the red
wire, the only way to complete a circuit and thus be able to use some of that power is
to tell the furnace to do something. So, unless you want the fan to run 24/7, you
need the thermostat to have its own power source. Unless, of course, you’re either tricky
or you have what’s called a C wire. That’s the blue one. Anyone who has installed a smart thermostat,
or even considered installing one, knows what the C wire is. Essentially it’s just a return path to the
furnace’s logic board that doesn’t command anything. This way, a thermostat can be powered by the
furnace itself by using the 24 volts potential across the red and blue wires all the time. To command either heat, cooling, or the fan,
the thermostat will shunt the red wire to either the white, green, or yellow just like
any other thermostat. But, because it can keep an active connection
across red and blue at all times, it doesn’t need its own power source. Some smart thermostats, like the Nest, have
a small rechargeable battery inside them that *usually* allows you to get away without a
C wire. That’s the being tricky option. What these do is charge the battery whenever
it’s commanding something, because remember there is a complete circuit across red and
one of these three so long as the furnace is actually supposed to be doing something. But, depending on your specific furnace or
heating system, this might not work out so well because the thermostat is of course putting
a load on that circuit that isn’t normally there, so the furnace might freak out and
not behave correctly at all. So that’s neat. Now there are certainly more complicated heating
and cooling systems out there that need more than 4 wires to work. For example many heat pump systems will have
a backup heat source, sometimes referred to as emergency heat, that the thermostat will command on if
the heat pump isn’t providing enough heat on its own. It’s for systems like these and other more
complicated ones that you sometimes find ridiculous terminal blocks inside some relatively basic
thermostats. While most systems just need heat/cool/fan/common,
some are a little more elaborate. Alright, and for my last demonstration of
the power of thermostats, we’ll need a toaster oven. And not just any toaster oven! One of those with the glowy quartz heating
elements. I promise this isn’t about toast! This is about the oven part. One of my favorite things is when I discover a connection between two seemingly distant technologies. [pregnant pause] And one day, I realized that
thermostats are kind of like a really slow precursor to pulse width modulation. I don’t want to get too into PWM right now (‘cause we’ll save that for another video!) but what PWM does is modulate the power output
of something by rapidly turning it on and off, and adjusting the percentage of time
that it’s on. And that’s exactly what thermostats do! Just much more slowly. They don’t regulate the actual amount of heat coming from the furnace or heating elements or whatever. They instead regulate the duty cycle of the
heat source; how long it runs over time expressed as a percentage. It’s a little different because it’s reactive,
being tripped by the actual temperature change, but the effect is the same as PWM. And that’s why we have the toaster oven. And now, a brief explanation into why the
role of Toaster Oven will be performed by a stunt double. [The opening theme to Auntie Mame plays] Here it is running in the oven mode at three
distinct temperatures. On the left, it’s set to 250 degrees. In the middle, 350, and on the right 450. If we speed this footage way way up, we’ll
see that the elements run for a longer period of time and more frequently as the temperature
increases. It spends a greater percentage of time outputting
power as the requested temperature goes up. This happens naturally because the thermostat
acts to keep the temperature within a set range, but if we worked out what the duty
cycle was, we could actually rig up a PWM circuit to control the oven. That would be a bad idea because we want a
reactive thermostat in the case of cooking–both to actually get it up to the right temperature
quickly, and because ambient temperature and the contents of the oven will change the required
duty cycle–but it would technically work. See, thermostats are in a sense a natural
duty cycle determination device. They don’t know that’s what they’re
doing, even though I’m fairly sure they might be sentient, but that is kind of what
they do. Yeah, really it’s just “it’s too cold,
run the heat” followed by “it’s warm now, shut if off” but if you take a step
back and look over time, it’s really just slow pulse width modulation. With a bit of imagination, anyway. So to recap–thermostats can’t affect how
much heating or cooling comes out of your furnace when it runs. They only affect how often it runs and for
how long. So cranking the heat up does not make it go
faster–it just makes it go longer. Same goes for A/C (usually). Because it’s a regulation of heating or
cooling output based upon time, it is kinda like pulse width modulation. Just a very slow, very old, not quite so exact
implementation of it. And before I go, I asked on Twitter for your
thermostat-related questions! Let’s go through those while these fine
folks who support the channel on Patreon start scrolling up your screen. Sneaky (The N1) asks, “Why is the sensor
of house thermostats in the controlling monitor itself instead of little devices placed in
certain areas of the house other than because it’s cheaper? Does putting it in the controlling monitor
give some sort of advantage I’m not entirely seeing?” It’s not that there’s no advantage, it’s
that there’s no disadvantage. With a central heating and cooling system
where you can’t influence the amount of heat any individual room gets, it really doesn’t
matter which room the thermostat is monitoring. They’re all going to get the same proportional
amount of heating and cooling regardless. More sensors could give you a more accurate
average, but it wouldn’t give you any actionable difference without motorized baffles in the
ductwork or some other zoning system. I’m A Mason Now asks, “Thermostat wire. Why does it exist? Why not just use Romex or phone cable or even
Ethernet?” Well I think it’s probably just down to
the color coding being pretty standardized now. In theory you could use any of those. Admittedly, at least one thermostat installation
instruction manual tells you to ignore the colors so… Visionary asks “Are you covering thermostatic
valves on radiators too?” No. Colin Cogle asks “Why did old thermostats
have a bulb full or mercury? I thought the bimetallic strip did all the
work!” In fact the bimetallic strip did do all the
sensing work, but back in the day thermostats used mercury tilt switches to control the
furnace. A little vial of mercury with a couple of
contacts poking in on one side would sit atop the bimetallic strip, and if it leaned to
the left–the mercury pooled to the left and no circuit. If it leaned to the right–now the mercury
pooled around the contacts and yes circuit. The weight of the mercury created the same
resistance that the magnet does in the modern thermostat, ensuring it cycled for a sufficient
period of time. Were it not for mercury’s rather toxic nature,
I’d wager this switch would still be preferred due to its potentially unlimited lifespan
and completely silent operation. Oh, but one downside was that the thermostat
had to be mounted exactly perfectly level in order for it to work correctly. And CantComeUpWithUsernames asks “is there
a thermostat that allows you to turn on the heat or AC for just one “cycle” without
actually adjusting the desired temperature?” Well, I don’t know, but that sounds like
a great idea! Say you just came in from mowing the lawn,
and want to cool off. Press a button and run the A/C for a half
hour, but then go back to the normal set temperature afterwards. I could totally get down with that. Nest. Update your thermostats to allow this, please. And if anyone knows of a thermostat that does
this now, let me know! ♫ temperately smooth jazz ♫

100 thoughts on “Thermostats: Cooler than you think!”

  1. Some additional information!

    Firstly, two-stage heating is sorta common so the notion that "there is no medium blast" is probably true but if you have a fancy pants HVAC system, then maybe cranking the heat up might make it go faster. No idea what percentage of homes have a two stage heating system, but I'd guess it's in the 10-20% range.

    In re: the thermostat wire question. Apparently, to this day, the current going through the contactors that actually turn on the high current loads such as your A/C or an electric furnace's heating elements is carried through the thermostat. So, it's more than just color coding; they are designed to carry some current, and thus need to be a minimum wire gauge. So while Cat5 cable or similar would probably work for most HVAC systems, it might not be able to carry enough current for others (and could, potentially, pose a fire risk under the right circumstances).

    On that note, and I'm mad at myself for not bringing this up, you might have noticed that in the mechanical thermostat, a separate insulated wire connects the R terminal to the contact on the bimetallic strip. This prevents the current from being carried through the bimetallic strip, which could inadvertently heat it up and prematurely stop the furnace. Neat!

  2. Late to the party, but regarding the feature you asked for at the end (run this temp for x-minutes
    , then go back to your regular programming): a thermostat called Tado allows you to do this in their app.

  3. The ecobee smart thermostat allows usersnto add sensors in different rooms to average out the house temperature. I can even thel the main unit to disregard some sensors either at night or when we are home in order to just take the temperature ofmsome portion of the house and heat or cool the house based on those temperature only. My bedroom is facing south and is always extra warm during summer time. So i only use the temperature from my bedroom sensor to tell my thermostat when to cool and when to stop.

  4. The thermostat we had when I was a kid was more basic, truely could only handle heat, and had only a single vacume-bulb containing mercury to make the circuit between the two wires.


  5. Today on tech connections, thermostats are cool. Tomorrow the pseudoscience of the higgs boson particle and its relation to nuclear fission

  6. 10:30 So that explains why the AC randomly stops working and it gets up to 90F indoors when I'm gone all day.

  7. I remember my dad explainer how it’s either on or off when I was like 5 and my mind was blown. I would always set the ac in the car to “low” instead of the default 72 because I thought it would cool faster.

  8. LOL before I watch this video I thought every thermostat is a PID controller that sends PWM to control furnace/heatpump!!!!

  9. Im 99.999% sure Nest can be set to run for specific period of time before reverting back to the scheduled setting. The thermostat @ my work does something similar. It's an dual auto thermostat in which it has an active heat setting and an active cool setting and is scheduled to run between if the temp moves outside that range. You can manually change the temp to turn on the AC/Heat but it reverts back to the schedule after a short period of time.

  10. In Germany a lot of older Houses dont have a HVAC or Central Heating Cooling System with air ducts.

    We have a heater in each room which uses hot water from the central heating thing which in most cases also heats the water and the water circulates through the building. The heater in each room has a Valve that controls the flow which is controlled by a mechanical thermostat. You can twist it and set the temperature and the coil inside will expand and retract to hold the temperature in each room. Its a pretty nice System and you dont have to fiddly with it. The benefit is that you always have the right temperature in each room.
    By the way i dont know a single household which has a air condition unit as its only hot on a few weeks around 30-42 degrees C (86-108F) in the summer and almost all houses are built with stone and are highly insulated. Double or even tripple glas windows are standard. The insulation keeps most homes at a nice temperature so most of the times we air out in the evening and night and close the blinds and windows during the day. Outside was 40C(104F) and inside was around 23C(73F). More modern Houses use geothermal heat or use photovoltaic on the roof.

    Also no AC in public transport sucks in the summer. 🙁

  11. 1st and 2nd stage heating furnaces do exist and are pretty common mostly newer ones for efficiency using different gas pressures for the stages

  12. why (or how) the car ar conditioner can make air at different temperatures, but the home`s one only runs on max?

  13. So if mercury is toxic why am I able to buy a laptop snap the lcd off of ittear the glass out and scrape the mucury of the glass and into a cup? I have also found it in a kids doodle board and in flu recent tubes.

  14. Our furnace is from 1977. It's as dumb as dumb can get, but still runs just fine and adequately quietly, much to the surprise of everyone who's ever serviced it, as well as those hoping to sell us a new one. 🙂 <== Engagement boosting comment ahoy!

  15. I build switch cabbinets for a living and nearly every switch cabbinet there is a thermostat and they are incredibly easy to hook up. From 2 up to 10 wires.

  16. As a Tidbit of knowledge, the PWM (Pulse Width Modulation) is also the basis of modern Electric Fuel Injection (EFI) on almost every ICE Engine. Also, an ICE car generally has a mechanical thermostat to regulate the engine temperature through the use of Coolant. It would be interesting to use an electric thermostat, such as these, to let coolant flow through the engine. It may add to much complication, as most mechanical thermostats fail in an open position.

  17. Me: "You stupid mother— industrial UART thermostats have existed since–"
    TechnologyConnections: "i'm sorry, we're engaged."

  18. Is it alright if I make bogus folders on google to bump up your subs…I apologise on behalf of humanity for letting you down.

  19. Heating and cooling system in the US seems to be so simple and easy? Whats about the efficientcy? I could image the a gas powered heating system with 11 kW that periodicaly turn on and of is less efficient as one that can controll the heating power?
    I know in Europe water based radiator systems including hot water preperating is much more complicated and no system have any standard. In every house you will find different systems, different cabels and hunderts of different controllers.

  20. To your lawnmoving scenario my Peco T1000 series does that. The presets are programmed in, don't have to do anything, if I want to override it, I ask the new desired temp and for how long, and off it goes. When the time interval expires, it goes back to the presets.

  21. Hey. I'm not a fun sucker! Also frame by frame advance is different on some keyboard layouts. German layout uses , and .

  22. 12:20 I put it on 0.25x an read it complete. Imma Not a sun fucker… No wait, the Other way around. Fun sucker

  23. I have a newer modulating Carrier furnace that has variable 'blast' which automatically selects between three flame levels, and has multiple fan speed levels. If the temperature difference is great, it will use the hither flame level to output more heat, and run the fans harder, but if it is just making up for a slight temperature drop, it runs at a low level to maintain the target temp.

  24. Yes, most digital thermostats that I've seen have a manual override setting, allowing you to temporarily increase or decrease the set temperature for a pre-specified period of time, before returning to the original set program. As to whether or not that pre-specidied time period can be altered on some devices, that I do not know. On ours, the program is split up into different time periods, one setup for weekdays and one for weekends, as far as know the temporary override lasts until the next program period begins, but some may be different.

  25. You should have mentioned the heat anticipator. That's somewhat interesting, and a lot more on-topic than the disjointed discussion about PWM.

  26. I had no idea how different home heating is in the US! . . .
    why tf do you have furnaces in your homes? do you cast your own cutlery? 😉

  27. For the "one cycle" question: most central air thermostats have a FAN AUTO/ON switch, switch that to on. It will turn on the fan to cycle air through out the house with turning on the rest unit, until the air reaches X set temperature.

  28. Fine, then I guess I won't type in the very inconveniently long text at 12:25 (I really don't want to no matter what). Instead I'll tell you guys what he wants me to say; use the speed in the player's settings or if on desktop use < and >. There, I'm not a fun sucker.


  29. In Europe we got OpenTherm for communication with the furnace. This allows for modulation with the temperature of the furnace resulting in higher efficiency.

  30. My dad has a boiler for baseboard heat and his thermostats have three wires each why is that? Also the thermostats have mercury switches

  31. My thermostat finally broke a few days ago. I live in an apartment so it wasn't a big deal. I've had this thermostat from the 70's or 80's in there for 10 years. It's never worked right, but I'm one of the people that hates to ask for things so I've just dealt with it in it's broken state, never properly holding the right temperature and sometime getting stuck on for hours. It's so nice just to have a thermostat that works right after 10 years!

  32. I know it’s a bit late but am in the uk and I have an HIVE thermostat and it has a boost mode that will run the heating or even hot water for a set time no matter what the temperature is set too.

  33. Heating is technically conditioning the air. In the most general sense, air conditioning can refer to any form of technology that modifies the condition of air (heating, (de-) humidification, cooling, cleaning, ventilation, or air movement). I better turn off the AC, it's getting cold.

  34. I don’t know about the rest of the world but in the UK there’s a standard, I think developed by Honeywell?,called openTherm that uses 2 low voltage connections to communicate with the boiler and regulate its output

  35. 240volt mechanical thermostats have a neutral connection connected through a resistor which heats up slightly to encourage air convection through the thermostat to increase it’s accuracy by a possible 30% or so

  36. I just found out your name was Alec too. Your now the 7th person that can quickly come to my head with that name.

  37. My Lennox iComfort allows override for a set amount of time, so blast cool air as I cool off from lawn mowing for 1 or 2 hours, then resume schedule, it has worked for me for years now

  38. I have been using YouTube pretty much since it was first made public and I was on dialup. And I had utterly no idea until this day that the , and . keys would step through a paused video one frame at a time.

    This is a very useful piece of knowledge to posses.

  39. That question about can you push a button and have ac run For 1/2 hour kind of exists. On my Lux you program a schedule for times to run. If you go up and manually turn it on to a special temperature it runs to that temperature until the next program time comes around then reverts to the program schedules.

  40. I run the webctrl for hundreds of rooms and coworkers have to call me to adjust temp on a PC you have no idea how little people know about the thermostat. Just like he said turning up to 80 doesn't make it go faster

  41. Then there’s my damn furnace. This thing has a c wire but can’t provide enough power to power a smart thermostat. Nest just freaks out and refuses to work.

  42. Interestingly, the end thing about the temperature at a temporary period is very doable on Smart thermostats with the help of the controlling software and/or schedule operation for one-time

  43. Technology connections I have a newer house. When changing the temp on the thermostat it asks if it’s a temporary or permanent change. So if you pick temporary and it only cools and keeps the temp for a little while is that what you meant in the last question about when you come in from mowing your lawn? I have seen other places with this type of choice so I don’t think its very new. Or are you talking about something else.

  44. Some electrical heating systems in the UK (where there isn't a boiler [furnace], rather the radiator heats itself up – until recently we had no need for AC over here!) have a Boost button which will turn the radiators on for a set time before turning themselves off again. Perfect for when you get in from work, and you're about to pop the kettle on. These have been around for quite a while, they're mainly useful on storage heaters. These have a block of concrete (or some variation thereupon) which – theoretically – will be heated overnight when the 'leccy is cheaper and then discharge their heat over the day. Trouble is, they aren't all that good at storing the heat so the boost button can tie you over till you get to the duty cycle again. In the UK, we can also vary the intensity of heat output from the boiler (furnace), usually by turning a dial on the boiler faceplate that will regulate the fuel coming into it. You usually cannot do this from the thermostat though.

  45. earlier today i was wondering what those keys where that would let me skip through a video frame by frame, but i couldn't be bothered to look it up, for this fun gag i used the playback speed function of the youtube player to allow me to pause the video in time to read the whole story, and as a bonus i got to hear a trippy introduction with the whole jittering slowvoice thing… anyway, now i know of the < and > keys.

    thanks 🙂

  46. In the Netherlands, most of us have no AC but the furnace regulates down to 30% (which is more efficient, actually). And there only two wires providing both power to the thermostat and digital two way communication

  47. The thermostat in my condo was located right next to the output vent, which was also in direct sunlight for several hours a day.
    Excellent design. chef kiss

  48. how is it even possible in 2019 to heat up a house by only messuring the temp in one room. In Denmark we have a hot water tank and then a system of thermostats in each room controlling valves circulating the hot water through pipes in the floor of each room to warm up. Windows, wind, sun and individual heat needs in different rooms, makes it impossible to only control a single point. Crazy Americans.

  49. Actually, you missed a very important part of these thermostats – the anticipation circuit. I think even the one you showed has it via that setscrew that determines how much force it takes to be removed from the contact point. With old school ones, if set to cool, a small little heater makes the thermostat turn on quicker so that it doesn't lag too much. You can set how strong that is with a slider. With heat, it turns on during heating to stop before it overshoots.

    Digital thermostats have it built in – all honeywell thermostats, even the basic ones, will learn over time how to anticipate temp changes.

  50. Its becoming more common to have 2 stage furnaces in the US. A full blast and a 3/4 blast or so. Supposedly more energy efficient in certain climates to have this option.

  51. With a Raspberry Pi, a cheap relay board, a temperature sensor, and some basic programming—you can build a DIY thermostat that does whatever you want it to.

  52. In the UK, they combine the heating and hot water together; the usually have an "1 hour" over-ride that you can press that gives you heat now, and then it returns to the usual "program". Air conditioning isn't common at all in homes.

  53. I learned 2 things this video. First, what the heck PWM means because I see it all over the pins on my Arduino and never knew what it meant, and second that < and > go frame by frame on a video.

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