Instruct: Given a question, retrieve passages that can help answer the question.
Query: How do thermostats work?
A thermostat exerts control by switching heating or cooling devices on or off, or by regulating the flow of a heat transfer fluid as needed, to maintain the correct temperature. A thermostat can often be the main control unit for a heating or cooling system, in applications ranging from ambient air control, to such as automotive coolant control. Thermostats are used in any device or system that heats or cools to a setpoint temperature, examples include building heating, central heating, air conditioners, as well as kitchen equipment including ovens and refrigerators and medical and scientific incubators.
The Nest Learning Thermostat (or Nest Thermostat) is a smart thermostat developed by Nest Labs and designed by Tony Fadell, Ben Filson, and Fred Bould.[1] It is an electronic, programmable, and self-learning Wi-Fi-enabled thermostat that optimizes heating and cooling of homes and businesses to conserve energy.[2]
In an attempt to mitigate the issues with human error involved with programmable thermostats, the smart thermostat utilizes a sensor that can determine occupancy patterns to automatically change the temperature based on occupant patterns and behaviors. The Nest Learning Thermostat in particular uses passive infrared (PIR) motion sensors inside the unit to sense occupancy in the vicinity of the thermostat. This sensor informs the thermostat whether or not the home is occupied. In the case that the home is not occupied, the thermostat can suspend heating/cooling until the sensor is reactivated by an occupant. This sensor is also used to determine the occupancy patterns to create the auto schedule. A grille member is placed in front of the sensor to visually conceal and protect the PIR motion sensor inside the thermostat. The grille also helps to make the thermostat visually pleasing.[2] While this sensor technology is important for conserving energy, it is not without flaws. One of the major issues is that the sensor must be activated by someone walking in front of or near the thermostat. It is possible that an occupant could be at home and not pass in front of the sensor. In this case, the thermostat would shut off the heating/cooling and decrease human comfort.[13]
On vintage cars you may find a bellows type thermostat, which has a corrugated bellows containing a volatile liquid such as alcohol or acetone. These types of thermostats do not work well at cooling system pressures above about 7 psi. Modern motor vehicles typically run at around 15 psi, which precludes the use of the bellows type thermostat. On direct air-cooled engines this is not a concern for the bellows thermostat that controls a flap valve in the air passages.
Manual thermostats (also known as analog thermostats) are the oldest and simplest type of thermostats. These thermostats are set to one temperature and do not change until the user manually adjusts the temperature.[5]
"Chaos and Order" criticises from a number of different perspectives this “professional infallibility”, arguing that we rather start to discern reality, after centuries aiming to adapt it to some theological or atheist faith’s ideal, thanks precisely to the understanding of the self-organisation phenomena. The work compares open and closed order modalities, some re-fed by the environment, such as the thermostat, and others isolated from it such as the clock, while ironising about the confusion between these two, as if the quarter and the convent’s order could be considered to be a synonym with what is real. Dogmatic thinking tries to do so by reducing, abstracting or forgetting as necessary in each case. But, according to Escohotado, doing so implies choosing the vicious circle to the detriment of the virtuous one - as Wiener’s says in his "Cybernetics"-, “ignoring the environment’s signals, as the clock which is sensitive only to its mainspring, in contrast with a thermostat which is permanently re-fed.”
A programmable thermostat is a thermostat which is designed to adjust the temperature according to a series of programmed settings that take effect at different times of the day. Programmable thermostats may also be called setback thermostats or clock thermostats.
Another study conducted on the issue determined that the biggest problem for programmable thermostats was the human using it. The technology inside a programmable thermostat is no doubt one of the most important factors in determining whether or not the thermostat will be successful in saving energy. But an equally important factor is the human who is using the thermostat. Unfortunately, many people who own programmable thermostats do not know how to use the thermostat or are not using all of the features that are offered. One study conducted a number of interviews, surveys, and observations to determine that the vast majority of programmable thermostat owners are not using the thermostats for their intended purpose. An online survey showed that 89% of respondents do not use the schedule feature on their programmable thermostat. Other results from the interviews and surveys show that a large number of people have misconceptions about heating/cooling and the use of programmable thermostats. One misconceptions is people believing that heating all of the time is more efficient than scheduling the heat to turn off. Another misconception noted in the study is that turning down the thermostat does not substantially reduce energy consumption. These misconceptions reaffirm the idea that the programmable thermostat itself could have all of the necessary tools, but if the user does not use them or uses them incorrectly, then these thermostats will fail at saving energy.[6]
Following the ecobee, EnergyHub released it's version of a smart thermostat in 2009 with the creation of the EnergyHub Dashboard. The co-founder of EnergyHub, Seth Frader-Thompson, got the idea for the Dashboard from his Prius. The Prius had screens on the dashboard that displayed the car's gas mileage in real time. Thompson felt that a house should have something that does the same. With that goal in mind, Thompson created a thermostat that could communicate with a home's furnace and appliances to determine the energy usage and efficiency and how much it was costing. The thermostat also had the capability to turn off appliances or raise and lower the temperature to save energy and cost. Ultimately, the goal of this thermostat was to display energy usage to users and to save energy and money. [10]
One of the issues with programmable thermostats that smart thermostats try to fix is the confusing user interface. Many owners of programmable thermostats found the controls and directions to be too confusing and opted out of using the scheduling feature completely. Others who used the feature used it incorrectly, due to the confusing directions, and saw an increase in energy usage.[6] Developers of smart thermostats have attempted to fix this issue by creating simple to use thermostats and providing proper direction. While this is an improvement on programmable thermostats, studies have shown that users desire more intense training from the installer of the thermostat on how to use the technical features. Additionally, many smart thermostats use a web portal where users can adjust the thermostat settings and look at their energy usage history. Again, studies have shown that users want this feature to be improved. Some complain that the web portal is not user friendly and they desire more training on how to use the web features during installation. [1]
It is not trivial to obtain a canonical ensemble distribution of conformations and velocities using these algorithms. How this depends on system size, thermostat choice, thermostat parameters, time step and integrator is the subject of many articles in the field.
Programmable thermostats, first introduced in the 1970s, are a type of thermostat that allows the user to set a schedule for different temperatures at different times. Most programmable thermostats also have a hold feature which suspends the schedule and effectively turns the thermostat into a manual thermostat.[5] The idea of the scheduling feature is that users will set a warmer or cooler temperature when the home is unoccupied to save energy and money. Due to this assumed energy savings, some building codes and government programs began requiring the use of programmable thermostats.[6] Unfortunately, due to human error in using these devices, many programmable thermostats result in more energy use than the basic manual thermostat. [7]
These are single Outlet Thermostatic Mixing Valves, often called "thermostatic faucets", "thermostat taps" or "thermostat valves".
Development of the smart thermostat began in 2007 with the creation of the ecobee thermostat. The founder of ecobee, Stuart Lombard, wanted to save energy and reduce his family's carbon footprint. After realizing that heating and cooling made up most of his home's energy usage[8], Lombard purchased a programmable thermostat in an attempt to reduce total energy usage. Lombard quickly discovered that the programmable thermostat was difficult to use and unreliable. Following difficulties with the programmable thermostat, he set out to create a smart thermostat that saved energy and was easy to use. With that goal, the ecobee company was created in attempt to offer users a thermostat that could truly save energy by fixing the issues with programmable thermostats.[9]
Many of the new things connected to the Internet will be Sentrollers. Sentrollers are either actuators, sensors, controllers, or combinations of these three things. One simple example is a home thermostat. A thermostat is a sentroller as it senses the temperature in the home, checks whether the home or room in which the thermostat is monitoring temperature is at the desired temperature, and if not, turns on the heater or the air conditioner. Therefore, a thermostat is a sensor and a controller – a sentroller. No human interaction with the thermostat or the cloud will be necessary for the thermostat to keep the heat in the home at the right level.
Since the release of smart thermostats, a number of third party studies have been conducted to determine if smart thermostats actually save energy and how they compare to manual and programmable thermostats with regards to savings. One study conducted an experiment in which 300 standard programmable thermostats were placed in homes and 300 Nest smart thermostats were placed in other homes. It is important to note that the homeowners involved in this study received proper training on how to properly use all of the thermostat functions. This effectively eliminated the issues regarding human error with programmable thermostats. All homes were located within one region of Indiana and had previously underwent home energy assessment. After 1 year of observation, the study concluded that Nest users reduced their heating gas consumption by 12.5% while users of a standard programmable thermostat reduced consumption by 5%. Additionally, it was concluded that Nest and standard programmable thermostat users reduced their cooling electric consumption by 13.9% and 13.1%, respectively. The major factors that allowed Nest to reduce consumption more than other thermostats was its ability to further reduce human error and set more efficient temperatures. The Nest thermostat used sensors and Wi-Fi connectivity to adjust the temperature on its own and provide more savings. This study helps to suggest that smart thermostats are in fact successful in reducing energy consumption. [21]
The ecobee4 is ecobee's flagship product which was originally launched May 3, 2017. It is a touchscreen thermostat that works with up to 32 remote temperature/motion sensors to adjust the thermostat based on where you are. It also has IFTTT integration. An updated version of the ecobee3 was released in 2015 that works with Apple HomeKit. The ecobee3 lite was released on October 17, 2016. The ecobee3 lite is a less expensive thermostat that resembles the ecobee3, but does not include any remote temperature sensors. Support for remote temperature sensors was added to the ecobee3 lite in March 2017.
To determine energy savings using actual data instead of energy models, in February 2015, Nest conducted a national study of Nest customers in 41 states who had enrolled in Nest's MyEnergy service. In May 2013, Nest acquired MyEnergy, a company that tracks and analyzes utility usage of people enrolled in the program. Upon acquiring MyEnergy, Nest was able to use the historical data to determine the energy savings of those who installed the Nest Learning Thermostat. This study looked at energy usage before and after the installation of a Nest Learning Thermostat and used a weather normalization procedure to prevent unusually cold or warm weather from skewing the data. The study had a sample size of 735 homes for gas usage analysis and 624 homes for electrical analysis. All of these homes were enrolled in the MyEnergy program and had sufficient energy data before and after the installation of a Nest Learning Thermostat. After observing the energy usage for one year, Nest determined that there was an average gas savings of 10% and a cooling savings of 17.5%. The savings varied from house to house depending on how occupants set their thermostat before the installation of a Nest thermostat, along with differences in occupancy patterns, house characteristics, and weather. [20]
HVAC systems with the ability to modulate their output can be combined with thermostats that have a built-in PID controller to achieve smoother operation. There are also modern thermostats featuring adaptive algorithms to further improve the inertia prone system behaviour. For instance, setting those up so that the temperature in the morning at 7a.m. should be 21°C (69.8°F), makes sure that at that time the temperature will be 21°C (69.8°F), where a conventional thermostat would just start working at that time. The algorithms decide at what time the system should be activated in order to reach the desired temperature at the desired time.[14] Other thermostat used for process/industrial control where ON/OFF control is not suitable the PID control can also makes sure that the temperature is very stable (for instance, by reducing overshoots by fine tuning PID constants for set value(SV)[15] or maintaining temperature in a band by deploying hysteresis control.[16])
Placebo thermostats work on two psychological principles, which are classical conditioning and the placebo effect. First, placebo thermostats work in accordance with classical conditioning. Classical conditioning was first discovered by Ivan Pavlov and is a type of learning which pairs a stimulus with a physiological response. Applied to placebo thermostats, this is when the employee adjusts the thermostat and hears the noise of hissing or a fan running and consequently physically feels more content. This is due to the countless trials involving the thermostat in their own home, which actually works. The employee has paired the sound of hissing or a fan running to being more physically content due to the actual temperature change and therefore when they experience the noise at work they feel the same way even though there is no change in temperature. As long as individuals get the result they are looking for (noise associated with temperature change) they will continue with the practice (changing the placebo thermostat). Additionally, placebo thermostats work due to the placebo effect. The placebo effect works on the basis that individuals will experience what they believe they will experience. This is attributed to Expectancy theory, which states that the placebo effect is mediated by overt expectancies. The most common example is in medical testing: inactive sugar pills are given to patients who are told they are actually medicine. Some patients will experience relief from symptoms regardless. According to expectancy theory, if people believe they are going to experience a temperature change after changing a placebo thermostat they may psychologically experience one without an actual change happening. Both psychological concepts of classical conditioning and the placebo effect may play a role in the effectiveness of placebo thermostats.
Even when there is no immediate error, a higher-level stance can simply fail to be useful. If we were to try to understand the thermostat at the level of the intentional stance, ascribing to it beliefs about how hot it is and a desire to keep the temperature just right, we would gain no traction over the problem as compared to staying at the design stance, but we would generate theoretical commitments that expose us to absurdities, such as the possibility of the thermostat not being in the mood to work today because the weather is so nice. Whether to take a particular stance, then, is determined by how successful that stance is when applied.
On many automobile engines, including all Chrysler Group and General Motors products, the thermostat does not restrict flow to the heater core. The passenger side tank of the radiator is used as a bypass to the thermostat, flowing through the heater core. This prevents formation of steam pockets before the thermostat opens, and allows the heater to function before the thermostat opens. Another benefit is that there is still some flow through the radiator if the thermostat fails.
One of the main objectives of smart thermostats is to reduce the issues involved with using traditional programmable thermostats. In order to understand how smart thermostats take on this task, it is important to understand the issues regarding programmable thermostats and how they affect energy consumption. Between 2008-2009, Florida Power & Light (FPL) provided 400 home owners with programmable thermostats and monitored their heating and cooling patterns. Out of the 400 participants, 56% of users used the programming feature while the remaining participants did not program the thermostat and left it on “hold”. It was determined that the users who used the programming feature actually consumed 12% more energy than the non-programmers. This consumption increase resulted from higher overnight duty cycles associated with lower thermostat setpoints (i.e. lower temperature setting), due to confusion with setting the schedule. This study reveals that programmable thermostats will not necessarily save energy. The smart thermostat attempts to combat this issue by taking the user out of the picture and relying on sensors and computers to save energy.[7]
A similar study conducted in 2012 with the ecobee thermostat also concluded that smart thermostats are capable of saving energy. The goal of this pilot program was to determine the gas and electric savings of smart thermostats. This study provided 86 households with 123 ecobee thermostats and monitored the homes for 12 months. The study included 69 houses from Massachusetts and 17 from Rhode Island. The participants either had manual or programmable thermostats before the study was conducted. Gas and electric billing data were provided for 12 months before the study was conducted to use as a baseline. After the 12 months of observation, the study concluded that ecobee thermostats led to an average electricity savings of 16% and an average gas savings of 10%. The gas savings for manual thermostat replacements (10% per thermostat) was found to be larger than for programmable thermostat replacements (8% per thermostat). The difference in electricity savings between homes whose prior equipment was a manual thermostat or programmable thermostat was found to be minimal. [1]
To show that their thermostats save energy and money, numerous smart thermostat producers have conducted models and studies to confirm their savings claims. One popular way that smart thermostat producers calculate energy usage is through energy modeling. In these models, the smart thermostat is compared to a thermostat set at a constant temperature, and savings are calculated. Using this method, ecobee calculated energy savings by correlating how long heating and cooling equipment run to local weather conditions. Energy savings were calculated relative to a constant temperature of 72°F. Upon conducting this model, ecobee determined a 23% savings on heating and cooling costs for those who switch to their smart thermostat.[19] Using a similar modeling method, Nest claimed a 20% energy savings for home owners who install a Nest Learning Thermostat. [20]