Routine maintenance is a crucial aspect of ensuring the efficiency and longevity of any HVAC system. One key component that often requires attention during these regular check-ups is the refrigerant levels within the system. Refrigerant is essential for the cooling process, as it absorbs and releases heat, allowing the HVAC system to regulate indoor temperatures effectively. Before the weather changes, it’s a good idea to check commercial HVAC repair so your HVAC system operates at peak efficiency.. Therefore, checking refrigerant levels should be an integral part of routine maintenance to maintain optimal performance and energy efficiency.
First and foremost, correct refrigerant levels are vital for the efficient operation of an HVAC system. When refrigerant levels are too low, the system has to work harder to achieve the desired temperature, resulting in increased energy consumption. This not only leads to higher utility bills but also places undue stress on the components of the HVAC system, potentially leading to premature wear and tear. By regularly monitoring and adjusting refrigerant levels, homeowners can ensure their systems operate smoothly and efficiently.
Moreover, inadequate refrigerant levels can compromise indoor air quality and comfort. An HVAC system with insufficient refrigerant may struggle to cool or heat a space evenly, leading to uncomfortable temperature variations throughout a home or building.
Additionally, maintaining proper refrigerant levels is environmentally responsible. Refrigerants can have significant environmental impacts if they leak into the atmosphere due to improper handling or neglect. Routine maintenance helps identify leaks early on, allowing for timely repairs that prevent further environmental damage while also complying with regulations aimed at protecting our planet.
Furthermore, addressing refrigerant issues during routine maintenance can help avoid costly repairs down the line. A small problem left unaddressed can escalate into a major issue requiring extensive repairs or even replacement of parts within the HVAC system. Regularly checking refrigerant levels ensures that potential problems are caught early before they develop into more severe complications.
In conclusion, incorporating refrigerant level checks into routine maintenance is an essential practice for maximizing HVAC efficiency and extending its lifespan. Properly maintained systems not only perform better but also consume less energy and provide consistent comfort indoors while minimizing environmental impact. For these reasons, prioritizing this aspect of routine maintenance benefits both homeowners' wallets and overall satisfaction with their living environments.
Understanding the importance of refrigerant levels is crucial for maintaining the optimal performance of HVAC systems. Refrigerants are the lifeblood of any cooling system, circulating to absorb and expel heat, thereby regulating temperatures.
Firstly, let's explore why the correct refrigerant level is so vital. When a system has too little refrigerant, it struggles to reach its designed cooling capacity. This insufficiency forces the compressor to work overtime, leading not only to increased energy consumption but also an elevated risk of overheating and subsequent mechanical failures. Conversely, an overcharged system can cause high pressure within the unit, potentially damaging components such as compressors and valves due to excessive strain.
Moreover, incorrect refrigerant levels can have wider implications beyond just mechanical failure or inefficiency. Inadequate cooling might result in uncomfortable environments that fail to meet consumer expectations or regulatory standards in commercial settings. For businesses relying on precise climate control-such as those in food storage or pharmaceuticals-this could even translate into financial losses if products are compromised due to inadequate temperature regulation.
Regularly checking refrigerant levels during routine maintenance helps prevent these issues by catching potential problems before they escalate. Technicians can adjust levels appropriately during inspections, ensuring that systems run at peak efficiency while minimizing energy costs and extending equipment lifespan. This proactive approach not only saves money but also avoids unexpected downtime caused by avoidable breakdowns.
Furthermore, maintaining proper refrigerant levels aligns with environmental responsibilities by reducing emissions associated with inefficient systems. Overworked systems tend to consume more power and may leak harmful substances into the atmosphere if neglected over time. Regular checks mitigate these risks by keeping everything running smoothly and sustainably.
In conclusion, incorporating refrigerant level checks into regular maintenance routines is not merely a recommendation-it's a necessity for anyone seeking efficiency and longevity from their HVAC systems. By ensuring correct refrigerant levels through consistent inspections and adjustments, we protect our investments while promoting sustainable practices within our communities. This preventative measure ensures our cooling systems perform optimally today while safeguarding against future challenges tomorrow.
In the realm of HVAC systems, ensuring optimal performance and longevity is crucial for both residential and commercial environments. One often overlooked aspect of maintaining these systems is checking refrigerant levels. Understanding the signs of low refrigerant and the potential consequences can underscore why this task should be an integral part of routine maintenance.
Refrigerants play a vital role in air conditioning systems, as they are responsible for absorbing heat from the environment and expelling it outside. When refrigerant levels drop below the required amount, the system's efficiency plummets. One of the most noticeable signs of low refrigerant is poor cooling performance; rooms might not reach desired temperatures or take longer to cool down. This inefficiency not only causes discomfort but also results in higher energy consumption as units work harder to achieve set temperatures.
Another telltale sign is ice buildup on evaporator coils. When there isn't enough refrigerant to absorb heat adequately, coils can become too cold, leading to condensation that freezes upon contact. Over time, this ice accumulation can damage parts of the system and further impede its functionality.
Additionally, low refrigerant levels may cause a noticeable increase in electricity bills. As mentioned earlier, when an air conditioning unit struggles due to insufficient refrigerant, it consumes more power to maintain performance levels. This increased energy usage directly translates into higher utility costs-a burden many homeowners and businesses would prefer to avoid.
Moreover, operating with low refrigerant can lead to compressor damage over time. The compressor is one of the most critical-and expensive-components within an HVAC system. If it operates without adequate lubrication provided by proper refrigerant levels, it risks overheating or failing entirely.
Routine maintenance checks that include assessing refrigerant levels can prevent these issues before they escalate into costly repairs or replacements. During a regular service appointment, technicians not only verify proper coolant amounts but also inspect for leaks-a common cause of decreased refrigerant that often goes unnoticed until significant problems arise.
Beyond immediate fixes and cost savings on utility bills, maintaining correct refrigerant levels contributes positively toward environmental sustainability efforts by reducing unnecessary energy consumption and preventing harmful leaks into the atmosphere.
In conclusion, while HVAC systems are marvels of modern engineering designed for comfort and convenience, their efficiency hinges significantly on maintaining appropriate refrigerant levels. Recognizing signs like reduced cooling capacity or rising energy bills can alert owners to potential issues early on. By incorporating regular checks into routine maintenance schedules-akin to changing oil in a car-we protect our investments against premature failure while promoting eco-friendly practices through efficient energy use. Thus, ensuring proper refrigeration management should be regarded not merely as an option but as a fundamental responsibility in preserving our appliances' health alongside contributing towards sustainable living standards globally.
Maintaining optimal performance in any mechanical system requires regular attention and care, and this is particularly true for refrigeration systems. One crucial aspect of this maintenance is regularly checking and maintaining proper refrigerant levels. This practice, often overlooked, can yield significant benefits that extend the lifespan of the equipment, improve energy efficiency, enhance performance, and reduce environmental impact.
Firstly, ensuring that refrigerant levels are correct directly contributes to the longevity of the refrigeration system. Refrigerants are vital for absorbing heat from within a space and expelling it outside. When levels are inadequate or excessive, it forces the system to work harder than necessary. Over time, this undue stress can lead to wear and tear on components such as compressors and condensers, potentially resulting in costly repairs or even premature replacement. By routinely checking refrigerant levels, these issues can be identified early on and rectified before they escalate into major problems.
Secondly, maintaining proper refrigerant levels plays a significant role in improving energy efficiency. A system low on refrigerant must operate longer cycles to achieve desired cooling effects, thus consuming more electricity and driving up utility bills. Conversely, overcharged systems can also experience inefficiencies due to increased pressure within the unit. Regular monitoring ensures that systems operate at peak efficiency by using only the necessary amount of energy required for optimal performance.
Moreover, consistent checking of refrigerant levels enhances overall performance reliability. Properly charged systems provide consistent cooling without fluctuations in temperature or unexpected breakdowns during critical times-such as during a hot summer day when refrigeration demands are at their peak. This consistency not only ensures comfort but also protects perishable goods stored within commercial refrigeration units from spoilage.
In addition to operational advantages, maintaining appropriate refrigerant levels carries environmental benefits as well. Refrigerants are potent greenhouse gases with significant global warming potential if released into the atmosphere due to leaks or improper handling during servicing activities like recharging or replacing components containing them (e.g., evaporators). By keeping an eye on these substances through routine checks-and promptly addressing leaks when detected-we contribute positively toward reducing our carbon footprint while complying with regulations aimed at protecting our environment from harmful emissions associated with HVACR operations worldwide today more than ever before given current climate change challenges facing us all globally now too importantly so indeed!
In conclusion then really: incorporating regular checks of your refrigeration system's fluid dynamics should be seen not just merely optional but rather essential preventive measure designed ultimately towards extending equipment life expectancy alongside enhancing both its efficacy plus ecological sustainability alike altogether thereby proving beneficial everybody involved whether homeowners businesses alike finally making sure everything runs smoothly seamlessly without interruption whatsoever thereby providing peace mind knowing everything under control!
In the realm of HVAC systems, the importance of regular maintenance cannot be overstated. Among the myriad tasks that technicians perform during routine checkups, checking and adjusting refrigerant levels is a critical component. This seemingly mundane task plays an essential role in ensuring the efficiency, longevity, and safety of air conditioning units and refrigeration systems. Understanding why this procedure should be part of routine maintenance requires delving into both its significance and methodology.
At the heart of any cooling system is the refrigerant, a substance that absorbs heat from indoor environments and releases it outside, thereby maintaining a comfortable indoor climate. Over time, however, various factors can lead to changes in refrigerant levels. Leaks are one common culprit; even tiny breaches can allow refrigerant to escape gradually. Similarly, incorrect initial charging or mishandling during repairs might leave an HVAC system with inadequate or excessive refrigerant.
Maintaining proper refrigerant levels is crucial for several reasons. First and foremost, it ensures optimal system performance. When a system operates with insufficient refrigerant, it must work harder to achieve desired temperatures, leading to increased energy consumption and higher utility bills. Conversely, overcharging the system with excess refrigerant can also result in inefficiencies and potential damage to components due to increased pressure within the unit.
Moreover, incorrect refrigerant levels can accelerate wear and tear on the system's compressor-a costly component often described as the "heart" of an air conditioning unit. Running a compressor under stress for prolonged periods due to improper refrigerant amounts not only shortens its lifespan but also increases the likelihood of unexpected breakdowns.
From an environmental perspective, maintaining appropriate refrigerant levels helps minimize the release of these substances into the atmosphere-an important consideration given their potential impact on global warming when released unchecked.
Now that we understand its importance let's explore how technicians accurately check and adjust these levels during maintenance visits. The process begins with connecting gauges to measure both high-side (discharge) and low-side (suction) pressures within the system while it's running. These readings provide valuable insight into whether there's too much or too little refrigerant present compared against manufacturer specifications.
If discrepancies are found indicating low levels due perhaps due leakage detection becomes imperative before proceeding further recharge avoiding future losses once rectified recharging involves carefully adding precise amounts ensuring neither under nor overfilling occurs employing scales digital tools assist achieving exact measurements required modern eco-friendly practices dictate use reclaimed rather virgin whenever possible reducing environmental impact coupled adherence governmental regulations governing handling disposal hazardous materials like fluorocarbons hydrocarbons used today's equipment
In conclusion diligent attention detail checking adjusting vital part maintaining health functionality longevity cooling heating alike incorporating comprehensive service routines ultimately benefits consumers lowering operational costs extending life expectancy contributing sustainable future planet Remember small steps preventive care make significant differences long run integral keeping systems peak condition delivering comfort peace mind year-round
In the realm of heating, ventilation, and air conditioning (HVAC) systems, ensuring optimal performance is essential for both efficiency and longevity. Among the myriad components that contribute to a well-functioning HVAC system, refrigerant plays a critical role. Despite its importance, there are several common misconceptions surrounding refrigerant usage that can lead to inefficiencies and potential damage if not addressed. One prevalent misunderstanding is the belief that refrigerant levels remain constant over time and do not require routine checks. On the contrary, regularly checking and maintaining appropriate refrigerant levels should be an integral part of any HVAC maintenance routine.
Many homeowners and even some professionals operate under the assumption that once an HVAC system is charged with refrigerant during installation or a major service, it remains at optimal levels indefinitely unless there's a leak. This misconception often leads to neglect in monitoring these levels routinely. However, like any other dynamic system component, refrigerants are subject to various factors that can impact their levels over time.
Firstly, while significant leaks might be obvious due to noticeable drops in cooling efficiency or higher energy bills, minor leaks can be insidious. These small leaks may not immediately affect performance but can gradually reduce cooling capacity and cause compressors to work harder than necessary. Over time, this increased workload can lead to more severe mechanical issues or even complete system failure.
Moreover, environmental conditions such as temperature fluctuations and pressure changes within the system can impact refrigerant behavior. For instance, expansion or contraction due to temperature shifts might slightly alter pressure dynamics within sealed components.
Regularly checking refrigerant levels also aligns with energy efficiency goals. An HVAC system operating with inadequate refrigerant must exert additional effort to achieve desired temperatures-resulting in increased energy consumption and higher utility costs. By ensuring that the system maintains proper refrigerant charge through periodic checks as part of routine maintenance schedules, homeowners can optimize energy use while extending equipment lifespan.
Furthermore, maintaining appropriate refrigerant levels helps minimize environmental impact-a crucial consideration given global efforts toward sustainability. Refrigerants are potent greenhouse gases; therefore preventing unnecessary emissions by promptly addressing any deficiencies contributes positively toward environmental preservation initiatives.
In conclusion, dispelling misconceptions about static refrigerant usage is vital for effective HVAC management practices today more than ever before-a task made simpler by incorporating regular assessments into established maintenance routines focusing on optimizing both operational efficiency alongside long-term sustainability outcomes alike! Homeowners who prioritize this aspect will find themselves enjoying improved comfort without unexpected disruptions coupled alongside reduced financial burdens stemming from avoidable repair scenarios down-line too thus maximizing return-on-investment regarding initial outlays involved ultimately delivering peace-of-mind knowing proactive steps have been taken safeguarding against preventable complications thereby securing home environments' integrity overall moving forwards assuredly so indeed!
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Geothermal heating is the direct use of geothermal energy for some heating applications. Humans have taken advantage of geothermal heat this way since the Paleolithic era. Approximately seventy countries made direct use of a total of 270 PJ of geothermal heating in 2004. As of 2007, 28 GW of geothermal heating capacity is installed around the world, satisfying 0.07% of global primary energy consumption.[1] Thermal efficiency is high since no energy conversion is needed, but capacity factors tend to be low (around 20%) since the heat is mostly needed in the winter.
Geothermal energy originates from the heat retained within the Earth since the original formation of the planet, from radioactive decay of minerals, and from solar energy absorbed at the surface.[2] Most high temperature geothermal heat is harvested in regions close to tectonic plate boundaries where volcanic activity rises close to the surface of the Earth. In these areas, ground and groundwater can be found with temperatures higher than the target temperature of the application. However, even cold ground contains heat. Below 6 metres (20 ft), the undisturbed ground temperature is consistently at the mean annual air temperature,[3] and this heat can be extracted with a ground source heat pump.
Country | Production PJ/yr |
Capacity GW |
Capacity factor |
Dominant applications |
---|---|---|---|---|
China | 45.38 | 3.69 | 39% | bathing |
Sweden | 43.2 | 4.2 | 33% | heat pumps |
USA | 31.24 | 7.82 | 13% | heat pumps |
Turkey | 24.84 | 1.5 | 53% | district heating |
Iceland | 24.5 | 1.84 | 42% | district heating |
Japan | 10.3 | 0.82 | 40% | bathing (onsens) |
Hungary | 7.94 | 0.69 | 36% | spas/greenhouses |
Italy | 7.55 | 0.61 | 39% | spas/space heating |
New Zealand | 7.09 | 0.31 | 73% | industrial uses |
63 others | 71 | 6.8 | ||
Total | 273 | 28 | 31% | space heating |
Category | GWh/year |
---|---|
Geothermal heat pumps | 90,293 |
Bathing and swimming | 33,164 |
Space heating | 24,508 |
Greenhouse heating | 7,407 |
Aquaculture pond heating | 3,322 |
Industrial uses | 2,904 |
Cooling/snow melting | 722 |
Agriculture drying | 564 |
Others | 403 |
Total | 163,287 |
There are a wide variety of applications for cheap geothermal heat including heating of houses, greenhouses, bathing and swimming or industrial uses. Most applications use geothermal in the form of hot fluids between 50 °C (122 °F) and 150 °C (302 °F). The suitable temperature varies for the different applications. For direct use of geothermal heat, the temperature range for the agricultural sector lies between 25 °C (77 °F) and 90 °C (194 °F), for space heating lies between 50 °C (122 °F) to 100 °C (212 °F).[4] Heat pipes extend the temperature range down to 5 °C (41 °F) as they extract and "amplify" the heat. Geothermal heat exceeding 150 °C (302 °F) is typically used for geothermal power generation.[6]
In 2004 more than half of direct geothermal heat was used for space heating, and a third was used for spas.[1] The remainder was used for a variety of industrial processes, desalination, domestic hot water, and agricultural applications. The cities of Reykjavík and Akureyri pipe hot water from geothermal plants under roads and pavements to melt snow. Geothermal desalination has been demonstrated.
Geothermal systems tend to benefit from economies of scale, so space heating power is often distributed to multiple buildings, sometimes whole communities. This technique, long practiced throughout the world in locations such as Reykjavík, Iceland;[7] Boise, Idaho;[8] and Klamath Falls, Oregon;[9] is known as district heating.[10]
In Europe alone 280 geothermal district heating plants were in operation in 2016 according to the European Geothermal Energy Council (EGEC) with a total capacity of approximately 4.9 GWth.[11]
Some parts of the world, including substantial portions of the western USA, are underlain by relatively shallow geothermal resources.[12] Similar conditions exist in Iceland, parts of Japan, and other geothermal hot spots around the world. In these areas, water or steam may be captured from natural hot springs and piped directly into radiators or heat exchangers. Alternatively, the heat may come from waste heat supplied by co-generation from a geothermal electrical plant or from deep wells into hot aquifers. Direct geothermal heating is far more efficient than geothermal electricity generation and has less demanding temperature requirements, so it is viable over a large geographical range. If the shallow ground is hot but dry, air or water may be circulated through earth tubes or downhole heat exchangers which act as heat exchangers with the ground.
Steam under pressure from deep geothermal resources is also used to generate electricity from geothermal power. The Iceland Deep Drilling Project struck a pocket of magma at 2,100m. A cemented steelcase was constructed in the hole with a perforation at the bottom close to the magma. The high temperatures and pressure of the magma steam were used to generate 36MW of electricity, making IDDP-1 the world's first magma-enhanced geothermal system.[13]
In areas where the shallow ground is too cold to provide comfort directly, it is still warmer than the winter air. The thermal inertia of the shallow ground retains solar energy accumulated in the summertime, and seasonal variations in ground temperature disappear completely below 10m of depth. That heat can be extracted with a geothermal heat pump more efficiently than it can be generated by conventional furnaces.[10] Geothermal heat pumps are economically viable essentially anywhere in the world.
In theory, geothermal energy (usually cooling) can also be extracted from existing infrastructure, such as municipal water pipes.[14]
In regions without any high temperature geothermal resources, a ground-source heat pump (GSHP) can provide space heating and space cooling. Like a refrigerator or air conditioner, these systems use a heat pump to force the transfer of heat from the ground to the building. Heat can be extracted from any source, no matter how cold, but a warmer source allows higher efficiency. A ground-source heat pump uses the shallow ground or ground water (typically starting at 10–12 °C or 50–54 °F) as a source of heat, thus taking advantage of its seasonally moderate temperatures.[15] In contrast, an air source heat pump draws heat from the air (colder outside air) and thus requires more energy.
GSHPs circulate a carrier fluid (usually a mixture of water and small amounts of antifreeze) through closed pipe loops buried in the ground. Single-home systems can be "vertical loop field" systems with bore holes 50–400 feet (15–120 m) deep or,[16] if adequate land is available for extensive trenches, a "horizontal loop field" is installed approximately six feet subsurface. As the fluid circulates underground it absorbs heat from the ground and, on its return, the warmed fluid passes through the heat pump which uses electricity to extract heat from the fluid. The re-chilled fluid is sent back into the ground thus continuing the cycle. The heat extracted and that generated by the heat pump appliance as a byproduct is used to heat the house. The addition of the ground heating loop in the energy equation means that significantly more heat can be transferred to a building than if electricity alone had been used directly for heating.
Switching the direction of heat flow, the same system can be used to circulate the cooled water through the house for cooling in the summer months. The heat is exhausted to the relatively cooler ground (or groundwater) rather than delivering it to the hot outside air as an air conditioner does. As a result, the heat is pumped across a larger temperature difference and this leads to higher efficiency and lower energy use.[15]
This technology makes ground source heating economically viable in any geographical location. In 2004, an estimated million ground-source heat pumps with a total capacity of 15 GW extracted 88 PJ of heat energy for space heating. Global ground-source heat pump capacity is growing by 10% annually.[1]
Hot springs have been used for bathing at least since Paleolithic times.[17] The oldest known spa is a stone pool on China's Mount Li built in the Qin dynasty in the 3rd century BC, at the same site where the Huaqing Chi palace was later built. Geothermal energy supplied channeled district heating for baths and houses in Pompeii around 0 AD.[18] In the first century AD, Romans conquered Aquae Sulis in England and used the hot springs there to feed public baths and underfloor heating.[19] The admission fees for these baths probably represents the first commercial use of geothermal power. A 1,000-year-old hot tub has been located in Iceland, where it was built by one of the island's original settlers.[20] The world's oldest working geothermal district heating system in Chaudes-Aigues, France, has been operating since the 14th century.[4] The earliest industrial exploitation began in 1827 with the use of geyser steam to extract boric acid from volcanic mud in Larderello, Italy.
In 1892, America's first district heating system in Boise, Idaho, was powered directly by geothermal energy, and was soon copied in Klamath Falls, Oregon in 1900. A deep geothermal well was used to heat greenhouses in Boise in 1926, and geysers were used to heat greenhouses in Iceland and Tuscany at about the same time.[21] Charlie Lieb developed the first downhole heat exchanger in 1930 to heat his house. Steam and hot water from the geysers began to be used to heat homes in Iceland in 1943.
By this time, Lord Kelvin had already invented the heat pump in 1852, and Heinrich Zoelly had patented the idea of using it to draw heat from the ground in 1912.[22] But it was not until the late 1940s that the geothermal heat pump was successfully implemented. The earliest one was probably Robert C. Webber's home-made 2.2 kW direct-exchange system, but sources disagree as to the exact timeline of his invention.[22] J. Donald Kroeker designed the first commercial geothermal heat pump to heat the Commonwealth Building (Portland, Oregon) and demonstrated it in 1946.[23][24] Professor Carl Nielsen of Ohio State University built the first residential open loop version in his home in 1948.[25] The technology became popular in Sweden as a result of the 1973 oil crisis, and has been growing slowly in worldwide acceptance since then. The 1979 development of polybutylene pipe greatly augmented the heat pump's economic viability.[23] Since 2000, a compelling body of research has been dedicated to numerically evidence the advantages and efficiency of using CO2, alternative to water, as heat transmission fluid for geothermal energy recovery from enhanced geothermal systems (EGS) where the permeability of the underground source is enhanced by hydrofracturing.[26][27] As of 2004, there are over one million geothermal heat pumps installed worldwide providing 12 GW of thermal capacity.[28] Each year, about 80,000 units are installed in the US and 27,000 in Sweden.[28]
Geothermal energy is a type of renewable energy that encourages conservation of natural resources. According to the US Environmental Protection Agency, geo-exchange systems save homeowners 30–70 percent in heating costs, and 20–50 percent in cooling costs, compared to conventional systems.[29] Geo-exchange systems also save money because they require much less maintenance. In addition to being highly reliable they are built to last for decades.
Some utilities, such as Kansas City Power and Light, offer special, lower winter rates for geothermal customers, offering even more savings.[15]
In geothermal heating projects the underground is penetrated by trenches or drillholes. As with all underground work, projects may cause problems if the geology of the area is poorly understood.
In the spring of 2007 an exploratory geothermal drilling operation was conducted to provide geothermal heat to the town hall of Staufen im Breisgau. After initially sinking a few millimeters, a process called subsidence,[30] the city center has started to rise gradually[31] causing considerable damage to buildings in the city center, affecting numerous historic houses including the town hall. It is hypothesized that the drilling perforated an anhydrite layer bringing high-pressure groundwater to come into contact with the anhydrite, which then began to expand. Currently no end to the rising process is in sight.[32][33][34] Data from the TerraSAR-X radar satellite before and after the changes confirmed the localised nature of the situation:
A geochemical process called anhydrite swelling has been confirmed as the cause of these uplifts. This is a transformation of the mineral anhydrite (anhydrous calcium sulphate) into gypsum (hydrous calcium sulphate). A pre-condition for this transformation is that the anhydrite is in contact with water, which is then stored in its crystalline structure.[35] There are other sources of potential risks, i.e.: cave enlargement or worsening of stability conditions, quality or quantity degradation of groundwater resources, Specific hazard worsening in the case of landslide-prone areas, worsening of rocky mechanical characteristics, soil and water pollution (i.e. due to antifreeze additives or polluting constructive and boring material).[36] The design defined on the base of site-specific geological, hydrogeological and environmental knowledge prevent all these potential risks.
During Roman times, warm water was circulated through open trenches to provide heating for buildings and baths in Pompeii.
This article needs additional citations for verification. (March 2009)
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A thermostat is a regulating device component which senses the temperature of a physical system and performs actions so that the system's temperature is maintained near a desired setpoint.
Thermostats are used in any device or system that heats or cools to a setpoint temperature. Examples include building heating, central heating, air conditioners, HVAC systems, water heaters, as well as kitchen equipment including ovens and refrigerators and medical and scientific incubators. In scientific literature, these devices are often broadly classified as thermostatically controlled loads (TCLs). Thermostatically controlled loads comprise roughly 50% of the overall electricity demand in the United States.[1]
A thermostat operates as a "closed loop" control device, as it seeks to reduce the error between the desired and measured temperatures. Sometimes a thermostat combines both the sensing and control action elements of a controlled system, such as in an automotive thermostat. The word thermostat is derived from the Greek words θερμÏŒς thermos, "hot" and στατÏŒς statos, "standing, stationary".
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 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, and air conditioners, kitchen equipment such as ovens and refrigerators, and medical and scientific incubators.
Thermostats use different types of sensors to measure temperatures and actuate control operations. Mechanical thermostats commonly use bimetallic strips, converting a temperature change into mechanical displacement, to actuate control of the heating or cooling sources. Electronic thermostats, instead, use a thermistor or other semiconductor sensor, processing temperature change as electronic signals, to control the heating or cooling equipment.
Conventional thermostats are example of "bang-bang controllers" as the controlled system either operates at full capacity once the setpoint is reached, or keeps completely off. Although it is the simplest program to implement, such control method requires to include some hysteresis in order to prevent excessively rapid cycling of the equipment around the setpoint. As a consequence, conventional thermostats cannot control temperatures very precisely. Instead, there are oscillations of a certain magnitude, usually 1-2 °C.[2] Such control is in general inaccurate, inefficient and may induce more mechanical wear; it however, allows for more cost-effective compressors compared to ones with continuously variable capacity.[3][clarification needed]
Another consideration is the time delay of the controlled system. To improve the control performance of the system, thermostats can include an "anticipator", which stops heating/cooling slightly earlier than reaching the setpoint, as the system will continue to produce heat for a short while.[4] Turning off exactly at the setpoint will cause actual temperature to exceed the desired range, known as "overshoot". Bimetallic sensors can include a physical "anticipator", which has a thin wire touched on the thermostat. When current passes the wire, a small amount of heat is generated and transferred to the bimetallic coil. Electronic thermostats have an electronic equivalent.[5]
When higher control precision is required, a PID or MPC controller is preferred. However, they are nowadays mainly adopted for industrial purposes, for example, for semiconductor manufacturing factories or museums.
Early technologies included mercury thermometers with electrodes inserted directly through the glass, so that when a certain (fixed) temperature was reached the contacts would be closed by the mercury. These were accurate to within a degree of temperature.
Common sensor technologies in use today include:
These may then control the heating or cooling apparatus using:
Possibly the earliest recorded examples of thermostatic control were built by a Dutch innovator, Cornelis Drebbel (1572–1633), about 1620 in England. He invented a mercury thermostat to regulate the temperature of a chicken incubator.[6] This is one of the first recorded feedback-controlled devices.
Modern thermostatic control was developed in the 1830s by Andrew Ure (1778–1857), a Scottish chemist. The textile mills of the time needed a constant and steady temperature to operate optimally, so Ure designed the bimetallic thermostat, which would bend as one of the metals expanded in response to the increased temperature and cut off the energy supply.[7]
Warren S. Johnson (1847–1911), of Wisconsin, patented a bi-metal room thermostat in 1883, and two years later sought a patent for the first multi-zone thermostatic control system.[8][9] Albert Butz (1849–1905) invented the electric thermostat and patented it in 1886.
One of the first industrial uses of the thermostat was in the regulation of the temperature in poultry incubators. Charles Hearson, a British engineer, designed the first modern incubator for eggs, which was taken up for use on poultry farms in 1879.[10]
This covers only devices which both sense and control using purely mechanical means.
Domestic water and steam based central heating systems have traditionally been controlled by bi-metallic strip thermostats, and this is dealt with later in this article. Purely mechanical control has been localised steam or hot-water radiator bi-metallic thermostats which regulated the individual flow. However, thermostatic radiator valves (TRV) are now being widely used.
Purely mechanical thermostats are used to regulate dampers in some rooftop turbine vents, reducing building heat loss in cool or cold periods.
Some automobile passenger heating systems have a thermostatically controlled valve to regulate the water flow and temperature to an adjustable level. In older vehicles the thermostat controls the application of engine vacuum to actuators that control water valves and flappers to direct the flow of air. In modern vehicles, the vacuum actuators may be operated by small solenoids under the control of a central computer.
Perhaps the most common example of purely mechanical thermostat technology in use today is the internal combustion engine cooling system thermostat, used to maintain the engine near its optimum operating temperature by regulating the flow of coolant to an air-cooled radiator. This type of thermostat operates using a sealed chamber containing a wax pellet that melts and expands at a set temperature. The expansion of the chamber operates a rod which opens a valve when the operating temperature is exceeded. The operating temperature is determined by the composition of the wax. Once the operating temperature is reached, the thermostat progressively increases or decreases its opening in response to temperature changes, dynamically balancing the coolant recirculation flow and coolant flow to the radiator to maintain the engine temperature in the optimum range.
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.
A thermostatic mixing valve uses a wax pellet to control the mixing of hot and cold water. A common application is to permit operation of an electric water heater at a temperature hot enough to kill Legionella bacteria (above 60 °C, 140 °F), while the output of the valve produces water that is cool enough to not immediately scald (49 °C, 120 °F).
A wax pellet driven valve can be analyzed through graphing the wax pellet's hysteresis which consists of two thermal expansion curves; extension (motion) vs. temperature increase, and contraction (motion) vs. temperature decrease. The spread between the up and down curves visually illustrate the valve's hysteresis; there is always hysteresis within wax driven valves due to the phase transition or phase change between solids and liquids. Hysteresis can be controlled with specialized blended mixes of hydrocarbons; tight hysteresis is what most desire, however some applications require broader ranges. Wax pellet driven valves are used in anti scald, freeze protection, over-temp purge, solar thermal energy or solar thermal, automotive, and aerospace applications among many others.
Thermostats are sometimes used to regulate gas ovens. It consists of a gas-filled bulb connected to the control unit by a slender copper tube. The bulb is normally located at the top of the oven. The tube ends in a chamber sealed by a diaphragm. As the thermostat heats up, the gas expands applying pressure to the diaphragm which reduces the flow of gas to the burner.
A pneumatic thermostat is a thermostat that controls a heating or cooling system via a series of air-filled control tubes. This "control air" system responds to the pressure changes (due to temperature) in the control tube to activate heating or cooling when required. The control air typically is maintained on "mains" at 15-18 psi (although usually operable up to 20 psi). Pneumatic thermostats typically provide output/ branch/ post-restrictor (for single-pipe operation) pressures of 3-15 psi which is piped to the end device (valve/ damper actuator/ pneumatic-electric switch, etc.).[11]
The pneumatic thermostat was invented by Warren Johnson in 1895[12] soon after he invented the electric thermostat. In 2009, Harry Sim was awarded a patent for a pneumatic-to-digital interface[13] that allows pneumatically controlled buildings to be integrated with building automation systems to provide similar benefits as direct digital control (DDC).
Water and steam based central heating systems have traditionally had overall control by wall-mounted bi-metallic strip thermostats. These sense the air temperature using the differential expansion of two metals to actuate an on/off switch.[14] Typically the central system would be switched on when the temperature drops below the setpoint on the thermostat, and switched off when it rises above, with a few degrees of hysteresis to prevent excessive switching. Bi-metallic sensing is now being superseded by electronic sensors. A principal use of the bi-metallic thermostat today is in individual electric convection heaters, where control is on/off, based on the local air temperature and the setpoint desired by the user. These are also used on air-conditioners, where local control is required.
This follows the same nomenclature as described in Relay § Terminology and Switch § Contact terminology. A thermostat is considered to be activated by thermal energy, thus “normal” refers to the state in which temperature is below the setpoint.
Any leading number stands for number of contact sets, like "1NO", "1NC" for one contact set with two terminals. "1CO" will also have one contact set, even if it is a switch-over with three terminals.
The illustration is the interior of a common two wire heat-only household thermostat, used to regulate a gas-fired heater via an electric gas valve. Similar mechanisms may also be used to control oil furnaces, boilers, boiler zone valves, electric attic fans, electric furnaces, electric baseboard heaters, and household appliances such as refrigerators, coffee pots and hair dryers. The power through the thermostat is provided by the heating device and may range from millivolts to 240 volts in common North American construction, and is used to control the heating system either directly (electric baseboard heaters and some electric furnaces) or indirectly (all gas, oil and forced hot water systems). Due to the variety of possible voltages and currents available at the thermostat, caution must be taken when selecting a replacement device.
Not shown in the illustration is a separate bimetal thermometer on the outer case to show the actual temperature at the thermostat.
As illustrated in the use of the thermostat above, all of the power for the control system is provided by a thermopile which is a combination of many stacked thermocouples, heated by the pilot light. The thermopile produces sufficient electrical power to drive a low-power gas valve, which under control of one or more thermostat switches, in turn controls the input of fuel to the burner.
This type of device is generally considered obsolete as pilot lights can waste a surprising amount of gas (in the same way a dripping faucet can waste a large amount of water over an extended period), and are also no longer used on stoves, but are still to be found in many gas water heaters and gas fireplaces. Their poor efficiency is acceptable in water heaters, since most of the energy "wasted" on the pilot still represents a direct heat gain for the water tank. The Millivolt system also makes it unnecessary for a special electrical circuit to be run to the water heater or furnace; these systems are often completely self-sufficient and can run without any external electrical power supply. For tankless "on demand" water heaters, pilot ignition is preferable because it is faster than hot-surface ignition and more reliable than spark ignition.
Some programmable thermostats - those that offer simple "millivolt" or "two-wire" modes - will control these systems.
The majority of modern heating/cooling/heat pump thermostats operate on low voltage (typically 24 volts AC) control circuits. The source of the 24 volt AC power is a control transformer installed as part of the heating/cooling equipment. The advantage of the low voltage control system is the ability to operate multiple electromechanical switching devices such as relays, contactors, and sequencers using inherently safe voltage and current levels.[15] Built into the thermostat is a provision for enhanced temperature control using anticipation.
A heat anticipator generates a small amount of additional heat to the sensing element while the heating appliance is operating. This opens the heating contacts slightly early to prevent the space temperature from greatly overshooting the thermostat setting. A mechanical heat anticipator is generally adjustable and should be set to the current flowing in the heating control circuit when the system is operating.
A cooling anticipator generates a small amount of additional heat to the sensing element while the cooling appliance is not operating. This causes the contacts to energize the cooling equipment slightly early, preventing the space temperature from climbing excessively. Cooling anticipators are generally non-adjustable.
Electromechanical thermostats use resistance elements as anticipators. Most electronic thermostats use either thermistor devices or integrated logic elements for the anticipation function. In some electronic thermostats, the thermistor anticipator may be located outdoors, providing a variable anticipation depending on the outdoor temperature.
Thermostat enhancements include outdoor temperature display, programmability, and system fault indication. While such 24 volt thermostats are incapable of operating a furnace when the mains power fails, most such furnaces require mains power for heated air fans (and often also hot-surface or electronic spark ignition) rendering moot the functionality of the thermostat. In other circumstances such as piloted wall and "gravity" (fanless) floor and central heaters the low voltage system described previously may be capable of remaining functional when electrical power is unavailable.
There are no standards for wiring color codes, but convention has settled on the following terminal codes and colors.[16][17] In all cases, the manufacturer's instructions should be considered definitive.
Terminal code | Color | Description |
---|---|---|
R | Red | 24 volt (Return line to appliance; often strapped to Rh and Rc) |
Rh | Red | 24 volt HEAT load (Return line Heat) |
Rc | Red | 24 volt COOL load (Return line Cool) |
C | Black/Blue/Brown/Cyan | 24 volt Common connection to relays |
W / W1 | White | Heat |
W2 | Varies/White/Black | 2nd Stage / Backup Heat |
Y / Y1 | Yellow | Cool |
Y2 | Blue/Orange/Purple/Yellow/White | 2nd Stage Cool |
G | Green | Fan |
O | Varies/Orange/Black | Reversing valve Energize to Cool (Heat Pump) |
B | Varies/Blue/Black/Brown/Orange | Reversing valve Energize to Heat (Heat Pump) or Common |
E | Varies/Blue/Pink/Gray/Tan | Emergency Heat (Heat Pump) |
S1/S2 | Brown/Black/Blue | Temperature Sensor (Usually outdoors on a Heat Pump System) |
T | Varies/Tan/Gray | Outdoor Anticipator Reset, Thermistor |
X | Varies/Black | Emergency Heat (Heat Pump) or Common |
X2 | Varies | 2nd stage/emergency heating or indicator lights |
L | Varies | Service Light |
U | Varies | User programmable (usually for humidifier) |
K | Yellow/Green | Combined Y and G |
PS | Varies | Pipe Sensor for two pipe heat/cool systems |
V | Varies | Variable speed (many can function as W2) |
Older, mostly deprecated designations:
Terminal code | Description |
---|---|
5 / V | 24 volt ac supply |
4 / M | 24 volt HEAT load |
6 / blank | Not heat to close valve |
F | Cool fan relay or Fault light |
G | Heat fan relay |
H | Heat valve |
M | Heat Pump compressor |
P | Heat Pump defrost |
R | Heat pump reversing valve |
VR | 24 volt auxiliary heat |
Y | Auxiliary heat |
C | Clock power (usually two terminals) or Cool relay |
T | Transformer common |
Z | Fan power source for "Auto" connection |
Line voltage thermostats are most commonly used for electric space heaters such as a baseboard heater or a direct-wired electric furnace. If a line voltage thermostat is used, system power (in the United States, 120 or 240 volts) is directly switched by the thermostat. With switching current often exceeding 40 amperes, using a low voltage thermostat on a line voltage circuit will result at least in the failure of the thermostat and possibly a fire. Line voltage thermostats are sometimes used in other applications, such as the control of fan-coil (fan powered from line voltage blowing through a coil of tubing which is either heated or cooled by a larger system) units in large systems using centralized boilers and chillers, or to control circulation pumps in hydronic heating applications.
Some programmable thermostats are available to control line-voltage systems. Baseboard heaters will especially benefit from a programmable thermostat which is capable of continuous control (as are at least some Honeywell models), effectively controlling the heater like a lamp dimmer, and gradually increasing and decreasing heating to ensure an extremely constant room temperature (continuous control rather than relying on the averaging effects of hysteresis). Systems which include a fan (electric furnaces, wall heaters, etc.) must typically use simple on/off controls.
Newer digital thermostats have no moving parts to measure temperature and instead rely on thermistors or other semiconductor devices such as a resistance thermometer (resistance temperature detector). Typically one or more regular batteries must be installed to operate it, although some so-called "power stealing" digital thermostats (operated for energy harvesting) use the common 24-volt AC circuits as a power source, but will not operate on thermopile powered "millivolt" circuits used in some furnaces. Each has an LCD screen showing the current temperature, and the current setting. Most also have a clock, and time-of-day and even day-of-week settings for the temperature, used for comfort and energy conservation. Some advanced models have touch screens, or the ability to work with home automation or building automation systems.
Digital thermostats use either a relay or a semiconductor device such as triac to act as a switch to control the HVAC unit. Units with relays will operate millivolt systems, but often make an audible "click" noise when switching on or off.
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 7 a.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.[18] 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)[19] or maintaining temperature in a band by deploying hysteresis control.[20])
Most digital thermostats in common residential use in North America and Europe are programmable thermostats, which will typically provide a 30% energy savings if left with their default programs; adjustments to these defaults may increase or reduce energy savings.[21] The programmable thermostat article provides basic information on the operation, selection and installation of such a thermostat.
With non-zoned (typical residential, one thermostat for the whole house) systems, when the thermostat's R (or Rh) and W terminals are connected, the furnace will go through its start-up procedure and produce heat.
With zoned systems (some residential, many commercial systems — several thermostats controlling different "zones" in the building), the thermostat will cause small electric motors to open valves or dampers and start the furnace or boiler if it is not already running.
Most programmable thermostats will control these systems.
Depending on what is being controlled, a forced-air air conditioning thermostat generally has an external switch for heat/off/cool, and another on/auto to turn the blower fan on constantly or only when heating and cooling are running. Four wires come to the centrally-located thermostat from the main heating/cooling unit (usually located in a closet, basement, or occasionally in the attic): One wire, usually red, supplies 24 volts AC power to the thermostat, while the other three supply control signals from the thermostat, usually white for heat, yellow for cooling, and green to turn on the blower fan. The power is supplied by a transformer, and when the thermostat makes contact between the 24 volt power and one or two of the other wires, a relay back at the heating/cooling unit activates the corresponding heat/fan/cool function of the unit(s).
A thermostat, when set to "cool", will only turn on when the ambient temperature of the surrounding room is above the set temperature. Thus, if the controlled space has a temperature normally above the desired setting when the heating/cooling system is off, it would be wise to keep the thermostat set to "cool", despite what the temperature is outside. On the other hand, if the temperature of the controlled area falls below the desired degree, then it is advisable to turn the thermostat to "heat".
The heat pump is a refrigeration based appliance which reverses refrigerant flow between the indoor and outdoor coils. This is done by energizing a reversing valve (also known as a "4-way" or "change-over" valve). During cooling, the indoor coil is an evaporator removing heat from the indoor air and transferring it to the outdoor coil where it is rejected to the outdoor air. During heating, the outdoor coil becomes the evaporator and heat is removed from the outdoor air and transferred to the indoor air through the indoor coil. The reversing valve, controlled by the thermostat, causes the change-over from heat to cool. Residential heat pump thermostats generally have an "O" terminal to energize the reversing valve in cooling. Some residential and many commercial heat pump thermostats use a "B" terminal to energize the reversing valve in heating. The heating capacity of a heat pump decreases as outdoor temperatures fall. At some outdoor temperature (called the balance point) the ability of the refrigeration system to transfer heat into the building falls below the heating needs of the building. A typical heat pump is fitted with electric heating elements to supplement the refrigeration heat when the outdoor temperature is below this balance point. Operation of the supplemental heat is controlled by a second stage heating contact in the heat pump thermostat. During heating, the outdoor coil is operating at a temperature below the outdoor temperature and condensation on the coil may take place. This condensation may then freeze onto the coil, reducing its heat transfer capacity. Heat pumps therefore have a provision for occasional defrost of the outdoor coil. This is done by reversing the cycle to the cooling mode, shutting off the outdoor fan, and energizing the electric heating elements. The electric heat in defrost mode is needed to keep the system from blowing cold air inside the building. The elements are then used in the "reheat" function. Although the thermostat may indicate the system is in defrost and electric heat is activated, the defrost function is not controlled by the thermostat. Since the heat pump has electric heat elements for supplemental and reheats, the heat pump thermostat provides for use of the electric heat elements should the refrigeration system fail. This function is normally activated by an "E" terminal on the thermostat. When in emergency heat, the thermostat makes no attempt to operate the compressor or outdoor fan.
The thermostat should not be located on an outside wall or where it could be exposed to direct sunlight at any time during the day. It should be located away from the room's cooling or heating vents or device, yet exposed to general airflow from the room(s) to be regulated.[22] An open hallway may be most appropriate for a single zone system, where living rooms and bedrooms are operated as a single zone. If the hallway may be closed by doors from the regulated spaces then these should be left open when the system is in use. If the thermostat is too close to the source controlled then the system will tend to "short a cycle", and numerous starts and stops can be annoying and in some cases shorten equipment life. A multiple zoned system can save considerable energy by regulating individual spaces, allowing unused rooms to vary in temperature by turning off the heating and cooling.
HVAC systems take a long time, usually one to several hours, to cool down or warm up the space from near outdoor conditions in summer or winter. Thus, it is a common practice to set setback temperatures when the space is not occupied (night and/or holidays). On the one hand, compared with maintaining at the original setpoint, substantial energy consumption can be saved.[23] On the other hand, compared with turning off the system completely, it avoids room temperature drifting too much from the comfort zone, thus reducing the time of possible discomfort when the space is again occupied. New thermostats are mostly programmable and include an internal clock that allows this setback feature to be easily incorporated.
It has been reported that many thermostats in office buildings are non-functional dummy devices, installed to give tenants' employees an illusion of control.[24][25] These dummy thermostats are in effect a type of placebo button. However, these thermostats are often used to detect the temperature in the zone, even though their controls are disabled. This function is often referred to as "lockout".[26]