We all enjoy the comforts our split ac system or ductless air conditioning can bring during a hot summer. As you feel the cool breeze coming out of the evaporator of your mini split, you may be wondering how split system air conditioning and mini split heat pump actually work. Especially if you are looking at one of today’s compact and light weight ductless heating and cooling or heat pump system. How can so much cooling/heating power come from such a small package? Heating and cooling units and mini split air conditioning, although evolved technologically and in design, utilize the same basic mechanics that all split system do (including ducted air conditioners and ductless window units.) Whether they use a duct system or not, air conditioning is all about heat transfer. The heat you want out during the summer and in during the winter (if you have installed a ductless mini split), is what your mini split air conditioner is all about! Your best air conditioner units, although compact, uses refrigerants to transfer heat, just like refrigerant and air conditioning technology has since its development in the 1920’s.
EXPLOITING CHEMISTRY: HOW REFRIGERANTS WORK
When we think about our heating - cooling, we generally think of the machinery involved. Whether you are a layman, or do it yourselfer, when you think of the installation or mechanics of heating & cooling, you probably imagine a large, compressor appliance, a fan, and perhaps some vents and ductwork. However, a major component that this fresh, cool air could not be created without is small and silent. None of these appliances could do their job without their chemical assistant, the refrigerant.
From the oldest mechanical room coolers, to the modern heating - cooling, actually do their job by transferring heat. During the hot days of summer, your heating & cooling transfers heat back to the outdoors, leaving you with a cool and comfortable climate indoors. During the winter, heating and cooling reverse the process, gathering small amounts of heat from outside and concentrating it into your indoor space. Physical heat is actually molecular energy. Therefore, using chemicals which have properties which allow us to guide the path way of the heat are a very efficient way to both heat and cool a home. Refrigerants do just that.
The boiling point of a substance is the temperature at which a substance makes the change from a liquid to a gas. Many oils and lubricants would be in a class of chemicals with a very high boiling point, as they can with stand high temperatures and retain their fluidity, which does not compromise their lubrication ability. Most of us are familiar with the use of oils, both natural and synthetic, when dealing with high heat applications. For example, to keep the engine of your car lubricated, we must use an oil that will with stand the high amounts of heat which are put off by the running of an engine. Also, when cooking, we use oils with a high boiling point, so rather than evaporating off, that oil will stay put in the pan!
Refrigerants are chemicals which have the opposite property. These are substances with a very low boiling point, which will change from a liquid to a gas in a flash. In the way that cooking oil is most stable as a liquid, refrigerants really want to be a gas. So, at very low temperatures (with very little molecular energy expended) liquid refrigerants will become a gas. This property is exploited by your heating and cooling, in order to transfer heat along the circuit, from compressor, to condenser, to evaporator; ultimately, bringing you all of the benefits you associate with your efficient heating - cooling.
The part of your heating & cooling that you are probably most familiar with is the evaporator/air handler. This is where you go to set your settings for cooling, heating, and dehumidifying. It is also where the reconditioned air comes out! It is the internal component of the split, in the case of heating and cooling. Fans with in the air handler direct the air flow of the unit into the space it is meant to service. But this is also the source of heat collection, from your interior space, by means of refrigerants.
Within the evaporator, there is a tiny, narrow hole, which is the entry point for cool, refrigerant liquid. As the evaporator accepts each tiny droplet of the liquid, the pressure on the refrigerant is released. All of a sudden, this liquid chemical, which desperately wants to be a gas, is exposed to all of the conditions necessary for it to do so! The lack of pressure(which allow the molecular particles to separate into a less-dense state) and any ambient heat in the room immediately allows the refrigerant to transform. The refrigerant evaporates, taking with it the heat in the room. In extracting this available heat, the refrigerant is returned to a cool, low-pressure gas, which is then sent down the conduit to the outdoor compressor unit.
In the compressor of your mini split, the refrigerant is compressed, or pushed on, in order to charge there frigerant with energy. That is where the compressor gets its name, it literally “compresses” the refrigerant, compacting its molecules and creating heat! There, the low pressure gas is squeezed with all of the compressors might, heating it significantly and creating energy that can be used (when the process is reversed) to heat your home. This may seem counter intuitive, if the heating and cooling process is mysterious to you. But, remember, heat is energy. That is what it takes to keep your home or office cool when outdoor temperatures remain high: energy! And heating - cooling is all about heat transfer. So, the compressor does the job of compressing the refrigerant, wringing the heat out like a wet rag into the outdoors.
The compressor could not do this job efficiently without the other component of your outdoor heating & cooling, the condenser. The condenser is built to work like the radiator of an automobile, fanning and dissipating the collected heat away from your home. And it does a fantastic job, lowering the temperature of the hot, compressed gas enough to create liquid refrigerant one again. This process of transforming a gas to a liquid is known, chemically, as condensation. So, the condenser is also known for what it does to the heating and cooling refrigerant. The temperature at which a gas returns to a liquid is also known as the “dew point,” so, it starts to make sense that the first heating - cooling(created for industrial use in the 1920’s by Willis Carrier) were stumbled upon as he and colleagues made observations and breakthroughs regarding dew point control.
Any how, the cooled liquid “condensed” by the condenser of your heating - cooling is destined to be recycled back to the evaporator again and again, until the desired indoor climate is reached. This is why, with heating & cooling, such a small conduit can be used to connect the indoor air handler to the outdoor unit. One of the major components of the conduit is a narrow passage way for the liquid refrigerant. The refrigerant makes its way back to your room, gathering more heat, and evaporating back down to the compressor. This type of heat transfer would not be possible without the use of these amazing chemicals.
CHALLENGES IN REFRIGERANT TECHNOLOGY
However, the development and implementation of refrigerants for our climate control needs has not come without pitfalls and disadvantages. Just think of how many refrigerators and room heating and cooling that are running right now, in the present day, to keep our food cool, our homes comfortable,and our offices functioning around the globe, 365 days a year. Although refrigerants can be used and recycled in minute quantities, in comparison to other chemicals that are used in great amount (such as oil, industrial chemicals and cleaners), in order to run today’s modern heating - cooling, our global use certainly adds up to a lot of refrigerant! There are many chemicals, both natural and manufactured, which have refrigerant qualities. However, the best choice to suit our growing need for them would be one that is abundant, economically feasible, and does the least harm to us and our environment.
Early on, many mechanical refrigeration systems used sulfur dioxide, methyl chloride, and ammonia. Sulfur dioxide and methyl chloride have the disadvantage that they are toxic substances. Although ammonia continues to be used today as a refrigerant in industrial applications, it is also toxic in the high concentrations needed for it to be used as a refrigerant. (Anhydrous ammonia used in heating & cooling is far more concentrated than the 10% solutions you might be familiarized with, such as in household cleaners.) This created a large problem for those attempting to create the domestic room-coolers (ancestors of the modern day heating - cooling) that would soon be desired in every home in America. Leaks of these potentially hazardous chemicals created an appliance whose risk may out weigh its benefits.
Carbon dioxide was another natural refrigerant which was used in some of the first ductless heating and cooling. Like ammonia, carbon dioxide is a natural substance with refrigerant properties which is abundant and economically feasible. Unlike ammonia, there was no risk of toxicity. However, because of the increased compression needed to return carbon dioxide gas back into a liquid form, it was not a very efficient system. Carbon dioxide, by and large, was abandoned as a potential refrigerant, in favor of these more toxic substances which required less, mechanically. (However, as I discuss later, a return to carbon dioxide may prove useful to the heating & cooling of the future!)
So, the use of toxic substances in heating - cooling continued to prove problematic for companies like GE, Kelvinator, and Frigidaire as they struggled to develop a marketable, domestic room ductless heating and cooling. The development of an alternative allowed Frigidaire to win the race, as they introduced Freon(CFC-12) to the industry. The safety of this new refrigerant was demonstrated by its discoverer Thomas Midgley Jr. at a meeting of the American Chemical Society in 1930. The chemist, famously, filled his lungs with the chlorofluorocarbon, Freon, and extinguished a candle. This introduced a chemical with refrigerant properties which was not poisonous, and not flammable. The development of chlorofluoro carbons ultimately lead to the development of heating & cooling at an exceptional pace, as they appeared to be a great replacement for the toxic sulfur dioxide and methyl chloride.
In the 1970’s, it was discovered that chloro fluorocarbons (CFCs), and hydrochlorofluorocarbons (HCFCs) had a damaging affect on the stratospheric ozone, the layer of our atmosphere which protects the earth from damaging radiation affects of the sun. The hydroflourocarbons are less stable in the lower atmosphere, which enables them to break down before reaching the ozone layer. However, a significant portion of them make it to the stratosphere before decomposing, which contributed more chlorine build up than anticipated, leading to what could have been an environmental disaster.
These CFC and HCFC compounds were being used not only in heating and cooling as refrigerants, but also in many household aerosol products. It was alarming to everyone to learn that, with much help from the CFCs, there was a hole in the ozone layer which was increasing skin cancer rates in Australia and, potentially, worldwide. There was an almost immediate interest in moving on from these newly dangerous chemicals. Naturally occurring hydrocarbons, such as propane and butane, began to gain favor as efficient alternatives. Hydrocarbons are one of the options becoming available in newly manufactured, high efficiency heating - cooling.
New environmental concerns arose with the theory of global warming. The United Nations Framework Convention on Climate Change ultimately contracted agreement with countries around the globe, in order to stabilize the effects of greenhouse gasses. CFC compounds were included in the 1997 Kyoto Protocol, in order to combat the impact of pollution from these compounds on climate change. This accelerated the challenge to fully eliminate CFCs from the global marketplace, including their widespread use in heating & cooling. The development of new refrigerants, as well as a rekindles interest in natural refrigerants, continues today.
Many new high-efficiency and heating - cooling ductless mini split use the most newly developed refrigerants on the market. One that is very commonly used is R-410A, a mixture of diflouromethane (R-32) and pentafluoroethane(R-125). This refrigerant was developed by the heating and cooling company now known as Honey well. It is sold under trademarked names such as Puron, EcoFluor, Genetron R410A, and AZ-20. Because this refrigerant operates at higher pressures (allowing for more compact systems, such as the heating & cooling), equipment manufacturers and installers all needed to be updated for proper handling, equipment, and safety techniques. The AC &C Safety Coalition was founded, in order to educate HVAC professionals about R-410A systems. It truly is/was an overhaul of the ductless heating and cooling industry. Unlike refrigerants which contain bromine or chlorine, R-410A contains only fluorine,and does not deplete the ozone. Slowly but surely, the new player is phasing out the old. R-22 has been phased out and replaced for residential and commercial heating - cooling use in Japan, Europe, and the United States. Today, many heating & cooling use R-410A.
However, even the newest in refrigerant technology does not come without new challenges. Although the R-410A used in many heating - cooling is efficient, energy conscious, and ozone safe, it does maintain a significant global warming potential. R-410A, used in most new-production heating and cooling today, has a global warming potential much like that of R-22; 1725 times the effect of carbon dioxide, one of the most sinister culprits of global heating. For this reason, natural refrigerants such as hydrocarbons and ammonia may be revisited. The original refrigerant, carbon dioxide, may actually turn out to be a useful ally in the reduction of greenhouse gasses, rather than a culprit…but new technologies will be needed. There may even be ways of using clean, albeit currently inefficient, natural refrigerants such as water and air. Although refrigerants have come a long way, throughout the history of heating & cooling, we still may have a long way to go in the search for a compound with favorable refrigerant properties that is also efficient, non-flammable, non-toxic, and non-detrimental to the environment and our ozone.
Natural refrigerants include hydrocarbons (such as propane, iso-butane, carbon dioxide, and ammonia. Water and air are also considered natural refrigerants. The benefits of using natural refrigerants is that, while they work as cooling agents as a heat transfer medium in refrigerators and heating - cooling, they do not harm the ozone layer like such as Freon. These natural coolants have no or negligible climate impact in their use, so are a more environmentally responsible choice. Ammonia continues to be used for industrial refrigeration plants, as it is deemed to be an environmentally friendly, economical, and energy efficient choice. When researching and/or purchasing coolants for your heating - cooling or heating & cooling system, you may see these natural coolants labeled or spoken of according to their chemical name or refrigerant class. These are as follows:
Air = (R729)
Water = H20 or (R718)
CarbonDioxide = CO2 or (R744)
Ammonia = NH3 or (R717)
Hydrocarbons = Iso-butane (R600a) and Propane (R290)
Air is a natural refrigerant which has been successfully used in some (albeit limited) heating & cooling applications. Air has success fully been used in residential and automotive heating - cooling units. It is also the refrigerant used in turbine-powered air craft. Air is abundant, found virtually everywhere, so is an extremely economical choice. As far as human and environmental safety is concerned, air also seems like a great option. Air is not harmful to most living things; infact, it is a necessity for most of us! So, it is not likely that leaks or disposal of this refrigerant would pose any environmental hazard or adverse effects. However, the perception that utilizing air as the choice refrigerant for ductless heating and cooling functions is not without merit. The use of air does require advanced compression and expansion technology, as air does not readily condense into a liquid. Furthermore, there is the added threat of a possible explosion; this could result from refrigeration type compressor lubricating oils being compressed together with the air. The last thing you need is for your heating - cooling mini split air conditioner to blow up! Until these disadvantages in efficiency and safety are resolved, it is not likely to be there frigerant of choice for heating & cooling of the near future.
Water is another abundant and environmentally neutral resource which can potentially be used as a refrigerant. Unlike air, water wants to be a liquid, rather than a gas. So, rather than efficient compression and condensation being the issue, the focus would have to be on the evaporator of the heating - cooling. Water-based heating & cooling are non-toxic and easy to build. The most popular example of heating - cooling devices which utilize water as refrigerants, are swamp coolers. This type of heating and cooling, in fact, often does not even require a compressor. The evaporated water is merely sent out into the space via a blower fan, which lowers the temperature and increases the humidity. Swamp coolers are more practical and popular in climates such as the American Southwest, where conditions tend to be hot and dry. This is reminiscent of some of the first heating & cooling mechanisms in ancient Egypt, where reeds with trickling water were applied to door ways in order to cool and humidify.
However, this type of cooling is not practical in places such as the Southeast, where the external humidity is significantly higher. Just as the efficiency of air based systems is limited by the abilities of modern compressors, swamp coolers face efficiency problems that a rise from a lack of a compressor within the cycle; since the water is merely evaporated into the space, it is not re-circulated (as a coolant would be in a heating - cooling). Water-based heating and cooling also does not have the capacity to sufficiently cool to a comfortable level when the outside temperatures exceed 110 degrees, which is probably when you need your heating - cooling the most! So, unfortunately, water is probably also not next in line to serve as the refrigerant component of heating & cooling.
Ammonia is a both economically feasible and environmentally conscious alternative to CFCs and HCFCs, which has also proven itself very efficient practical. It is an extremely stable compound, which will not interact with the compressor also lubricant, so it is not as potentially volatile as air might be. Ammonia operates at pressures which are always slightly higher than atmospheric pressure; therefore, if any leakage occurs, air will not leak into the system. This allows for the system to be recharged without the need for a vacuum seal. Ammonia has been used as the refrigerant in industrial applications of refrigeration and cooling for over 130 years. Ammonia (NH3) is actually comprised of two other gases: nitrogen and hydrogen. The molecule consists of three hydrogen atoms per each nitrogen atom. The ammonia associated with large freezing and refrigeration plants is “anhydrous,” meaning that it contains almost no water. NH3-based refrigeration systems cost a bit (10%-20%) less than a CFC based system, because it is a smaller molecule and therefore can pass through an arrowed passage way to the evaporator, reducing raw manufacturing materials. It is also slightly more efficient than the CFC heating and cooling. Although not as abundant as air or water, it is a relatively inexpensive refrigerant. And, the major advantage ammonia has over CFCs is that it is safe for the environment, with both an Ozone Depletion Potential (OPD) and Global Warming Potential (GWP) ratings of 0. According to the ASHRAE and the International Institute of Ammonia Refrigeration (IIAR), NH3 is a cost effective and efficient alternative to the environmentally hazardous CFC and HCFC heating - cooling of the past.
However, there are drawbacks to using ammonia as a refrigerant for modern heating and cooling air systems. First of all, ammonia is not compatible with the copper piping used to connect the outdoor condenser to the indoor evaporator of a split system. It is also poisonous to humans in the high concentrations that would be used in a compact and high-efficiency heating & cooling such as a heating - cooling.
Hydrocarbons include both iso-butane and propane, which can be used to keep things cool, aswell. These gases are very useful as refrigerants, as they change readily from liquid to gas and back to liquid again, as good refrigerants do. Hydrocarbon refrigerants are also more efficient than their CFC and HCFC counterparts, using up to 15% less energy. Hydrocarbon refrigerants also put less stress on the compressors, which may reduce maintenance costs and lengthen the life of your heating and cooling compressor. An additional aspect of hydrocarbons that relates to the functioning of heating & cooling is that, systems run on hydrocarbons tend to run quieter.
There are some definite downsides to the use of hydrocarbons for heating - cooling applications, including hazards to humans and depletion of the environment. Hydrocarbons are quite flammable, which can create a hazard in the event of a leak. For example, as little as 4 ounces of hydrocarbon refrigerant inside a vehicle can ignite upon lighting a cigarette (this would create yet anotherhealth pitfall for smokers!) Therefore, hydrocarbons are not an ideal choice for compact, enclosed spaces like an automobile. And although these gases are natural, and do not pose significant risk to the environment by way of ozone depletion, they are fossil fuels. Therefore, they are not as abundant as air, water, or other alternatives, and concerns may rise over whether or not they are a truly economical choice. However, some heating & cooling are designed to utilize hydrocarbon refrigerants.
Carbon dioxide is another naturally occurring substance with refrigerant qualities. Its use dates back to the beginning of heating and cooling and refrigeration technology, but it fell out of favor in exchange for the then “new” HFCs. However, now that we know how environmentally damaging HFCs can be, carbon dioxide may be making a comeback. Carbon dioxide is a non-flammable and non-toxic gas, in contrast to ammonia and hydrocarbons. Like other natural refrigerant alternatives, it is widely available, making it an economical choice. The lack of toxicity of carbon dioxide comes in useful for large central air systems, such as those used in supermarkets, which are prone to leakage. Carbon dioxide also has one practical advantage that relates directly to the compact nature of modern heating - cooling systems: the high operational pressures of Co2 provide the potential opportunity for system size and weight reduction. This is a major advantage for heating and cooling, which are designed to perform efficiently in smaller spaces.
Although carbon dioxide may very well be a natural refrigerant that finds its way into the heating - cooling market in the future, there are still some disadvantages to its use which need to be hashed out. Carbon dioxide runs into problems when it comes to practical efficiency. Like air, carbon dioxide has no problem retaining its gaseous form; however, like air, it requires a lot of pressure as well as a low temperature to transform into a refrigerant liquid. This chemical process requires five times the typical heating & cooling compression capacity. In order to take advantage of the benefits of carbon dioxide as a refrigerant for your home heating - cooling, the challenge remains to design a cost-effective and reliable system which can deliver the conditions required by carbon dioxide. The developments of new (and, in the case of carbon dioxide, old but never fully realized) refrigerant technology has always taken some time. So, although your heating & cooling may not be running on carbon dioxide tomorrow, it certainly should not be written off as heating and cooling technology develops.
RESPONSIBLE MANAGMENT OF HEATING & COOLING REFRIGERANTS.
As clean energy continues to develop, it is exciting to imagine a world where the by products of our daily life could actually become valuable fuel. One of the major hurdles the human race faces, with all of our extensive developments which make our lives more comfortable and easy, is what to do with our trash. Although refrigerant technology may some day offer us cleaner alternatives such as air or water, today that is unfortunately not the case. In order to use our heating - cooling responsibly, it is important that we handle them in the most environmentally responsible way. It is the right thing to do and, in many locations, the law.
After July 1, 1992, it is illegal in the United States to intentionally or accidently release refrigerants into the atmosphere. So, not only is it important to maintain your heating & cooling system properly, preventing any leaks of refrigerant, it is also important to dispose of them properly when they are removed. All the more reason not to maintain your system on your own…let an experienced heating and cooling technician remove and transport your refrigerant to a location where it can be recycled. There, contamination can be removed, and the refrigerant can be returned to a condition where it can be used again.
Another thing to note about refrigerants is that it is potentially hazardous to the environment, as well as dangerous, to mix refrigerants together outside of a facility licensed and equipped to do so. So, although you may have learned a ton about refrigerants today, it is neither legal nor wise to develop a new blend for your heating - cooling at home. Many refrigerants must be handled much like hazardous waste, even after recycling, and must be transported in accordance with strict legislation. Although refrigerants may be fascinating, they are not to be toyed with!
A Product Overview of Trane’s ILLUSION Line of Ceiling-Concealed HEATING - COOLING.
Heating - cooling are a great alternative when adding heat and cold to a new home or retrofit project. They do not require duct work, and provide all the comfort of central air. One of the major advantages of heating & cooling is their compact size and discreet operations. The heating - cooling air handler would usually be mounted to a wall. However, there are some heating - cooling on the market today that are mounted within the ceiling of your space. Ceiling mounted ac system can take the discreet, compact nature of heating and cooling and take it to the next level.
Trane has taken the discreet comfort of heating - cooling to the next level with their ceiling-concealed, MDC Series. These units range in capacity from 12,000 BTUto 60,000 BTU. These ILLUSION line heating and cooling are 50 and 60 Hz. The uncased models in the ILLUSION heating - cooling series are a mere 10.0 inches (254 mm)tall, making them ideal for squeezing in for tight ceiling applications. So, provided you have the space for this ultra compact unit, your home, office, or shop will have all of the comforts you would expect from efficient heating - cooling, without even noticing that you have an heating & cooling units!
The ILLUSION line of heating & cooling heat pump system also feature upgraded anti-humidity and condensate technologies. Trane’s super compact ceiling mounted ductless heating and cooling units also implement an innovative, three-layer drain pan to protect against condensate leaks. This drain is places at a 5% slope in order to eliminate contamination-prone standing water. Further protection is provided by dual drain connections, which prevent unwanted condensate overflow in the event that one of the connections becomes blocked.
Trane also makes improvements to operational noise and return air quality. This line also offers quieter operations, with an optional return air plenum on the 12,000 BTU – 36,000 BTU. Direct-drive, low CFM with full cooling capacity also provides whisper quiet operation. The 48,000 BTU and 60,000 BTU ILLUSION models feature the return air plenum as well as a 1 inch aluminum filter.
The Trane ceiling-mounted heating and cooling also offer all of the exceptional efficiency, versatility, and flexible control you would expect from a wall mounted heating - cooling. The low, medium, high, and extra high fan speed options of the motor allow the user great flexibility in airflow and at varied external static pressures. The system can also be configured into heating & cooling (two or more single-zone air handlers all driven by a central compressor/condenser) by using the 12,000 BTU and 18,000BTU models. Trane’s MDC series has been found to provide energy savings, as well as full cooling capacity, when tested in accordance with ARI standards.
Trane provides several options, as well, when choosing your outdoor heating & cooling compressor/condenser. The high efficiency condensing units recommended for use with the Trane MDC series ILLUSION heating and cooling air handlers include condensers of various capacities and sizes. They also offer a choice in how the air discharge is placed; horizontal and vertical air discharge mechanisms offer great flexibility to truly find the unit that is going to work best in your space. Furthermore, the option of a Trane heating & cooling condenser system allows two or three indoor unit air handlers to be matched to a single outdoor unit.