Commercial HVAC systems often operate on three phase power, as a standard method of alternating current electric power generation, transmission and distribution. Most conventional building HVAC applications are designed to operate the equipment at a constant speed. That being said, building loads aren’t constant and motors have to perform at full load at any given time. The technology itself controls the speed of a motor, converting incoming AC power to DC and then back to quasi-sinusoidal AC power using an inverter switching circuit, giving the advantage of more speed control.
Variable Frequency Drive is found to be very effective in assisting with energy management for HVAC systems. The main objective of this technology is to ensure that the motor only generates enough energy to power the compressor and no more. VFD provides constant load-matching capacity which results in the elimination of over-capacity running. Recently studied, current variable frequency drive benefits goes beyond the advantage of energy savings or energy efficiency. In conventional common application, the installation of variable frequency drive saves about 35% to 50% energy used by matching system capacity to the actual load.
In addition to energy savings, the equipment would benefit from savings on maintenance costs and enhanced motor lifetime. Installation of VFD applies low frequency and voltage to motors with controlled uprate, reducing vibration and motor wear which significantly contributes to longevity of the motor. Since VFD reduces the speed of compressors to match the need for performance, less mechanical stress is also applied to the component helping to reduce the chance of component failure.
VFD also affects starting currents, lowering a substantial amount of it without affecting the starting torque which would benefit the grid to affect less stress when the motors are powered up. With this capability, failure of electrical equipment can be reduced.
Freon (brand name by DuPont) used to be the regulated and most used refrigerant in the HVAC market. The chemical (R-22) was introduced to the refrigerant system in 1920. It consisted of hydrogen, carbon, fluorine and chlorine. HCFC was used in replacement to CFC or chloro-fluoro-carbon which is considered more dangerous. Within a few years, HCFC took over CFC’s role as the safer option.
Even though it was found to be safer than the alternative at the time, various recent studies state that R-22 is detrimental to the environment as it is a substantial ozone depleting substance that leads to greenhouse effects. Since January 2015, the maintenance or servicing of existing refrigeration, air condition and heat pump equipment using R22 has been prohibited by the EPA (Environmental Protection Agency) and related international agencies. Based on the Montreal Protocol, which prevents more damage to the ozone layer by banning all ozone deteriorating substances, R22 can no longer be used in any kind of application.
Since the use of R22 is currently prohibited, end users are left with the option to change the working fluid from current appliances which can be done with the help of professionals –this process might require making changes/switching out installed components to match the new requirements of the new working fluid. Another option would be replacing your current appliances to newer equipment.
Replacing Freon, R410A is found to be the closest substance to take over R22’s functionality. Not only does it have similar characteristics, it comes with added the benefit of being more environmentally friendly and also causes less vibrations in equipment. With less vibration, stress performed on the machine is less and equipment will generally have a longer life time.
In its natural state, heat flows from higher to lower temperature regions. Refrigeration cycles are utilized to modify or reverse this cycle, using work obliging heat to flow with the direction that is desired, and align with increasing temperature from low temperature region to higher.
During the earliest records of the “cooling” process being invented, people harvested ice to refrigerate, cool and conserve food. As time progressed, humanity’s basic needs changed and new ways to manipulate temperature started being explored. Major research into refrigeration began with the creation of pup to create a partial vacuum container which absorbs heat from the air. That being said, while the experiment was successful it did not have any practical applications.
In the early 1800’s, people preserved their food by storing food and ice in iceboxes. General Electric decided to design a refrigeration unit that was powered by gas which eliminate the use of motors, decreasing the size, and soon moved to a refrigeration system which was powered by electricity. The first commercial use of refrigeration was used to produce ice in regions with hotter climates. Refrigeration systems became the solution to ice shortages by enabling areas with environmental limitations to produce their own ice, thus reducing the products scarcity.
With the invention of chlorofluorocarbon, Frigidaire was able to make home and consumer use refrigeration systems better, cheaper, lighter and smaller. Of course, this was back in the times when CFC and Freon were still considered safe choices. Since then, many other refrigerants have been chosen to replace R22.
The thermodynamic cycle which is associated with the refrigeration process is known to be Carnot cycle -a reversible isothermal cycle, where heat is transferred at a constant temperature. To learn more regarding thermodynamic cycle of refrigeration please refer to one of our older post or contact our engineering team for our heat balance course and tool!
The majority of HVAC installations dating back to the 1990s have R-22 as their main working fluid. However, recent studies have proven that R-22 or as we commonly known as “Freon” (brand type) is not as environmentally friendly as we once thought it was. Ergo the use of this refrigeration type has been banned by the Environmental Protection Agency along with other substances which contributes to ozone depletion. With phasing out of R-22, HVAC manufacturers and end-users are forced to look into other comparable refrigerants which won’t negatively impact the environment as much.
R-410A offers a few benefits when compared to the traditional R-22 fluid – one of which is greater energy efficiency which translates into lower operational costs. This hydro-fluorocarbon has been approved for use in new systems and is classified as a non-ozone-depleting HFC. One note that has to be taken into consideration is that R-410A operates on roughly a 50% higher pressure than R-22, thus can only work with high pressure limit equipment.
R-407C has been set as the new standard for the U.S residential air conditioning system as of two years ago. Consequently, the commercial refrigeration system (including air conditioning and chilling units) R-407C was found to be the most frequent refrigerant to be used as a substitute of R-22. Of the higher temperature this type of refrigerant gives similar operating characteristic to R-22. R-407C, a non-ozone-depleting substance, gives better performance in comparison to Freon due to its higher pressure and refrigeration capacity.
R-134A is currently one of the most common refrigerant fluids; especially in HVAC applications in the automotive industry. Many machines are retrofitted to match this fluid from R-22; though one should be careful not to mix and cross contaminate R-22 with R-134A which can result to danger of raising compressor head pressure as well as unfavorable reliability. R-134A is made of one single component, which comes with the advantage of utilization of a single recovery machine and adding into that, according to recent studies, R-134A is environmentally friendly which makes it an even more attractive choice.
A few decades ago, opening and closing a window was enough air temperature control. In modern days though, the standard bar of comfortable living has become higher and the occurrence of global warming, which raises the world’s temperature to the extremes, is abundant. With all this in mind, temperature control becomes a major necessities. During this post, we will be exploring factors which should be considered for a new installation of a HVAC system either to modern or conventional homes.
Regardless of the size of property, ductwork that is balanced and well designed must be installed to make sure that the air and temperature circulation is optimal –especially for locations with extreme weather conditions. Externally insulated round ducts are found to be the most efficient. Installation of balance dampers in the ductworks should also be important to regulate airflow.
End users should also be paying attention to materials of the HVAC unit. The condenser coil type directly relates to the reliability and stability of the HVAC unit, which is even more important in harsh environments. In common applications, coils which are made from one types of metal are usually more reliable and generate better efficiency.
HVAC application has several types of working fluids also known as refrigerants. The main function of refrigerant fluid is to cool, dehumidify and distribute the low temperature air in the system. For a long time, R-22 or Freon happened to be the most common refrigerant in the market. Nowadays though, the use of Freon has been banned for the reason of being environmentally harmful. Currently, there are a couple other refrigerants that are commonly implemented in such application including R-134a, R-407c and many more. Those refrigerants have their own advantages and disadvantages which end users should compare themselves to see what would fit their needs the best.
Efficiency should be the most important aspect to study before settling on a type of HVAC system. There is minimum efficiency which is settled by the government, though aside from legal limit, this would be an ultimate factor to be analyzed by users since efficiency directly correlates to operational costs (the higher the SEER, the lower utility bill you get). Thus, an up-front investment might benefit in the long run.
A compressor unit is an important component in an air conditioning system used to remove the heat laden vapor refrigerant from the evaporator. The compressor raises the temperature and pressure of the working refrigerant fluid and transforms it to a high temperature and high pressure gas. Since the compressor is one of the most vital parts of a cooling system, to be able to have an efficient working cycle, an appropriate and optimum compressor design must be installed.
Generally, there are 5 types of compressor that can be used in HVAC installations, the most common of which being reciprocating compressors used within a smaller scale conditioning system. Reciprocating compressors utilize pistons and cylinders to compress the refrigerant and an electric motor is used to provide a rotary motion.
In recent application, scroll compressors are found to be increasingly popular as an alternative to reciprocating compressors in HVAC installation. This type of compressor outstands in the reliability and efficiency sector when compared to reciprocating compressors. Scroll compressors consist of one stationary scroll and a second moving scroll which compresses the refrigerant – giving this type of compressor fewer moving parts and thus, higher reliability and efficiency. At a smaller size, scroll compressors can achieve similar flow rates and outlet pressure when compared to reciprocating compressors.
There are different kinds of rotary compressors, the most common ones being rotary screw and rotary vane. Rotary vane compressors are known to be smaller, quieter and more reliable and are commonly used in smaller residential split system applications. The application works with a rotating shaft as the blades move around the cylinder. The other rotary compressor consists of stationary blades which are attached to the housing, used for larger applications in comparison to rotary vane compressors.
Last but not least is the centrifugal compressor. Centrifugal compressors are mostly used in industrial installations due to the ability to cool large capacity of air. No piston, valve or cylinder is incorporated in the design and it relies on centrifugal force enabling it to have very few moving parts leading to higher efficiency and reliability.
Interested in learning more! Check out AxSTREAM for your compressor design!
In the last post, we covered the area of HVAC dealing with air conditioning and refrigeration. For today’s blog post, we’d like to quickly go over the other major topic of HVAC industry – heating systems. In geographical areas where temperature fluctuation tends to be quite extreme, a good working heating system is a vital necessity –especially during the colder winter months. The main challenge of heating systems frequently comes from the heat distribution method. There are a couple types of heating system and it is important to take into account their functionality to decide which is the best type for your application.
The first systems we are going to focus on is central heating, which is the most common heating system in North American residential applications. This system comes with primary heating applications such as a furnace, boiler, and heat pumps. Each heat source is rather unique and uses different methods of distributing heat into the targeted environment. Furnaces use ducts to blow heated air through in order to disperse the generated energy. Implementation of such technology in the USA is controlled by the Annual Fuel Utilization Efficiency where it estimates seasonal efficiency, averaging peak and part-load situations. Boilers utilizes hot water which travels up to radiators and gets circulated around in a system – so instead of using a fan and ducts, appliances which utilizes boiler as a heat source commonly uses pump to flows the hot water to other parts of the house/building. Since circulation is the most recurring challenge in heating appliances, an optimal pump design must be installed into the system to make sure that the heat is distributed evenly to each part of site. Within central heating there is also heat pump system which works as two-way air conditioner (direct and reverse). During the hotter season, heat pumps work to moving heat from indoor (cooler) to outdoor (higher temperature), and vice versa during the colder months. Heat pumps generally use electricity to move heat from one place to another.
The second heating system utilizes direct heat. Usually direct heat is used to transfer heat /raise temperature in a small targeted area. In the most common cases, the heat output is relatively small. The most common installation nowadays which utilizes this system is gas fired space heaters or electric space heaters (for more modern implementation), whereas the more conventional one would be fireplaces. This type of heating is less effective for an overall building system.
During the past week we’ve talked about challenges, improvements and development of HVAC technology. But taking a step back, what is a HVAC system? Heating, ventilation, air conditioning systems and refrigeration (or known as HVAC&R) is a technology developed to manipulate environment temperature and air quality. The applications of such technology are based on the principles of thermodynamics, fluid mechanics and heat transfer.
Commonly HVAC systems are grouped into four main systems starting with the heating and air conditioning split system, which is the most ordinary implementation of residential applications encompassing both inside and outside installations. The application, which can be controlled with a central thermostat, consists of air conditioning system which cools the refrigerant to drop the temperature, and heating system which involves gas furnaces. Ducts used to circulate the adjusted air from both heating and conditioning, with the help of evaporator/fan coils – a terminal unit which is used to provide heating or cooling to the targeted space.
A split system is known for its simplicity, efficiency and low cost. That being said, the second type (hybrid heat split system) is actually found to benefit over the first one from an energy efficiency standpoint since the application utilizes heat pump systems. With the incorporation of heat pumps, the system is able to pump cooled or heated refrigerant to make both system able to be controlled through electric power. The heat pump is used to move energy using outside surrounding air as an air source for heating and heat sink for refrigeration/conditioning systems.
A duct free split system would benefit the most to be installed at locales where conventional ducts cannot fit or are not directly connected to central control thermostats. No ductwork would be needed in the system, thus enabling flexibility of delivering air directly to the targeted zones. Since the technology allows you to directly zone the cooled air, using ductless technology could improve efficiency, lower operation cost and reduce carbon footprints.
The last system to note is the packaged heating and air conditioning system – which is normally the system that is installed at locales where there is not enough spaces available for the components of the split system. A package unit has a heating and cooling system combined into one unit, making it easier to access for maintenance as well as to be conservative on installation space.
While the term of air conditioning in relation to automotive might instantly correlate to a system which provides passenger with a comfortable air temperature/environment, HVAC systems also are used for heating and cooling of batteries in such application as well as cooling of the vehicle fuel systems. Thermal management for automotive application isn’t easy though. Many factors have to be accounted for in order to build a dependable cooling system.
While talking about HVAC concerns and challenges which arise in automotive application, the biggest inconvenience commonly comes down to the lack of cold air produces. Mobile refrigeration/air conditioning systems come with quite a few concerns from two sides: the refrigeration side, where it removes heat and injects cold air, and from the electrical side which provides control. From the system, the most common challenges are found in moisture –which would fail the cooling system if present in the air, soiled condenser which would block air flow, and various other mechanical complications which might occurs.
While diagnosing an air conditioning issue, especially if environment temperature seems higher than it should be, there are few conditions that can be looked into including freon leak, failed blower, damaged or failed motor, damaged condenser to the most common problem usually arises from the compressor. Compressor, compressor clutch switch, fuses, wires, fan belt and seal are at the top of the list to be check for functional adequacy. Consequently, with many concerns arising from the compressor side of the system, a good and reliable compressor design must be implemented to avoid unwanted challenges during operation. Design your automotive turbomachinery with SoftInWay! Ask us about the projects that we’ve done in this field and how our turbomachinery development code will be helpful for your automotive and HVAC design, analysis and optimization activities.
Humid climates commonly come with the challenge of moisture standards. When HVAC (heating, ventilations, and air-conditioning) systems do not maintain proper moisture conditions/humidity control, it causes damages and defects to the building.
A humid climate is defined as a condition where the average monthly latent load (energy required to remove moisture from the air) of environment’s air is the same or higher than the average monthly energy needed to cool the air during the cooling season. Using air with high latent load easily brings moisture in and accumulates it in building materials.
Maintaining humidity control isn’t an easy task. The HVAC unit has to be able to support a proper pressurization system using dehumidified air to entire the building. In order to provide the right dehumidification, a HVAC system must be able to dehumidify the air that flows across the cooling oil (which means the precise sizing of cooling coil must be selected to meet the load of both outside and return air). That is not the only criteria that an HVAC system needs to fulfill though. The system must also meet the sufficient run time to remove moisture from the interior air. In a humid condition, temperature control is not enough. Moisture control comes second on the priority list ( though this has to be fulfilled without scarifying the main goal of giving comfortable temperature to users).
In geographical areas with humid weather, such as in the southeast, public housing generally uses chilled water and direct expansion for the cooling system. This requires an outdoor condenser unit to exchange heat to the outdoor air.