
Air conditioners remove heat and humidity from your home by using a cycle of refrigerant changing from liquid to gas. The system consists of components inside and outside your house.
Split-system systems with an indoor unit that contains the evaporator coil and blower fan and a separate outdoor unit with compressor and condenser coil are the most common. Also available are portable and ductless mini-split AC systems. Contact Cincinnati Air Conditioning for more details.
The Compressor
The compressor is the heart of your air conditioning system. It manipulates refrigerant between a liquid and gaseous state, changing states to absorb heat and humidity from the air inside your vehicle and give off cool air. The compressor compresses (squeezes) refrigerant vapor, raising its pressure and temperature and increasing its energy efficiency.
The motor of the compressor is powered by oil, which lubricates its internal moving parts and protects against corrosion. However, dirty oil can cause overheating and failure of the compressor. Checking and cleaning the air filter and oil separator on a weekly basis and replacing them at regular intervals—typically every 1000 hours—will keep your compressor running smoothly and efficiently.
A dynamic compressor uses an array of rotating and stationary airfoils to accelerate and redirect the flow of refrigerant vapor. The airfoils are shaped to increase the refrigerant’s kinetic energy, which is then converted into incremental increases in gas pressure. These types of compressors can achieve higher compression ratios than other compressors, which can improve your car’s fuel economy and environmental impact.
There are many different kinds of compressors used in industry and construction. They are categorized by how they decrease the volume of a gas, increase its pressure and temperature, and change its energy content. Ideally, the compressor would draw in a gas, then decrease its volume and expel it at a higher pressure without heating or losing energy. This is known as perfect isothermal compression or expansion.
A home air conditioning compressor, often called a condenser, is located outdoors, usually next to the evaporator coil. Warm indoor air blows over the cold evaporator coil full of refrigerant and is cooled as it passes through, turning the refrigerant into a gaseous state in the process. The refrigerant then travels back through the compressor and drops its pressure again before it heads into a large coil in the outdoor unit where it is rejected by a fan, rejecting the heat from your home and cooling the air. The cooled air is then blown into your home through ducts and vents.
The Evaporator
The evaporator is the component that cools your home’s air. It’s located in the indoor unit, typically near where return air ducts enter your house’s living spaces. In systems where the air conditioner shares an indoor cabinet with the furnace (common in central HVAC systems), it may be installed above or below the furnace heat exchanger. Alternatively, the evaporator coil may be placed in your home’s ductwork directly downstream of the blower fan (where return ducts return cooling air).
The warm, filtered air from your home’s air conditioner filters passes over the cold evaporator coil, absorbing its heat. The blower fan pushes this cooled air back through the return air ducts and into your living spaces. The evaporator coil cools the air by using a natural process known as adiabatic cooling.
This cools the air by transferring its heat to the refrigerant through an exothermic chemical process called vaporization. The vaporized refrigerant is then condensed into a liquid state in the evaporator’s coils and returned to the indoor air conditioner’s system of copper tubing.
Air conditioning systems use a simple trick to get this process to work. They lower the temperature of the refrigerant from its liquid state to below its flash point (the temperature at which it can change from a liquid to a gas). Then they raise that refrigerant’s pressure so that when it changes states again, it does so at a higher temperature and much faster rate.
This “hack” of manipulating the evaporation and condensation processes is why modern air conditioning units are so energy efficient. Advanced control technology helps maintain optimum thermal performance over time, and new surface coatings enhance the ability of the evaporator to absorb and transfer heat.
The evaporator also contains an important safety device. Its internal coils are filled with oil for lubrication, and they must be protected from damage by excessive friction from the moving refrigerant. This is accomplished by the use of a restriction valve to limit the amount of fluid that can flow through the coils. In addition, the evaporator coils contain a small amount of anti-foaming agent to reduce the possibility of refrigerant accumulating on the inside surfaces of the coils and causing them to become clogged with dirt and grime.
The Condenser
The air conditioner condenser is an outdoor component that releases or collects heat from your home, depending on the season. It works with the compressor to cool steam from the refrigerant and return it to liquid form. This is a vital step since it removes enthalpy and entropy, which is necessary for the system to operate.
The heat that is removed in the condenser is the latent heat of vaporization, which is energy that a liquid needs to reach its boiling point or melt a solid. This is the same type of heat that a car engine uses to cool its radiator.
A home ac system uses this process to exchange heat between the air in your house and the refrigerant that runs through its copper tubing. In a split-system AC system, your indoor unit contains the evaporator coil and blower fan that circulates air throughout the house. The outdoor unit holds the compressor and condenser coil.
While it’s possible to use a single unit for all of your home cooling needs, many homeowners opt for a central air conditioning system. These systems come with an indoor unit and an outdoor unit that work together to keep your home comfortable.
Both the indoor and outdoor units have the same components. The indoor unit contains the evaporator coil, compressor and blower fan that circulates the refrigerant to the outdoor unit. The outdoor unit has the condenser coil, compressor and fan that releases or collects heat from the indoor air and cools it down.
The condenser coil in the outdoor unit has multiple rows of aluminum fins that facilitate the transfer of heat from the refrigerant to the air. This coil is also surrounded by a large fan that pulls air over the surface, helping to increase the rate of heat transfer. The air temperature in the coil is much higher than that of the surrounding environment, allowing the refrigerant to absorb the heat faster. The condenser then releases this heat into the environment around it to complete its cycle. When it’s time to replace your air conditioner or upgrade to a new system, consider working with a Carrier dealer for top-quality products and expert service. Contact your local Carrier dealer today to learn more about the cooling solutions that can meet your home or business’s unique requirements.
The Thermostat
Thermostats come in many different shapes and sizes but they all work in similar ways. They are the brains of the home heating and cooling system; they detect ambient temperature and act as a control switch for your furnace and air conditioner. The way that they work can be broken down into three core steps: sensing, signaling and controlling.
The sensors inside a thermostat are designed to detect the slightest changes in air temperature and then react accordingly. When the sensor notices that the room temperature has drifted away from your desired set point it completes an electrical circuit which triggers action to bring the temperatures back to your preferred level. This process can take place either manually (with older electromechanical models such as bimetallic strips or mercury switches) or automatically using a digital electronic thermostat with a built-in thermistor.
For most people the thermostat is a fairly unobtrusive piece of equipment that doesn’t get changed very often once a comfortable temperature has been settled upon. However this does not mean that you should ignore your thermostat; even small changes in settings can make a big difference to energy usage and cost.
Most modern thermostats are programmable and can be set to switch on and off at specific times of the day. This can help save energy by having the heating switched off while you are at work, for example. It can also be useful for saving energy in large homes by regulating different areas with multiple zones, allowing you to heat and cool only the rooms that are being used.
A thermostat works because of the basic principles of physics. Liquids require a great deal of energy to boil and solids a similar amount to melt; this additional energy that is required to change the state of a substance is called latent heat. When a thermostat detects that the room temperature has changed state it will send an electric current to the heater or air conditioner to heat up or cool down as necessary. It is important that your thermostat is located in an area that has easy access and not blocked by furniture or walls. This allows it to be accessed easily for making adjustments and will prevent the system from needlessly cycling on and off which can waste energy and shorten equipment life.






