How it Works

Understanding How my Air Conditioner works

How does my Air Conditioner work?

To begin with we have to Realize that Heat moves from Hot to Cold. It is always a down hill slope. The greater the temperature difference the steeper the slope, and the faster heat will move. At the outside A/C unit on a hot day 100 degree air passes through a 135 degree condensing coil, heat from the coil is rejected into the 100 degree air because of the down hill slope. Likewise inside your home when 75 degree air passes through a 40 degree evaporator coil, heat is absorbed into the 40 degree evaporator, again because of the down hill slope. OK, I understand that but how did the coils get to be 135 & 40 degrees? Through the Refrigeration Cycle we are able to make one coil hot and the other coil cold.

Understanding the Refrigeration Cycle:

Superheat is the temperature of a vapor above it's boiling point and Subcooling is the temperature of a liquid below it's boiling point. Boiling point and condensing points are also known as Saturated. Saturated is simply a state where both liquid and vapor are present at a given pressure and temperature. In a sealed vessel (like a refrigeration system) as the temperature goes up so does the pressure. When refrigerant goes through a change of state VAST amounts of heat called latent or hidden heat are either rejected or absorbed. During the change of state the physical condition of the refrigerant is saturated. Change of State occurs in two directions:

  1. From a gas to a liquid, heat is rejected (condensed) this takes place in the condenser.

  2. From a liquid to a gas, heat is absorbed (evaporated) and takes place in the evaporator.

Understanding these two terms is key, however this is only the tip of the proverbial iceberg.

Sound Complex? Frankly the refrigeration cycle is very complex and it takes most Tech's years to get a good grasp of it. Many Tech's never get it, just ask them. "What was is my system Superheat and Subcooling?"

Measuring Superheat and subcooling is easy:

  1. Measure the pressures in the system at the Liquid tubing and Suction tubing

  2. Use a Temperature Pressure Chart (TP Chart) to obtain the Saturated temperature at that pressure. Or just read that temperature right off of the gauge .

  3. Measure the temperature of the refrigerant tubing at or near the point where the pressure is being measured.

  4. Liquid tubing temperature is subtracted from the saturated temperature of the condenser to obtain subcooling.

  5. Suction tubing the saturated temperature of the evaporator is subtracted from the tubing temperature.

Understanding what the superheat & subcooling measurements mean is the part that takes time for the Tech understand.

Understanding how superheat and subcooling applies to the refrigeration cycle the tech will know where the refrigerant is or isn't. Knowing where the refrigerant is or isn't, the tech can then determine which component is having issues, and how to properly charge the system. It is IMPOSSIBLE to properly charge a refrigeration system with out both a pressure gauge and thermometer. If your tech doesn't use a thermometer you know he doesn't know what he is doing! I have included a graphic of the refrigeration cycle that I created for my students when I taught at the VOTECH school.

Follow along as the Refrigeration Cycle is explained. The process will begin at the the top of the diagram at the compressor and will Flow in a clockwise direction with the Flow arrows.

Discharge from the compressor is the Hottest point in the system it is a high pressure superheated vapor shown in dark yellow which enters the condenser. The condenser begins rejecting heat to the point of saturation shown in red, which begins a change of state from a vapor to a liquid. The condenser continues rejecting vast amounts of latent heat through out the change of state until the final change of state F.C.S. occurs and there is no more vapor. The condenser is now only rejecting small amounts of heat which subcools the liquid below it's boiling point or point of saturation. Higher Subcooling means MORE liquid is present in the Condenser Coil, lower Subcooling means LESS liquid is present. From the F.C.S. point in the condenser to the Metering Device (the light yellow area) is the only area in the entire system where the refrigerant is 100% liquid.

Liquid passes through the Metering Device into the Evaporator which causes a pressure drop. Refrigerant now is in the Low Pressure side of the System. This pressure drop causes the liquid to boil and begins another change of state this time from a liquid to a vapor shown in blue. In the Evaporator vast amounts of heat are absorbed by the Saturated refrigerant causing the liquid to boil and evaporate until the final change of state occurs and there is no more liquid remaining. The evaporator continues to add small amounts heat to the vapor causing it to be superheated above it's saturated temperature shown in dark yellow. Higher Superheat indicates that LESS saturated refrigerant is present in the the Evaporator, LOWER Superheat indicates MORE saturated refrigerant is present. Notice that Superheat acts as an opposite of Subcooling.

The COOL superheated refrigerant vapor from the Evaporator goes through the Suction line into the compressor where the pressure is increased, also the heat of compression in addition to some heat from the electric motor is absorbed. The HOT refrigerant then enters into the High pressure side of the system into the discharge line completing the cycle.

The term Superheat may sound misleading but the superheated vapor in the low pressure side of the system returning to the compressor is actually COOL. This cool vapor is how the compressor is cooled. If your system is low on refrigerant or has a metering device problem the superheat will be high, the vapor is warmer and the compressor will run HOT. When a compressor runs hot it causes the refrigerant oil and the motor windings insulation to break down, the life of the compressor is shorten dramatically. Just a 25 degree Fahrenheit increase in the vapor returning to the compressor will cause the compressor to run very hot. At the compressor discharge line the temperature of the Refrigerant is the warmest. As the Refrigerant moves through the system it cools down. Just after the Metering Device the Refrigerant is the coolest while it is Saturated. As the refrigerant moves past the Saturated point (F.C.S.) in the evaporator it will increase in temperature as its makes its way back to the compressor.

Having your system annually checked in the Spring will reveal if your system is improperly charged or has other issues at the time of service. Repairs can be made before your system runs in a low refrigerant state which can cause costly repairs and down time. Goodman Heating & Cooling now offers a Remote Refrigeration monitoring system which will notify the Customer as well as Goodman Heating & Cooling that a problem trend is developing. This trend often is noticed BEFORE the homeowner ever notices that comfort has been affected. The monitor can show changing trends in Refrigerant, air flow, power consumption, motor or capacitor beginning to fail. Call Goodman Heating & Cooling today for more information.

NOTE: for the Chart above: The F.C.S (Final Change of State) pointers represents the level of saturated refrigerant in the Evaporator and Condenser. 5 - 15 degrees represent the approximate acceptable superheat and subcooling levels of saturated refrigerant in the system. Each Manufacture has it's own recommended levels of Superheat and Subcooling for their equipment.

Goodman Heating & Cooling uses Sophisticated instruments to measure Refrigerant pressures, line temperatures, Return Air & Supply Air temperatures both wet and dry bulb. We also use a sophisticated App that does all the math of calculating all the information from the instruments and delivering it in way that the Technician can use to properly and accurately evaluate your system. This eliminates math & look up table errors.

For a deeper understanding of how vast amounts of heat are absorbed and rejected in the Refrigeration Cycle study The Steam Table below. This steam table is for water, did you know every refrigerant has it's own Steam Table or Change of State Table.

Understanding Infrared Radiant Heating


In an infrared heating system the source of heat transfers its energy in the form of an electro-magnetic wave directly by radiation to whatever will absorb the energy, and this absorption results in a heating effect. There is no intermediate transfer medium such as air or water needed and fans are not required.

Perhaps the best example of infrared radiation is the sun. All the heat the earth receives comes from the sun in the form of infrared radiation. In reaching the earth these rays pass through a vacuum of space which does not absorb or alter the rays. When they strike the earth all objects absorb these rays and become warm. Infrared heat energy behaves much the same as light. But, instead of changing to illumination as a light source would, infrared energy is converted to heat.

To understand how radiant heat works and the substantial fuel savings and comfort levels that can result from its use it would be helpful to explain some of the fundamental factors involved.

First: Where a building is heated with a typical convection type heater such as a unit heater with a large fan on it, the heat energy is distributed by high velocity air circulation at an elevated temperature. The heated warm air will rise toward the ceiling. The resulting air temperature at the roof level will usually be very much higher than that at the floor level.

In the case of an infrared heating system, the heat energy is directed to the floor which absorbs the infrared energy. The mass of the building, floors, equipment, etc., become a very large heat exchanger or heat sink. This massive heat exchanger then re-radiates the infrared energy at a lower temperature than would be experienced in the heat exchanger of a unit heater and does not have the buoyant convective effect found in a convection system.

The heat which is warmest at floor level and decreases in temperature as it rises. Since the heat loss of a building is a function of the exposed surface times a “U” factor (measure of thermal resistance) times the differential of inside and outside temperatures it is readily understood that by maintaining a lower temperature of the walls, glass, and the ceiling the heat loss would be reduced considerably. In a typical application of this factor alone could reduce the heat loss 20 to 30 percent.

Second: there is very little air movement along exposed walls and ceiling. Since the convection part of the surface conductance is clearly affected by air movement, we may assume this will be reflected in the reduction of heat loss as it provides a measure of insulation without changing the construction.

Third: The comfort produced by the absorption of infrared rays (directly from the infrared radiation and from the mass of the building and its contents) is equivalent to a higher ambient temperature. There is less cooling effect on the body because air movement is greatly reduced over that which is experienced when heating air by convection methods. Most authorities agree that air temperatures of 5-7 degrees lower may be maintained with infrared systems to attain equivalent comfort levels.

Finally: Low intensity (tube type) infrared systems operate at relatively higher combustion and seasonal efficiencies that conventional convection heater. It is possible to have fuel savings of up to 50 percent or more. In as little as 3 years users can realize energy savings that would pay for the entire Infrared system compared to using a unit convection type heater.

How Insulation Works

How is the insulation effect created?

The answer is simple and once you understand the fundamentals, the choice of which insulation to use will become clear.

Heat moves is 3 basic ways and always moves form hot to cold.

Convection: Warm air rises and cold air takes its place. People often say heat rises which is not true, it is warm air that rises. Imagine you are standing at a campfire. You see the smoke rising upwards with the warm air and if you kick up a cloud of dust on the ground just outside of the campfire you see the dust cloud being drawn into the fire. You are watching a visual effect of the convection process.

Radiant: Heat energy travels through space and air without giving up its heat energy until it strikes a solid object. The darker the object the more heat energy that object will absorb, the lighter the object the more heat energy will be reflected off of that object. Imagine the campfire again and as you are standing there warming yourself, your backside becomes cold. You turn around so that you can warm your backside, then your front side gets cold so you turn around facing the fire again. The closer you are to the fire or the heat source the more intense the heat energy. This is an example of how radiant heat works.

Conduction: Heat will move through objects by conduction, just as electricity moves through a conductor like a wire. Conduction can be slowed by an insulator just like wiring which has insulation on the outside keeps the electricity inside the conductor and prevents the electricity from shocking us. Look around you; do you see both a wood object and a metal object such as a desktop and a metal filing cabinet? Touch the wood object with one hand and touch the metal object with the other hand. Which object is colder? You just picked the metal object didn’t you? If you were to measure the temperature of the both objects they would be the same, but the metal object feels colder because it is a conductor and the wood object feels warmer because it is an insulator. Try this same test with wood and glass, the results are not as dramatic but the glass feels colder.

Now that we understand how heat moves we can look at what makes a better insulator so that we can keep the warm air or cool air that we paid for in our home as long as possible.

The Thermal insulation Effect occurs when pockets of dead air (trapped air) have been created. Each pocket will slowly give up its heat to an adjacent pocket until the heat has moved through all of the pockets of dead air toward the colder space. Smaller pockets equals MORE Pockets. There is less convective movement of air in smaller pockets. An insulation with more smaller pockets tends to perform better.

The R-Value of Air based insulation, meaning insulation that uses air in the dead air pockets has a maximum of 4.0 R-Value per inch of thickness. Fiberglass, Cellulose, Rockwool, Mineral wool, Vermiculite, Blue jeans or denim, asbestos, etc. are examples of air based insulation. Foam insulation when new can have a 5.0 or higher R-Value per inch because the pockets have a gas in them other than air. The gas that causes the foam to expand from a liquid and cure into a solid has a higher R-Value similar to Argon between window panes provides a window with a higher R-Value. Studies have shown that this gas slowly escapes and is replaced by air over a 20 year period, which leaves the foam with a maximum R-Value of 4.0 per inch after about 20 years. R-Value stands for Resistance value the higher the resistance the better however R-Values alone is not a good way to judge insulation performance. Other factors play a major role in performance such as Air infiltration also sound and thermal mass have an effect on the performance of insulation.

Air Infiltration simply put is air leakage. If your car tire was leaking air you have to stop and add more air to keep the tire inflated so that you can drive on the tire. The larger the leak the more often you have to add air. Keeping your home warm or cool is similar to the tire, you have to keep adding or removing heat to the home to keep it comfortable. Insulation in your home only slows down the heat transfer it can't stop it. The amount of air leakage or air infiltration has a huge impact on a homes heating & cooling requirements. A new home insulated with fiberglass typically has an air infiltration factor of 1.0 or higher which means every hour 1.0 air changes occur. That equals 1 complete exchange of air every hour. A new home with cellulose insulation typically has an air infiltration rating of .3 meaning .3 air changes per hour. It takes over 3 hours for a home insulated with sprayed cellulose to have one complete exchange of air. A new home with sprayed foam insulation is about .2-.1 air infiltration rating, taking about 5-10 hours to have one complete exchange of air. Older fiberglass homes can reach 2.0 or higher. If you have a fireplace add 1.0 to the air infiltration factor for each fireplace no mater how your home is insulated. A 2500 square foot home having a 1.0 VS .3 air infiltration factor the heat loss is about 12,000 Btu's per hour more at design temperature. The difference between .3 VS .2 is about 2000 Btu's per hour. A loose home has a 1.0 or greater air infiltration rating and a tight home has a .5 or less rating.

Indoor Air Quality also known as IAQ. The single issue of IAQ is perhaps the most important issue when considering how we insulate our home. Unhealthy, stale and stinky air can develop in a home which is too tight. Proper air changes are required to maintain a home with good and healthy IAQ. Air changes allow for the carbon dioxide we exhale to be replaced with fresh air and with oxygen which we inhale, along with many other things that are in the air such as out gassing of carpet furniture and adhesives used in the construction of our home. If our home has a .2 or less air infiltration factor we must exchange the air mechanically by Ventilation in order to have a healthy environment that is safe to live in. Equipment manufactures make Mechanical Ventilation Heat Recovery (MVHR) devices to improve IAQ. The MVHR equipment has an initial cost, requires energy to operate, special filters to be replaced and regular maintenance in addition to the cost of heating or cooling the fresh air that is vented into and out of our home. MVHR equipment will cost about $1500 or more to have installed. Consider this very important fact there is a economical line when crossed that will cost us more money every month because we got our home too tight. We will have to continually spend money to operate and maintain our MVHR equipment to keep our IAQ healthy in addition to the extra money we spent on insulation and sealing to get our home too tight to begin with. If we have poor IAQ and we don't invest, operate and maintain our MVHR equipment, how much money will we spend on medical bills because we live in a home with unhealthy air? How much will poor IAQ in our home decrease our quality of life?

Thermal Mass is another consideration of heat movement. Thermal Mass is not an insulation it is heat Storage. The greater the Mass the greater the Amount of heat that is stored within that mass. Water and concrete are very dense and therefore have greater potential to store heat. If we placed in two identical sealed containers both at the same temperature water in one container and air in the other container the water will stay warm much longer, because of the Thermal Mass of water compared to air which has very little thermal mass. It takes time for objects high in density or thermal mass to absorb heat and it takes time for that same object to give up its heat. Example: large tanks or 55 gallon drums painted black are often used in greenhouses to absorb radiant heat from the sun during the day and because the water is high in thermal mass they will give up or reject that heat throughout the night helping to heat the green house. The next day the cycle repeats.

So what are some of our choices and how do they compare?

Cellulose Insulation is a well known and widely used product. It is a post consumer product made from recycled newspaper and cardboard which is made from wood pulp a natural hollow fiber. Cellulose fibers individual hollow cells are microscopic, remember smaller dead air space are better because there are more of them!. Newspaper is ground in a mill (uses small amounts of energy to manufacture) and treated with a fire retardant. Some cellulose manufactures use additional materials in their products such as adhesives and pest deterrents.


  • Low Cost material that can be applied by spraying into open wall stud cavities and attics. Custom fit into each stud cavity eliminating gaps and voids.

  • Cellulose out preforms fiberglass about 40%.

  • Wood is a great thermal insulator.

  • Cellulose has a larger Thermal Mass.

  • Hollow fibers provide consistent sized tiny dead air pockets.

  • Eliminates Drafts because air won’t easily pass through cellulose insulation.

  • Cellulose has a greater thermal mass than does fiberglass or foam.

  • MVHR equipment is typically not required.

  • Saves space in our landfills.

  • Uses post consumer materials and very little energy to manufacture.

  • Fibers don’t cause skin irritation.

  • Mice and insects will NOT nest in the treated cellulose.

  • Cellulose insulation acts as a fire retardant, dramatically slowing the progression of a fire.

  • No vapor barrier is needed.

  • Great sound barrier.

  • With the best cellulose insulation mold is proven not to grow in it.

  • Cellulose is Very Green for our planet and our budget.


  • Overhead applications are not as easy as fiberglass.

  • Slightly higher cost to install than fiberglass.

  • About 1/2 the cost of Foam insulation.

  • Requires special equipment to install.

Fiberglass Insulation is the most well known and widely used product. It is a man made solid fiber which is basically made from silica (sand) and other materials. The base material is heated to the melting point which uses a tremendous amount of energy, and then the molten material is extruded through small holes where it then cools to form a solid fiber. These fibers are then treated with a binder (adhesive) to form batts which are then cut to standard sizes, packaged and ready for installation.


  • Low Cost batts can be easily placed overhead between joists and rafters

  • and in stud cavities.

  • A knife and stapler is all that is required to install fiberglass.

  • MVHR equipment is typically not required.


  • Each batt has to be cut to size and properly positioned with no gaps or voids. 3%-5% gaps and voids reduce overall effectiveness 35%-50%. Studies have shown that the actual measured gaps of the installed batts are far greater than the 3%-5%. This proves that proper installation of batts is not easy to do and batts are typically installed incorrectly. An R-13 batt incorrectly installed does not perform at R-13 more like R-6 or less.

  • Produces toxic fumes when burned.

  • Glass is NOT a great thermal insulator.

  • Irregular shape and large size air pockets occur on the outside of the fibers.

  • Drafty, Air easily passes through fiberglass (some furnace filters are made of fiberglass).

    • When sheet rock or paneling has to be removed from a wall you will see that the batts in those now exposed wall cavities are dirty the first 3 or 4 feet up from the bottom. The dirt is the result of the filter effect of fiberglass due to all of the air that has passed through the fiberglass which has filtered out the dirt.

    • Some Fiberglass is now being manufactured to look like its dirty when new so that when it has aged and filtered a lot of air you won't be able to see the difference.

  • Mold will grow on the dirt trapped in fiberglass from the filtering effect when conditions are ripe for mold growth.

  • Fiberglass has a lower thermal mass than Cellulose.

  • Fiberglass requires new raw materials and a tremendous amount of energy to manufacture.

  • Fiberglas fibers cause itching, lung and skin irritation.

  • Mice and insects will readily nest in fiberglass insulation and use it for a bathroom.

  • Mice tunnels create even MORE gaps and voids further reducing the insulation's performance.

  • Vapor barrier is required.

  • Poor sound barrier.

  • Fiberglass performance is poor.

  • Fiberglass is not very green for our planet or our budget.

Note: Fiberglass can also be sprayed, bib and blown into cavities and attics. It improves the performance of fiberglass only slightly because it better fills gaps and voids make the voids smaller. However fiberglass is still made the same way and allows air to move through it.

Foam Insulation: Foam insulation’s are primarily made of 2 different materials, petroleum based and soy based. Foams use raw materials to manufacture and require a lot of energy to produce.


  • Foam is a great thermal insulator.

  • Foam has tiny cells that form dead air pockets.

  • Air won’t pass through foam.

  • Foam is a good performer, out performs fiberglass about 45%.


  • MVHR equipment is required.

  • Produces toxic fumes when burned.

  • Do a YouTube search for "Foam insulation gone wrong" this is an eye opener.

  • Foam insulation costs substantially more than fiberglass and cellulose insulation.

  • Breaks down over time. (shrinks)

  • Wall cavities generally are not filled leaving gaps and voids.

    • This is done to minimize labor, the installer must cut off excess foam that overfills the stud cavity.

    • Most foam installers will tell you "We don't need to completely fill the wall cavity".

    • Do a Google search and look at sprayed foam images, you will see the cavity is not completely filled in they have large voids in the wall.

  • When foam is being applied all other workers must leave the area because of strong toxic fumes.

  • Areas not intended to be foamed require masking and plastic covering to prevent being damaged by foam over spray.

  • Foam is flammable.

  • Foam is a light green for our planet and our budget.

  • Foam is not a great sound barrier.

Conclusion: Cellulose insulation is the best choice because of the initial cost, impact to the environment, and its performance thermally, acoustically, reducing air infiltration (drafts) and its thermal mass. When it comes to insulation, Cellulose insulation is the Greenest of the Green. However Not all Cellulose insulation’s are created equal. True the base products would be the same a wood pulp post consumer product but the extras that are added to the product will make a huge impact on the final products performance. For example Ammonia Sulfate is the primary fire retardant in the less expensive cellulose products. Ammonia Sulfate smells like urine and is corrosive. A product that has no Ammonia Sulfate but rather uses 100 % Boric Acid is a far better choice. Boric Acid is a common ingredient found in mouth wash, toothpaste, eye drops and Roach Proof insecticide. It is not corrosive and is a great fire retardant with the added benefits of insect deterrent. It is 6 times less toxic that table salt to humans. It does not smell like urine. How about an adhesive in the Cellulose? Products with adhesives will resist settling and will out perform a product that has no adhesive in it because it will maintain its thickness and R-Value. How about a fungicide in the Cellulose? Products with Board Defense an E.P.A. tested and approved ingredient will not allow fungi to grow on the cellulose even if the conditions are perfect for fungi growth. Can I have Cellulose insulation with all these benefits? The answer is YES you can! This is why Goodman Heating & Cooling exclusively uses Fiberlite Technologies, Inc products. We literally install the best insulation in the country.