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What Are the Indoor Coil and TXV?

The indoor coil is the portion of the air conditioner that absorbs the hot air from inside your home and transfers it to the refrigerant. It pairs with the condenser coil to create a continuous loop of heat transfer.

The TXV, which stands for thermostatic expansion valve, acts as a metering device for air conditioning systems. It regulates the rate at which liquid refrigerant flows into the indoor coil.

Where Are They Located?

An indoor coil will be located inside your home or business. The installation of the indoor coil is in line with the furnace, in a closet or in the attic.

You will likely find the TXV mounted near the indoor coil on the liquid line. Also the sensing bulb is mounted to the outside of the larger suction line.

How Do The Indoor Coil and TXV Work?

The radiator-like device mounted in the airstream is the indoor coil. As warm indoor air passes over the evaporator coil, heat from the home is absorbed into the refrigerant. Likewise moisture is naturally removed from the air . The combination of cooling and dehumidification provides the total cooling effect for the home. In contrast, a heat pump reverses this process. In the winter, heat transfers from the refrigerant into the home or business thru the indoor coil.

Through the liquid line, refrigerant enters the TXV valve at a high pressure. The TXV limits the amount of refrigerant entering the evaporator thus reducing it’s pressure. Along with this pressure drop, the saturation temperature, or “boiling point” of the refrigerant drops as well. This allows a change of state from liquid to gas which is the most efficient time to transfer large amounts of heat from the surrounding air into the refrigerant.

What Makes Them Important?

A well-maintained indoor coil is, along with the outdoor coil, essential to an efficient air conditioning system. Indoor coils that have fallen into disrepair will not be able to transfer heat effectively, causing your home or business to feel less cool. Restricted airflow to the coil can cause the coil to start icing up and even freeze over.

After regulation changes in 2006, most air conditioning systems now require a TXV. It controls the refrigerant flow to create maximum efficiency for the indoor coil. It also prevents excess refrigerant from returning to the compressor and flooding it.

Different Types of Indoor Coils and TXVs

The most common indoor coils in air conditioning systems are divided into three types:

“A” coils, which get their name from the shape they take, are common for vertically aligned air conditioners.

“N” or “W” coils, also named for their shape, work for vertical or horizontally aligned systems. They are smaller than other options.

Slab coils are less common and used for horizontally aligned air conditioning systems.

Similarly, uncased coils are uncommon as well. They easier to build as custom coils for unusual air conditioner designs. A third indoor coil design is the vertical coil, which is suitable for upward and downward air flow.

TXVs come in two major types, internally equalized and externally equalized, which refer to how the TXV senses pressure. Indoor coils with multiple refrigerant circuits typically use an externally equalized TXV.

Maintenance and Repairs

Dirty indoor coils are less efficient, sapping your air conditioner of its efficiency and leading to energy usage up to 30% above average. You can save money and keep cool by checking your air conditioner’s air filter monthly and replacing it as necessary. If you notice that the air filter looks “domed,” this is a sign that the air conditioner is not receiving enough airflow. Replace the filter immediately.

Do not attempt to clean the fins on the indoor coil as they are quite delicate and can bend easily. Instead, call a professional technician who has the right tools and expertise.

A faulty TXV forces an air conditioning system to work harder than necessary, putting stress on other components. Also improper installation of the TXV bulb, such as mounting it to the underside of the indoor coil’s output line, might provide false readings and cause malfunctions.

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What Are Refrigerants, Copper Pipes, and Filter Driers?

Refrigerant is the liquid chemical blend that soaks up heat and releases it as part of the air conditioning process; it is the lifeblood of the air conditioner. Copper pipes act as refrigerant lines to transport this vital fluid throughout the air conditioning system. The filter drier provides physical filtration and absorbs water and other contaminants that can be found in the refrigerant.

Where Is the Refrigerant & Filter Dryer?

Refrigerant runs throughout the air conditioner, from the evaporator coil to the condenser and back again, creating the basic flow necessary for cooling to occur. A technician can maintain refrigerant levels by access ports found on the outdoor unit.

The two main lines of copper piping run from the condenser to the evaporator coil and back. The larger is called the suction (or return, or vapor) line and the smaller one is the liquid line.

You will find the filter drier on the liquid line outside near the condenser or inside near the evaporator coil. It looks like a blue or grey soda can.

The Science Behind Refrigerant

Refrigerant is contained within copper coils inside an air conditioner. As the hot liquid refrigerant is pumped into your home to the indoor coil it is metered by the TXV which only allows a small amount to enter the coil. This creates a drop in temperature of the refrigerant allowing the heat from your home to soak up like a sponge and transfers into the refrigerant to be taken outside as a gas back to the compressor. Finally, once your thermostat senses that enough heat has been removed, it shuts off the system at just the right temperature.

Larger refrigerant lines that carry cold gas need to be insulated. For example; on a warm summer day condensation would form, like the outside of a glass of ice water. In contrast, the liquid line needs no insulation because it contains warm refrigerant.

Filter driers remove moisture from refrigerants. To acheive this, dryers use desiccants, such as activated alumina or silica. Some use molecular sieves, which trap moisture on a molecular level. Also, to keep out common contaminants, filter driers use screens and depth filters, such as bonded desiccant cores or fiberglass pad filters.

What Makes Them Important?

Refrigerants need to have low freezing and boiling points, a low condensing pressure, a high vaporization heat, high vapor density, and a high critical temperature. Moreover, they should be non-corrosive, non-flammable, and non-toxic. For those reasons, refrigerants are carefully synthesized chemicals.

The filter drier’s essential role is to remove water from the system. Water can cause freeze-ups and corrosion from organic acid compounds, so moisture must be eliminated.

As far as materials go, copper tubing is economical and eco-friendly since it is strong, light-weight, and relatively inexpensive. In addition, refrigerants are contained in copper tubing because the copper is efficient at transferring heat.

Different Types of Refrigerants, Copper Pipes, and Filter Driers

Refrigerants come in two types: the older version, R-22, commonly known as Freon; and R410A, known by its brand name, Puron. For many years the main refrigerant in air conditioning systems was R-22, but due to its effect on the ozone, it was severely restricted from production and will be banned entirely by 2020. R410A is the industry standard now. This is because it is efficient and less harmful for the environment, while providing the same cooling as R-22.

The two main types of copper pipes are hard-drawn copper and soft copper. Hard-drawn copper is very rigid and straight. Soft copper is flexible and comes in 25- or 50-foot rolls. There are markings that indicate that the pipes have been cleaned and dehydrated for use in air conditioning and refrigeration systems.

Filter driers come in various forms, including spun copper, steel liquid-line, steel suction-line, and steel bi-flow. Steel driers provide added filtration and water capacity over copper driers.

Maintenance and Repairs

Be aware that R-22 and R410A are not interchangeable. Your air conditioning system will use only one of these refrigerants. Newer air conditioners will use R410A as its refrigerant. A trained technician should handle refrigerant replacement because these coolants can be dangerous to handle and must be disposed in specific ways.

If you notice oil stains around your air conditioner, you might have a leak, potentially caused by damaged copper pipes. Harsh weather, internal contaminants, or installation in high traffic areas can damage copper pipes. Therefore never reuse old copper refrigerant lines when repairing or upgrading your air conditioner.

And finally, filter cores and drier shells may need to be replaced over time, but thankfully, the market provides a wide range of replacements. Often, these replacement cores and shells are a simple installation for a professional technician.

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What Are the Outdoor Condenser Coil and Fan?

The outdoor condenser coil, is very much like the radiator in your car. That is to say, copper tubes that run thru aluminum fins hold the refrigerant. This design allows air pass over them and efficiently release heat. The condenser fan is its sidekick in this endeavor, providing the necessary cool air for heat transfer.

Where Are the Outdoor Condenser Coil and Fan Located?

As the name suggests, in a traditional split air conditioning system, the outdoor coil is found outside. The condenser fan is also outdoors in the same unit. The outdoor coil is the silver or sometimes black looking wall that wraps around your entire outdoor unit. Also a metal grid or panels surrounds the coil is designed to protect the delicate fins. The outdoor condenser fan motor is attached under the top of your air conditioner to be able to pull air in thru the coil and out thru the top of the unit.

How Do They Work Together?

Refrigerant coming out of the compressor is in vapor form and very hot when it reaches the outdoor coil. The outdoor coil must cool the vapor back to a liquid form in order for the cooling cycle to continue. This is where the condenser fan becomes essential.

By blowing outdoor air, which is cooler than the hot refrigerant vapor, across the outdoor coil, heat transfers from the refrigerant to the outdoors. With enough heat transferred, the refrigerant starts to condense back into a liquid form halfway thru the coil and is fully liquid before it leaves the coil.

What Makes Them Important?

The better the outdoor coil releases its heat, the more efficient the air conditioner is. That is why higher efficient A/C units are larger in overall size, they have more coil surface area! A properly functioning outdoor fan keeps the right amount of air moving across the coils which causes that change from vapor to liquid. In addition, modern fan motors can run at various speeds depending on the cooling needs, saving energy. If your old fan motor goes out the compressor will overheat and shut off to protect it.

Maintenance and Repairs

Regularly clean outdoor coils to maximize cooling performance and ensure that your air conditioning system has a long and efficient life. For example, according to the U.S. Department of Energy, a dirty outdoor coil can increase a home’s energy consumption by up to 30 percent! Especially near the ocean, the salt air can destroy coils very quickly and need to be cleaned more often.

You can help by removing leaves, sticks, debris and cutting back any landscaping from around the your outdoor unit. However, opening up and cleaning a condenser coil is one of those projects that you should not attempt to do yourself. Leave it to a technician and schedule an annual maintenance call.

Condenser fans have a set temperature at which they will safely operate, often around 150 degrees Fahrenheit. However, sometimes they can overheat, often due to an incorrectly sized motor, poor airflow, lack of lubrication, or over-ramping.

You can quickly check if your condenser fan motor is working by placing your hand over the top of the outdoor unit; you should feel hot air blowing pretty strongly and see the fan spinning. If you hear your a/c running but don’t see or feel the fan working, you should call one of Bob Jenson’s professional technicians to diagnose the problem.

In the next article we will talk about the copper lines that connect the two parts of your split system and the interesting science behind how refrigerants remove heat from your home!

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What is an Air Conditioning Compressor?

The air conditioning compressor is at the core of how an air conditioning system functions. It’s basically a large electric motor that turns a compressing mechanism which pumps refrigerant thru the entire air conditioning system. It draws in cooler, low-pressure refrigerant gas and compresses it into a high-pressure gas. This allows the cooling cycle to move in a continuous fashion.

Where is the Air Conditioning Compressor Located?

The compressor is located in your outdoor unit. It’s in the center of the condenser and is the heaviest part of your outdoor unit. Look down thru the top of your outdoor condenser and you will see it sitting at the bottom.

How Does a Compressor Work?

Since most air conditioning compressors today are scroll compressors, we’ll explain how they work. When you turn down the temperature on your thermostat it allows electricity to run to the compressor. The motor inside the compressor requires a lot of power to start up. Because of this, a capacitor which stores electricity helps kickstart the motor. A scroll compressor has the ability to start up “unloaded”, then gradually begins to fully compress the refrigerant. To illustrate; If you try and push your car without power you would strain yourself. But if a few people helped you push until you got up momentum then you could easily do it.

The motor shaft turns a scroll within another scroll to compress the gas at several points along the way. Once the gas is compressed it is discharged thru the top of the compressor as a very hot gas. It now travels thru the outdoor coil to continue the next step of the process.

What makes the Compressor Important?

Without a properly functioning compressor, you won’t have a cool home. Like a pumping heart, a compressor moves refrigerant thru copper lines to complete the cycle of the air conditioning process. The only difference of an air conditioning system from your circulatory system is we are exchanging heat instead of oxygen!

Different Types of Compressors

Most newer air conditioners use scroll compressors, which use a single fixed scroll, with another scroll rotating within it. Scroll compressors have increased in popularity because they have fewer parts than conventional compressors and therefore require less maintenance. They also have many safety features built in to protect them from failure. They can handle small amounts of liquid refrigerant which would break most other compressors.

A common type of compressor used in older units is the reciprocating compressor. It uses pistons and cylinders much like the motor inside your car. These are less efficient compressors than the scroll and have more moving parts.

Rotary compressors are extremely quiet and small. They use a cylinder within a cylinder design to simultaneously push and compress refrigerant. A rotary compressor can only compress refrigerant gas at one point along the walls of the cylinders. They sometimes use external components that can vary the incoming electricity and refrigerant flow, to help them to become very efficient. A version of rotary compressors know as inverter compressors can vary their compressor speed based on the cooling needed. These are popular in small ductless mini-split systems.

Extra-large and industrial HVAC systems might use a centrifugal compressor. This type of compressor uses centrifugal force to rapidly spin refrigerant gas with an impeller. Centrifugal compressors have no valves, pistons, or cylinders, so they wear down less.

Maintenance and Repairs

You cannot directly maintain an air conditioning compressor because they are hermetically sealed. Most of the care of a compressor comes from basic system maintenance. Things like changing dirty air filters and cleaning coils debris will reduce stress on the compressor.

The most critical part of compressor care is the initial installation of the condensing unit. Air conditioner compressor parts should not come in contact with moisture; which turns into acid. Acid that enters the compressor, will result in reduced efficiency and will lead to damage of internal components. Using a vacuum pump and a micron gauge during will remove all traces of moisture before startup!

A system that loses its refrigerant charge due to a small leak will cause the compressor to overheat and shutoff. If you suspect a compressor issue, because your system won’t cool your home, call Bob Jenson’s helpful technicians immediately.