If anybody knows anything about air conditioning its the folks at ASHRAE, better known as the American Society of Heating, Refrigerating and Air-Conditioning Engineers.
Around since 1894 — before there was actual air conditioning — ASHRAE is a global society advancing human well-being through sustainable technology for the built environment.
That’s a mouthful, when basically the society and its members focus on building systems, energy efficiency, indoor air quality, refrigeration, and sustainability within the industry. Better, but let’s cut to the chase . . .
They know how to keep us cool in the hot Arlington, Fort Worth, and Dallas summers.
They know how to keep us warm in the unpredictable North Texas winters.
In this two-part Home Cooling 101 post, we take a look at ASHRAE’s not-so-David-Letterman-style list of Things Consumers Should Know About Air Conditioning.
What Is Air Conditioning?
ASHRAE says the first functional definition of air-conditioning was created in 1908 and is credited to G.B. Wilson. It is the definition that Willis Carrier, the “father of air conditioning” subscribed to when inventing the first actual air conditioner.
- Maintain suitable humidity in all parts of a building
- Free the air from excessive humidity during certain seasons
- Supply a constant and adequate supply of ventilation
- Efficiently remove from the air micro-organisms, dust, soot, and other foreign bodies
- Efficiently cool room air during certain seasons
- Heat or help heat the rooms in winter
- An apparatus that is not cost-prohibitive in purchase, service or maintenance
How an Air Conditioner Works
The job of your air conditioner is moving heat from inside your home to the outside, thereby cooling you and your house.
Air conditioners blow cool air into your home by pulling the heat out of that air. The air is cooled by blowing it over a set of cold pipes called an evaporator coil. This works just like the cooling that happens when water evaporates from your skin. The evaporator coil is filled with a special liquid called a refrigerant, which changes from a liquid to a gas as it absorbs heat from the air. The refrigerant is pumped outside the house to another coil where it gives up its heat and changes back into a liquid.
This outside coil is called the condenser because the refrigerant is condensing from a gas back to a fluid just like moisture on a cold window. A pump, called a compressor, is used to move the refrigerant between the two coils and to change the pressure of the refrigerant so that all the refrigerant evaporates or condenses in the appropriate coils.
The energy to do all of this is used by the motor that runs the compressor. The entire system will normally give about three times the cooling energy that the compressor uses. This odd fact happens because the changing of refrigerant from a liquid to a gas and back again lets the system move much more energy than the compressor uses.
Air conditioners are fairly robust appliances, especially when you have an Arlington, Fort Worth, or Dallas-area contractor service your heating, ventilation, and air conditioning (HVAC) at least once, if not twice, a year.
If you do not have an Arlington, Fort Worth, or Dallas contractor conduct annual or semi-annual service checkups, problems arise that may continue undetected for a while, reducing energy efficiency, costing you more in electricity bills each month, and adding additional wear and tear on the equipment.
What is a Ton of Cooling
Before refrigeration air conditioning was invented, cooling was done by saving big blocks of ice. When cooling machines started getting used, they rated their capacity by the equivalent amount of ice melted in a day, which is where the term “ton” came from sizing air conditioning.
A ton of cooling is now defined as delivering 12,000 BTU/hour of cooling. BTU is short for British Thermal Unit (and is a unit that the British do not use) The BTU is a unit of heating – or in this case, cooling – energy. It’s more important, however, to keep in perspective that a window air conditioner is usually less than one ton. A small home central air conditioner would be about two tons and a large one about five tons.
What Goes Wrong
Unlike most furnaces, air conditioners are complex mechanical systems that depend on a wide variety of conditions to work correctly. They are sized to meet a certain “load” on the house. They are designed to have certain amount of refrigerant. They are designed to have a certain amount of air flow across the coils. When any of these things changes, the system will have problems.
If you produce more heat indoors either from having more people or appliances or because of changes in the house, the air conditioning may not be able to keep up.
If the refrigerant charge on the system leaks out, it lowers the capacity of the system. You will simply get less cooling and system will not be able to keep up when the load gets high.
If airflow across the outdoor (condenser) coil is reduced, the ability to reject heat outdoors is reduced and the again the capacity of the system may go down, especially at higher outdoor temperatures.
In dry climates such as the Southwest United States, the same issues happen with regard to the indoor (evaporator) coil: higher airflow helps, lower airflow hurts. In humid climates, the situation is more complex. At higher airflows, there will be less dehumidification, leading to high indoor humidity levels. If the airflow gets too low, however, the evaporator coil may freeze. This makes performance worse and can damage the compressor until it fails – leaving you with an expensive repair bill and no cooling.
Arlington, Fort Worth, Dallas, and North Texas are a combination of heat and humidity, which places extreme demands on air conditioners from late spring to early fall. That’s why regular service and maintenance is essential to maintain peak performance.
What Filters Do
Almost every air conditioning system has a filter upstream of the evaporator coil. This can be in the return grille or in special slots in the duct system and can be a fuzzy-looking or a folded paper filter. This filter removes particles from the air stream to both keep the air conditioning system clean and to remove particles from the air.
As the filter does its job, it gets loaded with more and more particles. This actually has the effect of making it more efficient, but it also increases resistance and reducing airflow. When this happens, it is time to service or change the filter. How long it will take to happen depends on how dirty the air is and how big the filter is.
If you don’t change the filter, the air flow will go down, and the system will not perform well. Not only that, but if the filter is too dirty, it starts to become a source or air pollution itself.
If you take the filter out completely, you would solve the low air flow problem, but this victory would be short lived. The particles that the filter would have taken out will now build up on your evaporator coil and eventually cause it to fail. A new filter is a lot cheaper.
When you do buy a new filter, ASHRAE recommends getting one with a Minimum Efficiency Rating Value of MERV 6 or higher. These are available at home improvement centers, hardware stores, and other retail outlets throughout Arlington, Fort Worth, and Dallas.
Maintaining the System
Routine maintenance such as changing filters can be handled by most consumers, but others tasks such as checking refrigerant levels, re-charging refrigerant levels, and servicing or repairing the compressor, evaporator coils, furnace, condensate drain, among others, should be handled by a knowledgable HVAC contractor in the Arlington, Fort Worth, and Dallas area.