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Air Conditioning and Heat Pump Systems

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Submitted By Amgine
Words 1495
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Air Conditioning and Heat Pump Systems
Clinton Ward
COM155
February 17, 2013
Joyce Keeling

Air Conditioning and Heat Pump Systems
Air conditioners and heat pump systems are used by most people in the world today. They are used to cool in the summer time and to heat in the winter time. These machines are bought and used when most people do not even understand the principle on which they work. The machines are expected do what they are designed to do, and when they cease to do this, they can be costly to repair. Air conditioners and heat pumps are similar in appearance and operation, but while using the same components they can perform completely different tasks. Knowing the difference between the two and the principle in which they perform their tasks will enable each person to make an informed decision when the time comes to repair or replace a piece of equipment.
Air conditioners and heat pumps have several components that work in the same way. The compressor is the heart of the system. It is present in both an air conditioner and a heat pump. The compressor pumps the refrigerant throughout the system and enables the system to heat and cool. A few other components in an air conditioner and a heat pump are the metering device, the indoor coil, and the outdoor coil. These four basic components must be present for the cooling process to take place. There are a few components in heat pumps that do not show up in air conditioners. These devices are what make the air conditioner into a heat pump. The reversing valve reverses the refrigerant flow in an air conditioner to enable it to produce heat in the space where cooling is usually produced. A second metering device is present in the outdoor unit to enable the cooling effect to take place in the outdoor coil. The refrigerant is the substance that is pumped throughout the system and is used absorb heat and transfer it from one area to another. It is present in both heat pumps and air conditioners.
The most widely used refrigerant for household air conditioners and heat pumps is Refrigerant-22. There are several factors that make this a good substance to transfer heat. The ability to absorb heat and release it is the most important part of its makeup. Another aspect that makes it a good refrigerant is the fact that it is non-flammable and non-combustible. This means it is not dangerous when subjected to a spark or open flame. However, is has been shown to be detrimental to the environment because its makeup contains chlorine. For this reason, this refrigerant has been scheduled to be phased out for the use in air conditioning and heat pump systems. An alternative refrigerant has been designed to take the place of Refrigerant-22. This refrigerant, known as Refrigerant-410A, has the same beneficial properties as Refrigerant-22, but does not contain the environmental damaging component, chlorine. Also this refrigerant will not work with components designed to be used with Refrigerant-22. Refrigerant-410A has its own components designed for use with this type of refrigerant. The reason for this is because Refrigerant-410A operates at pressures much higher than that of Refrigerant-22. The medium in which the refrigerant releases the heat into can be the same in Refrigerant-22 and Refrigerant-410A.
Most air conditioners and heat pumps absorb heat from the air that is to be cooled and release the heat into the air that is outside the space that is conditioned. This process is known as air-to-air source cooling. The heat is absorbed, or cooled, in the space to be conditioned and is transferred to a space to be released, usually the outdoors. The pressure and temperature difference of the refrigerant related to the temperatures of the air outside and inside allow this to take place. Another method that is just as efficient is the use of water source cooling or heating. This process absorbs heat or releases heat to water that is circulated through a heat exchanger with the refrigerant. The same pressure and temperature differences make it possible to transfer the heat from the refrigerant to the water. The water itself is a very good medium for transferring heat from one place to another. Water that is used to absorb heat is usually transferred to an outside source for release of the heat to the outdoors. This occurs in a cooling tower that circulates the water through the outside air. These methods can be used in air conditioning and heat pumps systems in most temperate environments throughout the world.
Early in the life of these systems, electrical use was not a major factor in the design of these systems. Over the course of the development of these systems, it has become a more prominent factor when designing systems. For this reason, the industry developed a standard in which to measure the electrical use of air conditioning and heat pump systems. Seasonal Energy Efficiency Rating (SEER) is the measure of the amount of British Thermal Units (BTU) a system can transfer for each watt of electrical power consumed. The base amount at this time is 13 SEER. This means that for every watt of power used, the system can transfer 13 BTU’s of heat from one area to another. The higher the SEER number, the more BTU’s that can be transferred for the same watt of electricity used.
The amount of electricity that is used to operate a compressor is substantially lower than that used to operate electric heat coils. This was the reason for the design of the heat pump. The air conditioner or heat pump uses the same amount of electricity, whether it’s providing cooling for the space or heating. The only down fall for a heat pump is the fact that in an climate where the temperature is below freezing, the heat pump cannot absorb enough heat from the outdoors to realistically heat the indoors. For this reason, the use of auxiliary heat is used when this situation occurs. This auxiliary heat can be either the electric heat coils or a gas furnace designed to operate when the heat pump cannot perform. Electric heating coils are very efficient, but they are the most expensive to operate. Gas furnaces are not as efficient, but they are cheaper to operate.
The operation of the air conditioner versus the heat pump is the same with the exception of what the refrigerant is doing in the indoor coil and the outdoor coil. When the air conditioner is operating and providing cooling to the conditioned space, the refrigerant is providing a cooling effect on the indoor coil based on the operation of the metering device. This cooling effect enables the indoor coil to absorb heat from the indoor air circulated through the coil. The refrigerant absorbs the heat and transfers it through the compressor to the outdoor coil where air circulated through that coil absorbs the heat from the refrigerant. In the operation of the heat pump, the effects in each coil are reversed. The outdoor coil absorbs heat from the outside air and transfers it to the indoor coil where the air circulated there picks up heat form the refrigerant. This process does not create or destroy any heat. It only transfers the heat from one place to another.
The reversal of refrigerant flow in a heat pump is allowed to take place because of a reversing valve. This valve directs the flow of refrigerant to each coil depending on what type of process is needed. There are two types of valves manufactured for this purpose. The types depend on their position when they do not have any control voltage applied to the operating electric coil. A valve that is stated to Fail to Heat, allows the refrigerant to flow in the in the heating mode when there is not any control voltage applied to the valve. A valve that is stated to Fail to Cool, allows the refrigerant to flow in the cooling mode when there is not any control voltage applied to the valve. In this area of the United States, most valves are Fail to Heat.
With all the components in an air conditioner and a heat pump, most people would be surprised to find that most are the same in each piece of equipment. There are a few components needed for a heat pump to work that an air conditioner does not have. An air conditioner and a heat pump may appear to be the same, but they can perform different tasks, depending on which components they have in them. Knowing the difference between the two and understanding the principle in which they operate would enable any person to make an honest and informed decision concerning their interests in the repairing or replacement of any piece of equipment such as this.

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