A compressor is the heart of your air conditioner. It is used to compress the refrigerant to the point that is up to 8-10 times more than the evaporator to start the condensation process which uses outside air as the “cold” source. Inside the heat exchanger, very high refrigerant temperatures condense by heating the outside air and then returns to the liquid. The outside air reheats the fluid, and the process starts over.
A compressor circulates refrigerant inside a circuit. The coolant has to go through the compressor in a gaseous state to be condensed. The compressor will start to work when the source requires it and usually activates via a temperature control system. A compressor operates on a thermodynamic cycle and develops the evaporation of the refrigerant inside a closed loop circuit.
Not all refrigeration and air conditioning applications have the same requirements. Requirements can vary from project to project. Some of the significant variations is choosing a type of compressor includes capacity, noise produced, efficiency and operating range. The way compression works will differ from one form to another also.
There are five types of air conditioning compressors that today’s HVAC market utilizes. The types of compressors include:
A reciprocating compressor uses reciprocating movement to create compression. This is done by use of a piston to drive the refrigerant by crankshaft in a straight line in a back and forth motion. An electric motor is used to achieve this rotary motion. This type of compressor is very similar to how an automobile engine works. Reciprocating compressors are mostly used in homes and considered a workhorse.
There are one, two, four, and eight-cylinder reciprocating compressors available. When the piston moves up and down inside the cylinder, a suction line creates vapor that is transferred through the intake valve as the piston moves down. When the piston moves up, it then compresses the vapor refrigerant, and it pushes through the exhaust valve into the condenser. When a compressor has more than one cylinder it is called a multi-cylinder compressor.
These compressors have had success with relatively low pricing and easy maintenance, however, in recent years they are being replaced by rotary compressors. The main reason for this replacement is due to the compressors being noisy, and they also create considerable vibrations throughout the entire circuit. You can pick one up today, depending on size and brand for around $400.00 to $1000.00.
Rotary Vane Compressors
Rotary vane compressors use rotational movement to create compression. They are usually small, quiet, and very reliable. Rotary vane compressors generate minimal vibrations. You will find rotary vane compressors in window units, fridge-freezers, and other low capacity home applications. These compressors have the highest ratio between cooling capacity and compressor size.
One type of rotary vane compressor has blades that rotate with the shaft while the other type has a blade that remains stationary. The refrigerant intake is located in a larger area while the outtake is located in a smaller area. Due to eccentric rotation, this interior discrepancy forces the refrigerant into the smaller space to be compressed.
Depending on the BTU needed, currently, a rotary vane compressor can be purchased in a wide range of $50.00 up to $100.00. Always be sure you are buying the correct size unit for your applications.
A scroll compressor also goes by the name of scroll pump or scroll vacuum pump. If you research the different names, these are all one in the same. One advantage of a scroll compressor is it has fewer moving parts which create a quiet operation with minimally detectable vibration. Scroll compressors are used in home and commercial purposes and in heat pump and air conditioning applications.
A scroll compressor uses two scrolls, one remains in a fixed position and the other that moves via the motor power. The scrolls are inter-levered and rotate through the use of a swing link. This causes gradually thinner pockets of air that push the refrigerant between the two scrolls to the center causing the reduction of the volume of gas causing compression.
The price of a scroll compressor can vary. These compressors are a little pricier due to the advances in the development of technology in this type of compressor. If you are in need of a scroll compressor, you can pick one up for a range of $500.00 to $1500.00.
In HVAC applications, screw compressors are intended for systems exceeding a twenty-ton capacity. A screw compressor requires an abundant amount of lubrication due to the interworking of the two screw mechanisms inside the cylinder. Also, a special oil cooler is needed to assist with heat exchange.
Two intermeshing screws, called rotors, revolve in a cylinder. The low-pressure gas refrigerant enters one end of the compressor, and when the spaces between the lobes are full of fluid, it forces the coolant into an increasingly smaller area. When these intermeshing lobes or screws reach the endpoint, the refrigerant is discharged through the outlet port on the opposite end of the condenser.
You can buy a rotary-screw compressor anywhere in the range of $300.00 to $1200.00. Again, you would need to know the correct size to know the exact price.
Large capacity refrigeration systems are usually where centrifugal compressors can be utilized. Centrifugal is an excellent compressor choice because there are no valves, pistons, or cylinders. The housing on a centrifugal compressor is cast iron, and the impeller is made of aluminum alloy. The only parts that would ever need replacing in the future are the main bearings.
Vapor moves in a circular motion called centrifugal force. An impeller spins rapidly inside the housing which causes the gas vapors to gain velocity and push to the edge of the casing.
When the gas leaves the impeller, it has increased a significant amount of kinetic energy that is then converted to pressure energy by the diffuser and discharged into the condenser. The amount of cooling is adjusted by using fins that change the angle of refrigerant fluid entry at the impeller.
A centrifugal compressor is the costliest compressor on the market due to having high efficiency and the complete absence of oil and vibrations. Centrifugal compressors range from $1600.00 to $2400.00.