Air Conditioning Compressors

Types of Compressors Rotary- Small appliances Screw- Large Chillers Scroll- Central Air Conditioning; Newer Chillers Centrifugal- Large Chillers Reciprocating- Refrigeration and A/C Systems

Hermetic- Welded inside shell Semi Hermetic- Bolted together and can be serviced Open-Motor and Compressor are separate and are attached by a belt or coupling

Rotary Small and light weight Uses blades or vanes to move refrigerant

Operation Eccentric rotor (off center) Rotates inside cylinder Suction and discharge are separated Dome is on high side Ports (tube stubs)

Advantages Efficiency is higher than a reciprocating type Can pull a deeper vacuum No dead head space Less apt to blow fuses (trip breakers) on start up

Screw Compressor Used on large chilled water systems Available in sizes 20 tons and up Operation (helical screw compressor) Refrigerant vapor is drawn into the space between the lobes of the screws As the voids between the lobes gets smaller the gas is compressed and piped to the condenser Screw compressors will operate smoothly even when capacity is reduced to as low as 10%

Scroll Compressors Newest type of Compressor Has no intake or discharge valves except check valve on discharge. The refrigerant vapor is squeezed Very little wear and tear (few moving parts) Two offset spiral discs to compress the vapor Used in systems under five ton for now

Centrifugal Compressors Used in large commercial refrigeration systems over 50 ton Uses impeller or wheels Vapor is moved in a circular path using centrifugal force No valves or pistons Operates at high speeds

Reciprocating Compressors Domestic and Commercial use Compressors Piston type Normal RPM’s Older units – 1725 RPM Newer units – 3450 RPM

Hermetically sealed Motor and compressor are sealed in a steel dome External switching must be provided Dome is on the low side of the system Suction line ends at steel dome Fills the compressor with low pressure low temperature vapor

Main Parts Cylinder Pistons Connecting rods Crankshaft Clylinder Head Valves

Types of Reciprocating Compressors Hermetic Semi – Hermetic Open

Hermetic (fully welded) Sometimes called a tin can Disposable Cooled with suction vapor

Semi - Hermetic Motor and compressor are contained inside a single shell that is bolted together Can be serviced by removing bolts and opening Air cooled as well as refrigerant vapor cooled Sometimes water cooled

Motor and Compressor are separate. Connected by belt or coupling. Open Motor and Compressor are separate. Connected by belt or coupling.