Piston-type reciprocating compressors have been
the norm for heat pumps and air conditioners since the introduction of
residential air conditioning. During the refrigeration cycle refrigerant
gas is drawn into the compressor cylinder and compressed during the up-stroke of
the compressor piston.
The introduction of scroll compressor technology to today's residential systems has allowed for quieter, more efficient and more reliable systems. The scroll compressor is a relatively simple design. Two spiral-shaped parts (scrolls) fit inside one another. One of the spiral-shaped parts stays stationary while the other orbits around the stationary part. This orbital motion causes "continuous" crescent-shaped gas pockets to be formed. (See diagram below.) The orbiting motion draws gas into the outer pocket and seals it as the orbiting continues. This continuous orbiting motion causes the crescent-shaped gas pocket to become smaller and smaller in volume as it nears the center of the scroll form. Once at the center, the gas pocket is fully compressed and is discharged out of a portion of the non-orbiting scroll member.
The scroll compressor is used by all of the major manufacturers in both the air conditioner and heat pump lines. While the reciprocating compressor is still in use and found in many popular models it is becoming less prevalent in today's residential equipment. When you are making a purchase decision regarding new equipment for your home the compressor type should be one of the elements used to compare competing equipment.
