Suction Line Noise And Vibration - Emerson Copeland Scroll Series Application Manuallines

30 Suction Line Noise and Vibration

Copeland Scroll compressors inherently have low sound and vibration characteristics. However, in some respects, the
sound and vibration characteristics differ from reciprocating compressors and, in rare instances, could result in
unexpected sound complaints with plain air-conditioning systems. One difference is that the vibration characteristic of
the Scroll compressor, although low, includes two very close frequencies, one of which is normally isolated from the
shell by the suspension of an internally suspended compressor. These frequencies, which are present in all
compressors, may result in a low level "beat" frequency, which can be detected as noise coming along the suction line
into a house under some conditions. Elimination of the "beat" can be achieved by attenuating either of the contributing
frequencies. This is easily done by using one of the common combinations of design configuration described below.
A second difference of the Copeland Scroll compressor is that under some conditions the normal starting motion of
the compressor can transmit an "impact" noise along the suction line. This phenomenon, like the one described
above, also results from the lack of internal suspension, and can be easily avoided by using standard line isolation
techniques as described below.
Tubing configuration: small shock loop in the horizontal plane.
Service valve: "angled valve" fastened to unit/wall
Suction muffler: not required
Alternative configuration:
Tubing configuration: small shock loop
Service valve: "straight-through" valve fastened to unit/wall
Suction muffler: may be required
C6.2.7/0302-0903/E 13