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Figure 12: Shut-off valves and adapters
28 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.
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 that
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.
Recommended configuration (Figure 13):
Tubing configuration: small shock loop
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
C6.2.16/1004/E
(1)
pressure control connection
(2)
gauge connection
Figure 13: Suction tube design
12
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