TM 5-805-4/AFJMAN 32-1090
Table C-2. Sound Pressure Levels (in dB at 3-ft. Distance) for
C-5. Packaged Chillers With Centrifugal Com-
Packaged Chillers With Rotary Screw Compressors.
pressors.
These compressors range in size from 100 tons to
Sound Pressure
4000 tons and represent the leading manufactur-
Octave
Level, dB
ers. The noise levels may be influenced by the
motors, gears, or turbines, but the measurement
Band
1 0 0 - 3 0 0 Tons
positions are generally selected to emphasize the
Cooling Capacity
(Hz)
compressor noise. The noise levels given in figure
C - 2 and table C-3 represent the 80- to 90-
31
70
percentile values found when the units were di-
63
76
vided into the two size groups: under 500 tons and
500 or more tons. The low-frequency noise levels
125
80
reflect the increased noise found for off-peak loads
250
92
for most centrifugal machines. These data may be
used for packaged chillers, including their drive
500
89
units. For built-up assemblies, these data should
1000
85
be used for the centrifugal compressor only and
the suggestions of paragraph C-6 followed for
2000
80
combining the noise of other components.
4000
75
C-6. Built-Up Refrigeration Machines.
8000
73
The noise of packaged chillers, as presented in the
preceding paragraphs, includes the noise of both
A-weighted,
90
the compressor and the drive unit. If a refrigera-
dB(A)
tion system is built up of separate pieces, then the
noise level estimate should include the noise of
Figure C-2. Sound Pressure Levels of Centrifugal Compressors at 3-ft. Distance.
C-3
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