18 ALR 110F – 150F Product Manual ALR2-3
Figure 7, Sound Pressure Attenuation Due to Distance from Unit
(Plus or Minus from Table 7)
Air-Cooled Unit Orientation to Minimize Sound
The ALR chiller’s sound is directional in nature allowing the contractor/engineer to position the unit
to minimize potential noise problems. Because the sound pressure levels are lower at both ends of the
unit than at the sides, the chiller should be oriented such that the control box end or end opposite the
control box faces the direction where the lowest sound level is required.
The control box end provides an excellent acoustic barrier to the compressor sound as it covers one
full end of the unit. The sound pressure levels at the control box end will be 5 dBA less than on the
sides. On the end opposite the control box, the compressor sound is blocked by the coil structure,
evaporator and naturally attenuated by distance as the compressors are located approximately ¾ the
length of the unit away from this end. The sound pressure levels at the end opposite the control box
will be 4 dBA less than on the sides.
Figure 8, Sound Directionality
Sound Pressure Levels, Low Ambient Operation
Air-cooled unit operation below 95°F (35°C) will also result in lower sound pressure levels. The sound
pressure level will decrease 3 dB proportionally from 95°F to 65°F. For example, at 95°F the sound
pressure is per Error! Reference source not found., at 85°F one dB can be subtracted, at 75°F two dB
can be subtracted, and so on for any temperature between 65°F and 95°F.
C
o
n
t
r
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l
Compressor
Compressor
Sound pressure levels per Table 7
Sound pressure levels per Table 7
Sound pressure levels
here 4 dBA lower
than Table 7
Sound pressure levels
here 5 dBA lower
than Table 7
Evaporator
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