Manage sound and vibration
Typical sounds and vibrations in systems can be
broken down into the following three categories:
• Sound radiation (through air)
• Mechanical vibrations (through parts and
structure)
• Gas pulsation (through refrigerant)
The following sections focus on the causes and
methods of mitigation for each of the above
sources.
Compressor sound
radiation
For sound radiating from the compressors,
the emission path is air and the sound waves
are travelling directly from the machine in all
directions.
Sound levels are as follows:
• For compressors running alone:
Compressor model
Frequency RPS
380V
Acoustic hood
code number
Sound power
dB(A)
Attenuation
dBA
VLZ065
60
79
7
120Z5084
110
88
8
Sound power and attenuation are given at ARI conditions, measured in free space
Attenuation given with acoustic hood
Materials are UL approved
Mitigations methods:
We can consider two means to reduce
compressors sound radiations:
1. Acoustic hoods are quick and easy to install
and do not increase the overall size of the
compressors. Acoustic hoods are available from
Danfoss as accessories. Refer to the table above
for sound levels, attenuation and code numbers.
2. Use of sound-insulation materials on the inside
of unit panels is also an effective means to reduce
radiation.
Note: During compressor shut down, a short
reverse rotation sound is generated. The duration
of this sound depends on the pressure difference
at shut down and should be less than 3 seconds.
This phenomenon has no impact on compressor
reliability.
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