Danfoss VZH052 Manual page 26

Manage sound and vibration
Compressor sound
radiation
Compressor
Frequency RPS
model
60
VZH052-VZH065
90
Sound power and attenuation are given at ARI conditions, measured in free space
 Attenuation given with acoustic hood
Materials are UL approved
26
AB237586440343en-000601
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)
For sound radiating from the compressors,
the emission path is air and the sound waves
are travelling directly from the machine in all
directions.
200V
Sound power Attenuation
dB(A) dBA 
79 9
85 9
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.
• Gas pulsation (through refrigerant)
The following sections focus on the causes and
methods of mitigation for each of the above
sources.
Sound levels are as follows:
• For compressors running alone:
400V
Sound power Attenuation
dB(A) dBA 
79 9
85 9
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.
575V
Acoustic hood
Sound power Attenuation
dB(A) dBA 
79 9
85 9
code number
120Z5084