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Application Guidelines
Starting sound level
Running sound level
Stopping sound level
Sound generation in a
refrigeration system
Compressor sound
radiation
© Danfoss | Climate Solutions | 2022.03
Sound and vibration management
During start-up transients it is natural for the
compressor sound level to be slightly higher
than during normal running. MLZ/MLM scroll
compressors exhibit very little increased start-up
transient sound. If a 3-phase model is miswired,
the compressor will run in reverse. Reverse
MLZ/MLM are designed with features to reduce
the sound level when a compressor is running.
Model
Nominal
MLM/MLZ090
MLM/MLZ116
MLM/MLZ130
MLM/MLZ160
MLM/MLZ200
MLM/MLZ240
MLZ/MLM have a unique discharge valve design
that minimizes stopping noise. This results in very
Typical sound and vibration in refrigeration
systems encountered by design and service
engineers may be broken down into the
following three source categories.
Sound radiation: This generally takes an
airborne path.
For sound radiating from the compressor, the
emission path is airborne and the sound waves
are travelling directly from the machine in all
directions.
The MLZ/MLM scroll compressors are designed
to be quiet and the frequency of the sound
generated is pushed into the higher ranges,
which not only are easier to reduce but also do
not generate the penetrating power of lower
frequency sound.
compressor rotation is characterized by an
objectionable sound. To correct reverse rotation,
disconnect power and switch any two of the
three power leads at the unit contactor. Never
switch leads at the compressor terminals.
Sound levels are at rated (medium temperature)
conditions.
Sound level (dBA) –50Hz – -10/45/30/0
R22
Max
76
79
82
85
86
89
88
91
88
91
91
94
low shutdown sound.
Mechanical vibrations: These generally extend
along the parts of the unit and structure.
Gas pulsation: This tends to travel through the
cooling medium, i.e. the refrigerant.
The following sections will focus on the causes
and methods of mitigation for each of the above
sources.
Use of sound-insulation materials on the inside of
unit panels is an effective means of substantially
reducing the sound being transmitted to the
outside. Ensure that no components capable
of transmitting sound/vibration within the unit
come into direct contact with any non insulated
parts on the walls of the unit.
Because of the unique design of a full-suction gas
& oil cooled motor, compressor body insulation
across its entire operating range is possible.
Single compressors
R404A&R507A
Nominal
Max
76
79
84
87
86
89
88
91
88
91
91
94
AB243586442698en-000601
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