Sound and vibration management
Running sound level
Stopping sound level
Sound generation in a
refrigeration system
Compressor sound
radiation
MLZ/MLM are designed with features to reduce
the sound level when a compressor is running.
Sound levels are at rated (EN12900 medium
temperature) conditions.
MLZ/MLM have a unique discharge valve design
that minimizes stopping noise. This results in very
low shutdown sound.
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.
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.
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.
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.
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
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.
Starting sound level
Model
50 Hz
60 Hz
Sound power (dBA)
Without jacket
Sound power (dBA)
With jacket
Sound power (dBA)
Without jacket
Sound power (dBA)
With jacket
MLZ/MLM015
67
57
71
60
MLZ/MLM019
67
57
71
60
MLZ/MLM021
67
57
71
60
MLZ/MLM026
67
59
71
62
MLZ/MLM030
69
62
73
65
MLZ/MLM038
69
63
74
66
MLZ/MLM042
71
63
74
66
MLZ/MLM045
71
63
74
66
MLZ/MLM048
72
64
74
67
MLZ/MLM058
74
66
78
70
MLZ/MLM066
74
66
78
70
MLZ/MLM 076
74
66
78
70
Maximum sound is +5dBA
40
FRCC.PC.015.A8.02
Application Guidelines
