Danfoss MLZ, Selection & Application Manuallines

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A
PPLICATION GUIDELINES
S
OUND AND VIBRATION MANAGEMENT
Running sound level
Stopping sound level
Sound generation in a
refrigeration system
Compressor sound radia-
tion
MLZ/MLM are designed with features to reduce
the sound level when a compressor is running. Sound levels are at rated (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 sys-
tems encountered by design and service engi-
neers 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 di-
rections.
The MLZ/MLM scroll compressors are designed to
be quiet and the frequency of the sound gener-
ated 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 out-
side. Ensure that no components capable of trans-
mitting 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 compres-
sors exhibit very little increased start-up transient
sound. If a 3-phase model is miswired, the com-
pressor will run in reverse. Reverse compressor ro- tation 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 compres-
sor 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/MLM 015
MLZ/MLM 019 65 57 68 60
MLZ/MLM 021 65 57 68 60
MLZ/MLM026 67 59 70 62
MLZ/MLM 030 70 62 73 65
MLZ/MLM 038 71 63 74 66
MLZ/MLM 045 71 63 74 66
MLZ/MLM 048 72 64 75 67
MLZ/MLM 058 74 66 77 69
MLZ/MLM 066 74 66 77 69
MLZ/MLM 076 74 66 77 69
31 FRCC.PC.016.A1.22