Sound and vibration management
SM / SY / SZ compressors are equipped with a
discharge valve which closes at compressor shut
down and thus prevents the compressor from
running backwards. This reduces the stopping
sound to a metallic click caused by the closing
valve.
When the pressure difference or gas flow at shut
down should be very low, this can delay the
discharge valve from closing and lead to a longer
noise duration.
Running sound level
Stopping sound level
During start-up transients it is natural for the
compressor sound level to be slightly higher
than during normal running. SM / SY / SZ scroll
compressors exhibit very little increased start-up
transient sound. If a compressor 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
Typical sound and vibration in Refrigeration and
Air-Conditioning 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.
Sound generation in
a refrigeration or air
conditioning system
Model
50 Hz
60 Hz
Acoustic
hood code
number
Bottom
insulation
code n°
*
R22
R407C
R22
R407C
Sound power
dB(A)
Attenuation
dB(A)
Sound power
dB(A)
Attenuation
dB(A)
Sound power
dB(A)
Attenuation
dB(A)
Sound power
dB(A)
Attenuation
dB(A)
S 084
70
8
71
8
74
8
74
8
7755011
120Z0356
S 090
70
8
72
8
75
8
77
8
7755011
120Z0356
S 100
70
8
73
8
75
8
77
8
7755011
120Z0356
S 110
75
8
77
8
78
8
81
8
7755010
120Z0356
S 112
75
6
-
-
78
6
-
-
120Z0035
-
S 120
75
8
77
8
78
8
81
8
7755010
120Z0356
S 124
73
6
-
-
77
6
-
-
120Z0035
-
S 147
74
6
77
8
78
6
81
8
120Z0035
-
S 148
79
8
79
8
83
8
83
8
7755017
120Z0356
S 161
79.5
8
79
8
84
8
83
8
7755017
120Z0356
S 175
80
8
81
8
82.5
8
84
8
7755007
120Z0353
S 185
80
8
81
8
82.5
8
84
8
7755007
120Z0353
S 240
82
7
83.5
7
85
7
87
7
7755016
120Z0355
S 300
82
7
84
7
86
7
87.5
7
7755016
120Z0355
S 380
87
7
87.5
7
92
7
91
7
7755022
120Z0355
For SM/SZ147-3 - 50 Hz, use acoustic hood reference 120Z135
For SM148 - 161 code 3, no acoustic hood available
Sound power and attenuation are given at rated ARI conditions, measured in free space.
* Bottom insulations are provided in surface sump heater accessories.
Materials are UL approved and RoHS compliant.
Data given for code 4 compressor, for full data details and capacity tables refer to Online Datasheet Generator: www.danfoss.com/ODSG
Application guidelines
40
FRCC.PC.003.A5.22
