User Guide

Application guidelines
42 AB237986441643en-US0701
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 dierence or gas ow 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.