36
FRCC.PC.007.B8.02
Application guidelines
Sound and vibration management
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 focus on the causes and
methods of mitigation for each of the above
sources.
SH 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.
Sound generation in a
refrigeration or air
conditioning system
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. SH 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.
Compressor acoustic hoods have been
developed to meet speci c extra-low noise
requirements. The covers and bottom insulations
incorporate sound proo ng materials and o er
excellent high and low frequency attenuation.
Starting sound level
Model
50 Hz 60 Hz
Acoustic hood
code number
Bottom hood
code n°
Sound power
dB(A)
Attenuation
dBA
Sound power
dB(A)
Attenuation
dbA
SH090 70 6 72 6 120Z0034
Not available
SH105 71.5 6 74 6 120Z0035
SH120 72.5 6 75 6 120Z0035
SH140 * 72.5 6 76 6 120Z0035
SH161 * 73.5 6 77 6 120Z0035
SH184 75 6 78 6 120Z0135
SH180 80 6 85 4 120Z0022 120Z0353
SH240 82 6 86 4 120Z0022 120Z0353
SH295 82 6 86 4 120Z0022 120Z0353
SH300 82 6 86 4 120Z0022 120Z0353
SH380
83 6 87 4 120Z0022 120Z0353
SH485 89 4 91 4 120Z0022 120Z0353
Sound power and attenuation are given at ARI conditions, measured in free space
* For SH140 code 3 and SH161 code 3 use acoustic hood reference 120Z0135
Attenuation given with acoustic hood only
Bottom hood is provided in surface sump heater accessories for SH180-240-295-300-380-485 models. Additional attenuation
is 2 to 4 dBA.
Materials are UL approved and RoHS compliant
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