Sound And Vibration Management; Starting Sound Level; Running Sound Level; Stopping Sound Level - Danfoss CH290 Application Manuallines

Application Guidelines

Starting sound level

Running sound level

Stopping sound level

Sound generation in a
refrigeration or air
conditioning system

Sound and vibration management

During start-up transients it is natural for the
compressor sound level to be slightly higher
than during normal running. The CH scroll
compressors exhibit very little increased start-up
transient sound. If a compressor is miswired,
the compressor will run in reverse. Reverse
Compressor acoustic hoods have been
developed to meet specific extra-low noise
requirements. The covers and bottom insulations
Model
Sound power dB(A)
CH290
CH485
Sound power and attenuation are given at ARI conditions, measured in free space
 Attenuation given with acoustic hood only
 Bottom hood is provided in surface sump heater accessories. Additional attenuation is 2 to 4 dBA. Materials are UL approved and
RoHS compliant.
CH 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.
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.
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.
incorporate sound proofing materials and offer
excellent high and low frequency attenuation.
50 Hz
Attenuation
dBA 
82 6
89 4
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.
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.
Acoustic hood code Bottom hood code
number number 
120Z0022 120Z0353
120Z0022 120Z0353
FRCC.PC.026.A4.02
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