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Scroll compressors, CH290 and CH485 | Sound and vibration data
Sound and vibration data
Starting sound level
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 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.
Running sound level
Compressor acoustic hoods have been developed to meet specific extra-low noise requirements. The covers and
bottom insulations incorporate sound proofing materials and offer excellent high and low frequency attenuation.
Table 6:
Model
CH290
CH485
(1)
(1)
Bottom hood is provided in surface sump heater accessories. Additional attenuation is 2 to 4 dBA. Materials are UL approved and RoHS
Bottom hood is provided in surface sump heater accessories. Additional attenuation is 2 to 4 dBA. Materials are UL approved and RoHS
compliant.
compliant.
(2)
(2)
Attenuation given with acoustic hood only
Attenuation given with acoustic hood only
NOTE:
Sound power and attenuation are given at ARI conditions, measured in free space
Stopping sound level
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. 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.
Sound generation in a refrigeration or air conditioning system
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.
Compressor sound radiation
For sound radiating from the compressor, the emission path is airborne and the sound waves are travelling directly
from the machine in all directions.
The CH scroll compressors are designed to be quiet and the frequency of the sound generated 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 outside. Ensure that no components capable of transmitting sound/vibration within
the unit come into direct contact with any non-insulated parts on the walls of the unit.
© Danfoss | Climate Solutions | 2022.09
50 Hz
Sound power dB(A)
Attenuation dBA
82
89
Acoustic hood code number
(2)
6
120Z0022
4
120Z0022
Bottom hood code number
120Z0353
120Z0353
AB236986442743en-000501 | 12
(1)
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