Product Manual PM WSC/WDC 25
Sound
Sound Levels -- One Of The Quietest Centrifugal Chillers In The Industry
McQuay centrifugal chillers are one of the quietest units available in the marketplace. It is easy to make this
type of claim!! For us, it is just as easy to support!!
Unique!! --- Quiet full load sound levels and QUIETER part load sound levels.
The highest noise levels for McQuay chillers are at FULL load. As McQuay chillers unload, noise levels reduce.
Other chillers on the market are typically the opposite, with higher sound levels at part load. Be certain to
compare noise levels at several load conditions.
Unique!! --- Liquid refrigerant injection into compressor discharge
Although this sounds complex, this feature is quite simple. Most of the noise in all centrifugal compressors
results from high gas velocity in the discharge line.
The McQuay liquid injection system injects liquid refrigerant into the discharge gas through a radial array of
ports. This refrigerant mist absorbs sound energy (much like a foggy day) and the flash gas cools the discharge
gas leaving the compressor. The net result is significant noise reduction.
ADDITIONALLY !! By removing superheat from the discharge gas, the condenser becomes more efficient,
improving unit
efficiency.
Unique!! --- Moveable
Discharge Diffuser
The other unique
feature to reduce noise
and increase stability at
low loads is the unique
moveable discharge
diffuser. Less
refrigerant is circulated
as the chiller capacity
reduces. The left
drawing shows the
operation at full load of
a unit with a fixed compressor discharge section. At full load, a large quantity of gas is discharged with a fairly
uniform discharge velocity as indicated by the arrows.
The middle drawing shows a fixed compressor discharge at low capacity. Note that the velocity is not uniform
and the refrigerant tends to reenter the impeller. This is caused by low velocity in the discharge area and the
high pressure in the condenser, resulting in unstable surge operation and with noise and vibration generated.
The right side drawing shows the unique McQuay moveable discharge diffuser. As the capacity reduces, the
moveable diffuser travels inward, maintaining the refrigerant velocity, and allowing reduction to 10% load.
Discharge Line Sound Packages
For the extremely sensitive projects, an optional discharge line sound package is offered consisting of sound
insulation installed on the unit’s discharge line. An additional 2 to 4 dbA reductions normally occurs.
ARI Standard 575 Sound Ratings
Sound data in accordance with ARI 575 for individual units are available from your local McQuay
representative. These ratings are in accordance with ARI Standard 575. Due to the large number of component
combinations and variety of applications, sound data is not published in this catalog.
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