Specifications
Specification Value
Marley
/
MC
Fluid Cooler
/
Specifications: Options
26
■
Sound produced by a standard MC Fluid Cooler operating in an
unobstructed environment will meet all but the most restrictive noise
limitations—and will react favorably to natural attenuation. Where the
fluid cooler has been sized to operate within an enclosure, the enclo-
sure itself will have a damping effect on sound. Sound also declines
with distance—by about 5 or 6 dB(A) each time the distance doubles.
Where noise at a critical point is likely to exceed an acceptable limit,
you have several options—listed below in ascending order of cost
impact:
• Where only a slight reduction in noise will satisfy—and the source
of concern is in a particular direction—merely turning the fluid cooler
may be the answer. Less sound emanates from the cased face of the
fluid cooler than does from the air intake face.
• In many cases, noise concerns are limited to night time, when ambi
-
ent noise levels are lower and neighbors are trying to sleep. You can
usually resolve these situations by using two speed motors in either
full/half speed or full/
2
⁄
3
speed configuration, and operating the fans at
reduced speed without cycling “after hours”. (The natural night time
reduction in wet-bulb temperature makes this a very feasible solution
in most areas of the world, but the need to avoid cycling may cause
the cold water temperature to vary significantly.)
• Variable speed drives automatically minimize the fluid cooler's noise
level during periods of reduced load and/or reduced ambient with-
out sacrificing the system's ability to maintain a constant cold water
temperature. This is a relatively inexpensive solution, and can pay for
itself quickly in reduced energy costs.
• Where noise is a concern at all times (for example, near a hospital),
the best solution is to oversize the fluid cooler so it can operate con-
tinuously at reduced (
2
⁄
3
or ½) motor speed even at the highest design
wet-bulb temperature. Typical sound reductions are 7 dB(A) at
2
⁄
3
fan
speed or 10 dB(A) at ½ fan speed, but larger reductions are often pos-
sible.
• The most extreme cases may require inlet and discharge sound
attenuator sections—however, the static pressure loss imposed by
discharge attenuators may necessitate an increase in fluid cooler size.
Two stages of inlet or discharge attentuators supported by the fluid
cooler and designed and tested for the most stringent requirements
are available as an option. See page 13.
The advantage is yours. You now have the choices you need to bal-
ance your project’s performance, space and cost requirements with
your sound level needs for a win-win solution to your cooling system
design. Your Marley sales representative will be able to help you meet
your sound requirements.
Miscellaneous Options
Sound Control
1.2
Add the following paragraph
under Base:
The fluid cooler
shall be quiet operation, and
shall produce an overall level of
sound not higher than _______
dB(A) measured at the critical
location indicated on the plans.
