SPX Cooling Technologies Marley MD Specifications, Specification Value, Sound Control

Marley / MD CoolingTower / Specifications: Options

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	Specifications	Specification Value
	Sound Control
1.2	Add the following paragraph under	■ Sound produced by a standard MD tower operating in an unob-
	Base: The cooling tower shall be quiet	structed environment will meet all but the most restrictive noise
	operating, and shall produce an overall	limitations—and will react favorably to natural attenuation. Where
	level of sound no higher than ____	the tower has been sized to operate within an enclosure, the
	dBA, measured at the critical location	enclosure itself will have a damping effect on sound. Sound also
	indicated on the plans.	declines with distance—by about 5 or 6 dB(A) each time the dis-
		tance doubles. Where noise at a critical point is likely to exceed an
		acceptable limit, you have several options—listed below in ascend-
		ing order of cost impact:
		• In many cases, noise concerns are limited to night time, when
		ambient 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 tower's noise
		level during periods of reduced load and/or reduced ambient
		without 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 hos-
		pital), the best solution is to oversize the tower so it can operate
		continuously 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 possible.
		• The most extreme cases may require discharge sound attenuator
		sections—however, the static pressure loss imposed by discharge
		attenuators may necessitate an increase in tower size. Your Marley
		sales representative will be able to help you meet you sound
		requirements.