Noisy Operation and Excessive Vibration

Air Handling Unit and Fan Coil Unit Problem 2


Fan belt emitting burnt smell / noise

Design

Careful design is necessary to reduce vibration disturbances caused by impact force. Design must conform to noise control and elimination guidelines. Principles of vibration control must be used to determine noise control measures.

One of the main sources of vibration within the AHU is the blower with large excitation forces in the low-speed range. This vibration will result in structure-borne noise.

Consider vibration isolator for anti-vibration performance:

  • Restrained Spring Mounting
  • Unhoused Spring Mounting
  • Spring Neoprene Hanger
  • Neoprene Hanger
  • Neoprene Pad

Construction

SS 652: F.6.2.2
Use acoustic silencers, shock isolators, machine enclosures and partition walls to reduce noise disturbances.

Use vibration isolators or mounting equipment to minimize transmission of vibration from machine to load-bearing structure of the building in accordance with ANSI / AHRI Standard 260, CP 99 ISO 9996 or equivalents.

Work closely with manufacturer on the adequacy of the AHU frame for supporting different types of isolators, and select the most optimum vibration isolators for achieving the best vibration isolation values.

The stiffness of brackets must be at least 10 times more rigid than the vibration isolators.

Maintenance

ANSI / AHRI Standard 260
Inspections should be carried out to determine noise levels. Inspect chiller plants with maintenance experts if abnormal sound occurs.

SS 652: F.11.3.2.3
Isolation / Mounting systems should be provided to reduce mechanical vibration and shock in accordance with ISO 2017-1.

Vibration from bearings, sliding and rolling friction could be reduced by maintaining minimum clearances and proper lubrication in accordance with CP99, ANSI / AHRI Standard 260 or equivalents.

Regular monitoring of AHU fan vibration should be carried out and compared with vibration readings specified in ISO 10816-3.

One good practice is to install a connection box on the AHU for vibration monitoring.