Vibration Isolation Curbs are fully integrated roof curb and vibration isolation system to reduce the transmission of vibration from the roof top mounted HVAC unit (RTU) to the building structure.  Vibration Isolation Rails are a standalone product that can be used on our roof curbs or competitor roof curbs.  Vibration Isolation Rails can also be used on roof curbs adapters.

Transmitted vibration can cause unwanted noise levels throughout the building and the best way to reduce that transmission is through isolation mounting systems that have a negligible damping coefficient.  Elastomeric Isolators tend to have high damping coefficients, which is why we use only metal spring isolators in our products.  The table below shows the vibration transmission from the HVAC unit to the building structure as a percentage.  The data is presented as a function of the forced frequency of the unit and the deflection of the springs in a low damping design such as the Plenums Vibration Isolation Curb and Vibration Isolation Rail.  We offer static deflection up to 2 inches, but the 1-inch deflection is sufficient for most applications.   The highlighted green cells indicate the operating points that can be met by Plenums Vibration Isolation Products.

VIBRATION ISOLATION RAILS

Vibration Isolation Rail

VIBRATION ISOLATION CURBS

Vibration Isolation Curb
Vibration   Transmission - Percentage
1% 2% 3% 5% 10% 25% 40%
Forced Frequency
      (RPM)
Static Deflection Required   for Isolator (in) - no damping
3600 1.08 0.54 0.35 0.21 0.10 0.03 0.02
2400 2.44 1.21 0.80 0.47 0.22 0.07 0.04
1800 4.33 2.15 1.42 0.83 0.39 0.13 0.07
1600 5.49 2.71 1.79 1.05 0.50 0.17 0.08
1400 7.16 3.55 2.34 1.37 0.65 0.22 0.11
1200 9.75 4.83 3.18 1.87 0.89 0.30 0.15
1100 11.61 5.74 3.79 2.23 1.06 0.35 0.18
1000 14.04 6.95 4.59 2.69 1.28 0.43 0.21
900 17.34 8.58 5.66 3.33 1.58 0.53 0.26
800 21.94 10.86 7.17 4.21 1.99 0.66 0.33
700 28.66 14.18 9.36 5.50 2.61 0.87 0.43
600 39.01 19.31 12.74 7.49 3.55 1.18 0.59
500 56.17 27.80 18.34 10.78 5.11 1.70 0.85
400 87.76 43.44 28.66 16.84 7.98 2.66 1.33
300 156.02 77.22 50.96 29.94 14.18 4.73 2.36

Vibration Isolation Features

  • Efficient on-site assembly.
  • Integrated seismic and wind restraints.
  • Additional restraint stiffener.
  • Pre-loaded spring assembly.
  • High strength galvanized steel.

Vibration Isolation Options

  • 1" or 2" deflection.
  • Wind Certification.
  • Duct supports.
  • Island supports.
  • Pipe chase supports.

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