VIBRATION ISOLATION OF AIR CONDITIONING UNITS

Air conditioning units are present in a wide range of different building types, such as office buildings, hospitals and residential dwellings. These units are machines that generate unwanted noise and vibrations during their operation. If these machines are not correctly isolated, they can be uncomfortable for the occupants due to the noise and vibrations that can be transmitted through the air and also the building structure.

Air conditioning units consist of many different components which are assembled in modules, each of these modules are designed for a specific function and can have very different weights and dimensions. This can result in an uneven load distribution which must be taken into account when selecting the correct isolation mounts at each location on the machine. Another factor to take into account is ensuring that the chassis under which the mounts will be placed is rigid and strong enough to withstand these punctual loads.

If this is not the case, the recommendation is to install a UPN type metal profile (for example, UPN 120) along the entire perimeter of the machine, in order to place the mounts under it.

If the load is evenly distributed the mounts could be installed equidistantly under the machine chassis. A maximum distance between mounts of 1500mm should be respected in order to reduce the risk of exciting any structural vibration modes within the frame itself.

If the load distribution is even, the deflection of the mounts will also be consistent.

If the load distribution is uneven this can result in a significant difference between the mount deflections, differences bigger than 5mm between the mount with the biggest and smallest deflection would require a modification to the design. The lower profile will allow the mounts to move along it in order to achieve a more uniform distribution of load, giving a more similar deflection in all the mounts.

In cases where the position of the mounts cannot be changed, it will be necessary to use mounts with different stiffness in each point.

These recommendations are both for insulation using springs and for insulation using mounts with Sylomer.

In case that the height of the air conditioner is greater than the width or length of its base, the installation of a floating suspension can compromise the stability of the machine, especially if it has to face dynamic forces (such as wind forces if placed on a rooftop). In these cases, the installation of stabilizers on the upper part of the unit is recommended.

These recommendations are applicable both for air conditioning units in which the vibration isolators are placed under their base and also for equipment that must be suspended by hanging them from the ceiling.