**FAQ on McQuay Air Conditioning Repair; Principles of Vibration Isolation and Noise Reduction for Air Conditioning Equipment**
The compressor and condenser sections of modular air conditioning units, as well as the ventilators of large air conditioners, all require anti-vibration foundations.
When equipment such as ventilators and refrigeration machines are installed on vibration-isolating bases, their anti-vibration effects are better if supported by vibration isolators. Commonly used vibration isolators include spring-type isolators and rubber-chamber isolators.
The TJ1 type spring vibration isolator uses carbon steel wire for the spring, which can be composed of a single or multiple springs. Beneath the isolator is a 10mm thick rubber plate, along with anchor bolts. This type of isolator has advantages such as simple structure, clear force distribution, good vibration isolation effect, and durability. The rubber vibration isolator uses rubber as the vibration-damping material, which offers excellent elasticity, a simple structure, and low cost. However, it cannot withstand extreme temperatures and is prone to aging, so its application is somewhat limited.
**While considering vibration isolation, noise reduction should also be taken into account. A common method is to install silencers in the ventilation duct system, also known as mufflers.** Silencers consist of sound-absorbing materials and an outer shell. Sound-absorbing materials include fiberglass, slag wool, urethane foam plastic, wood fiber boards, etc. The outer shell of the silencer is made of thin steel plates or concrete (used inside the fan mixing chamber).
There are many types of silencers, and those commonly used in air conditioning projects include elbow silencers, tubular silencers, and panel silencers for soundproof rooms. Elbow silencers are made by attaching sound-absorbing materials to the inner walls of bends in the ductwork. In round-cornered elbow bends, 50mm thick superfine glass wool is filled inside, with cotton sheets and perforated plates used as decorative surfaces, or short chord guide vanes installed inside. Tubular silencers involve attaching sound-absorbing materials to the inner walls of ducts. To eliminate noise caused by airborne sound transmission, sound-absorbing materials (30~50mm thick glass wool) can be adhered to the inner walls of supply and return air ducts.
In supply air ducts, the length of the sound-absorbing lining should be no less than 8 meters; in return air ducts, the length of the sound-absorbing lining should be no less than 5 meters. When higher noise requirements are placed on air conditioning equipment, all supply and return air ducts should either be lined with sound-absorbing materials or equipped with modular silencers.
**Beijing McQuay Air Conditioning Maintenance Center, August 10, 2011.**