Engineering Bulletin - Trane

1 EngineeringBulletinRLC-PRB009-ENSound Data and Application GuideFor the New and Quieter Air-CooledSeries R ChillerModel RTAC140-500 Tons (60 Hz)140-400 Tons (50 Hz) 2002 American Standard Inc. All rights New, Quieter Air CooledSeries R Chiller Model RTACThe sound levels of the air-cooledSeries R Model RTAA chillers havebeen steadily improved since theirintroduction in 1990. With the advent ofthe Model RTAC, sound levels arereduced significantly by addressingthree major sources: the compressor, therefrigerant piping, and the compressor has been designed tominimize sound at its point of was accomplished by conductingfinite element analysis on thecompressor housing to find areas thatwould amplify the frequencies generatedfrom compression.

2 These areas werethen redesigned to reduce refrigerant components and pipinghave been optimized to reduce vibrationand sound propagation throughout source of sound originates fromthe condenser fans. Fan sound powercan be as much as half of the overall unitsound power levels. Carefulconsideration was taken when designingand selecting the next generationcondenser fans to be engineered into theModel RTAC. The sound levels achievedon the Model RTAC represent the lowestsound levels ever on Trane air-cooledscrew compressor water installing any chiller, forethoughtshould be given to the chiller and itsrelationship with the structure. Issuessuch as sound and vibration should beconsidered and factored into thebuilding design and chiller locationwithin a given structure.

3 These issuesare not unique to chillers but should beconsidered when any mechanical deviceis located in or on a Bulletin is not intended to be areplacement for a sound consultant, butrather a tool for you to advise owners,engineers and contractors of useful tipswhen designing and installing chillerinstallations. This Engineering bulletinprovides guidelines for addressing bothunit location and airborne sound wheninstalling air-cooled Series R LocationGround Level EquipmentRoof-Mounted EquipmentAirborne NoiseSound LevelsAppendix AAppendix B23444781618 RLC-PRB009-EN4 UnitLocationOutdoor HVAC equipment must belocated to minimize noise and vibrationtransmission to the occupied spaces ofthe building structure it serves.

4 Also, theequipment must be located to preventobjectionable noise levels at adjacentproperty lines or building choosing a location for theequipment, consider the followingapplication material for both groundlevel and roof mounted additional concern for the designer isthe resulting noise level at adjacentproperty lines. When commercial sizeequipment is installed near a residentiallot line, there is potential for a soundproblem. In this situation, the problem isnot the commercial equipment butrather locating the equipment too closeto a quiet zone! For equipment operatingadjacent to residential areas, zoneordinances require maximum lot linedBA levels of 50-55/45 (day/night).

5 Incommercial areas 60-65/55-60 (day/night). In industrial areas typical levelsmandated by local code authorities are65-70/65-70 (day/night). The reader iscautioned that the foregoing valueslisted are those typically seen acrossmajor cities of the The requirementsvary by locality so the designer iscautioned to always check thecriteria and local requirementsbefore selecting equipmentlocationsA. Ground Level Equipment1. If the equipment must be located inclose proximity to a building, it shouldbe placed next to an unoccupied spacesuch as a storage room, mechanicalroom, switch gear/electrical room orother typically unoccupied space. It isnot recommended to locate theequipment near occupied, soundsensitive areas of the building or nearwindows.

6 Also, do not locate theequipment adjacent to other buildingwalls or large objects which mayreflect the sound back to the soundsensitive Seal all piping and electrical conduitpenetrations in the building envelopewith an approved fire safe insulated, dielectricallycompatible sleeves at wallpenetrations to properly support thepiping and provide vibration flexible couplings andvibration isolators for the watercirculating pump and connections toprevent the transmission of soundthroughout the Install the unit on a pad isolated fromthe building or install the unit withproper vibration isolation underneaththe unit to prevent machine vibrationsfrom being transmitted to thestructure of the Roof Mounted Equipment1.

7 Roof Location The single most effectiverecommendation to prevent soundproblems within a building is to locatethe unit over non-critical areas such ascopy rooms, restrooms, storagerooms, and other similar non-occupiedareas of the building. It is notrecommended to locate a unit directlyover or in close proximity to soundsensitive areas such as conferencerooms, executive office spaces,libraries, etc. It is not recommended to locate theequipment near occupied, soundsensitive areas of the building or nearwindow glass. Also, do not locate theequipment adjacent to other buildingwalls or large objects which may reflectthe sound back to the sound Building Structure When mounting the chiller on theroofline, it is not recommended tolocate the unit on a beam or structureat mid-span of the column grid.

8 Rather,directly support the unit over is it recommended to locate theunit in the middle of a horizontal to avoid large column spans. Thiswill minimize the roof deflectionvibration transmission. When directly mounting chillers onI-beams that are above the roofline andmounted to the building supportcolumns, there exists the potential for aresonant frequency at which higherthan normal vibration may betransmitted to the rest of the cognizant of this application. Aconsultant may be required SupportPoorConcentration of equipment weightbetween beams causes excessive roofdeflection and vibration transmission,even for isolated addition of housekeeping padand additional beams add mass andstiffness to GoodA column directly under the equipmentgives the roof a very high local stiffness,but some equipment vibration stillenters the roof directly mounting chillers on I-beams (at the roofline) that are mounted to thebuilding, support columns potentially can transmit higher than normal vibration at aresonant frequency to the rest of the building.

9 The following drawing depicts whattype of prevention methods can be Base It is not recommended to bolt downvibrating equipment directly tofoundation without using isolators. Install the unit upon an inertia base orconcrete pad structure with vibrationisolation to match the characteristics ofthe roof structure. Beware oflightweight roof structures which aredifficult to isolate from vibration. Use an inertia base or solid concretepad as a base for the chiller. This mass,properly supported, will maximizevibration dampening and help preventnoise from penetrating through theroof directly below the unit. Floors andceiling should be concrete Isolators Isolate chiller on ELASTOMERIC isolators.

10 Originally intended forreciprocating compressors, springisolators are not as effective atabsorbing movement and vibration onair-cooled Series R chiller is because air-cooled Series Rchillers have higher frequency vibration(900 Hz) than reciprocating chillers (lessthan 125 Hz). Isolate the unit on elastomeric isolatorsselected to match the characteristics ofthe roof structure. It is notrecommended that equipment beapplied to buildings with a lightweightroof structure unless column supportsare provided which are independent ofthe roof Chilled Water Piping Provide flexible couplings and vibrationisolators for the water circulating pumpconnections to prevent thetransmission of sound throughout thebuilding.