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RTAA Sound Attenuation
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Source：Internet Author：Unknow Pubdate：2008-04-15
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AbbyNormal (Mechanical)
17 Apr 07 18:36
Have a chiller noisier than expected.
The discharge piping makes the casing and the oil separator resonate at a high pitch. Trane sells a sound deadening kit. It is not cheap, basically insulation to wrap the copressor, discharge piping, oil seperator.
Anyone ever try this kit? Did it work? Take the "V" out of HVAC and you are left with a HAC(k) job.
Vellum (Mechanical)
18 Apr 07 8:30
I've dealt with noise issues in the past and they are a pain. If the problem is noise complaints in adjacent occupied spaces then treating it at the source probably would be easier then treating it at the mechanical room wall. I would ask Trane what the dB difference is for the kit (make sure it's for all octave bands) if the difference is 10 dB across all octave bands then the sound should be cut in half. Just focus more on the higher frequencies when evaluating the information.
字串8
AbbyNormal (Mechanical)
18 Apr 07 13:27
This situation is a pair of 70 ton air cooled chillers at a school. A subdivision has encroached on the school, and their are backyards 100 yards away from the chiller compound, separated by brush.
There is a loud high pitch whine from the compressor discharge piping, the frame holding the condenser coil, and oil separators that resonate like a bell.
I was in the subdivision, they have a valid complaint. In particualr those who like to try and open the windows rather than run the AC.
These units are louder than a pair of 90 ton, same model line, in the general vicinity at a church. Take the "V" out of HVAC and you are left with a HAC(k) job.
NCDesign (Mechanical)
18 Apr 07 14:19
Kinda off topic but it makes me curious. If the neighbors over 100 yards away are complaining why isn't anyone from within the school complaining? I would expect that the chiller is within 10 to 20 feet of a building wall.
字串2
AbbyNormal (Mechanical)
18 Apr 07 18:13
Chillers are at the end of the school site where it is a loading zone, storage rooms etc. The windows are closed, the building is concrete.
The subdivision, people hear it sitting in their back yards, and indoors if they open their windows.
There is a pumphouse on one side of the chiller compound, thinking about an L shaped wall to shield the subdivision. Take the "V" out of HVAC and you are left with a HAC(k) job.
NCDesign (Mechanical)
19 Apr 07 8:32
Well from my past experience the wall will probably be cheaper than the insulation kit. Be sure and keep the required clearance and make sure that the wall is not taller than the chillers. This is probably not as big a concern since the wall will not go completely around the chiller, but it ensures you don't recirculate your condenser air.
字串2
Vellum (Mechanical)
19 Apr 07 9:25
If you don't like the information from the manufacturer about the sound dampening then you need to install an acoustical screen wall on the roof this will allow for the sound to 'bounce' away from the houses. Note that high pitched frequencies are attenuated easily with mass. Do, however, keep the solid screen wall away from the units per the manufacturers recommendations.
ChrisConley (Mechanical)
19 Apr 07 12:18
Quote:if the difference is 10 dB across all octave bands then the sound should be cut in half.
If the difference is 3 dB the sound should be cut in half no?
Vellum (Mechanical)
19 Apr 07 13:45
People can perceive a 2-3 dB difference.
字串7
SylvestreW (Mechanical)
19 Apr 07 17:25
Lagging material is quite common for the problem you are describing. Here's a useful link:
http://www.insulation.org/articles/article.cfm?id=IO970901
AbbyNormal (Mechanical)
19 Apr 07 18:41
Thanks but the lagging link still looks like buyer beware. Any buyers of trane's package on this site? Take the "V" out of HVAC and you are left with a HAC(k) job.
SylvestreW (Mechanical)
20 Apr 07 8:59
I would suggest x-posting this to "Mechanical Acoustics/Vibration engineering"
Grendil (Mechanical)
26 Apr 07 19:03
I have used the Wrap, it works ok. What DB reading were you getting it will definately help but prob not to there liking. build a structure.
字串9
DrRTU (Mechanical)
29 Apr 07 9:28
I feel your pain. I had a problem with 2 larger units on a hotel. I would do lagging on the units and install a sound screen wall around the units. The wall panels are a fiberglass / metal sandwich with a perforated face inside towards the chiller. The intent is to breakup the sound and minimize the reverberated sound. Hire a sound consultant – they always have a brand they want to represent. Example http://www.enoisecontrol.com/Air_Cooled_Chiller_Noise_Control_Case_Study.htm
DrRTU (Mechanical)
3 May 07 12:20
Try these guys, the local reps are very helpful. http://www.kineticsnoise.com/industrial/knp.html
AbbyNormal (Mechanical)
4 May 07 12:27
Thanks Dr Take the "V" out of HVAC and you are left with a HAC(k) job.
字串7
redgdon (Mechanical)
4 May 07 17:58
Installed 4 x 1.2MW Trane chillers, with acoustic enclosure, also supplied by Trane. The only way to tell if they were running was to put your hand on the casings and feel the vibration.
AbbyNormal (Mechanical)
5 May 07 12:11
The acoustic enclosure was the insualtion on the discharge piping and oil seperators, or a wall? Take the "V" out of HVAC and you are left with a HAC(k) job.
Drivewizard (Mechanical)
6 May 07 13:28
After working on numerous aircooled and water cooled chillers with sound blankets on compressors I can tell you they are a pain in the *** to remove and put back on. They never go back on as well as they originally did or should.
My advice from a service standpoint is to go with the wall. 字串7
If you have to you can install chimmneys on the fan discharges to get leaving cond air up and away from coils to prevent recirc.
The blankets do help cut the sound, but you pay a price in serviceablity.
redgdon (Mechanical)
7 May 07 13:36
The acoustic enclosure was in effect wall. It was made up of a series of panels which sat perpendicular to the chiller along it's length.
AbbyNormal (Mechanical)
9 May 07 19:00
Just an observation
With fire alarms, a rule of thumb is as you double the distance from a horn, the sound drops by 6 dB. The RTAA seemed to follow this pattern.
Take the "V" out of HVAC and you are left with a HAC(k) job.
FSD (Mechanical)
10 May 07 14:19
pls, check that: 字串7
http://www.trane.com/Commercial/DNA/View.aspx?i=975.
Regards
AbbyNormal (Mechanical)
6 Jul 07 15:59
ended up building a block wall.
RTAAs were running louder than the spec
Have to measure the sound in the subdivision sometimes, but the neighbours seem appeased. Take the "V" out of HVAC and you are left with a HAC(k) job.
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