RTAA Sound Attenuation 2

[AbbyNormal]

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]

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.

 

[AbbyNormal]

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]

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.

 

[AbbyNormal]

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]

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.

 

[Vellum]

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]

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]

People can perceive a 2-3 dB difference.

 

[SylvestreW]

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]

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]

I would suggest x-posting this to "Mechanical Acoustics/Vibration engineering"

 

[Grendil]

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.

 

[DrRTU]

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]

Try these guys, the local reps are very helpful.

http://www.kineticsnoise.com/industrial/knp.html

 

[AbbyNormal]

Thanks Dr

Take the "V" out of HVAC and you are left with a HAC(k) job.

 

[redgdon]

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]

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]

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.
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]

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.