ashrae hvac applications

7/24/2019 Ashrae Hvac Applications

1/21

Title footer may contain company info 5/11/2007

TheTheASHRAE HVAC Applications HandbookASHRAE HVAC Applications Handbook::

What Building Owners and Engineers ShouldWhat Building Owners and Engineers Should

Know AboutKnow About Noise and VibrationNoise and Vibration

Steve Wise

Wise AssociatesMadison, WI608-233-7683

[email protected]

Presentation Title 11/24/2010


2/21

Slide Footer NO Company ID here Slide 21/24/2010

Architects*Understand noise transmission in construction options

Owners*Beware that HVAC Equipment Makes Noise*Set acceptable noise level specifications

Equipment Suppliers*How to provide useful acoustical data

HVAC Engineers

*Maintain noise control design vigilanceContractors*Avoid value-engineering acoustical pitfalls

*Understand impact of subtle installation variances


3/21


CHAPTER 47 - NOISE AND VIBRATION CONTROL

Path Noise Estimation and Control (continued)

Mechanical Equipment Room Sound Isolation

Special Construction Types

Floating Floors and Barrier CeilingsSound Transmission in Return Air Systems

Sound Transmission Through Ceilings

Sound Control for Outdoor Equipment

Fume Hood Duct Design

HVAC Noise Reduction Design Procedures

Vibration Isolation and Control

Vibration Measurements and Criteria

Specification of Vibration Isolation

Internal Versus External Isolation

Isolation of Vibration and Noise in Piping Systems

Seismic ProtectionVibration Investigations

Room Noise Measurements,

Commissioning

Trouble-Shooting

References/ Resources

Data Reliability

Acoustical Design of HVAC Systems

Indoor and Outdoor Sound Criteria

Basic Acoustical Design Techniques

Source Sound Levels

Fans

Terminal Units

Rooftop Mounted Air HandlersAerodynamic Sound in Ducts-

Room Air Devices (GRD)

Chillers / Compressors

Emergency Generators

Path Noise Estimation and Control

Plenums

Ducts, Branches and End Reflections

Duct Silencers

Duct Sound Radiation ( Breakout and Breakin)

Receiver Room Sound Correction


4/21


DATA RELIABILITY

Data in this chapter comes from both from consulting

experience and research studies. Use caution when

applying the data, especially for situations that

extrapolate from the framework of the original research.Although specific uncertainties cannot be stated for each

data set, the sound levels or attenuation data are

probably within 2 dB of measured or expected results.However, significantly greater variations may occur,

especially in low frequency ranges and particularly in

the 63 Hz octave band. Specific data sets may have awide uncertainty range, but experience suggests that, if

done correctly, system estimates that combine data sets

usually compare within about 5 dB of measured levels.


5/21


Paths ofTransmissionSources of Noiseor Vibration

=Sound Level

at Receiver Location

+Where to get data,

or how to estimate it

How to identify and

evaluate them

What is desired, and what will result


6/21

Slide Footer NO Company ID here Slide 61/24/2010Typical Paths of Noise Transmission from HVAC Systems

Path A: Structureborne through floor

Path B: Airborne through supply air system

Path C: Duct breakout from supply air duct

Path D: Airborne through return air system

Path E: Airborne through MER wall

E

A

DC B




Path D: Airborne through return air system





Path B: Airborne through supply air systemPath A: Structureborne through floor


7/21


10

20

30

40

50

60

70

31.5 63 125 250 500 1000 2000 4000

Octave Band Frequency (Hz)

Sound Levels From Various HVAC Noise Sources

Fans / AHUs

Fan coils / VAVs

Gril les / Diffusers

Total


8/21


Guidelines for HVAC-Related Background Sound in Rooms

Room Types / Uses RC(N) (QAI


9/21


Guidelines for HVAC-Related Background Sound in Rooms

Room Types / Uses RC(N) (QAI


10/21


0

10

20

30

40

50

60

70

80

90

63 125 250 500 1000 2000 4000 8000

Sound

Pressure

Level(dB)


Noise Criteria (NC) Curves

Room Noise is NC 43

NC-65

NC-60

NC-55

NC-50

NC-45NC-40

NC-35

NC-30

NC-25

NC-20

NC-15


11/21


0

10

20

30

40

50

60

70

80

90

16 31 63 125 250 500 1000 2000 4000

Sound

Pres

sure

Level(dB)


Room Criteria (RC) Curves

Room Noise is RC 35 rumbly

RC Rating Curve

RC55

RC50RC45

RC40

RC35

RC30

RC25

RC20

A - clearly noticeable vibrations

B - mildly noticeable vibrations

A

B

LF MF HF

RC-35

Rumbly


12/21


Guidelines for HVAC-Related Background Sound (2011?)

Room Types / Uses RC/NC

Residences, Apartments, Condos

Bathrooms, kitchens, utility space

Performing Arts Spaces

Drama theaters, concert and recital halls

Music teaching studios

Music practice rooms

Office Buildings

Executive and private offices

Conference roomsTeleconference rooms

Open-plan offices

With sound masking

Corridors and lobbies

30

3025

40

35

45

25

25

30

30

35

dBA

35

3530

45

40

50

30

30

35

35

40

dBC

55

5550

65

60

70

50

50

55

55

60


13/21


Sound Source Path No.

Circulating fans; grilles; registers; diffusers; unitary equipment in room 1

Induction coil and fan-powered VAV mixing units 1, 2

Unitary equipment located outside of room served; remotely located air-handling equipment,

such as fans, blowers, dampers, duct fittings, and air washers

2, 3

Compressors, pumps, and other reciprocating and rotating equipment (excluding air-

handling equipment)

4, 5, 6

Cooling towers; air-cooled condensers 4, 5, 6, 7

Exhaust fans; window air conditioners 7, 8

Sound transmission between rooms 9, 10

No. Transmission Paths Noise Reduction Methods

1 Direct sound radiated from sound source to ear Direct sound can be controlled only by selecting

quiet equipment.

Reflected sound from walls, ceiling, and floor Reflected sound is controlled by adding soundabsorption to room and to equipment location.

2 Air- and structureborne sound radiated from casingsand through walls of ducts and plenums is

transmitted through walls and ceiling into room

Design duct and fittings for low turbulence; locatehigh-velocity ducts in noncritical areas; isolate

ducts and sound plenums from structure withneoprene or spring hangers.


14/21


63 125 250 500 1000 2000 4000

Mineral fiber 1 0.625 13 16 18 20 26 31 36

0.5 0.625 13 15 17 19 25 30 33Glass fiber 0.1 0.625 13 16 15 17 17 18 19

0.6 2 14 17 18 21 25 29 35

Glass fiber

with TL

backing

0.6 2 14 17 18 22 27 32 39

Gypsumboard tiles

1.8 0.50 14 16 18 18 21 22 22

Solid gypsum

board ceiling

1.8 0.50 18 21 25 25 27 27 28

2.3 0.625 20 23 27 27 29 29 30

Double layer

of gypsumboard

3.7 1 24 27 31 31 33 33 34

4.5 1-1/2 26 29 33 33 35 35 36

Mineral fiber

tiles,

concealed

spline mount.

0.5 to 1 0.625 20 23 21 24 29 33 34

Tile Type

Density,

lb/ft2

Thickness,

in.

Octave Midband Frequency, Hz

Ceiling/Plenum/Room Attenuations in dB for Generic Ceiling

in T-Bar Suspension Systems


15/21


Sound Transmission Class (STC) and Transmission Loss Values of

Typical Mechanical Equipment Room Wall, Floor, and Ceiling Types,dB

63 125 250 500 1000 2000 4000

8 in. CMU* 50 35 35 41 44 50 57 64

8 in. CMU with 5/8 in. GWB* on

furring strips53 33 32 44 50 56 59 65

5/8 in. GWB on both sides of 3 5/8

in. metal studs38 18 16 33 47 55 43 47

5/8 in. GWB on both sides of 3 5/8

in. metal studs with fiberglass

insulation in cavity

49 16 23 44 58 64 52 53

2 layers of 5/8 in. GWB on both

sides of 3 5/8 in. metal studs withfiberglass insulation in cavity

56 19 32 50 62 67 58 63

Double row of 3 5/8 in. metal studs,

1 in. apart, each with 2 layers of 5/8

in. GWB and fiberglass insulation in

cavity

64 23 40 54 62 71 69 74

6 in. solid concrete floor/ceiling 53 40 40 40 49 58 67 76

6 in. solid concrete floor with 4 in.

isolated concrete slab and

fiberglass insulation in cavity

72 44 52 58 73 87 97 100

6 in. solid concrete floor with two

layers of 5/8 in. GWB hung on

spring isolators with fiberglass

insulation in cavity

84 53 63 70 84 93 104 105

Room Construction Type STC

Octave Midband Frequency, Hz


16/21


Note 22. Steel springs are the most popular and versatile isolators for HVAC applications

because they are available for almost any deflection and have a virtually unlimited life.

Spring isolators may have a rubber acoustical barrier to reduce transmission of high-

frequency vibration and noise that can migrate down the steel spring coil. They should be

corrosion-protected if installed outdoors or in a corrosive environment. The basic types

include:

Note 23. Open spring isolators (type 3) consist of top and bottom load plates withadjustment bolts for leveling equipment. Springs should be designed with a horizontal

stiffness of at least 80% of the vertical stiffness (kx/ky) to ensure stability. Similarly, the

springs should have a minimum ratio of 0.8 for the diameter divided by the deflected

spring height.

Note 24. Restrained spring isolators (type 4) have hold-down bolts to limit vertical as

well as horizontal movement. They are used with (a) equipment with large variations

in mass (e.g., boilers, chillers, cooling towers) to restrict movement and prevent strain

on piping when water is removed, and (b) outdoor equipment, suchas condensing

units and cooling towers, to prevent excessive movement due to wind loads. Spring

criteria should be the same as open spring isolators, and restraints should have

adequate clearance so that they are activated only when a temporary restraint isneeded.

Closed mounts, orHoused spring isolators consist of two telescoping housings

separated by a resilient material. These provide lateral snubbing and some vertical

damping of equipment movement, but do not limit the vertical movement. Care

should be taken in selection and installation to minimize binding and short-circuiting.

LENGTHY SECTION ON TYPES OF VIBRATION ISOLATORS


17/21


Table 3 Maximum Recommended Duct Airflow Velocities to Achieve Specified

Acoustic Design Criteria

Main Duct Location

Design

RC(N)

Maximum Airflow Velocity,

fpm (m/s)

Rectangular

Duct Circular Duct

In shaft or above drywall ceiling 45 3500 5000

35 2500 3500

25 1700 2500

Above suspended acoustic ceiling 45 2500 4500

35 1750 300025 1200 2000

Duct located within occupied space 45 2000 3900

35 1450 2600

25 950 1700

Aerodynamically

Generated

Sound

in

Ducts

Aerodynamic sound is generated when airflow turbulence occurs at duct elements such as duct

fittings, dampers, air modulation units, sound attenuators, and room air devices. For details on airmodulation units and sound attenuators, see the sections on Variable Air Volume Systems and

Duct Silencers.


18/21



19/21


Description

Supply air fan, 7000 cfm, 2.5 in. of water

22 in. dia., 90 rad. unlined elbow

22 44 in. long sound attenuator

22 in. dia., 8 ft long unl ined duct

10 in. dia. branch, 22 in. dia. main, branch path

10 in. dia. branch, 22 in. dia. main, main path


VAV terminal


10 in. dia., 90 rad. unlined elbow

10 in. dia. diffuser, end reflection15 15 in. rectangular diffuser

ASHRAE room correction: point source

Path Element Sound Calculation Reference

Data Source Reference

Manufacturers data

Attenuation: Table 18

Manufacturers data





Manufacturers data



Attenuation: Table 24Manufacturers data

Equation (22), Tables 32 and 33


20/21


,

Estimated Sound Level Build-Up in Mechanical

Rooms for ARI 575 Chiller Sound Levels

Example:

For ARI 575 test area 15 x 30 x 10

and a room area 30 x 40 x 16

Area ratio =19200/4500 = 4.25

If the room is LIVE (block walls)

the sound level could be 13 dB

louder than ARI submittal sound

rating.

Absorptive wall treatments may

reduce the sound by 10 dB+.


21/21


Troubleshooting (Oops)

Determining Problem Source

Fans, Diffusers, etc.

Determining Problem Type

Noise or Vibration

Testing Vibration Isolator Systems

Floor Flexibility Problems

Vibration Isolation System Resonance

Building Resonances

ashrae hvac applications

Documents