Trane Round In/Round Out Lista de partes descargar pdf (Pagina 153)

VAV-PRC011M-EN 153

Application Considerations

Path Attenuation

Sound is generated by a terminal unit can reach the occupied space along several paths. The

terminal unit generated sound will lose energy—i.e., the energy is absorbed by path obstacles—

as it travels to the occupied space. This acoustical energy dissipation as it travels to the occupied

space is called path attenuation. The amount of energy lost along a particular path can be

quantified and predicted using the procedure outlined in AHRI-885. Each path must be considered

when determining acceptable sound power generated by a terminal unit.

The term “transfer function” is often used to describe the entire path attenuation value for each

octave band (i.e., the sum of all components of a particular path).

Examples of path attenuation include locating the terminal unit away from the occupied space,

increasing the STC (sound transmission classification) of the ceiling tile used, internally lining

ductwork, drywall lagging the ceiling tiles or enclosing the terminal unit in drywall. All of these

choices have costs associated with them that must be weighed against the benefits. Some of these

alternatives can be acoustically evaluated from application data provided in AHRI-885. Others may

require professional analysis from an acoustical consultant.

Computer Modeling

Computer modeling of acoustical paths is available to help estimate sound levels and determine

problem sources. The software used by Trane for computer modeling is called Trane Acoustics

Program (TAP™).

TAP can analyze different room configurations and materials to quickly determine the estimated

total sound levels (radiated and discharged) in a space. The Trane Official Product Selection System

(TOPSS™) can also be used to determine sound levels of terminal units. You can base selections

on a maximum sound level and enter your own attenuation factors (defaults based on AHRI-885

are also available).

Other Resources

Refer to “Additional VAV System and Product References,” p. 156 to see a list of publications to help

with the basics of acoustical theory and modeling. You can also contact your local Trane

salesperson to discuss the issue.

Duct Design

Designing cost-effective VAV duct systems is challenging. Some duct design methods result in

better pressure balance than others do. Duct shape and duct material can influence duct system

design and cost. In addition, duct layout is properly designed for optimal duct installation and

operation.

Duct Design Program

Trane has developed a computer program, VariTrane™ Duct Designer, to aid in the duct design

process. This program is used to calculate duct sizes, fitting sizes, terminal unit sizes, and pressure

drops according to the equal friction or static regain method. The duct design program can be

easily incorporated into the selection of VAV terminal units. The inputs and outputs for the program

enable VariTrane units to be selected based on the conditions you require. This makes selecting and

Concert Hall NC-22

Hospital Room NC-30

School Room NC-35

General Office NC-40

Cafeteria NC-45

Factory NC-65

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