Trane Performance Air Handlers Manual de instalación descargar pdf (Pagina 18)

18 CLCH-SVN05A-EN

Assembly and Installation

Ductwork Recommendations

Sound Attenuation

Noise is produced by unit supply fans, and exhaust fans. Supply fan noise is substantially

attenuated by the ductwork, provided it is properly constructed.

SMACNA recommendations for metal gauge thickness and installation should be followed

carefully. Lightly constructed ductwork can produce “oil canning”-a rapid in-and-out pulsating

motion of the duct walls-resulting in sound problems.

Note: If roof decking cannot be placed under the unit, an acoustical barrier can be installed.

Corrugated steel decking is acoustically ideal for the installation of the roof curb and connecting

ductwork. Closely toleranced holes must be cut in the roof deck for the supply and return ductwork.

When the duct is installed, caulking must be used to seal the decking to the duct. Even a small air

leak between the duct and the deck will destroy most of the attenuation available from the steel

decking.

In addition, special consideration may be required to ensure that the weight of the unit does not

crush the roof deck at those points where the deck is between the curb and support joist. Poured

insulation will usually add the required strength, while the use of rigid insulation may require

placement of three-inch support channels on the decking.

As a general rule, exhaust fan noise is not a problem and can be adequately attenuated by the

return ductwork. For critical applications where return ductwork is not required, however,

installation of an acoustically-lined “return T” is recommended; see Figure 21.

Supply and Return Air Ductwork

Ductwork for all units must be fabricated and installed by the installing contractor; to ensure proper

duct construction and installation, SMACNA recommendations should be closely followed.

Below are several typically used guidelines for ductwork construction:

• Elbows with turning vanes or splitters are recommended to minimize air noise and resistance.

Figure 21. Typical supply and return ductwork

Coil

space

Vertical

discharge

3 fan

diameters

Return

air

Use lined duct for all returns (1-inch thick, 6-pound density fiberglass recommended).

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Trane Performance Air Handlers Manual de instalación Pagina 18