Material Galvanized steel Polyurethane and Phenolic Fiberglass duct

Material • • • Galvanized steel Polyurethane and Phenolic Fiberglass duct Flexible tubing Fabric Ducts

• Residential – Supply ducts may be steel or aluminum

• Commercial – NFPA Standard 90 A states that ducts must be iron, steel, aluminum, concrete, masonry, or clay tile. – Galvanized steel, uncoated carbon steel, or aluminum are the most frequently used for industrial air handling

Type of Duct Rectangular duct Round duct Flexible duct

• Duct that located outside of the building must be: – Waterproofing – Resistance to external loads (wind, snow, and ice) – Degradation from corrosion, ultraviolet radiation, or thermal cycles – Heat transfer – Susceptibility to physical damage – Hazards at air inlets and discharges – Maintenance needs

Example ducting system outdoor-air inlet flexible sheet-metal supply duct VAV terminal return-air central inlet air handler diffuser

Fittings for duct

Round duct fittings Elbow 90° Elbow 45°

Transition (round to round) Fire Damper Transition (round to rectangular)

Wye (‘Y’) 45° converging Wye (‘Y’) 60° converging

Wye (‘Y’) 45° diverging

Tee (‘T’) diverging

Cross diverging

Rectangular duct fitting Elbow

Elhow 90° Single-Thickness Vanes

Damper parallel blade Damper opposed blade

Fire Damper

Transition Tee Wye

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