Ductwork Accessories | HVAC Ductwork Design

Ductwork Accessories | HVAC Ductwork Design

7.1     Access Doors

7.1.1    Access doors shall be provided where indicated on the drawings and where access is necessary for cleaning, service or inspection.

7.1.2    Rigid and close-fitting doors shall be fabricated of galvanized steel with sealing gaskets and quick fastening locking devices. Access doors shall be airtight and suitable for duct pressure class. For insulated ductwork, a minimum 25 mm thick insulation shall be installed, “K” value at 24° C of 0.42 W/(m2·K), with sheet metal cover.

7.1.3    Access doors shall be provided with two hinges and two sash locks for sizes up to 460 mm square, two hinges and two compression latches with outside and inside handles for sizes up to 610 mm x 1220 mm. An additional hinge shall be provided for larger sizes.

7.1.4    Access doors shall be provided in duct work at each damper. Fire, smoke and combination fire smoke dampers access doors shall be combination access, viewing window, and pressure relief type and shall be installed downstream from dampers.

7.2     Fire and Smoke Dampers

7.2.1    Fire and Smoke dampers shall be installed as per IBC and NFPA 90A requirements.

7.2.2    Fire and Smoke dampers shall be integrally hinged folding curtain type with folded curtain in pocket out of duct size air stream. Fire dampers shall be UL labeled and constructed in accordance with UL Standard 555, and shall conform to NFPA 90A.

7.2.3    Fire and Smoke dampers shall be installed in accordance with SMACNA – Fire, Smoke and Radiation Damper Installation Guide for HVAC Systems.

7.2.4    Electronic type fusible links shall be set or selected for 71°C release.Fusible links on fire dampers shall be constructed to UL Standard 33.

7.2.5    Position indication: Visual indicator type

7.2.6    Fire Dampers: Fire dampers shall be UL listed and labeled as a unit; conform with NFPA 90A; minimum 0.85 mm thick vertically stacked steel blades with interlocking joints; Fusible links shall have a temperature rating approximately 28°C (50°F) above the maximum temperature that normally is encountered when the system is in operation or shut down; Fusible links shall have a temperature rating not less than 71°C (160°F), minimum 0.85 mm thick one piece roll-formed galvanized steel frame of all welded construction.

7.2.7    Combination Fire and Smoke Dampers: Combination fire and smoke dampers shall have UL listed and labeled fire damper; minimum 0.92 mm thick steel vertically stacked blades with rolled edge; 60 mm blade width; electrically operated smoke release; fusible link set for 71 degree C; stainless steel spring; 38 mm x 38 mm steel sleeve and having a rust inhibitor coating.

7.2.8    Re-setting of fire dampers shall be demonstrated to a representative and authorities having jurisdiction.

7.3     Volume Dampers

7.3.1    Dampers shall be provided at each point as required, indicated on the drawings, or both for supply, return, exhaust or fresh air duct systems to ensure a balanced system.

7.3.2    Damper frames shall be minimum 1.0 mm thick, galvanized steel. Blade axles shall be either 13 mm or 19 mm stainless steel with stainless steel bearings. Linkage shall be stainless steel. Sleeve bearing for linkage shall be stainless steel. Blade shall be of galvanized or stainless steel construction (dependent on duct material) and shall carry blade seals. ; complete with key operated regulator having dial indications. Regulators on insulated ducts shall have raised base to depth of insulation.

7.3.3    Dampers, including motorized and isolation dampers shall be furnished with position indicators.

7.4     Blast Damper

7.4.1    Blast dampers shall be provided where indicated on the drawings to resist the impact of a blast occurrence. The blast dampers shall meet the following minimum design criteria:

7.4.2    The valve blocks shall be suitable for mounting in type of wall in which it will be installed (i.e. cast in place concrete, concrete block, pre-cast concrete).

7.4.3    Each valve shall close the air passage in response to the positive and negative phase of the blast.

7.4.4    Valves shall be designed to withstand multiple blast loadings having a specified peak reflective overpressure with unrestricted duration.

7.4.5    Valves shall be completely corrosion resistant.

7.5     Flexible Connections

7.5.1    Flexible duct connections shall be UL listed neoprene coated double glass fabric.

7.5.2    Connections exposed to weather or other moisture conditions shall have a rubber exterior finished.

7.5.3    Fabric shall be glass cloth with a minimum weight of 880 g/m2 double coated with polychloroprene for indoor use. Fabric shall be glass cloth with a minimum weight of 880 g/m2 double coated with a synthetic rubber, weatherproof coating resistant to the sun’s ultraviolet rays for outdoor use.

7.5.4    Fabric shall be fire retardant, non-combustible and UL Listed. Provide a minimum of 100 mm clearance between metal.

7.6     Flexible Duct

7.6.1    For exposed ceiling (no acoustic ceiling) flexible duct shall not be used.

7.6.2    Flexible duct shall be factory pre-insulated as per ASHRAE 90.1 minimum requirements with a double lamination of tough polyester encapsulating a steel wire helix for the core and insulated with 38 mm thick fiberglass insulation.

7.6.3    Insulation shall have an outer and inner jacket of polyethylene film.

7.6.4    Branch take-offs of flex duct shall be twist-in conical spin-in fittings with 45° extractor and volume damper with locking quadrant.

7.6.5    Flexible duct shall be UL 181, Class 1 air duct.

7.6.6    Maximum length of 2400mm

7.7     Turning Vanes:

7.7.1    Turning vanes shall be double thickness. Single thickness turning vanes shall not be acceptable.

7.7.2    Constructed in compliance with SMACNA Standards Figure 2-3.

7.8     Backdraft Dampers

7.8.1    Frame constructed of  minimum 2.3 mm extruded aluminum channel with front flange and mitered corners

7.8.2    Blades:

a. Style: Single-piece, overlap frame.

b.    Action: Parallel.

c. Orientation: Horizontal.

d. Material: Minimum 0.6 mm 6063-T5 formed aluminum.

e.    Width: Maximum 152 mm.

7.8.3    Bearings: Corrosion-resistant, long-life, synthetic, formed as single piece with axles.

7.8.4    Blade Seals: Extruded vinyl, mechanically attached to blade edge.

7.8.5    Linkage: Concealed in frame.

7.8.6    Axles: Corrosion-resistant, long-life, synthetic, locked to blade and formed as single piece with bearings.

7.8.7    Finish: Mill aluminum.

7.8.8    Actuator:

1. Electric
2. Fail Position: Open
3. Mounting: External side-plate

7.8.9    Duct Transition Connection: Rectangular.

7.8.10  Factory Sleeve: Minimum 20 gage (1.0 mm) thickness, minimum 152 mm length.

7.8.11  Testing in accordance with AMCA 500.D

7.9     Gravity Ventilators

7.9.1    The hood shall be construction of minimum 18 gauge aluminum bolted to 8 gauge support structure.

7.9.2    Provided with lifting lugs.

7.9.3    Rain gutter shall be provided

7.9.4    Bird screen constructed of 12.5 mm galvanized mesh mounted on hood.