STANDARD FOR INSTALLATION OF FACTORY-MADE AIR DUCTS Sealing of fibrous glass duct board to the sheet metal sleeve must be made with glass fabric and mastic, except where operating pressure is less than one (1) inch W.G. (249 Pa) and the sheet metal surfaces are carefully cleaned, in that case pressuresensitive aluminum foil tape may be used. See Section 6.503 for methods. A.6.506 Hangers and Supports (A) General. Fibrous glass ducts are light in weight, so that they can be supported with a minimum of hangers if care is taken as to placement of the supports. The charts and examples illustrated in this section show that the hanger treatment and spacing required is dependent on duct dimensions. Trapeze-style channels, suspended by twelve (12) gauge (2.8 mm) (minimum) hanger wire (see Figure 6-5-25) are the preferred method of support. Channel gauge and profile vary with duct size, but in no case should the supporting channel be less than two (2) inches (51 mm) wide. Channels may also be suspended by means of metal rods of one (1) inch-wide (25.4 mm) (minimum) galvanized steel straps. When channel reinforcement members occur within maximum hanger spacing as shown in Table No. 6-5-5, sheet metal straps may be bolted to the channel reinforcement as shown in Figure No. 6-5-26. Support may also be made with twelve (12) gauge (2.8 mm) (minimum) wire. (B) Hanger Design. Occasionally, hanger channels must be extended considerably beyond the duct sides so that the supports will clear other obstructions. The total extension (E + E ) of the supports beyond the duct sides (see Figure 6-5-27), governs the minimum dimensions (see Table 6-5-6) of the channel. TABLE 6-5-5 Original Reinforcement Location Door Door * Spacing Per Schedule Window Type Sash Lock Gasket 4" (102 mm) 1 Gasket Female Shiplap FIGURE 6-5-22 Access Door Location Interfering with Reinforcement DETAIL G Window-Type Sash Lock, Flanged Door #10 x 1-1/4" Sheet Metal Screws and 2-1/2" Square Washers, 12" (Max.) O.C., to attach duct board to sheet metal sleeve Maximum Hanger Duct Size, Inches Spacing, Feet (x 25.4 for mm) (x 304.8 for mm) 48" wide or greater 4 Less than 48" wide and less than 12" deep 6 Width between 24" and 48" and greater than 24" deep 6 Less than 48" wide and depth between 12" and 24" 8 Width 24" or less and depth greater than 12" 8 Closure APPENDIX A, UMC STANDARD 6-5 Fire Damper Sheet Metal Sleeve Through Fire Wall as specified in fire damper manufacturer's instructions Closure 1-1/2" (Nom.) FIGURE 6-5-24 Attachment to Fire Damper Sleeves TABLE 6-5-6 Channel Selection If Total Extension is Min. Channel Min. Channel Not Greater than: Gauge Profile 6" 24 3" x 1.5" 18" 22 3" x 2" 30" 18 3" x 2" 347
APPENDIX A, UMC STANDARD 6-5 UNIFORM MECHANICAL CODE Gasket Framing Access Door Opening: #10 x 1-1/4" Sheet Metal Screws and 2-1/2" Square Washers 6" O.C. Duct Wall Door 1" x 1" x 3", 22 Gage (0.030 in) (0.76 mm) U-Channel Framing Around Door Opening Framing Access Door: 1" x 1" x 1", 22 Gage (0.030 in) (0.76 mm) Z-Channel Framing Around Access Door 1" x 2", 22 Gage Framing, Spot Welded or Pop Riveted to Z-Channel 6" (Max.) O.C. to Secure Fibrous Glass Duct Board Fibrous Glass Duct Board Door Fastened to Opening Framing with #10 Sheet Metal Screws, 6" (Max.) O.C., Min. 2 Per Side FIGURE 6-5-23 Duct Opening Frame (C) Spacing. Hanger spacing per Table 6-5-5 or Figure 6-5-28 is based upon three (3) inch (76 mm) -wide (minimum) channels. For ducts not over forty-eight (48) inches wide by twenty-four (24) inches high (1219 mm by 610 mm), two (2) inch wide by 1-1/2 inch channels (51 mm by 38 mm), spaced not more than four (4) feet (1219 mm) apart may be installed. The total extension of the hanger supports shall not exceed six (6) inches (152 mm). Hanger design and spacing for fibrous glass ducts is based upon extensive testing with loads exceeding twice the duct weight located between supports to assure the integrity of the duct system. Recommended hanger spacing is shown in Figure 6-5-28. Caution should be taken with other types of hanger systems to assure that excessive stress is not placed on the hanger or the fibrous glass duct system. (D) Fittings. Proper support of duct fittings may require that additional hangers be installed. For an elbow, hangers should be on each leg, within twelve (12) inches (305 mm) of the throat. If the width of the duct is greater than eighteen (18) inches (457 mm), an additional hanger must be installed (see Figure 6-5-29) so that it is approximately two-thirds of the diagonal distance from throat to heel. Tees require support on the trunk as shown in Figure 6-5-30. If a tee runout hanger falls where the trunk duct is located, add hangers on either side of trunk. Do not exceed maximum hanger spacing. Branch ducts are treated in a similar manner with hanger spacing on the trunk duct in accordance with Figure 6-5-28. For diffuser drops, hangers are installed within three (3) inches (76 mm) of each side of the drop. The connection of the drop to the duct is reinforced in accordance with Figure 6-5-31. If the drop assembly, including the diffuser, weighs more than twenty-five (25) pounds (11.3 kg), the diffuser must be separately supported. (E) Hanging Rigid Round Duct. Preformed round fibrous glass duct should be hung so the hanger will not damage the duct facing. Straps or saddles in contact with the duct must be not less than 5/8 inch (15.9 mm) wide. Avoid sharp edges and burrs. Space hangers at a maximum of six (6) feet (1829 mm) on center. Where practical, hangers should be located at circumferential joints. Provide hanger support at all fittings. Part B Flexible Ducts A.6.507 Suitable Installations (A) General (1) The routing and length of flexible duct, the number of bends, the number of degrees of each 348
STANDARD FOR INSTALLATION OF FACTORY-MADE AIR DUCTS APPENDIX A, UMC STANDARD 6-5 Hanger Wire, 12 Gauge (2.8 mm) (Min.) or Hanger Rod Channel (See Table No. 6-5-6 for sheet metal gage and dimensions.) FIGURE 6-5-25 Attachment to Fire Damper Sleeves Hanger Strap, 1" (25.4 mm) Wide (min.) 6" (152 mm) max. E Total Hanger Extension (E + E') See Table No. 6-5-6 FIGURE 6-5-27 Hanger Spacing and Extension Using 3-Inch (76 mm) Wide Channels No. Channel Reinforcement FIGURE 6-5-26 Hanging from Channel Reinforcement bend and the amount of sag allowed between support joints will have serious effects on system performance due to the increased resistance each introduces. Use the minimum length of flexible duct to make connections. It is not recommended that excess lengths of ducts be installed to allow for possible future relocations of air terminal devices. (2) Avoid installations where exposure to direct E' Maximum Hanger Spacing See Table 6-5-5 3" (76 mm) or indirect sunlight can occur, e.g., turbine vents, skylights, canopy windows, etc. Prolonged exposure to sunlight will cause degradation of the vapor barrier. Direct exposure to UV light from a source lamp installed within the HVAC system will cause degradation of some inner core/liner materials. (3) Terminal devices shall be supported independently of the flexible duct. (4) Repair torn or damaged vapor barrier jackets with approved duct tape listed and labeled to Standard UL 181B. If the internal core is penetrated, replace the flexible duct or treat it as a connection. (B) Installation (1) Install duct fully extended. Do not install in the compressed state or use excess lengths. This will noticeably increase friction losses. (2) Avoid bending ducts across sharp corners or placing in incidental contact with metal fixtures, pipes, or conduits. The radius at the centerline shall not be less than one duct diameter. (3) Do not install near hot equipment (e.g., furnaces, boilers, steam pipes, etc.) that is above the recommended flexible duct use temperature. A.6.508 Connecting, Joining, and Splicing Flexible Duct (1) All connections, joints, and splices shall be made in accordance with the manufacturer s installation instructions. (2) Unless specified by the manufacturer, adhesives are not recommended for use with nonmetallic flexible duct as they will chemically 349
APPENDIX A, UMC STANDARD 6-5 UNIFORM MECHANICAL CODE in. x 25.4 = mm ft.. x 304.8 = mm Duct Width, Inside (Inches) 48 44 40 36 32 28 24 20 16 12 8 4 0 8 ft. Max. 2/3 of the diagonal distance from throat to heel (approx.) 6 ft. Max. 6 ft. Max. 4 ft. Max. 8 16 24 32 40 48 56 64 72 80 88 96 Duct Width, Inside (Inches) Figure 6-5-28 Minimum Hanger Spacing, Straight Duct, 3 Inch Wide (76 mm) Channel 45 (.79 rad) Required only when duct is greater than 18" (457 mm) in width 12" (305 mm) Max. FIGURE 6-5-29 Elbow Support 350
STANDARD FOR INSTALLATION OF FACTORY-MADE AIR DUCTS APPENDIX A, UMC STANDARD 6-5 Run-Out Do Not Exceed Standard Hanger Spacing per Tables Nos. 6-5-5 and 6-5-6 Trunk FIGURE 6-5-30 Tee Support Run-Out 12" Max (304.8 mm) react with the duct materials, causing deterioration and degradation. Tapes, mastics, and non-metallic clamps used with flexible air ducts shall be listed and labeled to Standard UL 181B. (3) Sheet metal collars fittings to that the which the flexible ducts with plain ends are attached shall be beaded and have a minimum of two (2) inches (51 mm) in collar length. Beads are optional for fittings when attaching metallic flexible ducts. (4) Sheet metal sleeves used for joining two sections of flexible duct shall be a minimum of four (4) inches (102 mm) in length and beaded on each end. Beads are optional for sleeves when joining metallic flexible ducts. (5) Flexible ducts secured with non-metallic clamps shall be limited to six (6) inches w.g. (1500 Pa) positive pressure. Installation Instructions for Nonmetallic Air Ducts with Plain Ends (A) Connections (1) After the desired length is determined, cut completely around and through duct with a knife. Cut the wire with snips or side cutters. (2) Pull back the jacket and insulation from the core. Slide at least one (1) inch (25.4 mm) of core over collar, pipe, or fitting. Tape with at least two wraps of approved duct tape. Secure with approved clamp. (3) Pull the jacket and insulation back over the cores. Tape the jackets together with two wraps of approved duct tape. (B) Splices. (1) Peel back the jacket and insulation from the core. Butt the two cores together on a minimum four (4) inch wide (102 mm) collar. 3" x 3" (76 mm x 76 mm) Angle Tap Diffuser Sheet Metal Angle Brackets, 3" x 3" (76 mm x 76 mm), 22 Gage (0.030 in) (0.76 mm) to Attach Diffuser Drop to Trunk Duct #10 x 1-1/4" (32 mm) Sheet Metal Screws and 2-1/2" (64 mm) Square Steel Washers, Min. 2 Per Side, 12" (305 mm) (Max.) O.C. Fibrous Trunk Duct Glass Drop Screws Diffuser or Grille Washers FIGURE 6-5-31 Diffuser Connection Wire, 12 Gauge (2.1 mm) 5/8" (16 mm) (min.), 26 gage (0.019 in) (0.48 mm) Hangers to Support Weight of Diffuser 3" (76 mm) (Max.) Both Sides of Drop FIGURE 6-5-32 Hanging Round Duct with Saddle and 12 Gauge Wires D 1 x D RIGHT WRONG FIGURE 6-5-33 Extend Duct Fully Steam Pipes FIGURE 6-5-34 Wrong Method of Support 351
APPENDIX A, UMC STANDARD 6-5 UNIFORM MECHANICAL CODE FIGURE 6-5-35A End Connectors FIGURE 6-5-35B FIGURE 6-5-36B FIGURE 6-5-35C FIGURE 6-5-36A FIGURE 6-5-36C 352
STANDARD FOR INSTALLATION OF FACTORY-MADE AIR DUCTS Connections 1. After desired length is determined, cut completely around and through duct with knife or scissors. Cut wire with wire cutters. Fold back jacket and insulation. 2. Slide at least 1 (25 mm) of core over fitting and past the bead. Seal core to collar with at least 2 wraps of duct tape. Secure connetion with clamp placed over the core and tape and past the bead. 3. Pull jacket and insulation back over core. Tape jacket with at least 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape. Splices APPENDIX A, UMC STANDARD 6-5 1. Fold back jacket and insulation from core. Butt two cores together on a 4'' (100mm) length metal sleeve. 2. Tape cores together with at least 2 wraps of duct tape. Secure connection with 2 clamps placed over the taped core ends and past the beads. 3. Pull jacket and insulation back over cores. Tape jackets together with at least 2 wraps of duct tape. Note: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use beaded sheet metal fittings and sleeves. 3. Use tapes listed and labeled in accordance with Standard UL 181B and marked 181B-FX. 4. Nonmetallic clamps shall be listed and labeled in accordance with Standard UL 181B and marked 181B- C. Use of nonmetallic clamps shall be limited to 6 in. w.g. (1500 Pa) positive pressure. 353
APPENDIX A, UMC STANDARD 6-5 UNIFORM MECHANICAL CODE Alternate Installation Instructions for Air Ducts and Air Connectors Nonmetallic with Plain Ends Connections and Splices Step 1: After desired length is determined, cut completely around and through duct with knife or scissors. Cut wire with wire cutters. Pull back jacket and insulation from core. Step 2: Apply mastic approximately 2'' (50 mm) wide uniformly around the collar of the metal fitting or over the ends of a 4'' (100 mm) metal sleeve. Reference data on mastic container for application rate, application thickness, cure times and handling information. Step 3: Slide at least 2'' (50 mm) of core over the fitting or sleeve ends and past the bead. Step 4: Secure core to collar with a clamp applied past the bead. Secure cores to sleeve ends with 2 clamps applied past the beads. Step 5: Pull jacket and insulation back over core ends. Tape jacket(s) with at least 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape. Notes: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use beaded sheet metal fittings and sleeves. 3. Use mastics listed and labeled in accordance with Standard UL 181B and marked 181B-M on container. 4. Use tapes listed and labeled in accordance with Standard UL 181B and marked 181B-FX. 5. Nonmetallic clamps shall be listed and labeled in accordance with standard UL 181B and marked 181B- C. Use of nonmetallic clamps shall be limited to 6 in. w.g. (1500 Pa) positive pressure. 354
STANDARD FOR INSTALLATION OF APPENDIX A, UMC STANDARD 6-5 FACTORY-MADE AIR DUCTS Installation Instruction for Air Ducts and Air Connectors Metallic with Plain Ends Connections and Splices 1. After cutting duct to desired length, fold back jacket and insulation exposing core. Trim core ends squarely using suitable metal shears. Determine optional sealing method (step 2 or 5) before proceeding. 2. When mastics are required and for pressure 4'' w.g. (1000 Pa) and over, seal joint with mastic applied uniformly to the outside surface of collar/sleeve. (Disregard this step when not using mastics and proceed to step 3). 3. Slide at least 1'' (25mm) of core over metal collar for attaching duct to take off or over ends of a 4'' (100 mm) metal sleeve for splicing 2 lengths of duct. 4. Secure to collar/sleeve using #8 sheet metal screws spaced equally around circumference. Use 3 screws for diameters under 12'' (300mm) and 5 screws for diameters 12'' (300mm) and over. 5. For pressure under 4'' w.g. (1000 Pa) seal joint using 2 wraps of duct tape applied over screw heads and spirally lapping tape to collar/sleeve. (Disregard this step when using mastics per Step 2). 6. Pull jacket and insulation back over core. Tape jacket with 2 wraps of duct tape. A clamp may be used in place of or in combination with the duct tape. Notes: 1. For uninsulated air ducts and air connectors, disregard references to insulation and jacket. 2. Use mastics listed and labeled to Standard UL 181B and marked 181B-M on container. 3. Use tapes listed and labeled to Standard UL 181B and marked 181B-FX. 4. Nonmetallic clamps shall be listed and labeled in accordance with Standard UL 181B and marked 181B-C. 355
APPENDIX A, UMC STANDARD 6-5 UNIFORM MECHANICAL CODE FIGURE 6-5-37 Ceiling Joists 6' (1829 mm) Max. 4'-0" (1219 mm) Max. Sag 1/2" Per Foot (42 mm/m) of Support Spacing 1-1/2" (38 mm) Min. FIGURE 6-5-38 Proper Support Wire Wire 1-1/2" (38 mm) Min. (2) Tape together with at least two wraps of approved duct tape. Secure with two approved clamps. (3) Pull the jacket and insulation back over the cores. Tape the jackets together with two wraps of approved duct tape. Notes: (a) For uninsulated duct/connector, disregard reference to insulation and jacket. (b) See manufacturer s installation instructions for approved tapes and clamps. (c) Use beaded fittings for pressures exceeding four (4) inches W.G. (995 Pa) and for diameters twelve (12) inches (305 mm) and larger. A.6.509 Supporting Flexible Duct (A) Flexible duct shall be supported at manufacturer s recommended intervals, but at no greater distance than four (4) five (5) feet (1219 1524mm). Maximum permissible sag is 1/2 inch per foot (42 mm/m) of spacing between supports. A connection to rigid ducting or equipment shall be considered a support joint. Long horizontal duct runs with sharp bends shall have additional supports before and after the bend approximately one duct diameter distance from the centerline of the bend. (B) Hanger or saddle material in contact with the flexible duct shall be of sufficient width to prevent any restriction of the internal diameter of the duct when the weight of the supported section rests on the hanger or saddle material. In no case will the material contacting the flexible duct be less than 1-1/2 inches (38 mm) wide. (C) Factory-installed suspension systems integral to the flexible duct are an acceptable alternative hanging method when manufacturer s recommended procedures are followed. (D) Flexible ducts may rest on ceiling joists or truss supports. Maximum spacing between supports shall not exceed the maximum spacing per manufacturer s installation instructions. (E) Support the duct between a metal connection and a bend by allowing the duct to extend straight for a few inches before making the bend. This will avoid possible damage of the flexible duct by the edge of the sheet metal collar. (F) Vertically installed duct shall be stabilized by support straps at a maximum of six (6) feet (1829 mm) on center. Note: Factory-made air ducts may not be used for vertical risers in air duct systems serving more than two stories. See Section 604.2 of this code. 356
STANDARD FOR INSTALLATION OF FACTORY-MADE AIR DUCTS A.6.510 Checklist The following checklist is provided for the benefit of the inspector, as well as the installer. It is designed so that the correct answer to all questions is yes. General Yes No Product Have all tears or punctures to facing material been repaired using the proper technique? ( ) ( ) Are all sheet metal accessory items galvanized? ( ) ( ) Is the UL label present? (Although ( ) ( ) each board is labeled, each section may not be, since there is only one label per sheet.) Fabrication and Installation When metal parts are attached, are 2-1/2 inch (64 mm) minimum square steel washers used on 16-inch (406 mm) maximum centers? ( ) ( ) When staples cannot be used, are 8 inch (203 mm) cross-tabs of approved closure being used in place of staples? APPENDIX A, UMC STANDARD 6-5 Are tab spacing requirements 12 inches, (305 mm) on center minimum one per side. ( ) ( ) Are all system joints tight, free from bulges, with taped joints showing good workmanship? ( ) ( ) Have offsets been installed so duct sections are not forced to bend around obstructions? ( ) ( ) Fire Dampers See Section A. 6.505 Yes No Is sheet metal sleeve present? Is duct properly attached to sleeve with screws and washers 16 inches (406 mm) on center? (Fibrous glass ducts must not penetrate assemblies required to have a fire damper.) ( ) ( ) Access Doors Is installation in accordance with Section A. 6.504(E)6? ( ) ( ) Grills, Diffusers, Registers See Section A. 6.506 Is the extra weight of the item being separately supported and not dependent on the duct alone for support? (Exception: Registers not greater than 150 square inches (96.7 x 103 mm2) in area may be attached to the duct with metal channel, without other support.) ( ) ( ) Connection to Units Are sheet metal screws and washers used to secure the duct system to flange extensions? (Securing the duct to the unit flange without mechanical fasteners is sufficient.) ( ) ( ) Closures See Section A. 6.503 Are all joints in the system properly sealed? ( ) ( ) Are closure materials for rigid duct systems of a listed type as evidenced by presence of UL instruction sheet in duct board carton or imprinted UL 181A on the tape? ( ) ( ) 356A
APPENDIX A, UMC STANDARD 6-5 UNIFORM MECHANICAL CODE Yes No Yes No Are closure materials for flexible duct systems of a listed type as evidenced by presence of UL instruction sheet in the duct carton and imprinted UL 181B on the tape, mastic, and nonmetallic clamps? Are there staples or cross-tabs, properly spaced, on circumferential joints? ( ) ( ) Are all pressure-sensitive tape closures rubbed down adequately, with staples or scrim infacing clearly visible through the tape? ( ) ( ) If heat-sealable tape closure was used, was it applied correctly, as evidenced by dot color change? ( ) ( ) If glass fabric and mastic are used, is the mesh of the glass fabric completely filled with mastic? ( ) ( ) Reinforcement See Section A. 6.504 Is the reinforcement system in accordance with Section A. 6.504? ( ) ( ) Is the tie rod spacing correct according to duct span, board type, and static pressure? ( ) ( ) Are tie rod washers 2-1/2 inches (64 mm) square? ( ) ( ) Do tie rod washers have turned edges facing away from duct board so they will not cut into it? ( ) ( ) Are anti-sag devices used on ducts 48 inch (1219 mm) span or greater to support top panel of ducts? ( ) ( ) Are heels of tees, elbows, and end caps reinforced (formed sheet metal channel, tie rod, or combination)? ( ) ( ) When formed sheet metal channel reinforcement is used, are sheet metal gauges, dimensions, and spacing correct? ( ) ( ) For return ducts, are sheet metal channel reinforcements attached to ducts with screws and 2-1/2 inch (64 mm) square washers or 2 inch by 6 inch (51 x 152 mm) clips? ( ) ( ) Hangers and Supports See Sections A. 6.506 and A. 6.509 Are hangers installed in accordance with Section 6.506? ( ) ( ) Are hanger designs in accordance with Table 6-5-6? ( ) ( ) Are accessories that add weight to the duct system separately supported so as not to stress the system? (See Section A. 6.506(4).) ( ) ( ) If formed sheet metal reinforcements are used as hangers, are attachments within 6 inches (152 mm) of duct sides? ( ) ( ) If tie rods reinforce a butt joint, are rods used on both sides of the butt joint?( ) ( ) Are all fittings supported by hangers? ( ) ( ) Is wire termination one of those documented in Section 6.504(B)? ( ) ( ) 356B