Uniform Mechanical Code- 2009 Appendix a 6-5

8/14/2019 Uniform Mechanical Code- 2009 Appendix a 6-5

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A.6.501 Scope.

These requirements are intended to supplementinformation contained in the manufacturer sinstallation instruction sheets included in each cartonof material, which cover fabrication, closuremethods, reinforcement, and hanging of factory-made rigid and flexible air ducts complying with UL181, Standard for Factory-Made Air Ducts and AirConnectors. The standard is divided into two parts:

Part A covering rigid ducts and Part B coveringflexible ducts.

Part A Rigid Ducts.

A.6.502 General.

The use of these ducts is governed by UMC Section602.1, together with the restrictions contained inSection 604.2. For information regarding thefabrication of rectangular ducts from flat sheets of duct board, refer to the document upon which thisstandard is based and the manufacturers instructionsheet.

A.6.503 Closure Systems.(A) General. Closure systems are a vital element in

the proper assembly of fibrous glass ductsystems. They provide both the structuralconnection and sealing of seams and joints forair tightness. Only listed closure systemsidentified in the manufacturers installationinstructions are suitable for use with rigidfibrous glass duct systems. Listed closuresinclude the following:(1) Pressure-sensitive aluminum foil tapes.

(2) Heat-activated aluminum foil/scrim tapes.(3) Mastic and glass fabric tape systems.Listed closure systems may be used on listedduct board materials.

(B) Surface Preparation. In order to obtainsatisfactory adhesion and bonding, the surfaceon which closures will be applied must be freefrom dust, dirt, oil, grease, moisture, and similarsubstances.

(C) Joint and Seam Preparation. Longitudinalseams are fabricated with a shiplap joint that isclosed with the use of outward-clinching staplesat two (2) inches (50 mm) on center through thestapling f lap of the jacketing material .Transverse joints between two duct sections areprepared by joining two duct sections, pullingthe staple flap over the adjoining section, andstapling as shown in Figure 6-5-1. When stapleflaps are not present, crosstabs are used to holdseams and joints in position for reinforcing theclosure system. Cross-tabs, made from eight (8)inch (203 mm) minimum lengths of closure tape,are to be equally spaced on each side of the joint.Cross-tabs are spaced on twelve (12) inch (305 mm)maximum centers, with at least one cross-tab perduct side (Figure 6-5-2). Cross-tabs may beplaced either under or over the closure tape.

(D) Application of Pressure-Sensitive AluminumFoil Tapes. Use minimum 2 -1/2 inchwide (64 mm)listed pressure-sensitive tape. Position the tapealong the edge of the flap in a manner that will

allow one (1) inch minimum (25 mm) overlap onadjacent surfaces.If tape has been stored at temperatures less

than 50F (10C), it should be conditioned priorto use by placement in a warm environment inorder to improve the initial tack.

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APPENDIX AUNIFORM MECHANICAL CODE STANDARD NO. 6-5

STANDARD FOR INSTALLATION OF FACTORY-MADE AIR DUCTS

Based on the 1989 Fibrous Glass Duct Construction Standards published by the Thermal InsulationManufacturers Association, and the Guidelines for installing Flexible Ducts published by the Air Diffusion

Council. See Section 602.3 of the Uniform Mechanical Code .

FIGURE 6-5-1 Tape Closure Joint with StapleFlap.


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If the duct board has been located in anatmosphere of less than 50F (10C), the surfacesto be taped must be preheated to ensure asatisfactory bond of the tape. Using any suitableheating iron with the plate temperature set at400F (+25F) (204C + 14C), preheat the area to be taped. Quickly position the tape on thepreheated area and press in place. Pass the irontwo or three times over the taped area using arapid ironing motion (see Figure 6-5-4).

Rub tape firmly with a plastic squeegee(Figure 6-5-3) until the facing reinforcementshows through the tape.

When operating pressure is less than one (1)inch W.G. (249 Pa) (positive pressure), and sheetmetal surfaces are cleaned in accordance withtape manufacturers instructions, pressure-sensitive tape may be used to seal fibrous glassduct to sheet metal.

UNIFORM MECHANICAL CODE

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APPENDIX A, UMC STANDARD 6-5

FIGURE 6-5-2 Tape Closure Joint Without StapleFlap.

FIGURE 6-5-3 Pressure-Sensitive Tape.

FIGURE 6-5-6 Glass Fabric into Mastic.

FIGURE 6-5-7 Second Coat of Mastic.

FIGURE 6-5-4 Heat-Activated Tape.


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(E) Application of Heat-Activated Tapes. Positionthe 2-1/2 inch (64 mm) minimum tape along theedge of the flap in a manner that will allow a one(1) inch minimum (25.4 mm) overlap on adjacentsurfaces. Using a suitable heating iron with aplate temperature between 550F and 600F

(287C and 316C), pass the iron along the tapeseam with sufficient pressure and dwell time toactivate the adhesive (see Figure No. 6-5-4). Asatisfactory bond has been achieved when theheat indicator dots have darkened.

Use a second pass of the iron to completethe bond by applying pressure to the front edgeof the iron in a smearing action.

Allow all joints and seams to cool below150F (65C) before any stress is applied. Avoidpuncturing the tape at staple locations withexcessive pressure from the iron.

(F) Application of Glass Fabric and Mastic TapeSystems. Apply a thin coat of mast icapproximately 3-1/2 inches (89 mm) wide overthe center of the joint seam. Firmly press thethree (3) inch (76 mm) wide glass fabric into themastic (see Figure 6-5-6).

Apply a second coat of mastic over the glassfabric, filling the scrim pattern as indicated inFigure 6-5-7.

Follow the manufacturers label instructionson application rate, safety precautions,ventilation requirements, shelf life limitations,and minimum setup time required before stresscan be applied to the joint or seam.

When connecting fibrous glass duct systemsto sheet metal, as in connections to flanges orcentral air equipment, fasteners such as sheetmetal screws and washers must be used to carrythe mechanical load. Glass fabric and mastic canthen be applied to seal the connections at thesepoints. Usually, two widths of glass fabric will be required.

A.6.504 Reinforcement.(A) General. Reinforcement is used to limit the

deflection of the duct surface caused by internalstat ic pressure loading. The maximumdimension of unreinforced ducts, which is afunction of the system operating pressure, isshown on the manufacturers label, affixed toeach piece of duct board.

Duct systems made from Types 475 and 800fibrous glass duct board may use one or more of the following reinforcement methods:

(1) Tie rod reinforcement.(2) Channel reinforcement.

The reinforcement schedules contained inTables 6-5-1, 6-5-2, and 6-5-4 are suitable for zero(0) inch to two (2) inch W.G. (0 Pa to 498 Pa)duct systems.

While some duct dimensions may notrequire any reinforcement in straight sections,certain fittings of the same dimension mayrequire reinforcement. This requirement is notedwherever applicable in this standard and inTab le 6 -5 -4 . F it ti ng r einforcement i saccomplished by the use of tie rods whereverpossible and with channel reinforcement appliedwhere tie rods cannot be used.

(B) Tie Rod ReinforcementPositive Pressure.(1) Tie Rods. Tie rods consist of straight lengthsof twelve (12) gauge (2 mm) galvanized steel

wire with flat steel volcano-type washers andany of three approved termination devices (seeFigure 6-5-8). The 2-1/2 inch (64 mm) squareshall be installed so turned edges face away fromthe duct board facing.

When butt joints are used instead of shiplap joints, tie rods are placed in rows located at three(3) inches (76 mm) on either side of the joint.

Alternate: A single tie rod reinforcementmay be used if the butt joint is glued with anadhesive system documented by the duct boardmanufacturer.

(2) Location. In relation to transverse joints, thetie rods are spaced four (4) inches (102 mm) fromthe end of the female joint, as shown in Figure6-5-9.(3) Spacing. Tie rods are placed in rows of two(2) to five (5) rods, across the face of the duct,with row spaces varying from sixteen (16) inchesto forty-eight (48) inches (406 mm to 1,219 mm);depending on duct size and operating pressure.

The spacing of tie rods is shown in Table 6-5-1.When the sides of the duct exceed the

dimensions that require reinforcement (see Table6-5-1), horizontal tie rods are also installed per the

schedule.(4) Typical Tie Rod Reinforcement Examples,Positive Pressure Ducts. See Section 6.504(B)2 forplacement of tie rods and sag supports in relationto joints. Sag support is required in ducts forty-eight (48) inches (1,219 mm) and greater in width.

The number of tie rods across the ductwidth shall be as required in the schedulecontained in Table No. 6-5-1.

STANDARD FOR INSTALLATION OFFACTORY-MADE AIR DUCTS


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FIGURE 6-5-8 Terminations: Fasloop Pop Rivet Sleeve Locking Cap.


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The longitudinal spacing of the rows of tierods is based upon the schedule in Table 6-5-10.This spacing will vary from forty-eight (48)inches (1,219 mm) on center to as close as sixteen(16) inches (406 mm) on center.(5) Sag ControlTie Rod ReinforcementShiplapped Joints. Top panels of fibrous glassduct sections or fittings, forty-eight (48) inches(1,219 mm) wide or greater, may sag due to theweight of the duct board when the system is notpressurized. To control this condition, sagsupports must be provided. Figure No. 6-5-11Ashows a typical installation.

Sag supports do not replace tie rod assembliesas called for in the reinforcement schedule, butmust be installed in addition to them. Hangersmust be located within twelve (12) inches (305mm) of the sag supports.

For easier mating of fittings and ductsections during installation, a 1/2 inch (12.7mm) diameter steel conduit and washers may beadded to an existing tie rod assembly at thefemale shiplap end.

When ducts are fabricated with butt joints,sag supports must be installed on both sides of the joint. A hanger must be installed withintwelve (12) inches (305 mm) of the sag support.

(C) Channel Reinforcement.(1) General. Another reinforcement system, foruse in either positive-or negative-pressure ductsystems, consists of formed sheet metal channelswrapped around the perimeter of the duct.

When channels must be attached to theduct, for sag control or negative-pressurereinforcement, No. 10 plated sheet metal screwsand 2-1/2 inch (64 mm) square, 0.020-inch (0.5mm) (minimum) thick sheet metal washers are



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FIGURE 6-5-8 continued.

FIGURE 6-5-9 Tie Rod Placement.

FIGURE 6-5-10 Tie Rod Reinforcement Rows onTwenty-four (24) Inch (610 mm) Centers, Forty-eight (48) Inch (1219 mm) Duct Section.

F IG UR E 6 -5 -11A S ag C on tr ol -Tie R odReinforcement.

FIGURE 6-5-11B Sag Control Detail.


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used. These must have turned edges to preventcutting into the duct board. In positive-pressureapplications, wraparound channels need not beattached to the duct board except when requiredfor sag control.

Table No. 6-5-2 gives longitudinal spacing,sheet metal gauge, channel height dimensions of reinforcement depending on the duct boardtype, maximum inside dimensions, and staticpressure. This is a minimum reinforcementschedule applying to straight sections. Thisschedule will also apply to fittings, but asimplified schedule may also be used (seeTable 6-5-3).

(2) Channels. Channels must be fabricatedfrom galvanized sheet metal of the gaugeshown in Table 6-5-2. Channels are three (3)inches (76 mm) wide, with a height (H) asshown in Table 6-5-2.

Each reinforcement may be fabricated froma continuous length of channel having three 90degree(1.57 rad) bends and a fourth 90 degree(1.57 rad) corner that is fastened with bolts,screws, rivets, spot welds, or staples. Reinforcementsmay also be fabricated with two (2), three (3), orfour (4) securely fastened corners.


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TABLE NO. 6-5-1Tie-Rod System Reinforcement Schedule (Positive Pressure Only)

*Straight ducts of these dimensions do not require reinforcement. However, some fittings of these dimensions may requirereinforcement.Notes : 1. Tie rods and washers must be no more than 16" (406 mm) on centers across duct dimension.

2. Ducts of 48" (1,219 mm) width and over require use of anti-sag devices. See Fig. 6-5-11A.3. For duct dimensions over 96" (2,438 mm), maintain tie rod spacing on 16" (406 mm) centers across the duct

dimension following longitudinal spacing for the design pressure.

Maximum Type 475 Board Type 800 BoardPositive InsideDuct No. Rods Maximum No. Rods No. Rods Maximum No. RodsStatic Dimension Across Longitudinal per 4 Ft. Across Longitudinal Per 4 Ft.Pressure Inches Dimension Spacing Section Dimension Spacing Section

(x248.8 forPa) (x 25.4 for mm) (x 25.4 for mm) (x 25.4 for mm)0 through 0-36 * *1/2" 37-42 2 24" 4 2 48" 2W.G. 43-48

49-60 3 6 3 361-64 24" 665-80 4 8 4 881-96 5 10 5 10

Over 1/2" 0-24 * *through 25-30 1 24" 2 1 48" 11" W.G. 31-32 24" 2

33-36 2 4 2 437-4849-64 3 6 3 665-80 4 8 4 881-96 5 10 5 10

Over 1" 0-15 * *through 16-18 1 24" 2 *2" W.G. 19-24 1 24" 1

25-32 16" 3 24" 233-48 2 6 2 449-60 3 9 3 6

61-64 16" 965-80 4 12 4 1281-96 5 15 5 15


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(3) Location of Channels. Channels arenormally offset four (4) inches (102 mm) from theend of the duct section to facilitate installation of sag supports and the closure system.

Where wraparound channels without sagsupport are used, the channel is slipped over theclosure tape after the tape is applied, centered overthe female shiplap end for maximum support.(4) Sag Support and Typical ChannelReinforcement. When the duct is forty-eight(48) inches (1219 mm) wide or greater, channelsare secured to the top for sag support with No.10 plated sheet metal screws and 2-1/2 inch (64mm) square washers (see Detail A in Figure 6-5-

12). The number of channels along the duct shall be in accordance with Table No. 6-5-2 .

(D) Negative-Pressure Channel Reinforcement.(1) Locating Reinforcing Channels. In

negative-pressure applications such as return-airducts, the channel reinforcement is applied overthe male shiplap. Special clips are installedinside the duct (see Figure 6-5-13) that willsupport both the male and female sides of theduct joint. The clips are fastened in place withtwo sheet metal screws.(2) Clips. Clips are formed from 20 gauge(0.036 inch) (0.91 mm) galvanized steel, withturned edges as shown in Detail B.



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TABLE NO. 6-5-2Channel System Reinforcement Schedule

*Straight ducts of these dimensions do notrequire reinforcement. However, some fittings of these dimensions may require reinforcement.Note: Ducts of 48" (1,219 mm) maximum width and over require use of anti-sagdevices.

Maximum Type 475 Board Type 800 Board

InsideDuct Maximum Channel H Maximum Channel HStatic Dimension longitudinal gauge dimension longitudinal gauge dimensionPressure (I.D.), in. spacing (see below) spacing (see below)(x248.8 for Pa) (x 25.4 for mm) (x 25.4 for mm) (x25.4 for mm)0 -

negative0-30 * *

1/2" 31-36 24" 22 1" 48" 22 1"W.G. positive 0-36 * *0 through 37-42 24" 22 1" 48" 22 1"1/2" W.G. 43-48positive or 49-60 1-1/2"negative 61-72 24" 1"

73-8485-96 1-1/4"

Over 1/2" 0-24 * *

through 1" 25-30 24" 22 1" 48" 22 1"W.G. 31-36 24"positive or 37-42negative 43-48

49-6061-72 18 1873-84 1-1/4" 1-1/4"85-96

Over 1" 0-15 * *through 2" 16-18 24" 22 1" *W.G. 19-24 24" 22 1"positive or 25-36 16"negative 37-48 1-1/4"

49-60

61-72 18 16" 18 1"73-84 1-1/4" 1-1/4"85-96 1-1/2" 1-1/2"

H

3"

Gauge asspecified


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FIGURE 6-5-12 16-Inch (406 mm) Centers, 48-Inch (1219 mm) Duct Sections.

FIGURE 6-5-13 Channel Reinforcement for Negative Pressure Systems.


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Clips are spaced not more than sixteen (16)inches (406 mm) apart and not more than sixteen(16) inches (406 mm) from the sides of a duct.The number of clips required is shown in Table6-5-3.

TABLE 6-5-3Detail BClip, Negative-Pressure Systems

Fastener Requirements, Negative PressureTransverse Minimum Number of Clips orDimension Washers per Reinforcing Member

in. x 25.4 = mm16" - 32" 133" - 48" 249" - 64" 365" - 80" 481" - 96" 5

Note: The foregoing arrangements are importantand, if not followed closely, may result in systemfailure.

(3) Additional Fasteners. When additionalchannels are required (as with twenty-four (24) inchand sixteen (16) inch [610 mm and 406 mm] spacing),they are attached to the duct with No. 10 platedsheet metal screws and 2-1/2 inch (64 mm) squarewashers (see Detail A of Figure No. 6-5-12).

The spacing of the fasteners through eachreinforcement channel is the same as for joint clips (seeTable 6-5-3). A typical layout for negative pressureductwork is shown in Figure 6-5-14 and Detail C.(E) Fitting ReinforcementPositive-PressureSystems.

(1) General. Fittings are reinforced with tie rodsor channels based upon the duct dimensionsusing the criteria found in Tables 6-5-1 and 6-5-2.

Some fittings, branches, tees, or offsets mayrequire reinforcement even though schedules forstraight ducts of the same dimension may showreinforcement is not required.(2) Partial Wraparound Reinforcement.Where reinforcement is required but cannot befastened to opposite sides of a duct section orfitting, it is necessary to install formed sheetmetal channels that partially wrap around afibrous glass duct system fitting at the requiredlocation. (See Table 6-5-2 for appropriate gaugeand profile.) In such cases, No. 10 by 1-1/4 inch(32 mm) plated sheet metal screws and 2-1/2inch (64 mm) square washers, 0.020 inch (0.51mm) (minimum) thick are used to attach theends of the channels to the duct board. (SeeDetail D and Table 6-5-4.)(3) Fitting Reinforcement90 Degree (1.57rad) Elbows. If neither dimension A nor B (see



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TABLE NO. 6-5-4Partial Wraparound Reinforcement Schedule

Type 475 Board Type 800 Board

Positive Maximum MaximumStatic Inside Duct Longi- Dimen- No. of Inside Duct Longi- Dimen- No. ofPressure Dimension, tudinal sion screws, Dimension, tudinal sion screws,

Inches spacing L each end Inches spacing L each end(x248.8forPa) (x 25.4 for mm) (x 25.4 for mm)

0" through 0-36 Not required 0-36 Not required1/2" W.G. 37-96 24" 4" 1 37-60 48" 4" 1

61-96 24"Over 1/2" 0-24 Not required 0-24 Not requiredthrough 1" 25-48 24" 4" 1 25-30 48" 4" 1W.G. 49-64 7" 2 31-48 24"

65-80 10" 3 49-64 7" 281-96 13" 4 65-80 10" 3

81-96 13" 4Over 1" 0-15 Not required 0-18 Not requiredthrough 2" 16-24 24" 4" 1 19-24 24" 4" 1W.G. 25-32 16" 25-32 7" 2

33-48 7" 2 33-48 10" 349-64 10" 3 49-60 13" 465-80 13" 4 61-64 16" 10" 381-96 16" 5 65-80 14"

81-96 16" 5


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Figure No. 6-5-16) is greater than the maximumunreinforced duct dimension (see Table 6-5-1), but diagonal X-Y is greater than the maximumunreinforced duct dimension in accordancewith Table 6-5-1, install tie-rod reinforcement atthe midspan of the diagonal at point No. 1 in

Figure 6-5-16.If either A or B is greater than the maximumunreinforced duct dimension:

Reinforce in accordance with Table 6-5-1.Reinforce four (4) inches (102 mm) upstreamfrom female shiplap joints.Reinforce at point No. 1 (Figure 6-5-16)where center lines intersect.

Note: Turning vanes in Figure No. 6-5-16 areomitted for clarity. Turning vanes do not replacereinforcement.

Heel and Throat Panels. If duct dimension H(see Figure 6-5-16) is less than the maximumunreinforced duct dimension from Table 6-5-1, but more than twenty-four (24) inches (610 mm),install sheet metal angle in accordance withDetail E below. (Angle may also be installed oninside of throat.)

When duct dimension H normally requiresreinforcing, install sheet metal angle as shown atNo. 2, Figure 6-5-17. Install tie rods through theangle on the upstream side, sixteen (16) inches(406 mm) on centers, in accordance with Table 6-5-1, with angle of length L from table below.

No. Tie Rods 1 2 3 4 5Angle Length L, inches 4 20 36 52 68

Ins ta ll three (3) inch (76 mm) channelreinforcement on heel panels as shown in Figure6-5-17, spaced in accordance with Table 6-5-4and fastened in accordance with Figure 6-5-15.Note: Attachment of angles is best done afterclosure is completed. This requires sections to beshort enough to allow the installer to reach

inside to install the 2-1/2 inch (64 mm) squarewashers.Note: For reinforcement of mitered elbows, referto reinforcement standards for offsets.

(4) Branch Connections (Tees). Many branches may require reinforcement eventhough schedules for straight ducts of the samedimensions may show reinforcement is notrequired.


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FIGURE 6-5-14 Channel Reinforcement onTwenty-four (24) Inch (610 mm) Centers, Forty-eight (48) Inch (1,219 mm) Duct Section.

FIGURE 6-5-15 Partial WraparoundReinforcement.

C


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Angled branches and positive takeoffs may be reinforced using the same methods as fortees. The amount and type of reinforcementdepend on the dimensions of the takeoff and thesystem pressure (see Table 6-5-1).

If H is not greater than sixteen (16) inches (406

mm) and W (see Figure No. 6-5-18) is greater thantwelve (12) inches (305 mm), install reinforcementin accordance with Detail E on the top of the branch where it intersects the trunk duct.

If H is greater than sixteen (16) inches (406mm) and W i s l es s t han the max imumunreinforced duct dimension, reinforce the sideof the branch as shown at No. 2, Figure 6-5-18.Note: The maximum unreinforced dimension isthirty-six (36) inches (914 mm) at 1/2 inch W.G.(124 Pa), twenty-four (24) inches (610 mm) at one(1) inch W.G. (249 Pa), and sixteen (16) inches(406 mm) at two (2) inches W.G (498 Pa).

If H (Figure 6-5-18) is greater than sixteen(16) inches (406 mm) and W is greater than themaximum unreinforced duct dimension (seeTable 6-5-1), install long angle cl ips inaccordance with tie rod reinforcement throughthe branch and trunk ducts (similar to Figure 6-5-17), as required by Table 6-5-1. A combinationof tie rods and partial wraparound reinforcement(see Figure 6-5-15) may be used.

If A (see Figure 6-5-19) is less than themaximum unreinforced duct dimension, butdiagonals X-Y or Y-Z exceed the maximum

allowable unreinforced duct dimension, installtie rods as shown at No. 2, four (4) inches (102mm) from female shiplaps.



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FIGURE 6-5-16 Tie Rod Reinforcement a tDiagonal X-YMidspan.

FIGURE 6-5-17 Sheet Metal Angle at Throat,Large 90-Degree (1.57 rad) Elbows.

FIGURE 6-5-18 Sheet Metal Angle Reinforcement Sides of Branch.


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I f A is greater than the maximumunreinforced duct dimension and B is greater thanone-half the maximum unreinforced ductdimension, install tie rods four (4) inches (102 mm)from female shiplap joints as shown at No. 2 andalso along branch centerlines and, additionally,spaced per Table 6-5-4 in the trunk duct.

Where a splitter damper interferes with tierod reinforcement, wraparound channels must be used in their place.Note: Turning vanes do not r ep lacereinforcement.(5) Offsets. Offsets require different types of reinforcement for the cheek panels (sides, asshown in Figure 6-5-20) and the heel and throatpanels (top and bottom, per Figure 6-5-21).

I f B i s g reat er t han the max imumunreinforced duct dimension and cheek panelshave shiplap joints, reinforce in accordance withNo. 1, four (4) inches (102 mm) from femaleshiplap (see Figure 6-5-20) with spacing inaccordance with Table 6-5-1.

If the fitting uses butt joints, install therequired spacing of tie rods three (3) inches (76mm) on each side of the butt joint.

Where Table 6-5-1 requires more than onerow of reinforcement, the rows shall be parallelto the edges of the duct, and the spacing between sets of tie rods shall be in accordancewith Table 6-5-1.

The reinforcement for heel and toe joints is

in accordance with Figure No. 6-5-21. Additionaltie rods may be installed by using a longer plateat the heel, and also in the duct panel, spaced inaccordance with Table No. 6-5-1.

The penetrat ions at the toe plate aregrouped as close to the break in the metal aspossible.

When dimension A requires more than onetie rod (see Table 6-5-1), sets of tie rods withmetal angles shall be installed in rows parallel tothe side of the duct.


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FIGURE 6-5-19 Tee ReinforcementNormal TieRod Locations.

FIGURE 6-5-20 Offset Reinforcement CheekPanels with Shiplap Joints.

FIGURE 6-5-21 Offset Reinforcement with SheetMetal Plates and Tie Rods.


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Transitions are reinforced in the samemanner with a tie rod extending from the flatside of the duct, through a plate or platespositioned on twelve (12), the heel joint of thefitting.(6) Access DoorsPositive Pressure. If theaccess door width is not greater than themaximum longitudinal reinforcement spacingf rom Tab le 6 -5 -1 , but i nt er fe re s withreinforcement locations required by the table,install tie rods four (4) inches (102 mm) from both sides of the door opening in accordancewith No . 1 , F igure 6 -5-22 . Max imumreinforcement spacing must be in accordancewith Table 6-5-1.

If access door height is greater than sixteen(16) inches (406 mm) and its width is greaterthan the maximum longitudinal reinforcementspacing shown in Table 6-5-1, install the framefor the access door inside the duct, securing it to

the duct wall with screws and washers (seeFigure 6-5-23).Install tie rods near the vertical sides of the

door frame (Figure 6-5-22) and also near the topand bottom sides of the frame, spaced asspecified in Table 6-5-1 with a minimum of onetie rod on each side of the frame.Note: Use channel reinforcement in place of tierods between access door and fire damperwhere tie rods would interfere with damperaccess or operation.

The duct door is fabricated from one (1) inch(25 mm) duct board installed with one (1) x one

(1) x one (1) inch (25 x 25 x 25 mm) twenty-two(22) gauge (0.76 mm) Z-channel framing aroundthe access door. Doors are gasketed and securedin place with sheet metal screws, or they may behinged with sash lock fasteners as shown inDetail G.

A.6.505 Fire Dampers.When fire dampers are required at penetrations of fire-rated walls, fibrous glass ducts must terminate ateither side of such walls. Fire dampers shall beins ta lled in accordance with the dampermanufacturers instructions and must be installed in

a steel sleeve. The opening in the wall shall be largeenough to allow for thermal expansion of the sleeveand to permit installation of 5/8 inch (16 mm)gypsum board between the sleeve and framing.

The sleeve must extend not less than three (3)inches (76 mm) beyond the face of the wall so thatthe duct can be slipped onto the sleeve. The duct issecured to the sleeve with screws and washers, asshown in Figure 6-5-24.

Sealing of fibrous glass duct board to the sheetmetal sleeve must be made with glass fabric andmastic, except where operating pressure is less thanone (1) inch W.G. (249 Pa) and the sheet metal

surfaces are carefully cleaned, in that case pressure-sensitive aluminum foil tape may be used. SeeSection 6.503 for methods.



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FIGURE 6-5-22 Access Door Location Interferingwith Reinforcement.

DETAIL G Window-Type Sash Lock, FlangedDoor

FIGURE 6-5-24 Attachment to Fire DamperSleeves.


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A.6.506 Hangers and Supports.(A) General. Fibrous glassducts are light in weight, so

that they can be supported with a minimum of hangers if care is taken as to placement of thesupports.

The charts and examples illustrated in thissection show that the hanger treatment andspacing required is dependent on ductdimensions. Trapeze-style channels, suspended by twelve (12) gauge (2.8 mm) (minimum)hanger wire (see Figure 6-5-25), are the preferredmethod of support. Channel gauge and profilevary with duct size, but in no case should thesupporting 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 mm) (minimum) galvanized steel straps.

When channel reinforcement membersoccur within maximum hanger spacing asshown in Table No. 6-5-5, sheet metal strapsmay be bolted to the channel reinforcement as

shown in Figure No. 6-5-26. Support may also bemade with twelve (12) gauge (2.8 mm)(minimum) wire.

(B) Hanger Design. Occasionally, hanger channelsmust be extended considerably beyond the ductsides so that the supports will clear otherobstructions. The total extension (E + E) of thesupports 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

Maximum HangerDuct Size, Inches Spacing, Feet

(x 25.4 for mm) (x 304.8 for mm)

48" wide or greater 4Less than 48" wide and less than

12" deep 6Width between 24" and 48" and

greater than 24" deep 6Less than 48" wide and depth

between 12" and 24" 8Width 24" or less and depth greater

than 12" 8

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"


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FIGURE 6-5-23 Duct Opening Frame.


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(C) Spacing. Hanger spacing per Table 6-5-5 or

Figure 6-5-28 is based upon three (3) inch (76mm) wide (minimum) channels.For ducts not over forty-eight (48) incheswide by twenty-four (24) inches high (1,219 mm by 610 mm), two (2) inch wide by 1-1/2 inchchannels (51 mm by 38 mm), spaced not morethan four (4) feet (1,219 mm) apart may beinstalled. The total extension of the hangersupports shall not exceed six (6) inches (152 mm).

Hanger design and spacing for fibrous glassducts is based upon extensive testing with loadsexceeding twice the duct weight located betweensupports to ensure the integrity of the ductsystem. Recommended hanger spacing is shownin Figure 6-5-28. Caution should be taken withother types of hanger systems to ensure thatexcessive stress is not placed on the hanger or thefibrous glass duct system.

(D) Fittings. Proper support of duct fittings mayrequire that additional hangers be installed.

For an elbow, hangers should be on eachleg, within twelve (12) inches (305 mm) of thethroat. If the width of the duct is greater thaneighteen (18) inches (457 mm), an additionalhanger must be installed (see Figure 6-5-29) sothat it is approximately two-thirds of thediagonal distance from throat to heel.

Tees require support on the trunk as shownin Figure 6-5-30. If a tee runout hanger fallswhere the trunk duct is located, add hangers oneither side of trunk. Do not exceed maximumhanger spacing.

Branch ducts are treated in a similar mannerwith hanger spacing on the trunk duct inaccordance with Figure 6-5-28.



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FIGURE 6-5-25 Attachment to Fire DamperSleeves.

F IG UR E 6 -5 -2 6 H an gi ng f ro m C ha nn elReinforcement.

FIGURE 6-5-27 Hanger Spacing and ExtensionUsing 3-Inch (76 mm) Wide Channels.


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For diffuser drops, hangers are installedwithin three (3) inches (76 mm) of each side of the drop. The connection of the drop to the ductis reinforced in accordance with Figure 6-5-31.

If the drop assembly, including the diffuser,weighs more than twenty-five (25) pounds (11.3kg), the diffuser must be separately supported.

(E) Hanging Rigid Round Duct. Preformed roundfibrous glass duct should be hung so the hangerwill not damage the duct facing.

Straps or saddles in contact with the ductmust 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(1,829 mm) on center. Where practical, hangersshould 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, thenumber of bends, the number of degrees of each bend, and the amount of sag allowed betweensupport joints will have serious effects on systemperformance due to the increased resistance eachintroduces. Use the minimum length of flexibleduct to make connect ions . I t i s not re-commended that excess lengths of ducts beinstalled, to allow for possible future relocationsof air terminal devices.(2) Avoid installations where exposure to directsunlight can occur, e.g., turbine vents, skylights,canopy windows, etc. Prolonged exposure tosunlight will cause degradation of the vapor barrier. Direct exposure to UV light from a sourcelamp installed within the HVAC system willcause degradation of some inner core/linermaterials.(3) Terminal devices shall be supportedindependently of the flexible duct.(4) Repair torn or damaged vapor barrier

jackets with approved duct tape listed andlabeled to Standard UL 181B. If the internal coreis penetrated, replace the flexible duct or treat itas a connection.

(B) Installation.(1) Install duct fully extended. Do not install inthe compressed state or use excess lengths. Thiswill noticeably increase friction losses.(2) Avoid bending ducts across sharp corners orplacing in incidental contact with metal fixtures,

pipes, or conduits. The radius at the centerlineshall not be less than one (1) duct diameter.(3) Do not install near hot equipment (e.g.,furnaces, boilers, steam pipes, etc.) that is abovethe recommended flexible duct use temperature.

A.6.508 Connecting, Joining, and SplicingFlexible Duct.(1) All connections, joints, and splices shall bemade in accordance with the manufacturersinstallation instructions.(2) Tapes, mastics, and nonmetallic clamps usedwith flexible air ducts shall be listed and labeledto Standard UL 181B.(3) Sheet metal fittings to which the flexibleducts with plain ends are attached shall be beaded and have a minimum of two (2) inches(51 mm) collar length. Beads are optional forfittings when attaching metallic flexible ducts.

(4) Sheet metal sleeves used for joining twosections of flexible duct shall be a minimum of four (4) inches (102 mm) in length and beadedon each end. Beads are optional for sleeveswhen joining metallic flexible ducts.(5) Flexible ducts secured with nonmetallicclamps shall be limited to six (6) inches w.g.(1,500 Pa) positive pressure.

Installation Instructions for Air Ducts withPlain Ends.

A.6.509 Supporting Flexible Duct.

(A) Flexible duct shall be supported at manufacturersrecommended intervals, but at no greaterdistance than five (5) feet (1,524mm).Maximum permissible sag is 1/2 inch per foot(42 mm/m) of spacing between supports.

A connection to rigid ducting or equipmentshall be considered a support joint.

Long horizontal duct runs with sharp bendsshall have additional supports before and afterthe bend, approximately one (1) duct diameterdistance from the centerline of the bend.

(B) Hanger or saddle material in contact with theflexible duct shall be of sufficient width toprevent any restriction of the internal diameterof the duct when the weight of the supportedsection rests on the hanger or saddle material. Inno case will the material contacting the flexibleduct be less than 1-1/2 inches (38 mm) wide.

(C) Factory-installed suspension systems integral tothe flexible duct are an acceptable alternativehanging method when manufacturersrecommended procedures are followed.


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317

48

44

40

36

32

28

24

20

16

12

8

4

08 16 24 32 40 48 56 64 72 80 88 96

8 ft. Max.

Duct Width, Inside (Inches)

6 ft. Max.

4 ft. Max.

D u c t W i d t h

, I n s i d e ( I n c h e s )

in. x 25.4 = mmft.. x 304.8 = mm

6 ft. Max.

FIGURE 6-5-29 Elbow Support .

Figure 6-5-28 Minimum Hanger Spacing, Straight Duct, 3-Inch-Wide (76 mm) Channel.


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(D) Flexible ducts may rest on ceiling joists or trusssupports. Maximum spacing between supportsshall not exceed the maximum spacing permanufacturers installation instructions.

(E) Support the duct between a metal connectionand a bend by allowing the duct to extend

straight for a few inches before making the bend.This will avoid possible damage of the flexibleduct by the edge of the sheet metal collar.

(F) Vertically installed duct shall be stabilized bysupport straps at a maximum of six (6) feet(1,829 mm) on center.

Note: Factory-made air ducts may not be used forvertical risers in air duct systems serving more thantwo stories. See Section 604.2 of this code.


318


FIGURE 6-5-30 Tee Support.

FIGURE 6-5-31 Diffuser Connection.


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319

FIGURE 6-5-33 Extend Duct Fully.

FIGURE 6-5-32 Hanging Round Duct with Saddle and 12 Gauge Wires.

FIGURE 6-5-34 Wrong Method of Support.


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320


Connections1. After desired length is determined, cutcompletely 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 andpast the bead. Seal core to collar with at least 2wraps of duct tape. Secure connection with clampplaced 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 clampmay be used in place of or in combination with theduct tape.

Splices

1. Fold back jacket and insulation from core. Butt

two cores together on a 4'' (100mm) length metalsleeve.

2. Tape cores together with at least 2 wraps of ducttape. Secure connection with 2 clamps placed overthe 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.

The following figures contain the information in the previous edition Figures 6-5-35 and 6-5-36.


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321

Alternate Installation Instructions for Air Ducts and Air Connectors Nonmetallic with Plain Ends.

Connections and Splices Step 1: After desired length is determined, cutcompletely around and through duct with knife orscissors. Cut wire with wire cutters. Pull back jacketand insulation from core.

Step 2: Apply mastic approximately 2'' (50 mm)wide uniformly around the collar of the metal fittingor over the ends of a 4'' (100 mm) metal sleeve.Reference data on mastic container for applicationrate, application thickness, cure times, and handlinginformation.

Step 3: Slide at least 2'' (50 mm) of core over thefitting or sleeve ends and past the bead.

Step 4: Secure core to collar with a clamp appliedpast the bead. Secure cores to sleeve ends with 2clamps applied past the beads.

Step 5: Pull jacket and insulation back over coreends. Tape jacket(s) with at least 2 wraps of ducttape. A clamp may be used in place of or incombination 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 181BC. Use of nonmetallic

clamps shall be limited to 6 in. w.g. (1,500 Pa) positive pressure.


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322


Installation Instruction for Air Ducts and Air Connectors Metallic with Plain Ends.

Connections and Splices1. After cutting duct to desired length, fold back jacket and insulation exposing core. Trim core endssquarely using suitable metal shears. Determineoptional sealing method (step 2 or 5) beforeproceeding.

2. When mastics are required and for pressure 4''w.g. (1,000 Pa) and over, seal joint with mastic

applied uniformly to the outside surface of collar/sleeve. (Disregard this step when not usingmastics and proceed to step 3).

3. Slide at least 1'' (25mm) of core over metal collarfor attaching duct to take off or over ends of a 4'' (100mm) metal sleeve for splicing 2 lengths of duct.

4. Secure to collar/sleeve using #8 sheet metalscrews spaced equally around circumference. Use 3screws for diameters under 12'' (300 mm) and 5screws for diameters 12'' (300 mm) and over.

5. For pressure under 4'' w.g. (1,000 Pa), seal jointusing 2 wraps of duct tape applied over screw headsand 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 beused in place of or in combination with the ducttape.

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.


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A.6.510 Checklist.

The following checklist is provided for the benefit of the inspector, as well as the installer. It is designed sothat the correct answer to all questions is yes.

General Yes No

___ Have all tears or punctures tofacing material been repaired usingthe proper technique? ( ) ( )

___ Are all sheet metal accessoryitems galvanized? ( ) ( )

Product

___ Is the UL label present?(Although each board is labeled,each section may not be, sincethere is only one label per sheet.) ( ) ( )

Fabrication and Installation

___ When metal parts are attached,are 2-1/2 inch (64 mm) minimumsquare steel washers used on 16-inch(406 mm) maximum centers? ( ) ( )

___ When staples cannot be used, are8 inch (203 mm) cross-tabs of approved closure being used inplace of staples? ( ) ( )

___ Are tab spacing requirements12 inches, (305 mm) on centerminimum one per side. ( ) ( )

___ Are all system joints tight, free from bulges, with taped joints showinggood workmanship? ( ) ( )

___ Have offsets been installed so ductsections are not forced to bendaround obstructions? ( ) ( )



323

FIGURE 6-5-37.

FIGURE 6-5-38 Proper Support.


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Fire DampersSee Section A. 6.505 Yes No

___ Is sheet metal sleeve present?Is duct properly attached tosleeve with screws and washers

16 inches (406 mm) on center?(Fibrous glass ducts must notpenetrate assemblies required tohave a fire damper.) ( ) ( )

Access Doors

___ Is installation in accordance withSection A. 6.504(E)6? ( ) ( )

Grills, Diffusers, RegistersSee Section A. 6.506

___ Is the extra weight of the item beingseparately supported and notdependent on the duct alone forsupport? (Exception: Registers notgreater than 150 square inches(96.7 x 103 mm2) in area may beattached to the duct with metalchannel, without other support.) ( ) ( )

Connection to Units

___ Are sheet metal screws andwashers used to secure theduct system to flange extensions?(Securing the duct to the unitflange without mechanicalfasteners is sufficient.) ( ) ( )

ClosuresSee Section A. 6.503

___ Are all joints in the systemproperly sealed? ( ) ( )

___ Are closure materials for rigidduct systems of a listed type,as evidenced by presence of UL instruction sheet in duct board carton or imprintedUL 181A on the tape? ( ) ( )

Yes No

___ Are closure materials for flexibleduct systems of a listed type, asevidenced by presence of UL

instruction sheet in the ductcarton and imprinted UL 181Bon the tape, mastic, andnonmetallic clamps? ( ) ( )

___ Are there staples or cross-tabs, properlyspaced, on circumferential joints? ( ) ( )

___ Are all pressure-sensitive tape closuresrubbed down adequately, with staplesor 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 themesh of the glass fabric completelyfilled with mastic? ( ) ( )

ReinforcementSee Section A. 6.504

___ Is the reinforcement system inaccordance with Section A. 6.504? ( ) ( )

___ Is the tie rod spacing correct accordingto duct span, board type, and staticpressure? ( ) ( )

___ Are tie rod washers 2-1/2 inches(64 mm) square? ( ) ( )

___ Do tie rod washers have turned edgesfacing away from duct board so theywill not cut into it? ( ) ( )

___ If tie rods reinforce a butt joint,are rods used on both sides of the butt joint? ( ) ( )


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Yes No

___ Is wire termination one of thosedocumented in Section 6.504(B)? ( ) ( )

___ Are anti-sag devices used on ducts48 inch (1,219 mm) span or greater tosupport top panel of ducts? ( ) ( )

___ Are heels of tees, elbows, andend caps reinforced (formedsheet metal channel, tie rod, orcombination)? ( ) ( )

___ When formed sheet metal channelreinforcement is used, are sheetmetal gauges, dimensions, andspacing correct? ( ) ( )

___ For return ducts, are sheet metalchannel reinforcements attached toducts with screws and 2-1/2 inch(64 mm) square washers or 2 inch by6 inch (51 x 152 mm) clips? ( ) ( )

Hangers and SupportsSee Sections A. 6.506 andA. 6.509

___ Are hangers installed in accordancewith Section 6.506? ( ) ( )

___ Are hanger designs in accordance withTable 6-5-6? ( ) ( )

___ Are accessories that add weight to theduct system separately supported so asnot to stress the system?(See Section A. 6.506(4).) ( ) ( )

___ If formed sheet metalreinforcements are used ashangers, are attachmentswithin 6 inches (152mm) of duct sides? ( ) ( )

___ Are all fittings supported byhangers? ( ) ( )



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UNIFORM MECHANICAL CODEAPPENDIX A, UMC STANDARD 6-5

Uniform Mechanical Code- 2009 Appendix a 6-5

Documents

Transcript of Uniform Mechanical Code- 2009 Appendix a 6-5