HVAC Duct Construction. Bob Wasilewski Project Manager, Technical Resources SMACNA

HVAC Duct Construction Bob Wasilewski Project Manager, Technical Resources SMACNA

HVAC Duct Construction Standards WHAT? WHY? HOW?

Today's Program 1 st 2 nd Edition HVAC-DCS Review Joints and Limitations Transverse Joints & Reinforcements Use of the Pressure Class Tables Tie Rod Addendum

Documents Preceding 2nd Edition HVAC-DCS Low Velocity Systems Duct Manual First Edition 1959 Second Edition 1963 Third Edition 1967 Low Velocity Duct Construction Standard 1969

Documents Preceding 2nd Edition HVAC-DCS Low Pressure Duct Construction Standard Fifth Edition 1976 High Velocity Duct Systems Manual First Edition 1965 High Velocity Duct Construction Standards Second Edition 1969

Documents Preceding 2nd Edition HVAC-DCS High Pressure Duct Construction Standards Third Edition 1975 Duct Liner Application Standard First Edition 1971 Second Edition 1975

Documents Preceding 2nd Edition HVAC-DCS Flexible Duct Installation Standards First Edition 1979 Second Edition 1980 HVAC Duct Construction Standards -- Metal and Flexible First Edition 1985

Major Changes from First Edition GENERAL Text edited to be more reader-friendly Reading aids added Static pressure only as the basis for duct construction classification -- velocity levels deleted (Table 1-1)

Major Changes from First Edition Chapter 7 revised to facilitate use for equivalent and comparable tests and ratings Model project specification added Reminders to designers to show all required fire, smoke, radiation and volume control dampers on contract drawings are accented

Major Changes from First Edition Boiler breeching omitted Volume damper construction is more specific Lead radiation shielding added Metrics are included Air terminal runouts and supports are revised

Major Changes from First Edition RECTANGULAR DUCT REVISIONS Negative pressure construction given for 4", 6", and 10" w.g. Six feet reinforcement schedules added Reinforcement schedules extended to 120" width

Major Changes from First Edition Tie rod alternatives expanded for both positive and negative pressures TDC and TDF joint systems included and rated as T-25a and T-25b joints T-24a joint added as a modification of T-24

Major Changes from First Edition Use of 26 gage added for 4", 6" and 10" pressures Trapeze hanger tables expanded to cover the 120" width range Duct liner pin schedule adjusted Infrequently used joints (T-4, 8, 17, 18, 19, 20 and 23) omitted

Major Changes from First Edition Round, Flexible and Oval Duct Revisions Duct pressure classes revised to be positive and negative at 2", 4" and 10" w.g. Crimped joint connection length changed from 1" to 2" Rectangular branch taps into round added for straight or 45 degree lead-in-entry

Major Changes from First Edition Type 1 reinforcement of oval duct now has an internal tie rod (based on ASHRAE test program) Maximum support spacing for round flexible duct and connector changed from 10 feet to 5 feet Additional riser support details are provided

DUCT SYSTEMS SIZINGS FITTINGS, ETC. FIRE/SMOKE PROTECTION CODE COMPLIANCE DUCT CONSTRUCTION CODE COMPLIANCE SMACNA HVAC-DCS 2 ND ED. 1995 INSPECTION CODE COMPLIANCE

DUCT SYSTEMS ENGINEER Design Considerations: CFM Static Pressure Duct Size Fitting Type Construction Pressure Class CONTRACTOR Construction Considerations: Panel Thickness (Gage) Pressure Class (as specified) Panel Width/Height Joint Type/Spacing Intermediate Reinforcement Type/Spacing

DEPENDENT VARIABLES

REGULAR DUCTS Maximum Deflection Joint and Reinf. 1/4" on 48" w. W/200 on 49"-120" Sheet: 3/8" on 12" Dn. 1/2" on 13"-18" 5/8"on 19"-24" 3/4" on 25"-84" 1" on 85"-120" Maximum Test Pressure Lab: Class Rating + 50% Field: Class Rating + 25% Tolerance: +7.5% Tolerance: +10%

Duct Systems Used for the movement of air in HVAC/Exhaust systems Ducts are classified based on maximum operating pressure 0.5" w.g. positive or negative 1.0" w.g. positive or negative 2.0" w.g. positive or negative

Duct Systems (Continued) Ducts are classified based on maximum operating pressure 3.0" w.g. positive or negative 4.0" w.g. positive or negative 6.0" w.g. positive or negative 10.0" w.g. positive or negative

TABLE 1-2 STANDARD DUCT SEALING REQUIREMENTS

EXAMPLE 1 Duct Size 24" x 24" Pressure Class 2" w.g. Sheet Stock Joints/Reinforcements 8 ft / 4 ft Standing S

EXAMPLE 2 Duct Size 42" x 24" Pressure Class 3" w.g. 5 ft Coil Line Joints/Reinforcements 5 ft / 2 ½ ft TDC or TDF

MIDPANEL TIE ROD (MPT) ½" w.g. - 6" w.g. 37" - 96" Duct Dimension Rectangular Duct

Mid Panel Tie Rod Addendum Joints All Tie Rods Threaded Rod or Tubing/Conduit with Threaded Insert Additional Application Tables, Qualifications and Reader Aids Included

FIGURE 1-3 TIE ROD ATTACHMENTS

FIGURE 1-4 TRANSVERSE (GIRTH) JOINTS

FIGURE 1-4 TRANSVERSE (GIRTH) JOINTS

FIGURE 1-4A SPECIAL JOINT PROFILES

FIGURE 1-5 LONGITUDINAL SEAMS RECTANGULAR DUCT

TABLE 1-24 UNREINFORCED DUCT (WALL THICKNESS)

TABLE 1-25 T-1 FLAT DRIVE ACCEPTED AS REINFORCEMENT

FIGURE 1-7 UNREINFORCED DUCT

FIGURE 1-8 CROSSBROKEN DUCT & BEADED DUCT

FIGURE 1-9 DUCT REINFORCED ON TWO SIDES

FIGURE 1-10 DUCT REINFORCED ON ALL SIDES

FIGURE 1-12 DUCT OVER 120" (3048 MM) WIDE

FIGURE 1-15 CORNER CLOSURES - FLANGES

FIGURE 2-22 DUCT LINER INTERRUPTION

TABLE 3-2A ROUND DUCT GAGE UNREINFORCED POSITIVE PRESSURE

TABLE 3-2B ROUND DUCT GAGE NEGATIVE PRESSURE

FIGURE 3-1 SEAMS ROUND DUCT AND FITTINGS

FIG. 3-2 TRANSVERSE JOINTS ROUND DUCT

FIGURE 3-6 FLAT OVAL DUCTS

FIGURE 3-9 FLEXIBLE DUCT SUPPORTS

FIGURE 3-10 FLEXIBLE DUCT SUPPORTS

TABLE 4-1 RECTANGULAR DUCT HANGERS MIN. SIZE

TABLE 4-2 MINIMUM HANGER SIZES FOR ROUND DUCT

FIGURE 4-4 LOWER HANGER ATTACHMENTS

Questions & Answers