HVAC Metal Duct Installation | HVAC Engineering

This article is about HVAC Metal Duct Installation as per International Codes and standards.

HVAC Metal Duct Installation

1. Duct Work shall be installed in accordance with Construction Drawings, Specifications, and Manufacturer’s Installation Manual.
2. Duct reinforcements shall be provided as per the requirements of the attachment No. 1 (Tables A-6-F thru A-6-1-1-Q). (UMC Section 6.105 Appendix “”A”” Standard 6-1)”
3. Rectangular elbows shall be provided with Turning Vanes.
   Note: For low velocity systems only.
   Exception: No turning vanes required if the throat radius is equal to the duct width “
4. Ducts shall be isolated from their Air Handling System (Fan, Fan Coil, AHUs, etc) by Flexible Connections
5. Flexible Duct Connector shall not exceed 5 feet in overall length and shall not have bends greater than 45 degrees.
6. Splitter dampers shall not be used for duct branch take-offs
7. All building exhausts shall be directly to the outside with a point of discharge of at least 1.5 m away from any openable window or door, and a minimum of 1m above and 3 m horizontally away from any air intake.
8. Metal ducting shall be grounded, provide jumpers at flexible duct.
9. Internal duct lining shall not be used or installed, except in acoustically sensitive areas and only with the prior approval of Chairman, HVAC Standards Committee.
10. All materials in the return air plenum shall be non-combustible or limited combustible.
11. Metal Ducts shall be installed with at least 4 inches of separation from Earth (UMC Para 603.1 )
12. Metal ducts when installed in or under concrete slab shall be encased in at least 2 inches of concrete. (UMC Para 603.1)
13. Joints, seams and fittings of duct systems shall be made substantially airtight by means of tapes, mastic, gasketing or other approved methods (UMC Para 601.6)
    Note: Other methods shall have Saudi Aramco approval”
14. Externally insulated ducts located outside of buildings shall be sealed before being insulated, as though they were inside.
    (SMACNA Para S1.9 g)”
15. If air leaks sites in ducts located outside of buildings are exposed to weather, they shall receive exterior duct sealant (SMACNA Para S 1.9 g)
    Note: Exterior duct sealant is defined as a sealant that is marked specifically as forming a positive air-and watertight seal, bonding well to the metal involved, remaining flexible with metal movement, and having a service temperature of -34 °C to 79 °C.
16. Exterior duct sealant if exposed to direct sunlight shall be ultraviolet ray-and ozone-resistant or shall, after curing, be painted with a compatible coating that provides such resistant (SMACNA Para S1.9 g)
17. Duct sealing shall be provided for both positive and negative pressure modes of operation (SMACNA Para S1.9 f)
18. Seal class A shall be provided for 4” w.g. and higher pressure class duct construction (SMACNA S 1.9 Table 1-2)
    Class A: All transverse joints, longitudinal seams, and duct wall penetration”
19. Seal class B shall be provided for 3” w.g. pressure class duct construction (SMACNA S 1.9 Table 1-2)
    Class B: All transverse joints and longitudinal seams only”
20. Seal class C shall be provided for 2″ w.g. pressure class duct construction (SMACNA S-1.9 Table 1-2)
    Class C: Transverse joints only.

Standards Codes and References HVAC Metal Duct Installation

1-SAES-K-001 — Heating, Ventilating and Air Conditioning (HVAC), 25 November, 2006
2-SAES-K-100 — Saudi Aramco Mechanical (HVAC) Code, 31 May, 2004
3-Uniform Mechanical Code (UMC), 1997

4-SMACNA — HVAC Duct Construction Standards Metal and Flexible, 1995.

HVAC Metal Duct Hangers and Support Installation

HVAC Metal Duct, Hangers and Supports and Insulation Receiving

HVAC Duct System Handling, Storage and Preservation

Essential Operating Facilities (EOF) HVAC Requirements

Attachment 1

Table A6-1-G Rectangular Duct Transverse Reinforcement for Duct Material Thickness from 0.058”