510.0 Exhaust Duct Systems
Drains shall be provided at low points in horizontal ducts. Where provided, drains shall be continuously welded to the exhaust duct or listed grease duct drains in accordance with the terms of the listing and the manufacturer's installation instructions.
Ducts shall be installed without forming dips or traps. In manifold (common duct) systems, the lowest end of the main duct shall be connected flush on the bottom with the branch duct. [NFPA 96:7.1.4 — 220.127.116.11]
- Factory-built grease duct listed in accordance with UL 1978 shall be permitted to incorporate non-welded joint construction in accordance with their listing. [NFPA 96:18.104.22.168.1]
- Duct-to-hood collar connections as shown in Figure 510.5.3 shall not require a liquid-tight continuous external weld. [NFPA 96:22.214.171.124]
- Penetrations shall be permitted to be sealed by other listed devices that are tested to be greasetight and are evaluated under the same conditions of fire severity as the hood or enclosure of listed grease extractors and whose presence does not detract from the hood or the duct's structural integrity. [NFPA 96:126.96.36.199]
- Internal welding shall be permitted, provided the joint is formed or ground smooth and is readily accessible for inspection. [NFPA 96:188.8.131.52]
For SI units: 1 inch = 25.4 mm, °C = (°F—32)/1.8
- Telescoping joint, as shown in Figure 510.5.3.2(1).
- Bell-type joint, as shown in Figure 510.5.3.2(2).
- Flange with edge weld, as shown in Figure 510.5.3.2(3).
- Flange with filled weld, as shown in Figure 510.5.3.2(4). [NFPA 96:184.108.40.206]
For SI units: 1 inch = 25.4 mm
- Duct size decreases (going upward) with each telescope.
- Smaller (inside) duct section shall be above or uphill (on sloped duct), to be self draining into larger (outside) duct.
For SI units: 1 inch = 25.4 mm
- Duct size stays the same throughout the duct system.
- Smaller (inside) male duct end is always above or uphill (on sloped duct), to be self draining into larger (outside) female duct end.
Exception: The continuous enclosure provisions shall not be required where a field-applied grease duct enclosure or a factory-built grease duct enclosure (see Section 507.4.4 through Section 507.4.6) is protected with a listed duct-through-penetration protection system equivalent to the fire resistance rating of the assembly being penetrated, and where the materials are installed in accordance with the conditions of the listings and the manufacturer's installation instructions and are acceptable to the Authority Having Jurisdiction. [NFPA 96:220.127.116.11]
Exception: Clearance from the outer surfaces of field-applied grease duct enclosures and factory-built grease duct enclosures to the interior surfaces of construction installed around them shall be permitted to be reduced where the field-applied grease duct enclosure materials and the factory-built grease duct enclosures are installed in accordance with the conditions of the listings and the manufacturer's installation instructions and are acceptable to the Authority Having Jurisdiction. [NFPA 96:18.104.22.168.4]