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603.6 Flexible Air Ducts and Flexible Air Connectors

Mechanical Code 2018 of Maryland > 6 Duct Systems > 603 Duct Construction and Installation > 603.6 Flexible Air Ducts and Flexible Air Connectors

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Flexible air ducts, both metallic and nonmetallic, shall comply with Sections 603.6.1, 603.6.1.1, 603.6.3 and 603.6.4. Flexible air connectors, both metallic and nonmetallic, shall comply with Sections 603.6.2 through 603.6.4.

603.6.1 Flexible Air Ducts

Flexible air ducts, both metallic and nonmetallic, shall be tested in accordance with UL 181. Such ducts shall be listed and labeled as Class 0 or Class 1 flexible air ducts and shall be installed in accordance with Section 304.1.

603.6.1.1 Duct Length

Flexible air ducts shall not be limited in length.

603.6.2 Flexible Air Connectors

Flexible air connectors, both metallic and nonmetallic, shall be tested in accordance with UL 181. Such connectors shall be listed and labeled as Class 0 or Class 1 flexible air connectors and shall be installed in accordance with Section 304.1.

603.6.2.1 Connector Length

Flexible air connectors shall be limited in length to 14 feet (4267 mm).

603.6.2.2 Connector Penetration Limitations

Flexible air connectors shall not pass through any wall, floor or ceiling.

603.6.3 Air Temperature

The design temperature of air to be conveyed in flexible air ducts and flexible air connectors shall be less than 250°F (121°C).

603.6.4 Flexible Air Duct and Air Connector Clearance

Flexible air ducts and air connectors shall be installed with a minimum clearance to an appliance as specified in the appliance manufacturer's installation instructions.