ARLINGTON, Va. - The Air Conditioning Contractors of America (ACCA) has released a revised and updated version of Manual D - Residential Duct Systems. The book is the industry standard for residential HVAC duct design.

The new version of Manual D maintains the popular and accurate procedure of the original manual, but has been enhanced with a number of improvements, including:

• New equivalent length values for flex duct junction boxes.

• Updated guidance, with examples, for variable air volume (VAV).

• Impacts of excess length, sag, and compression in flexible ducts.

Authored by Hank Rutkowski with the oversight of a committee made up of professionals from different sectors of the HVACR industry, the updated Manual D was approved as the national standard for residential duct design by the American National Standards Institute (ANSI) on Jan. 22, 2009.

The Manual D principles and calculations can be applied to constant volume systems and zoned variable air volume systems, over a full range of modern construction materials.

Manual D may be purchased online (go to ACCA’s online store at www.acca.org/store and look in “Technical Manuals, Standards & References”) or by calling 888-290-2220.

Publication date: 02/16/2009