ARLINGTON, Va. — The Air Conditioning Contractors of America Educational Institute (ACCA-EI) Standards Task Team (STT) has announced an American National Standards Institute (ANSI) public review period for “BSR/ACCA 1 Manual D - 201x, Residential Duct Systems” as a revised and redesignated industry standard. The public review period has a comment deadline of Feb. 24, 2014.

Manual D uses heating and cooling loads to determine space air delivery requirements for residential applications, noted ACCA. The Manual D procedures match duct system resistance (pressure drop) to blower performance (as defined by the manufacturer’s blower performance tables). This delivers appropriate airflow to the rooms and spaces, while ensuring that system airflow is compatible with the operating range of the HVAC equipment. The capabilities and sensitivities of the Manual D procedures are compatible with single-zone and multi-zone systems. The primary equipment may feature single-, multi-, or variable-speed blowers.

Although the underlying Manual D procedures and processes remain unchanged, the review draft has a number of updates as compared to the prior 2009 ANSI-recognized version. The major changes include:

• Design ESP Criteria for ECM Motors: A simpler Friction Rate Work Sheet approach by specifying 0.70 ESP as a maximum design target.

• Duct Airway Sizing for Zoned Applications: Specific duct sizing instructions and example problems for zoned systems remain in Manual D. Guidance related to load calculations, selecting zones, zoning equipment, etc., were removed from the Manual D volume; practitioners are pointed to ANSI/ACCA 11 Manual Zr – 2012 (Residential Zoning), which more fully address these topics.

• Low Resistance Return Path: Revisions to Group 14 details (pertaining to transfer grilles and transfer duct design) in Appendix 3 of Manual D.

• A new Air-Balance Column in the Duct Sizing Worksheet: A new column is added to the Manual D Duct Sizing Worksheet as a useful-information aid for air balancing work.

The review version of the proposed second edition of Manual D, the public review response form, as well as an overview on the major changes can all be downloaded at

Publication date: 1/20/2014

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