The Air Conditioning Contractors of America Educational Institute (ACCA-EI) Standards Task Team (STT) announces an American National Standards Institute (ANSI) public review period for the “BSR/ACCA 1 Manual D – 201x, Residential Duct Systems” as a revised and redesignated industry standard. The 45 day public review period started on January 10, 2014 with a comment period deadline of February 24, 2014.
Manual D uses heating and cooling loads to determine space air delivery requirements for residential applications. 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 (dated December 16, 2013), the public review response form, as well as an overview on the major changes can all be downloaded from www.acca.org/ansi.