ACCA's Updated Manual D Out For ANSI Public Review

August 19, 2016

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 industry standard. The 45-day public review period started on August 19, 2016 with a comment period deadline of October 3, 2016.

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.

The revised standard has been divided into two portions: normative and informative.  Four normative sections (Normative Requirements) contain the minimum requirements for conducting a residential duct system design. The informative sections and appendices that follow contain additional explanation, details, and examples on the normative requirements. The underlying Manual D procedures and processes remain unchanged from the prior 2014 ANSI-recognized version.  
The principle changes to the proposed Manual D from the 2014 version are:
The addition of four normative sections:

  • N1: Normative Requirements for System Design, 4 pages (new)
  • N2: Manual D Worksheets (and how to complete same), 8 pages (partially new)
  • N3: Normative Tables, 1 page
  • N4: Fitting Equivalent Lengths, 28 pages.  These 28 pages are identical to what is currently in Appendix 18 of the 2014 version of Manual D … EXCEPT some slight changes (or additions of notes) to Group 7 (“Panned Joists”, now page N32) and Group 11 (“Flexible Duct Junction Boxes”, now page N38). 

The balance of the Manual D content remains unchanged in the 2016 version EXCEPT: 

  • The informative Overview has been updated to reflect the new layout, etc.
  • The informative Introduction was made shorter.
  • The original (i.e., 2014 version) Manual D Sections and Appendices – which contain background information, discussion, example problems, etc. – have each been marked as being informative.
  • The “Fitting Equivalent Length Values” (the 28 pages noted above) that were contained in Appendix 3 have been relocated to N4.
  • The Manual D Worksheets (as noted above) from Appendix 18 have been relocated to Normative Section N2.
  • Removal of informative zoning content (e.g., the zoning damper example problems) for subsequent placement into a revised Manual Zr (Residential Zoning) to be released in 2017,
  • Additional informative discussion regarding accessing of hand balancing dampers that are located in runout ducts,
  • Additional discussion on system design impact when bypass dehumidifiers are added to an HVAC system.
  • A number of non-substantive revisions within the document for clarification or grammatical/editorial corrections. 

The review version of the updated Manual D (dated August 16, 2016) and the public review response form can be obtained from Comments and questions are to be submitted to ACCA on the Public Response Form, which can be found at


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ACCA is a non-profit association serving more than 60,000 professionals and 4,000 businesses in the indoor environment and energy services community. Our member firms are the nation's most professional contracting businesses, serving residential and commercial customers in every state. With roots stretching back a century, ACCA was incorporated in its present form nearly 50 years ago. Today, ACCA sets the standards for quality comfort systems, provides leading-edge education for contractors and their employees, and fights for the interests of professional contractors throughout the nation. Learn more about ACCA here.