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 www.acca.org/ansi/. Comments and questions are to be submitted to ACCA on the Public Response Form, which can be found at www.acca.org/ansi.