Manual D® - Residential Duct Systems [ANSI/ACCA 1 Manual D - 2016]
The Third Edition of the ANSI-recognized Manual D: Residential Duct Systems will help you design a duct system in less time. This new edition includes updated and expanded VAV guidance, with detailed examples; impacts of excess length, sag, and compression in flexible ducts; new equivalent length values for flex duct junction boxes; and additionally identifying normative requirements in related informative material. Manual D, from the Air Conditioning Contractors of America (ACCA), provides a single set of ANSI-recognized duct sizing principles and calculations that apply to all duct materials.
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The newly released Manual D has been significantly revised to include:
- Updated and expanded VAV guidance, with detailed examples.
- Impacts of excess length, sag and compression in flexible ducts.
- New equivalent length values for flex duct junction boxes.
Manual D consists of three normative sections, thirteen sections, and seventeen appendices that assist in procedures and regulations surrounding residential duct systems.
Normative Content of Manual D
- Section N1 - Normative Requirements
This section includes the engineering calculations that are listed in Manual D, alongside mandatory duct system features and attributes. Manual D calculation tools, such as worksheets and third-party software, are also included, with instructions pertaining to proper use as well. Prohibited practices are also listed.
- Section N2 - Manual D Worksheets
This section includes detailed instructions for the proper usage of Manual D worksheets, alongside a set of blank worksheets.
- Section N3 - Normative Tables
This section includes several informational tables, N3-1 and N3-2. These tables provide maximum air velocity values for duct airways, supply air grilles, return air grilles, and door undercuts for returning air.
- Section N4 - Fitting Equivalent Lengths
The final normative section provides the default fitting length values regarding equivalent feet of straight duct. These values provide input data for the Effective Length Worksheet.
Normative Content of Manual D
- Sections 1 and 2 - Basic Duct Sizing Principles and System Operating Point
The first two sections detail duct system physics, duct airflow, blower airflow, and the interactions between a given blower and a given duct system.
- Section 3 - Blowers
This section pertains to blower performance, blower motors, and performance pertaining to altitude.
- Section 4 - System Performance Issues
This section is about duct system physics and the relationship to pressure drops of varying types of system components. The use of structural framing for duct airways and the usage of a door undercut for a return air path is also covered.
- Section 5 - Air Distribution System Design
This section provides an executive overview of duct system design procedures, additionally covering the use of a branch take off fitting at the end of a supply air trunk duct.
- Section 6 - Duct Sizing Calculations
This section covers the duct system design procedures in detail. These procedures are embedded in the Manual D worksheets. This section also explains why balancing air dampers is required.
- Section 7 - Air Zoned Systems
This section goes over the procedures that apply to single-zone constant Cfm systems and to air-zoned systems, also covering that some air-zoned systems have unique problems. This section defers information to ACCA's Manual ZR, for details regarding duct system design for air-zoned systems.
- Sections 8 through 13 - Examples Problems Demonstrating the Use of Manual D for Various Applications
- Section 8 - Sizing Rigid Constant Cfm Duct Systems
- Section 9 - Sizing Flexible Constant Cfm Duct Systems
Manual D Appendices
- Appendix 1 - Tables and Equations
- Appendix 2 - Friction Charts, Duct Slide Rules and Shape Equivalency Tables
- Appendix 3 - Fitting Equivalent Length Concept
- Appendix 4 - Fitting Equivalent Length Adjustments
- Appendix 5 - Terminology
- Appendix 6 - Duct Construction Standards
- Appendix 7 - Standard of Care and Continuity
- Appendix 8 - Residential Air Distribution Systems
- Appendix 9 - Equipment and Air-Side Components
- Appendix 10 - Duct System Efficiency
- Appendix 11 - Duct Leakage and System Interactions
- Appendix 12 - Air Quality Issues
- Appendix 13 - Noise
- Appendix 14 - Testing and Balancing
- Appendix 15 - Air Velocity for Ducts and Grilles
- Appendix 16 - Excessive Length and Sag In Flexible Duct
- Appendix 17 - Symbols and Abbreviations
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Additional Manual D Resources
ACCA Speed-Sheets are Excel spreadsheets available for purchase that can be used in conjunction with ACCA Technical Manuals, which assist in learning important system design concepts. Speed-Sheets are not a replacement for the full Technical Manual, and are not a replacement for ACCA-approved software.
Learn more about ACCA's Speed-Sheets
Primer for using an ACCA Manual D Speed Sheet:
HVAC Essentials - Understanding Manual D
ACCA has approved software that works in conjunction with regulations, tables, procedures and worksheets that appear in Manual D.
Learn more about ACCA's Approved Software