Manual Q - Low Pressure, Low Velocity Duct System Design
ACCA’s Manual Q: Low Pressure, Low Velocity, Duct System Design serves as a comprehensive guide for designing commercial, low velocity, low-pressure air distribution systems. This Manual provides time-saving, quick-fitting loss tables and a complete set of fitting loss tables compiled from the ASHRAE and SMACNA handbooks.
Additionally, Manual Q replaces all current and previous editions of ACCA Manual Q: Equipment Selection and System Design Procedures for Commercial Summer and Winter Air Conditioning.
PURCHASE MANUAL Q
Manual Q is divided into twenty-one informative sections, with an additional nine appendices for supplementary information.
Section 1 - Duct System Classification
Section 1 begins by classifying duct systems by function, path geometry, velocity range, pressure class, construction material, and class.
- Classifications
- Function
- Paths
- Velocity
- Pressure
- Materials
- Shape
Section 2 - Duct System Requirements and Design Parameters
Section 2 covers the intricate system requirements, equipment requirements, and design parameters required for HVAC Duct System installations.
- Classifications
- Duct System Design Parameters
- Architectural Considerations
- Construction Costs and Operating Costs
Section 3 - Basics
Section 3 discusses some basic duct system principles and equations.
- Flow and Pressure Equations
- Duct Pressure Measurement Units
- Duct Pressures - Total, Static and Velocity
- Frictionless Regain and Conversion
- Affect of Friction on Duct Pressure
- Affect of Friction on Regain and Conversion
- Pressure Measurement
- Fan Performance Curves
- Duct System Curves
- Operating Point
- Friction Charts and Duct Sizing Slide Rules
- Correction for Duct Material
- Altitude and Temperature Corrections
- Duct Performance - Non-Standard Air
- Fan Performance - Non-Standard Air
- Operating Point - Non-Standard Air
- Correction for Shape
- Equal Friction Shape Conversion
- Hydraulic Diameter
Section 4 - Duct System Pressure Changes
Section 4 goes over the duct system pressure changes, pressure loss, and pressure drops, and what component may be responsible for a pressure change.
- Duct System Pressure Loss
- Straight Section Pressure Drop
- Fitting Pressure Drop
- Fan Inlet and Outlet Pressure Drop
- Airside Device Pressure Drop
- Supply Outlet and Return Inlet Pressure Drop
- Example of Duct System Pressure Changes
- Duct System Total Pressure Drop
- Duct System Static Pressure Drop
Section 5 - Fitting Losses
Section 5 details friction losses based on various aspects of the duct system.
- Fitting Friction Loss
- Fitting Dynamic Loss
- Equivalent Length
- General Comments on Fitting Design
- Dynamic Loss Coefficient
- Examples
- Elbow Loss
- Branch Take-off Fitting Loss
- Diverging Flow Transitions
- Converging Flow Transitions
- Discharge into a Plenum
- Exit from a Plenum
- Offsets
Section 6 - Fan and Duct System Interface
Section 6 provides a general discussion of the “system effect” and its relation to various types of fan outlets and inlet configurations.
- System Effect
- Fan Performance Tables
- Field Performance
- Effective Duct
- Ideal Return
- Loss Coefficients
- Density Correction
Section 7 - Fan Outlet System Effects Losses
Section 7 details the system losses when a duct is not 100% effective.
- System Effect at Fan Discharge
- Blast Area and Outlet Area
- Fan Discharge
- Into Open Space
- Into a Plenum
- Into Elbow
- Into an Outlet Diffuser
- Fan Discharge Volume Control Dampers
- Fan Discharge into Tees and Branch Take-offs
- Air-Handler Cabinet Discharge Connections
Section 8 - Fan Inlet System Effect Losses
Section 8 discusses potential procedures that can be used to estimate how system factors affect pressure losses.
- System Effect at Fan Inlet
- Inlet Area
- Non-ducted Inlets
- Ducted Inlets
- Fan Inlet Elbows
- Documented Inlet Elbow Loss Coefficients
- Undocumented Inlet Elbow Loss Coefficients
- Fans Located in Plenums or Cabinets
- Inlet Obstructions
Section 9 - Air Side Devices
Section 9 categorizes various types of airside devices and provides information about their performance characteristics.
- Pressure Loss Data
- Velocity
- Filters
- Dampers
- Louvers, Penthouses, and Hoods
- Coils
- Supply Air Outlets and Return Inlets
- Air Distribution Devices
- Humidifiers
- Energy Recovery Equipment
- Miscellaneous Equipment
Section 10 - Duct Sizing Methods
Section 10 goes over the various methods for duct sizing and fan selection.
- Equal Friction Method
- Modified Equal Friction Method
- Extended Plenum Method
- Semi-extended Plenum Method
- Static Regain Method
- Constant Velocity Method
- Velocity Reduction Method
Section 11 - Duct System Design Procedure
Section 11 discusses components to consider when beginning the duct design process.
- Design CFM Values
- Select and Locate Air Distribution Devices
- Locate the Central Equipment
- Preliminary Layout
- Sizing Calculations
- Calculate the System Total Pressure Loss
- Select the Fan
- Noise
- Final Drawings and Specifications
Section 12 - Example, Constant Volume System
Section 12 showcases examples of Constant Volume Systems in a variety of different commercial buildings.
- Design Friction Rate for the Supply Ducts
- Supply Duct Runs
- Return Duct Friction Rate and Pressure Loss
- Return Duct Runs
- Summary
Section 13 - Examples of VAV Designs
Section 13 showcases examples of how to design an air distribution system for modulating and dumping VAV systems.
- Modulating VAV Systems
- Example Problem, Modulating VAV Systems
- Dumping VAV Systems
- Examples Problem, Dumping VAV Systems
Section 14 - Application of Selected Types of VAV Equipment
Section 14 discusses how to design systems that utilize self-powered VAV diffusers and fan-powered VAV boxes.
- Self-Powered VAV Supply Diffusers
- Examples, Self-Powered VAV Diffusers
- Fan-Powered VAV Box
- Examples, Fan-Powered VAV Box
Section 15 - VVT, Rooftop Multizone, Radial and Flexible Duct Systems
Section 15 goes over design considerations that are specific to VVT systems, rooftop multizone systems, radial systems, and flexible duct/junction box systems.
- VVT Systems
- Designing the CO/BP-VAV System
- Rooftop Multizone System
- Designing the Rooftop Multizone Duct System
- Radial Duct Systems
- Designing the Radial Duct System
- Flexible Duct - Junction Box Systems
- Designing the Flexible Duct System
Section 16 - Fans
Section 16 provides detailed information regarding the design, performance, and application of different types of centrifugal and axial fans.
- Fans
- Definitions
- Fan Types
- Centrifugal Fans
- Axial Fans
- Fan Laws
- Fan Control
- Fan Economics
- Factors that Affect Fan Selection
- Fan Specification
- Series and Parallel Fans
- Standards
Section 17 - Building Pressure
Section 17 goes into detail about building pressure and considerations during the design process.
- Room Air Balance
- Economizer Cycle
- Single Fan System
- Supply Fan and Return Fan System
- Supply Fan and Exhaust Fan System
- Intake Openings
- Control Dampers
- Mixing Boxes and Stratification
Section 18 - Exhaust Air Systems
Section 18 discusses three broad categories of exhaust air systems, including human comfort, health and safety, and material handling systems.
- Comfort Conditioning Exhaust Requirements
- Exhaust System Applications
- Codes and Regulations
- Air Balance
- Make-up Air
- Toilet, Locker, and Shower Exhaust Systems
- Kitchen Exhaust Systems
- Non-ducted Exhaust Systems
- Industrial Exhaust Systems
Section 19 - Provisions for Testing and Balancing the System
Section 19 details procedures and provisions for testing and balancing newly installed systems.
- Design and Installation Affect the At&B Work
- Balancing Dampers Required
- Make Provisions for Performing the Balancing Work
- Document the Design
Section 20 - Duct Insulation and Duct Leakage
Section 20 talks about the dangers and preventional measures against duct leakage.
- Recommended Insulation Levels
- Effective R-Values for Various Materials
- Estimating Duct Wall Conduction Losses
- Vapor Barries
- Duct Sealing Requirements
- Duct Leakage
Section 21 - Noise
Section 21 discusses noise and what it means for the HVAC system
- Frequency
- Sound Pressure
- Decibel
- Sound Power
- Frequency Spectrum
- Octave Bands
- Loudness Chart
- Noise Criteria Rating
- Acceptable NC for Various Applications
- Sound Meters
- Equipment Performance Data
- Sones and Phones
- Attenuation
- Regenerated Noise
- Room Absorption Effect
- Breakout Noise
- Transmission and Transmission Loss
- Crossstalk
- Vibration Isolation
- Designing for Noise Control
Appendix 1 - Equations
Appendix 2 - Friction Charts
Appendix 3 - Charts and Design Data
Appendix 4 - Device Pressure Drop and Performance Data
Appendix 5 - System Effect Loss Coefficients
Appendix 6 - Fitting Loss Coefficients
Appendix 7 - Drawing Standards
Appendix 8 - Guidelines and Checklists
Appendix 9 - “Quick" Fitting Tables