2025-06-28

Table of Contents

  1. Introduction to Flex Duct in HVAC Systems
  2. Parameters for Using Flex Duct in Return Air Systems
  3. Installation Guidelines
  4. Subo Company Solutions for Flex Duct in Return Air
  5. Conclusion
  6. References

Introduction to Flex Duct in HVAC Systems

Flexible ducting, commonly referred to as flex duct, is a type of duct used in heating, ventilation, and air conditioning (HVAC) systems. Particularly popular due to its adaptability and ease of installation, flex duct is an essential component in modern HVAC systems. While traditionally used for supply air, its role in return air systems is gaining traction.

Parameters for Using Flex Duct in Return Air Systems

Flex duct can indeed be used for return air, but certain parameters must be adhered to for optimal performance:

  1. Diameter and Length: Ensure the flex duct has an appropriate diameter, typically ranging from 6 to 12 inches, to handle the return air volume without causing excessive pressure drop.
  2. Pressure Loss: Maintain a pressure loss no greater than 0.1 inches of water gauge per 100 feet of ductwork to ensure efficiency.
  3. Velocity: Keep air velocity within 400 to 600 feet per minute (FPM) to minimize noise and turbulence.
  4. Insulation: Use a minimum of R-4 to R-6 insulation to reduce condensation and energy loss, especially in non-conditioned spaces.

Installation Guidelines

Proper installation of flex duct for return air systems is crucial for energy efficiency and system longevity:

  • Support flex duct every 4 to 5 feet to prevent sagging and maintain airflow.
  • Avoid sharp bends to prevent restriction of airflow; bends should have a minimum radius equal to the duct diameter.
  • Secure connections with clamps or zip ties and seal with mastic or UL-181 tape to prevent air leakage.

Subo Company Solutions for Flex Duct in Return Air

Subo Company offers a range of solutions tailored for the use of flex duct in return air systems:

  • High-Quality Flex Duct: Featuring robust construction with reinforced inner cores to handle high volumes of return air.
  • Insulation Options: Provides various insulation levels, including R-8, to enhance thermal efficiency.
  • Custom Sizing and Lengths: Offers bespoke solutions to fit any specific project requirements, ensuring optimal performance.

Conclusion

Flex duct is a viable option for return air systems in HVAC if installed and maintained correctly, with the proper consideration given to critical parameters such as diameter and insulation. Subo Company’s tailored solutions can further enhance the applicability and efficiency of flex duct in these settings.

References

  1. ASHRAE Handbook - Fundamentals (2021), American Society of Heating, Refrigerating and Air-Conditioning Engineers.
  2. ACCA Manual D Residential Duct Systems (2018), Air Conditioning Contractors of America.
  3. Subo Company Product Brochure (2023), Subo HVAC Solutions Division.

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