A flow hood is a large fabric hood that captures all air exiting a supply or return register, measuring total volumetric flow by directing captured air across an internal anemometer array. This enclosure-based approach eliminates velocity profile assumptions and provides accurate cfm measurement for registers of any size. Flow hoods are essential for precise register-level flow confirmation in residential and commercial systems.
Technical Details
Flow hoods measure airflow from 50 to 4,000 cfm depending on model size. The internal vane anemometer array samples multiple velocity points across the hood interior, averaging results over 10-30 second intervals for reading stability. Hoods are typically 24 by 24 inches to 48 by 48 inches, accommodating registers from small residential diffusers to large commercial grilles. Accuracy is within 5-8% of reading when properly sealed to register surrounds.
HVAC Applications
Flow hoods measure supply and return register airflow, verify equipment performance at individual outlets, and validate system balance across multiple zones. They are standard tools for TAB work and residential system verification.
Practical Significance
Accurate register-level flow data confirms proper system distribution and identifies obstructed or misaligned equipment affecting comfort and efficiency.