ACCA Manual D • 0.1 in. wg Friction2000 CFM • 5 TonsStandard Residential (<900 FPM)
2,000 CFM Duct Size: 5.0 Ton HVAC Main Supply Trunk
Calculated duct sizing specifications for 2000 CFM of conditioned airflow. Sized via the Equal Friction Method and Huebscher equivalent rectangular equation to maintain static pressure and eliminate air rush noise.
Round Duct Size18" RoundSpiral / Snaplock Pipe
Air Velocity1132 FPMFeet Per Minute
Cooling Tonnage5 Tons@ 400 CFM / Ton
Register / Grille16x28Face Dimension
Equivalent Rectangular Duct Sizing Schedule
Exact rectangular sheet metal dimensions offering equivalent airflow resistance to a 18" round pipe
| Height (Depth) | Width | Cross Area | Air Velocity | Aspect Ratio | SMACNA Status |
|---|---|---|---|---|---|
| 12" Deep | 34" Wide | 408 sq in | 706 FPM | 2.8:1 | Optimal (<2:1) |
| 14" Deep | 30" Wide | 420 sq in | 686 FPM | 2.1:1 | Optimal (<2:1) |
| 16" Deep | 26" Wide | 416 sq in | 692 FPM | 1.6:1 | Optimal (<2:1) |
Air Terminal & Grille Sizing Guidelines
Recommended face velocities to prevent whistling diffuser vanes
Supply Register Specifications
Recommended Grille Size:16x28 Supply Trunk / Dual 20x25 Return Air Grilles
Maximum Target Velocity:500–700 FPM at register face
Diffuser Throw:Spread toward outside walls
Return Air Intake Rules
Return Velocity Target:<450 FPM through filter face
Filter Surface Requirement:Minimum 2 sq ft per Ton
Return Friction Target:0.05 – 0.08 in. wg / 100 ft
HVAC Sheet Metal & Installation Directives
- 5.0 tons is the largest residential split system category. 2,000 CFM requires substantial duct area: 14x30 or 16x26 rectangular trunk.
- CRITICAL CONTRACTOR WARNING: Under-ducted 5-ton systems are the #1 cause of premature compressor burnout and high static pressure noise. Dual return air drops are mandatory.
Frequently Asked Duct Sizing Questions
What size duct does a 5-ton AC unit need?
A 5-ton AC unit needs 2,000 CFM of airflow, requiring a 14x30 or 16x26 rectangular trunk line or a 20-inch round spiral duct.