Duct Layout
The Layout pane is where you design the duct distribution system, including routing, sizing, and component selection.
Duct Routing
Section titled “Duct Routing”Creating Duct Runs
Section titled “Creating Duct Runs”Draw duct runs on the floor plan:
- Select the duct tool
- Click to place duct segments
- Connect to terminals and registers
- Close loops where needed
Duct Types
Section titled “Duct Types”Select the appropriate duct type:
- Supply duct - From AHU to terminals
- Return duct - From spaces back to AHU
- Exhaust duct - From spaces to exhaust fan
- Outdoor air - From intake to AHU
Routing Considerations
Section titled “Routing Considerations”Plan duct routes to:
- Minimize total length
- Avoid obstructions
- Allow for insulation and access
- Fit within available plenum space
Duct Sizing
Section titled “Duct Sizing”Sizing Criteria
Section titled “Sizing Criteria”Each duct is sized against the criteria of its duct type. HVAKR picks the smallest size that satisfies all of them at the duct’s design airflow:
Max Velocity
Section titled “Max Velocity”Caps air velocity for noise control:
- Higher limits = smaller ducts
- Lower limits = quieter system
- Typical: 1500-2000 FPM main, 800-1200 FPM branch
Max Pressure Drop
Section titled “Max Pressure Drop”Caps the friction rate (pressure drop per 100 ft):
- Typical: 0.08-0.10 in. wg per 100 ft
- Keeps fan power reasonable on long runs
Max Height
Section titled “Max Height”Caps the duct height so it fits the available plenum space. Rectangular ducts get wider instead of taller once the limit is reached.
Automatic Sizing
Section titled “Automatic Sizing”HVAKR automatically sizes ducts:
- Assign a duct type with the sizing criteria you want
- HVAKR sizes each duct to meet all criteria
- Review and adjust as needed
Fittings and Transitions
Section titled “Fittings and Transitions”Fitting Types
Section titled “Fitting Types”Select fittings for duct connections:
- Elbows - 90°, 45°, or radius
- Tees - Branch takeoffs
- Transitions - Size changes
- Offsets - Vertical or horizontal shifts
Fitting Loss Coefficients
Section titled “Fitting Loss Coefficients”Fittings add pressure loss:
- ASHRAE fitting loss coefficients
- Based on fitting geometry
- Included in total pressure calculation
Reducing Losses
Section titled “Reducing Losses”Minimize fitting losses:
- Use larger radius elbows
- Avoid abrupt transitions
- Use turning vanes where needed
Pressure Calculations
Section titled “Pressure Calculations”Pressure Graph
Section titled “Pressure Graph”View the pressure profile through the system:
- Static pressure at each point
- Velocity pressure
- Total pressure
Critical Path
Section titled “Critical Path”Identify the critical path:
- Highest pressure drop path
- Determines fan sizing
- Other paths need balancing
Fan Sizing
Section titled “Fan Sizing”The fan must overcome:
- Total duct pressure drop
- Terminal unit pressure drop
- Filter pressure drop
- Coil pressure drop
3D Visualization
Section titled “3D Visualization”View the duct layout in 3D:
- Rotate and zoom the model
- Check for interferences
- Verify routing and sizing
Best Practices
Section titled “Best Practices”- Route before sizing - Establish routing first
- Use consistent duct types - Keep sizing criteria consistent within a run
- Check velocities - Stay within acceptable ranges
- Verify pressure drop - Within equipment capability
- Document routing - For construction drawings