To Load Duct System Sizing

A complete HVAC route needs to be available in the current model. The terminal units —Grilles, Diffusers, or Plenum Boxes used in the route are already set for required Air Flow Rate (CFM) values.

Select (Duct System Sizing).
The Duct Sizing Section Summary dialog opens. The summary table displays empty records.
Click Settings to review the duct sizing settings prior to calculate.
The Duct Sizing Settings dialog opens.
Review or set unit, design data, size criteria and report parameters in the Settings dialog and click OK to apply the revised settings or Cancel to retain past settings and dismiss the Settings dialog.
The Duct Sizing Settings dialog closes.
In the Duct Sizing summary click Load System, and in the view select the air handling source component of the route.
Opens the Assign & Analyze Connection dialog for mapping flow types to available ends and when proceeded, the Duct Sizing Summary dialog populates section data. The Limit Duct Velocity is assigned to main duct at the start of the flow in Section:1. Duct lengths and default Correction factor values are populated.
Set desired terminal airflow and outlet pressure values (if needs to override default values set in DataGroup Instance Data) and click Calculate.
The summary gets refreshed with the revised values and the critical path report pops up indicating the path numbers of critical flow.
Note: You can lock pressure or velocity value of a duct section before recalculations.
Complete the Duct System Sizing properties and setting allowable values, aiming to achieve a minimal, constant pressure loss at all paths.
Double click in Summary of FLC column to review, assign/reassign correct ASHRAE fittings and correct loss coefficient and as required, override any values in the Fittings Loss Coefficient (FLC) Summary dialog.

The revised values effect in Duct Sizing Summary table. The FLC Summary dialog is kept open, as needed to revisit.
Review the pressure drop values in the critical path and redo revising duct sizing values in the duct section summary data.
Repeat the calculation to arrive at desired pressure loss.

Note: Use the Reports > Sections option to run the Critical Path report to review section to fix in critical path.
When done, close the dialog by clicking the windows [X] to unload Duct Sizing. A confirmation message prompts before closing, alerting "Data will not be retained after re-opening".

Fittings in critical loss section are set right by retuning their loss coefficient and correction factor values in FLC Table.