System Types

The System Types page defines project-wide system design parameters: a system description for reports, the duct types available for duct layout, fitting loss coefficients used in pressure calculations, and the register criteria used to select registers for each space type.

Central and terminal unit equipment is configured per system in System Design > Configuration, not here.

System Description

A free-text description of the project’s HVAC system approach. This appears in reports such as the Basis of Design.

Duct Types

Duct types define the sizing criteria HVAKR uses when it sizes ducts in the Duct Layout pane. Click Create Duct Type to add one. Click Import to bring duct types in from a template.

Properties

• Duct Type - Descriptive name (e.g., “Supply Trunk”, “Low-Velocity Branch”)
• Max Pressure Drop - Maximum friction rate, in inches of water per 100 feet
• Max Velocity - Maximum air velocity, for noise control
• Max Height - Maximum duct height, for fitting within plenum space. Liner thickness is included in this measure
• Liner Thickness - Duct liner thickness, which reduces the free area
• Color - Display color used when rendering ducts on sheets

Max Pressure Drop and Max Velocity are the two criteria a sized duct must meet. Max Height is not a pass or fail test. It caps the height as the duct grows. It also turns a round duct into a rectangular one. See Duct Sizing for the full sizing behavior.

Fitting Loss Coefficients

Each auto-placed fitting type adds pressure loss through a project-wide loss coefficient (Cʟ). Set Cʟ (Main) for every type, plus Cʟ (Branch) for wyes.

HVAKR ships a default coefficient for each type that you can override here. A selected fitting in Duct Layout can still override these defaults locally.

Register Criteria

Register criteria are set per space type. They build each space’s register schedule. The schedule gives the number of registers, the inlet size they use, and the airflow, face velocity, and NC each register runs at. The API returns this schedule with the rest of the calculator results. Click Create Space Type to add a row.

For each of supply, return, and exhaust you can set:

• Register Model - The register product model to use. It is required. A space type without one is reported as an error instead of scheduled
• Max Flow Rate - Maximum airflow per register. It also sets the register count. HVAKR divides the space’s design airflow by this value and rounds up
• Max Velocity - Maximum face velocity
• Max NC - Maximum noise criterion rating

HVAKR then takes the first inlet size of the selected model that meets all three limits. When no inlet size meets them, it adds one more register and tries again.

Best Practices

1. Use separate duct types for mains and branches - Branches typically need lower velocity limits for noise control
2. Set realistic height limits - Match the available plenum depth
3. Set NC limits by space type - Noise-sensitive spaces like conference rooms need lower NC ratings