System Types
System types define the configuration of HVAC systems in your project. A system type includes the central unit, terminal units, and ductwork parameters.
Central Unit Types
Section titled “Central Unit Types”Central units are the main air handling equipment that conditions air before distribution.
Air Handling Units (AHU)
Section titled “Air Handling Units (AHU)”Factory-assembled or field-erected units with:
- Supply fan
- Cooling coil
- Heating coil (optional)
- Filters
- Outdoor air intake
Rooftop Units (RTU)
Section titled “Rooftop Units (RTU)”Packaged equipment installed on the roof:
- Self-contained with all components
- DX cooling with gas or electric heating
- Economizer for free cooling
Split Systems
Section titled “Split Systems”Separated indoor and outdoor components:
- Indoor air handler with fan and coil
- Outdoor condensing unit
Fan Coil Units
Section titled “Fan Coil Units”Terminal units that can also serve as central units for small zones:
- Local fan and coil
- Connected to chilled/hot water
Terminal Unit Types
Section titled “Terminal Unit Types”Terminal units provide zone-level control of airflow and temperature.
VAV Boxes
Section titled “VAV Boxes”Variable Air Volume terminals:
- Cooling only - Modulates airflow for cooling
- With reheat - Adds heating coil for zone heating
- Fan powered - Includes fan for increased airflow
Fan Coil Units
Section titled “Fan Coil Units”Local air handling with:
- Fan for air circulation
- Cooling and/or heating coil
- Connection to central plant
Constant Volume Terminals
Section titled “Constant Volume Terminals”Fixed airflow with:
- Temperature control via coil
- Used for simple applications
Duct Types
Section titled “Duct Types”Define ductwork parameters for the system.
Duct Material
Section titled “Duct Material”- Sheet metal - Most common, lowest friction
- Flexible - Easy installation, higher friction
- Fiberglass ductboard - Integrated insulation
- Fabric - Specialty applications
Sizing Method
Section titled “Sizing Method”- Velocity method - Size for target velocity
- Equal friction - Size for constant pressure drop per length
- Static regain - Maintain static pressure at branches
Duct Properties
Section titled “Duct Properties”- Friction rate - Pressure drop per 100 feet
- Maximum velocity - Limit for noise control
- Insulation - R-value for thermal protection
Register and Grille Types
Section titled “Register and Grille Types”Supply Registers
Section titled “Supply Registers”- Ceiling diffusers - Square, round, linear
- Sidewall registers - For perimeter delivery
- Floor registers - For underfloor systems
Return Grilles
Section titled “Return Grilles”- Ceiling returns - For plenum return
- Wall returns - Ducted return
- Transfer grilles - Between spaces
Creating System Types
Section titled “Creating System Types”- Go to Basis of Design > System Types
- Click Add System Type
- Configure the central unit, terminals, and ductwork
- Save for use in your project
System Type Templates
Section titled “System Type Templates”HVAKR includes templates for common system configurations:
- Single-zone RTU
- VAV with central AHU
- Fan coil with DOAS
- VRF/VRV systems
System Configuration Parameters
Section titled “System Configuration Parameters”Supply Air Temperature
Section titled “Supply Air Temperature”The design temperature of supply air:
- Cooling - Typically 55°F (13°C) for dehumidification
- Heating - Varies by system type
Airflow Limits
Section titled “Airflow Limits”- Minimum airflow - For ventilation (30-50% of peak)
- Maximum airflow - Peak cooling airflow
Coil Parameters
Section titled “Coil Parameters”- Cooling coil delta-T - Temperature drop across coil
- Heating coil capacity - Sized for heating load
Best Practices
Section titled “Best Practices”- Match system to building type - Use appropriate systems for the application
- Consider zones - Size systems for expected zone loads
- Plan for diversity - Account for simultaneous peak factors
- Specify realistic parameters - Use manufacturer data when available