Configuration

The Configuration pane is where you set up the HVAC equipment for each system. Equipment is defined by its components: you enable the components each unit has (coils, outside air, energy recovery, return air) and configure each one, rather than picking from a list of named equipment types.

Central Unit Configuration

Components

Enable the components your central unit has:

• Outside Air - The unit brings in outdoor air for ventilation
• ERV - An energy recovery wheel preconditions outdoor air with exhaust air
• Return Air - The unit recirculates return air
• Cooling Coil - The unit provides cooling
• Heating Coil - The unit provides heating
• Fan Heat - Accounts for the heat the supply fan adds to the airstream

Outside Air

Choose how the outdoor airflow is determined:

• Sum of Spaces - Total of each space’s ventilation requirement
• Multi-Zone - ASHRAE 62.1 multi-zone calculation using system ventilation efficiency
• Percent - A fixed percentage of supply air
• Custom - A fixed flow rate you enter

ERV

For units with an energy recovery wheel, set the ERV Wheel Effectiveness — the fraction of the exhaust-to-outdoor-air temperature difference recovered.

Cooling Coil

• Coil Type - Chilled Water or Direct Expansion
• CHW ΔT - Chilled water temperature rise, for chilled water coils
• Cooling Supply Air Temperature - Design temperature of air leaving the coil; typically 55°F (13°C) for dehumidification

Heating Coil

• Coil Type - Heating Hot Water, Direct Expansion, Gas Fired, or Electric
• HHW ΔT - Heating water temperature drop, for hot water coils
• Heating Supply Air Temperature - Design temperature of air leaving the coil

Supply and Return Air

Account for gains and losses between the unit and the spaces:

• Fan Heat Gain - Heat added to the airstream by the supply fan motor
• Other System Inefficiencies - Miscellaneous system losses
• Supply Duct Heat Gain/Loss and Supply Duct Leakage
• Return Duct Heat Gain/Loss and Return Duct Leakage

Energy Configuration

For energy estimates, configure:

• Heating Equipment Type - Heat Pump or Gas Furnace
• Cooling SEER (BTU/W·hr) - Cooling efficiency
• Heating COP - Heat pump coefficient of performance
• Heating AFUE - Gas furnace efficiency
• Operating Schedule - 24/7, 9am-5pm, or a custom hourly schedule
• Hours of Warm-up and Warm-up Capacity - Morning warm-up before occupancy

Terminal Unit Configuration

Terminal units are configured per zone using the same component approach:

• Return Air Component - Whether the terminal recirculates zone air
• Cooling Coil Component and Heating Coil Component - With the same coil type, ΔT, and supply air temperature settings as central units
• Outside Air Method - How outdoor air is apportioned to the terminal
• Pressure Loss - The terminal’s air pressure drop, used in duct pressure calculations

For example, a VAV box with hot water reheat is a terminal with a heating coil (Heating Hot Water) and no cooling coil, while a four-pipe fan coil has both coils.

Airflow Diagram and Psych Chart

Selecting a central unit, terminal unit, or space in the Configuration pane shows an airflow diagram above its data. Click the fullscreen button (Open the airflow diagram and psych chart) in the panel header to open a larger dialog with the diagram and a psychrometric chart side by side.

• Central and terminal units — the diagram shows the unit’s air states: mixed, coil-leaving, and supply. Its components connect these states. The chart plots the same states. The unit’s mixing, coil, and recovery processes connect them.
• Spaces — the diagram shows supply entering on the left and return and exhaust leaving on the right, with the differential below. For a decoupled terminal, direct outside air also enters on the left. The chart plots the space type’s indoor setpoint against the supply air the serving equipment delivers.

Comfort Zones

The chart shades one or more comfort zones. Each zone is a design condition a served space’s space type asks for: its cooling or heating setpoint ± its temperature range, and its target relative humidity ± its humidity range. Spaces that share the same design condition combine into one zone. The zone with the most floor area shades darkest. Hover a zone to see its Dry Bulb Min, Dry Bulb Max, RH Min, RH Max, and Floor Area.

A space with no space type, no setpoint, or no target humidity has no comfort zone to shade.

Space SHR Line

When a served space’s sensible heat ratio is available, the chart adds a dashed Space SHR line at that ratio’s slope — the split between sensible and latent heat the room itself carries, not the coil’s total split.

• Central and terminal units — the line runs through the floor-area weighted average setpoint of the served spaces. Where the unit’s supply point falls relative to the line shows whether the supply air carries the space load at the ratio the rooms actually split it.
• Spaces — the line runs from the supply air state toward the setpoint’s dry bulb (right in cooling, left in heating) and marks where it lands with an ×, unless the line reaches the saturation curve first, in which case no marker is drawn. When the setpoint sits off that landing, the supply air reaches the room drier or wetter than the space’s load split.

Space Airflows

Select a space in the Configuration pane to balance its airflows. The Design column is editable and the Required column shows the calculator’s minimum:

• Supply - Conditioned air the unit delivers to the space; defaults to the largest of the load-driven, code-driven (ACH/area), and ventilation requirements
• Return - Air drawn back from the space to be reconditioned
• Exhaust - Air discharged outdoors, driven by the space type’s exhaust requirement
• OA (VRP, Mixed) / OA (VRP, Direct) - Outdoor air required by the ASHRAE 62.1 Ventilation Rate Procedure. The label reads Mixed when outdoor air is blended into the supply at the unit, or Direct when a dedicated outdoor-air system (DOAS) delivers it straight to the space
• Transfer In and Transfer Out - Air moved to or from adjacent spaces
• Differential - Net balance: supply plus transfer in, minus return, exhaust, and transfer out. A positive value pressurizes the space.

HVAKR warns when a space is out of balance, so you can adjust return, exhaust, or transfer air until supply matches the air leaving the space.

Verification

After configuration, verify:

• Capacity meets peak loads
• Airflow is adequate for ventilation
• Pressure drop is within limits
• Equipment selections are realistic