Zone Air Terminal Units regulate the volume of conditioned primary air from Central Systems to Zones. Each zone has its own air terminals, which are available in several different types, each designed to suit specific applications. Terminal units may contain reheat coils, cooling coils, or neither.


CAV No Reheat (CAV Box)

  • Max Air Flow Rate [CFM (IP) | L/S (SI)]: The design maximum volume flow rate. Defaults to Autosized.


CAV Reheat (Hydronic)

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: The heating capacity of the coil at the rated inlet and outlet air and water temperatures. Does not account for the effect of supply air fan heat.

  • Rated Entering Temperature [°F (IP) | °C (SI)]: The inlet air temperature corresponding to the rated heating capacity.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The inlet water temperature corresponding to the rated heating capacity.

  • Max Reheat Air [°F (IP) | °C (SI)]: This is the max temperature limit of the air leaving the terminal unit reheat coil (and being delivered to the zone). If the user leaves this field blank, no maximum reheat air temperature is enforced.

  • Heating Source: Heating Plant acts as the heating source for the coil.


CAV Reheat (Electric)

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the electric coil. Defaults to Autosized

  • Max Reheat Air [°F (IP) | °C (SI)]: This is the max temperature limit of the air leaving the terminal unit reheat coil (and being delivered to the zone). If the user leaves this field blank, no maximum reheat air temperature is enforced.

  • Electric Heat Efficiency %: This is user-inputted efficiency and can account for any loss. In most cases for the electric coil, this will be 100%.


VAV No Reheat (VAV Box)

  • Max Air Flow Rate [CFM (IP) | L/S (SI)]: The design maximum volume flow rate. Defaults to Autosized.

  • Min Airflow Fraction %: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.

  • Control for Outdoor Air: Options are On or Off


VAV Reheat (Hydronic)

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the hydronic coil. Defaults to Autosized.

  • Rated Entering Temperature [°F (IP) | °C (SI)]: The inlet air temperature corresponding to the rated heating capacity.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The inlet water temperature corresponding to the rated heating capacity.

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: The outlet water temperature corresponding to the rated heating capacity.

  • Minimum Airflow Fraction: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.

  • Max Reheat Air [°F (IP) | °C (SI)]: This is the max temperature limit of the air leaving the terminal unit reheat coil (and being delivered to the zone). If the user leaves this field blank, no maximum reheat air temperature is enforced.

  • Heating Source: Ideal Heating Plant acts as the heating source for the coil.


VAV Reheat (Electric)

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the electric coil. Defaults to Autosized

  • Max Reheat Air [°F (IP) | °C (SI)]: This is the max temperature limit of the air leaving the terminal unit reheat coil (and being delivered to the zone). If the user leaves this field blank, no maximum reheat air temperature is enforced.

  • Electric Heat Efficiency %: This is user-inputted efficiency and can account for any loss. In most cases for the electric coil, this will be 100%.

  • Minimum Airflow Fraction: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.


Induction Units

Air Flow Sizing Parameters

  • Max Airflow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate discharged from the unit. Since this is a constant air volume unit, this is also the design, rated airflow rate of the unit. Note that this is the total discharge flow rate – including both central supply and induced air.

  • Induction Ratio %: The ratio of induced airflow rate to primary supply airflow rate. Defaults to 250%.

  • Max Heating Fluid Flow [GPM (IP) | L/S (SI)]: The maximum hot water volumetric flow rate through the unit’s heating coil

  • Max Cooling Fluid Flow [GPM (IP) | L/S (SI)]: The maximum hot water volumetric flow rate through the unit’s heating coil

Cooling Coil Configuration

  • Design Air Flow [CFM (IP) | L/S (SI)]: The maximum possible air volume flow rate through the coil. Defaults to Autosized.

  • Design Fluid Flow [GPM (IP) | L/S (SI)]: The maximum possible water volume flow rate through the coil. Defaults to Autosized.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The design inlet water temperature. Defaults to Autosized.

  • Entering Air Temperature Drybulb [°F (IP) | °C (SI)]: The design inlet air temperature. Defaults to Autosized.

  • Entering Air Humidity Ratio: The highest value of humidity ratio possible for the design inlet air stream. Defaults to Autosized.

  • Leaving Air Temperature Drybulb [°F (IP) | °C (SI)]: The outlet air condition desired for design flow. Defaults to Autosized.

  • Leaving Air Humidity Ratio: The value of humidity ratio for the design outlet air stream. Defaults to Autosized.

  • Heat Exchanger Type: Options are:

    • Counter Flow

    • Cross Flow

  • Cooling Source: Defaults to Ideal Cooling Loop

Heating Coil Configuration

  • Design Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the hydronic coil. Defaults to Autosized.

  • Design Fluid Flow [GPM (IP) | L/S (SI)]: The maximum hot water volumetric flow rate through the unit’s heating coil. Defaults to Autosized.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The inlet water temperature corresponding to the rated heating capacity.

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: The outlet water temperature corresponding to the rated heating capacity.

  • Entering Air Temperature Drybulb [°F (IP) | °C (SI)]: The inlet air temperature corresponding to the rated heating capacity.

  • Leaving Air Temperature Drybulb [°F (IP) | °C (SI)]: The outlet air temperature corresponding to the nominal heating capacity.

  • Heating Source: Defaults to Ideal Heating Loop


4-Pipe Chilled Beam

  • Primary Air Flow [CFM (IP) | L/S (SI)]: This is the airflow rate of the primary air entering the beam from the central air handling unit. Defaults to Autosized.

  • Design Heating Fluid Flow [GPM (IP) | L/S (SI)]: The maximum hot water flow rate for the unit(s) serving the entire zone. Defaults to Autosized.

  • Design Cooling Fluid Flow [GPM (IP) | L/S (SI)]: The maximum chilled water flow rate for the unit(s) serving the entire zone. Defaults to Autosized.

  • Rated Primary Air Flow per Length [CFM/ft (IP) | L/S/m (SI)]: This is the primary air volume flow rate at rating conditions divided by the length of the beam.

  • Rated Cooling Capacity per Length [Btu/h/ft (IP) | Watts/m (SI)]: This is the beam cooling capacity at rating conditions divided by the length of the beam.This is only the cooling contributed by the cold water circulating through the convector and is separate from any cooling that may also be provided by the primary air.

  • Rated Heating Capacity per Length [Btu/h/ft (IP) | Watts/m (SI)]: This is the beam heating capacity at rating conditions divided by the length of the beam. This is only the heating contributed by the hot water circulating through the convector and is separate from any heating that may also be provided by the primary air.

Cooling Coil Configuration

  • Rated Room Air to Fluid Difference [°F (IP) | °C (SI)]: This input defines the value of the temperature difference between the room air and entering chilled water at the rating point.

  • Rated Fluid Flow per Length [GPM/ft (IP) | L/S/m (SI)]: This input defines the value of the chilled water flow rate per meter length of the beam at the rating point.

  • Cooling Source: Defaults to Ideal Cooling Loop

Heating Coil Configuration

  • Rated Room Air to Fluid Difference [°F (IP) | °C (SI)]: This input defines the value of the temperature difference between the entering hot water and the room air at the rating point.

  • Rated Fluid Flow per Length [GPM/ft (IP) | L/S/m (SI)]: This input defines the value of the hot water flow rate per meter length of the beam at the rating point.

  • Heating Source: Defaults to Ideal Heating Loop


2-Pipe Chilled Beam

  • Chilled Beam Type: Options are:

    • Active - primary air is supplied through the beam, inducing some secondary zone air into contact with the coil. This unit acts as an active convector.

    • Passive - simply a passive, finned convector. Primary air is supplied through a normal diffuser.

  • Cooling Source: Defaults to Ideal Cooling Loop.

  • Primary Air Flow [CFM (IP) | L/S (SI)]: This is the airflow rate of the primary air entering the beam from the central air handling unit.

  • Max Cooling Fluid Flow [GPM (IP) | L/S (SI)]: The maximum chilled water flow rate for the unit(s) serving the entire zone.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The design inlet water temperature.

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: The design outlet water temperature.


Parallel Fan Powered Box (Hydronic)

  • Primary Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate of primary air through the unit. This is the primary airflow rate at full cooling load when the primary air damper is fully open.

  • Secondary Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate of secondary air through the unit. This flow rate can be any amount but is commonly less than the maximum primary airflow rate.

  • Minimum Primary Airflow Fraction: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.

Heating Coil Configuration

  • Entering Air Temperature [°F (IP) | °C (SI)]: The inlet air temperature corresponding to the rated heating capacity.

  • Leaving Air Temperature [°F (IP) | °C (SI)]: The outlet air temperature corresponding to the nominal heating capacity.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The design inlet water temperature.

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: The design outlet water temperature.

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the hydronic coil. Defaults to Autosized.

  • Heating Source: Defaults to Ideal Heating Loop.


Parallel Fan Powered Box (Electric)

  • Primary Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate of primary air through the unit. This is the primary airflow rate at full cooling load when the primary air damper is fully open.

  • Secondary Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate of secondary air through the unit. This flow rate can be any amount but is commonly less than the maximum primary airflow rate.

  • Minimum Primary Airflow Fraction: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.

Heating Coil Configuration

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the electric coil. Defaults to Autosized

  • Max Reheat Temperature [°F (IP) | °C (SI)]: This is the max temperature limit of the air leaving the terminal unit reheat coil (and being delivered to the zone). If the user leaves this field blank, no maximum reheat air temperature is enforced.

  • Electric Heat Efficiency %: This is user-inputted efficiency and can account for any loss. In most cases for the electric coil, this will be 100%.


Series Fan Powered Box (Hydronic)

  • Max Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate through the unit. Since this is a constant air volume unit, this is also the design, rated airflow rate of the unit.

  • Primary Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate of primary air through the unit. This is the primary airflow rate at full cooling load when the primary air damper is fully open.

  • Minimum Primary Airflow Fraction: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.

Heating Coil Configuration

  • Entering Air Temperature [°F (IP) | °C (SI)]: The inlet air temperature corresponding to the rated heating capacity.

  • Leaving Air Temperature [°F (IP) | °C (SI)]: The outlet air temperature corresponding to the nominal heating capacity.

  • Entering Fluid Temperature [°F (IP) | °C (SI)]: The design inlet water temperature.

  • Leaving Fluid Temperature [°F (IP) | °C (SI)]: The design outlet water temperature.

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the hydronic coil. Defaults to Autosized.

  • Heating Source: Defaults to Ideal Heating Loop.


Series Fan Powered Box (Electric)

  • Max Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate through the unit. Since this is a constant air volume unit, this is also the design, rated airflow rate of the unit.

  • Primary Air Flow [CFM (IP) | L/S (SI)]: The maximum volumetric airflow rate of primary air through the unit. This is the primary airflow rate at full cooling load when the primary air damper is fully open.

  • Minimum Primary Airflow Fraction: This numeric field defines the minimum air volume flow rate to the zone while the system is operating, specified as a fraction of the maximum airflow rate. The minimum zone fraction is normally specified to meet the minimum ventilation requirement for the occupants. This value must be between 0 and 1.

Heating Coil Configuration

  • Rated Capacity [Btu/h (IP) | Watts (SI)]: This is the maximum capacity of the electric coil. Defaults to Autosized

  • Max Reheat Temperature [°F (IP) | °C (SI)]: This is the max temperature limit of the air leaving the terminal unit reheat coil (and being delivered to the zone). If the user leaves this field blank, no maximum reheat air temperature is enforced.

  • Electric Heat Efficiency %: This is user-inputted efficiency and can account for any loss. In most cases for the electric coil, this will be 100%.

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