Properties
Properties
The properties section gives all the details of the system and its various components. Here, equipment libraries can be selected for each component and sizing and control information can be entered. Most of the properties can be edited however properties specific to a piece of equipment (i.e. coil full load energy rate) are read only and can only be edited in the equipment library.
Zone Level Equipment
If there are any zone level equipment included in the system, they will be listed in the Zone Level Equipment tab. As pieces of equipment are added or removed, the list in the tab will update. The equipment libraries can be selected here.
Component Name
This is the name of the specific component in the system and will match the tag name above the component in the system diagram. This name is editable.
Category
This is the library where this specific component is found.
Type
This is a subcategory in the library where this specific component is found.
Library Items
This is the actual library member that will be used to represent this component.
Zone Equipment Availability Manager
The Zone Equipment Availability Manager tab contains information on night purge, schedule, fan cycling, and optimum start for the zone level equipment.
Night Purge
This control is used to precool the building during unoccupied hours by increasing the outdoor airflow.
Schedule
The schedule defines during which hours night purge may be applied.
Ventilation Maximum Limit Type
If the ventilation maximum limit type is set to constant, then the ventilation maximum limit will be a single temperature. If this is set to variable, then the ventilation maximum limit will vary throughout the day based on a schedule.
Ventilation Maximum Limit
This field defines either the ventilation maximum temperature if the limit type is set to constant or the ventilation maximum schedule if the limit type is set to variable.
Ventilation Temperature Difference
Default: 2°F
Typical Range: N/A
Min Max: infinity–infinity
Units: °F; °C
Typical Range: N/A
Min Max: infinity–infinity
Units: °F; °C
This is the difference between the indoor and outdoor temperature above which night purge can occur. If the difference between the indoor and outdoor temperature is lower than this value, the night purge will turn off.
Ventilation Minimum Limit
Default: 2°F
Typical Range: N/A
Min Max: infinity–infinity
Units: °F; °C
Typical Range: N/A
Min Max: infinity–infinity
Units: °F; °C
If any zone on this system is at a temperature lower than the ventilation temperature low limit, night purge will be turned off.
Ventilation Flow
Default: 1
Typical Range: N/A
Min Max: 0–infinity
Units: dimensionless
Typical Range: N/A
Min Max: 0–infinity
Units: dimensionless
This is the fraction of the design supply airflow that can be admitted as outside air during night purge. This can be greater than 1.
Control Zone Name
This is the zone used to compare the indoor air temperature to the outdoor air temperature to calculate the ventilation temperature difference. This field is only available in the project and only after zones have been assigned to the system. Note, in the project this field will be shown even before zones have been assigned but cannot be edited until after zones have been assigned to the system. By default, the first zone assigned to the system will be set as the control zone but any zone assigned to the system can be selected from this dropdown.
Fan Performance Modifier
This allows the fan to use different performance parameters when running in night purge mode.
Fan Cycling
This availability manager defines the conditions under which the fans will cycle. Note, to cycle the fans based on occupancy, go to the Schedule tab of the Availability Manager properties and select Cycle with occupancy in control zone or Cycle with occupancy based on all zones from the dropdown.
Schedule
The schedule defines during which hours this fan cycling may be applied.
Control Type
● No Fan Cycling: This availability manager will have no affect and the fans will follow the operation dictated by the fan schedule.
● Cycle with all loads: The system will cycle on if any of the spaces on the system are outside the temperature setpoints.
● Cycle with loads in controlled zone: The system will cycle on only if a particular zone on the system is outside the temperature setpoints.
● Cycle with zone fans on load: The zone fans (not system fans) will cycle on if any of the spaces on the system are outside the temperature setpoints.
● Cycle with cooling load: The system will cycle on if any of the spaces on the system are outside the cooling temperature setpoint.
● Cycle with heating load: The system will cycle on if any of the spaces on the system are outside the heating temperature setpoint.
● Cycle zone fans on heating load: The zone fans (not system fans) will cycle on if any of the spaces on the system are outside of the heating temperature setpoint.
Thermostat Tolerance
Default: 1
Typical Range: N/A
Min Max: -infinity–infinity
Units: °F; °C
Typical Range: N/A
Min Max: -infinity–infinity
Units: °F; °C
This is the number of degrees outside the temperature set points at which the system will cycle on.
Cycling Run Time
Default: 3600 seconds
Typical Range: N/A
Min Max: -infinity–infinity
Units: seconds
Typical Range: N/A
Min Max: -infinity–infinity
Units: seconds
This is the number of seconds that the system will run after it has cycled on.
Schedule
Systems can be controlled to run based on an on/off schedule or based on occupancy.
Fan Cycling based on Occupancy/Schedule
The fans can be cycled on and off based on a simple schedule or based on the occupancy of a single zone or all the zones on the system.
Scheduled
The schedule can be chosen from the schedules library.
Cycle with occupancy in controlled zone
Fans will remain on when a particular zone is occupied and will cycle on and off when that zone is unoccupied. Note, the control zone can only be selected in the project, not in the library.
Cycle with occupancy based on all zones
Fans will remain on when any zone on the system is occupied and will cycle on and off when all zones on the system are unoccupied.
Optimum Start
The optimum start availability manager allows the heating and cooling equipment to start operating before the building becomes occupied so that by the time the building becomes occupied, the building is no longer at the drift point temperature but has been brought to the set point temperature for occupant comfort.
Schedule
The schedule defines during which hours this availability manager may be applied.
Control Type
Optimum Start Based on Control Zone: The optimum start controls will be controlled to one specific zone. This field is only available in the project and only after zones have been assigned to the system. Note, in the project this field will be shown even before zones have been assigned but cannot be edited until after zones have been assigned to the system. By default, the first zone assigned to the system will be set as the control zone but any zone assigned to the system can be selected from this dropdown.
Optimum Start based on fan schedule: This control will turn on the system based on the fan schedule.
Optimum Start Based on All Zones: The control will look at all the zones on the system and determine the earliest time that the equipment needs to start to serve all zones.
Terminal Devices
The Terminal Devices tab contains properties on airflow and equipment in the terminal device. Each system is required to have one and only one terminal device. Terminal devices can be changed for different zones on the same system in the Configure Zone Equipment tab in the project.
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Diffuser (no properties)
The Diffuser represents a diffuser into a zone that has no VAV damper, fan, or coil.
CV Terminal Reheat
The Constant Volume with reheat terminal device is used in constant volume systems in order to reheat the supply air before it enters the zone.
Reheat Coil Type: This is the heating coil library sub category which also defines the energy type that is used to heat the coil.
Reheat Coil: This is the specific heating coil library that will be used as the heating coil.
Maximum Reheat Air Temperature: This is the maximum temperature to which the supply air can be heated by the reheat coil. If this field is left blank, there will be no upper limit to the supply air temperature.
VAV Terminal
The VAV Terminal is used to control the supply air of a VAV system using a VAV damper but has no coil or fan.
Damper Heating Action: There are three different options for how the supply airflow can be controlled when the system is in heating mode.
Normal: During heating mode the damper will always remain at the minimum position and the supply air temperature will be increased as the heating load increases. The equipment will be sized so the peak heating load can be satisfied at the minimum heating supply airflow and maximum heating supply air dry bulb.
Dual Maximum: During heating mode, the damper will remain at the minimum position and the supply air temperature will be increased as the heating load increases. Once the supply air temperature reaches a maximum, the VAV damper will start to open, increasing the supply airflow at the maximum supply air temperature. The maximum heating supply airflow will be less than the maximum cooling supply airflow. This control type is only used for hot water reheat coils.
Dual Maximum 100% in Heating: During heating mode, the damper will remain at the minimum position and the supply air temperature will be increased as the heating load increases. Once the supply air temperature reaches a maximum, the VAV damper will start to open, increasing the supply airflow at the maximum supply air temperature. The maximum heating supply airflow will be equal to the maximum cooling supply airflow. This control type is only used for hot water reheat coils.
Clg VAV min Type
The cooling VAV minimum can either be set to a constant value or the VAV minimum can vary. According to a schedule.
Clg VAV min
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Default: 30% Clg Airflow
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: % Clg Airflow; cfm; cm3/s; m3/s; m3/hr
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When the Clg VAV min type is set to constant, this is the minimum supply air flow rate for the VAV system in terms of a percent of the maximum design air flow rate or as an airflow rate value.
When the Clg VAV min type is set to variable, a schedule can be chosen in this field that defines the changing VAV minimum.
VAV w/Reheat
The VAV with reheat terminal device is used to control the supply air of a VAV system using a VAV damper. The terminal box also contains a reheat coil to heat supply air before it enters the space.
Clg VAV min type: The VAV with reheat terminal device is used to control the supply air of a VAV system using a VAV damper. The terminal box also contains a reheat coil to heat supply air before it enters the space.
Clg VAV min
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Default: 30% Clg Airflow
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: % Clg Airflow; cfm; cm3/s; m3/s; m3/hr
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When the Clg VAV min type is set to constant, this is the minimum supply air flow rate for the VAV system in terms of a percent of the maximum design air flow rate or as an airflow rate value.
When the Clg VAV min type is set to variable, a schedule can be chosen in this field that defines the changing VAV minimum.
Reheat coil type: This is the heating coil library sub category.
Reheat coil: This is the specific heating coil library that will be used as the heating coil.
Damper Heating Action: There are three different options for how the supply airflow can be controlled when the system is in heating mode.
● Normal: During heating mode the damper will always remain at the minimum position and the supply air temperature will be increased as the heating load increases. The equipment will be sized so the peak heating load can be satisfied at the minimum heating supply airflow and maximum heating supply air dry bulb.
● Dual Maximum: During heating mode, the damper will remain at the minimum position and the supply air temperature will be increased as the heating load increases. Once the supply air temperature reaches a maximum, the VAV damper will start to open, increasing the supply airflow at the maximum supply air temperature. The maximum heating supply airflow will be less than the maximum cooling supply airflow. This control type is only used for hot water reheat coils.
● Dual Maximum 100% in Heating: During heating mode, the damper will remain at the minimum position and the supply air temperature will be increased as the heating load increases. Once the supply air temperature reaches a maximum, the VAV damper will start to open, increasing the supply airflow at the maximum supply air temperature. The maximum heating supply airflow will be equal to the maximum cooling supply airflow. This control type is only used for hot water reheat coils.
Maximum Reheat Temperature
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: °F; °C
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This is the maximum temperature the heating supply air is allowed to reach.
Htg VAV max
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Default: Autosize
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Typical Range: N/A
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Min Max: -infinity to infinity
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Units: % Clg Airflow; cfm/sq•ft (floor); (m3/s)/sq•m (floor); (m3/hr)/sq•m (floor)
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This field is only used if the Damper Heating Action is set to “Dual Maximum Control”. This value indicates the maximum supply airflow during heating when the VAV damper increases from the minimum value as the heating load increases. This can be input as a percent of the total cooling supply airflow or as an air flow rate per floor area.
VAV Fan Assisted Reheat
The VAV with fan assisted reheat terminal box contains a VAV damper to control airflow into the space as well as a heating coil in series with a variable speed fan. The fan controls the amount of supply air entering the zone and is commonly found in UFAD systems.
Clg VAV min
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Default: 30% Clg Airflow
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: % Clg Airflow; cfm; cm3/s; m3/s; m3/hr
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This is the minimum supply air flow rate for the VAV system in terms of a percent of the maximum design air flow rate or as an airflow rate value.
Heating Coil Type: This is the heating coil library sub category.
Heating Coil: This is the specific heating coil library that will be used as the heating coil.
Fan Type: This is the fan library sub category.
Variable Volume Fan: This is the specific fan library that will be used as the fan in this system.
Parallel Fan Powered VAV
The parallel fan powered VAV boxes contain a VAV damper to control airflow into the zone as well as a heating coil in parallel with a constant volume fan that recirculates air from the zone. Only the recirculated air passes through the fan but both the recirculated and supply air passes through the heating coil. The air entering the zone is equal to the sum of the supply air and the recirculated air.
Clg VAV min
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Default: 30% Clg Airflow
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: % Clg Airflow; cfm; cm3/s; m3/s; m3/hr
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This is the minimum supply air flow rate for the VAV system in terms of a percent of the maximum design air flow rate or as an airflow rate value.
Heating Coil Type: This is the heating coil library sub category.
Heating Coil: This is the specific heating coil library that will be used as the heating coil.
Fan Type: This is the fan library sub category.
Constant Volume Fan: This is the specific fan library that will be used as the fan in this system.
Fan Flow Fraction
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Default: Autosize
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Typical Range: 0–1
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Min Max: 0–1
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Units: dimensionless
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The secondary fan in the terminal box doesn’t always need to run. The fan flow fraction represents the ratio of the current supply airflow to the maximum design supply airflow. When the current flow fraction is above this value, the secondary fan will not run. When the fan flow fraction is below this value, the secondary fan will run. For example, a fan flow fraction of 1 means the secondary fan will run all the time. If the fan flow fraction is 0.7, the secondary fan will only operate when the supply airflow is at 70% or less than the design supply airflow.
Series Fan Powered VAV
The series fan powered VAV boxes contain a VAV damper to control airflow into the zone as well as a heating coil in series with a constant volume fan that recirculates air from the zone. Both the recirculated and supply air pass through the fan and the reheat coil. The air entering the zone is equal to the sum of the supply air and the recirculated air.
Clg VAV min
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Default: 30% Clg Airflow
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: % Clg Airflow; cfm; cm3/s; m3/s; m3/hr
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This is the minimum supply air flow rate for the VAV system in terms of a percent of the maximum design air flow rate or as an airflow rate value.
Heating Coil Type: This is the heating coil library sub category.
Heating Coil: This is the specific heating coil library that will be used as the heating coil.
Fan Type: This is the fan library sub category.
Constant Volume Fan: This is the specific fan library that will be used as the fan in this system.
Dual Duct CV (no properties)
The dual duct constant volume terminal device is only available in the Dual Duct system category. Dual duct systems have separate air paths for hot and cold air. These air streams are mixed in this terminal device in order to adequately condition the space. Different proportions of the hot and cold air may be mixed but the sum of the airflows will be constant.
Dual Duct VAV
The Dual Duct VAV terminal device is only available in the Dual Duct system category. Dual duct systems have separate air paths for hot and cold air. These air streams are mixed in this terminal device in order to adequately condition the space. Different proportions of the hot and cold air may be mixed and the total supply airflow may vary.
Clg VAV min
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Default: 30% Clg Airflow
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: % Clg Airflow; cfm; cm3/s; m3/s; m3/hr
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This is the minimum supply air flow rate for the VAV system in terms of a percent of the maximum design air flow rate or as an airflow rate value.
Four Pipe Induction
The Four Pipe Induction terminal device comes with a water cooling coil and water heating coil. Centrally conditioned air is forced through this terminal unit through a nozzle, inducing room air to flow over these terminal coils. The unit has two inlets and two outlets so the unit can do cooling and heating simultaneously. This terminal device is only available in the Chilled Beam and Induction category.
Induction Ratio
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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The induction ratio is the ratio of the induced airflow through the unit to the primary supply airflow rate.
Heating Coil Type: This is the heating coil library sub category.
Heating Coil: This is the specific heating coil library that will be used as the heating coil.
Cooling Coil Type: This is the cooling coil library sub category.
Cooling Coil: This is the specific cooling coil library that will be used as the cooling coil.
Chilled Beam (Active) and Chilled Beam (Passive)
The Chilled Beam terminal device is used to do sensible cooling on centrally conditioned and dehumidified supply air. This terminal device includes a cooling coil. The chilled beam can be set to active or passive in the terminal device properties. This terminal device is only available in the Chilled Beam and Induction category.
Chilled Beam Type: Either active or passive chilled beams can be modeled. An active chilled beam supplies air through the unit in order to induce room air to pass over the beam. A passive chilled beam however uses only natural convection to cool the air.
Number of Beams
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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This is the number of chilled beams in the zone. This can be autosized based on the design load of the zone.
Beam Length
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: ft; m
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This is the length of each individual beam. This can also be autosized based on the design load in the zone.
Design Inlet Water Temperature
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: °F; °C
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This is the inlet water temperature as it enters the chilled beam.
Design Outlet Water Temperature
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: °F; °C
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This is the outlet water temperature as it leaves the chilled beam.
Coil Parameters
The advanced parameters can be used to define information to characterize the performance of the chilled beam using these equations.
Beam cooling output per unit length [W/m]
Coil heat transfer coefficient [W/(m2K)]
Room air mass flow rate across coil [kg/(m2s)]
Room air volumetric flow rate across coil per unit length [m3/(s•m)]
Where:
ΔT is the room air – water temperature difference (average water temperature is used) in degrees C.
ω is the water velocity in m/s.
qpr is the supply air flow rate per unit length [m3/(s•m)]
Coil Surface Area per Coil Length
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: m2/m
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Coefficient in the above equations
Coefficient a
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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Coefficient in the above equations
Coefficient n1
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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Coefficient in the above equations
Coefficient n2
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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Coefficient in the above equations
Coefficient n3
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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Coefficient in the above equations
Coefficient a0
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: m2/M
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This is the free area of the coil in plan view (for the air flow) per unit beam length.
Coefficient K1
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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Coefficient in the above equations
Coefficient n
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: dimensionless
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Coefficient in the above equations
Induction Ratio
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Default: blank
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Typical Range: N/A
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Min Max: 0 to 4
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Units: dimensionless
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Coefficient in the above equations. This value is sometimes known as the coefficient of conduction or Kin.
Leaving Pipe Inside Diameter
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Default: blank
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Typical Range: N/A
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Min Max: 0 to infinity
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Units: m
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This is the inner diameter of the leaving pipe.
Zone Sizing
The Zone Sizing tab contains information for zone level sizing properties.
Cooling Supply Air Dry Bulb
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Default: 55°F
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Typical Range: N/A
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Min Max: -infinity to infinity
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Units: °F, °C
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This is the temperature of the supply air as it enters the zone in cooling mode. Note: This temperature field is only used if there is a zone level cooling coil or a terminal box cooling coil. Otherwise this field will be ignored. Additionally, if the “Apply System Cooling SAT to Zone” field in the Sizing Properties tab is set to “yes”, this field will also be ignored and the “Supply Air Dry Bulb Cooling” temperature on the Sizing Properties tab will be used to size zone level cooling equipment. If the system level cooling equipment and zone level cooling equipment are sized to the same temperature, unmet hours could result.
Heating Supply Air Dry Bulb
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Default: 125°F
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Typical Range: N/A
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Min Max: -infinity to infinity
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Units: °F, °C
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This is the temperature of the supply air as it enters the zone in heating mode. Note: This temperature field is only used if there is a zone level heating coil or a terminal box heating coil. Otherwise this field will be ignored. Additionally, if the “Apply System Heating SAT to Zone” field in the Sizing Properties tab is set to “yes”, this field will also be ignored and the “Supply Air Dry Bulb Heating” temperature on the Sizing Properties tab will be used to size zone level heating equipment. If the system level heating equipment and zone level heating equipment are sized to the same temperature, unmet hours could result.