Four Pipe Induction (Passive or Active)

Stencil:  Zone HVAC Stencil: 4-Pipe Induction Active HeatCool

Type: Air Terminal

Sub Type: CAV_PassiveFourPipeInduction

 

Stencil:  Zone HVAC Stencil: 4-Pipe Induction Passive HeatCool

Type: Air Terminal

Sub Type: CAV_ActiveFourPipeInduction

 

Note: Requires a connection to a chilled water loop and a hot water loop

EnergyPlus IDF Objects

EnergyPlus Object - AirTerminal:SingleDuct:ConstantVolume:FourPipeInduction

Component Information

Note: The property information is the same for both components.  The user selects which type with the Sub Types drop down list.

 

When the user is in the Zone HVAC Groups Diagram workspace or the Air Loops Diagram Workspace and they select a  Four Pipe Induction component shape, the following properties will be displayed in the lower left section of the workspace.

 

The four pipe induction terminal unit provides local hot water heating or chilled water cooling of induced zone air which then mixes with centrally conditioned supply air. An air conditioning system consisting of these terminal units is effectively a mixed central air / local hydronic system. The centrally conditioned air supplied to the induction terminal units is constant volume at quite high pressure. The central air is discharged through a nozzle in the terminal unit, inducing a flow of room air over a hydronic heating/cooling coil. The coil is connected either to a single inlet and outlet pipe (2 pipe unit) or to 2 inlets and 2 outlets (4 pipe unit). The heated or cooled induced air mixes with the centrally conditioned air before being discharged into the zone. The terminal units are usually expected to do only sensible cooling – any dehumidification is done by the central air conditioning system.

 

The EnergyPlus model of the four pipe induction terminal unit is a compound component consisting of a hot water heating coil, a chilled water cooling coil, and an air mixer. The unit has two inlet air streams: the centrally conditioned supply air and the induced air from the zone. The induced air passes first through the heating coil, then through the cooling coil and finally through the mixer. The central supply air goes directly into the mixer. The water flow through the hot or cold water coil is varied to meet the zone air conditioning requirement. Note that EnergyPlus models the four pipe induction terminal unit as having separate heating and cooling coils whereas real units have only a single coil used for both heating and cooling. Note also that the four pipe induction unit model can be used to model a two pipe unit by simply adjusting the heating and cooling coil schedules so that the heating coil is off when the cooling coil is on and vice versa.

 

The Four Pipe Fan Induction Unit is zone equipment that contains a number of different components, including:

 

Figure - Simergy Component Properties Table

 

The properties in bold are required Value Entries or selections.  

Name

Simergy automatically defines a unique name for each component.  This can be changed by the user if desired.

Availability Schedule Name

The availability is established by selecting an available library entry from the drop down list.  The source for the options listed is Libraries:Schedules:Schedule Editor:Availability Schedules (Schedule Types)

Maximum Total Air Flow Rate

The maximum volumetric air flow rate discharged from the unit in cubic meters per second. Since this is a constant air volume unit, this is also the design, rated air flow 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 air flow rate to primary supply air flow rate. The default is 1.0 –the supply air induces an equal amount of zone air.

Heating Coil Name

The name of the heating coil component that composes part of the fan coil unit.  See table below for selection options source.

Maximum Hot Water Flow Rate

The maximum hot water volumetric flow rate (m3/sec) through the fan coil unit’s heating coil.

Minimum Hot Water Flow Rate

The minimum hot water volumetric flow rate (m3/sec) through the fan coil unit’s heating coil.

Heating Convergence Tolerance

The convergence tolerance for the control of the unit heating output. The unit is controlled by matching the unit output to the zone demand. For units with water coils, the model must be numerically inverted to obtain a specified output. The heating convergence tolerance is the error tolerance used to terminate the numerical inversion procedure.

Cooling Coil Name

The name of the cooling coil component that composes part of the fan coil unit .   See table below for selection options source.

Maximum Cold Water Flow Rate

The maximum cold water volumetric flow rate (m3/sec) through the fan coil unit’s cooling coil.

Minimum Cold Water Flow Rate

The minimum cold water volumetric flow rate (m3/sec) through the fan coil unit’s cooling coil.

Cooling Convergence Tolerance

The convergence tolerance for the control of the unit cooling output. The unit is controlled by matching the unit output to the zone demand. For units with water coils, the model must be numerically inverted to obtain a specified output. The cooling convergence tolerance is the error tolerance used to terminate the numerical inversion procedure.

 

For remaining property descriptions - please refer to the EnergyPlus Input Output Reference for this object.

 

 

 

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