Unit Ventilator

Stencil:  Zone HVAC Stencil: Unit Ventilator

Type: UnitaryZoneEqmt

Sub Type: Unit Ventilator

EnergyPlus IDF Objects

EnergyPlus Object - ZoneHVAC:WatertoAirHeatPump

The Unit Ventilator is zone equipment that contains a number of different components, including:

• Cooling Coil

• Heating Coil

• Supply Air Fan

Component Information

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

Figure - Simergy Component Properties Table

The properties in bold are required Value Entries or selections.  

The unit is controlled to meet the zone (remaining) heating or cooling demand. If there is a heating demand, the cooling coil is off and the hot water flow through the heating coil is throttled to meet the demand. The hot water control node must be specified (same as the hot water coil inlet node). If there is a cooling demand from the zone, the hot water coil is off and the chilled water flow through the cooling coil is throttled to meet the load. The cooling coil

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 Supply Air Flow Rate

This field allows the user to control how outdoor air is used in the unit ventilator system. The unit ventilator system described by this syntax has its own outdoor air handler. The three options for outdoor air control are “VariablePercent”, “FixedTemperature” and “FixedAmount”. Those keys are the only allowed choices for this parameter. In general, the variable percent control will attempt to vary the amount of outdoor air between some minimum and maximum schedules of fractions (see next two fields) to best meet the current heating or cooling load. The fixed temperature control will vary the amount of outdoor air between the minimum schedule (fraction of maximum, see next field) and 100% available outdoor air to come as close as possible to a desired mixed air temperature (see 2 fields down) that can be scheduled. The fixed amount control will fix the outdoor air flow rate as minimum outdoor air flow rate and schedule specified by the user and automatically set the maximum and minimum outside flow rate to be equal by ignoring the maximum outdoor air flow rate.

Minimum Outdoor Air Flow Rate

This field allows the user to enter the minimum volumetric flow rate of outdoor air (in m³/sec) that will be brought in to the unit ventilator. The actual minimum outdoor air flow rate will be this number multiplied by the schedule value from the minimum outdoor air schedule. If “FixedAmount” type is selected as the outdoor air control strategy, the outdoor air flow rate will be fixed as this field and the unit ventilator will automatically set the maximum and minimum outside flow rate to be equal by ignoring the maximum outdoor air flow rate.

Minimum Outdoor Air Schedule

This field contains a schedule name (ref: Libraries:Schedules: Schedule Editor) that should contain values for the minimum outdoor air used by the unit ventilator system for IAQ or other reasons. Note that if the unit ventilator is scheduled off or if there is no load sensed in the zone that the system will not operate even to achieve the minimum air fraction. However, if the system is operating, it will always bring in this fraction of the minimum air flow rate (see minimum air flow rate field above). If “FixedAmount” type is selected as the outdoor air control strategy, the actual outdoor air flow rate will be this number multiplied by the minimum outdoor air flow rate in the field above. The unit ventilator will automatically set the maximum and minimum outdoor air schedule to be equal by ignoring the maximum outdoor air schedule.

Maximum Outdoor Air Flow Rate

This field allows the user to enter the maximum volumetric flow rate of outdoor air that can be brought into the unit ventilator system in m³/sec. This parameter should be some real number greater than zero. Note that the value for this parameter may be less than the maximum air flow rate of the unit ventilator and this may affect the maximum fraction of outdoor air within the control strategy defined above. This parameter is an absolute maximum and will supercede any scheduled fraction of the unit ventilator maximum airflow rate. If “FixedAmount” type is selected as the outdoor air control strategy, this field will be ignored and be automatically set to be equal to the minimum outdoor air flow rate specified in the field above.

Maximum Outdoor Air Fraction or Temperature

This field can have one of two meanings depending the type of control selected in the outdoor air control type parameter above. If “VariablePercent” or “FixedAmount” was selected, then this field is a schedule name (ref: Schedule) corresponding to a maximum air fraction schedule. Furthermore, if “FixedAmount” type is selected as the outdoor air control strategy, this field will be ignored and be automatically set to be equal to the minimum outdoor air fraction specified in the field below. Note that this is a fraction of the maximum airflow rate field (see parameter above) for the unit ventilator. If “FixedTemperature” control was selected, then this field is still a schedule name (ref: Libraries:Schedules: Schedule Editor), but it corresponds to a schedule of mixed air temperatures that the outdoor air control will try to attain.

Supply Air Fan Name

This field specifies the type of supply air fan used by this unit ventilator. The supply air fan is part of the unit ventilator compound object. See table below for selection options source.

Coil Option

This field allows the user to specify the coil operating options as one of the following options: None, Heating, Cooling or HeatingAndCooling. If None is selected, the unit ventilator does not have any coils, and any other input will be ignored. If either Heating or Cooling is selected, only a heating or cooling coil, respectively, is present. Thus, only four more inputs will be expected. If HeatingAndCooling is selected, both heating and cooling coil input must be entered, and the unit ventilator will have both a heating and a cooling coil.

Heating Coil Name

This field is the type of coil that is used for heating in the unit ventilator system. It is used in conjunction with the heating coil name (see next field) to specify the heating coil present within the system.   See table below for selection options source.

Heating Convergence Tolerance

The control tolerance for the unit heating output. This field allows the user some control over how closely the heating coil will control the air side conditions. The relative size of this parameter relates directly to the closeness of the control. A very small value in this field will result in tight control and will probably result in larger numbers of iterations. A large value in this field will result in looser controls and could result in unsatisfactory fluctuations in supply conditions (that could in turn result in excessive iterations). Initial experience with this parameter lends to the recommendation of using 0.001 as a starting point. This field is ignored for gas and electric heating coils.

Cooling Coil Name

This field is the type of coil that is used for cooling in the unit ventilator system. It is used in conjunction with the cooling coil name (see next field) to specify the cooling coil present within the system.   See table below for selection options source.

Cooling Convergence Tolerance

The convergence tolerance for the unit cooling output. This field allows the user some control over how closely the cooling coil will control the air side conditions. The relative size of this parameter relates directly to the closeness of the control. A very small value in this field will result in tight control and will probably result in larger numbers of iterations. A large value in this field will result in looser controls and could result in unsatisfactory fluctuations in supply conditions (that could in turn result in excessive iterations). Initial experience with this parameter lends to the recommendation of using 0.001 as a starting point.

Availability Manager List Name

This optional input field is the name of an AvailabilityManagerAssignmentList object. An Availability Manager Assignment List is a list of Availability Managers giving both Availability Manager type and name. The availability managers in the list apply to this unit ventilator object’s fan. If the unit ventilator is available (per the Availability Schedule Name input field above) and this input field has a valid availability manager assignment list name, then the availability managers in the list determine when and if the fan of this unit ventilator object should be on or off.

Property Value Drop Down List Sources

EnergyPlus InputOutput Reference Unit Ventilator description  

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