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Air Conditioner Standalone

Stencil: Zone HVAC Stencil: AC Standalone

Type: Unitary Zone Equipment

Sub Type: Air Conditioner Window

EnergyPlus IDF Objects

EnergyPlus Object - ZoneHVAC:WindowAirConditioner

The Window Air Conditioner is a unit of zone equipment made up of other components. Each window air conditioner consists of an outdoor air mixer, a fan, and a direct expansion (DX) cooling coil. The input for a window air conditioner requires the names of these three pieces of equipment, and also requires the name of an availability schedule, the maximum unit airflow rate, and the maximum outdoor airflow rate for the unit.

A supply air fan operating mode schedule must also be specified. The supply air fan operating mode schedule value determines if the supply air fan can run continuously with the DX coil cycling on/off to match the zone cooling demand or the fan and DX coil can cycle on/off together to meet the cooling demand. The placement of the supply air fan, in relation to the DX coil, must also be specified (blow through or draw through). The cooling convergence tolerance is required, which is the tolerance denoting how closely the window air conditioner will meet the cooling load. The tolerance is always relative to the zone load (i.e., the unit will operate to meet the zone load to within the tolerance value times the zone load for each simulation timestep). Finally, the DX cooling coil type must be specified.

Component Properties

The table shows the properties that are displayed when the component is selected while in diagram mode. The second column shows the selection options available that are dictated by EnergyPlus or it shows the source for the library entries that are displayed in the drop down list.

Property Name	Value Sources/Options
Name	Simergy provides unique name (editable)
Availability Schedule Name
Maximum Supply Air Flow Rate	0-Min, Autosize
Maximum Outdoor Air Flow Rate	0-Min, Autosize
Supply Air Fan Name	Libraries/Fans&Pumps/SupplyFan/ConstantVolume
DX Cooling Coil Name	Libraries/Coils & HX Eqmt/CoolingCoilDX/CoilAirCoolingDXSingleSpeed
Supply AIr Fan Operating Module Schedule Name
Fan Placement	Draw through, Blow through
Cooling Convergence Tolerance	0-Min; 0.001 Default
Availability Manager List Name	Libraries/ControlSchemeList/SchemeList/AirLoopAvailabilityMgrScheme

Name

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

Field: Availability Schedule Name

Schedule that this component will operate or is available to operate.

Field: Maximum Supply Air Flow Rate

The maximum volumetric airflow rate through the window air conditioner in cubic meters per second. Since the unit operates by cycling on/off, this is also the design, rated airflow rate of the unit.

Field: Maximum Outdoor Air Flow Rate

If the window air conditioner uses outdoor air, this field specifies the outdoor air volumetric flow rate in cubic meters per second. This flow rate should be less than or equal to the maximum airflow rate. A value of zero specifies no outdoor air. Note that the outdoor airflow rate is fixed: it cannot change during the simulation

Field:Supply Air Fan Name

The name of a constant volume fan component that composes part of the window air conditioner. Note that the fan’s maximum flow rate should be the same as the maximum airflow rate of the window air conditioner. A fan of type Fan:OnOff may be used with either cycling or continuous fan, and a fan of type Fan:ConstantVolume is used only with continuous fan (see Supply Air Fan Operating Mode Schedule field below). The fan’s inlet node should be the same as the outdoor air mixer’s mixed air node (for blow through) or the DX coil’s outlet node (for draw through). The fan’s outlet node should be the same as the DX coil’s air inlet node (for blow through) or the window air conditioner’s air outlet node (for draw through).

Field: DX Cooling Coil Name

The name of a DX cooling coil component that composes part of the window air conditioner unit. The DX coil air inlet node should be the same as the fan outlet node (for blow through) or the outdoor air mixer’s mixed air node (for draw through). The DX coil air outlet node should be the same as the window air conditioner’s air outlet node (for blow through) or the fan’s inlet node (for draw through).

Field: Supply Air Fan Operating Mode Schedule Name

This alpha field specifies the name of the supply air fan operating mode schedule. The supply air fan operating mode may vary during the simulation based on time-of-day or with a change of season. Schedule values of 0 denote that the supply air fan and the heating or cooling coil cycle on and off together to meet the heating or cooling load (a.k.a. AUTO fan). Schedule values other than 0 denote that the supply air fan runs continuously while the heating or cooling coil cycles to meet the load. If this field is left blank, the model assumes the supply air fan cycles with the heating or cooling coil throughout the simulation.

Field: Fan Placement

This input field has two choices: BlowThrough or DrawThrough. The first choice stands for “blow through fan”. This means that the unit consists of an outdoor air mixer followed by a fan followed by a DX coil. The fan “blows through” the DX coil. The second choice stands for “draw through fan”. This means that the unit consists of an outdoor air mixer followed by a DX coil followed by a fan. The fan “draws air through” the coil.

Field: Cooling Convergence Tolerance

This input field defines the convergence tolerance for the unit’s cooling output. This field allows the user some control over how closely the air conditioner 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 zone air temperature. Initial experience with this parameter lends to the recommendation of using 0.001 as the starting point.

The window air conditioner is controlled by matching its sensible (temperature) cooling output to the zone sensible load (demand). Because the performance of the DX coil is frequently non-linear, the air conditioner model must call the DX coil model several times (iterate) to determine the proper run time fraction to meet the zone load. The cooling convergence tolerance is the error tolerance used to terminate the iteration procedure when the following equation is satisfied:

The maximum number of iterations is limited, with a warning message generated if the above equation is not satisfied within the maximum number of iterations.

Field: 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 window air conditioner or object’s fan. If the window air conditioner 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 window air conditioner object should be on or off.

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