Packaged Terminal Air Conditioners
The packaged terminal air conditioner (PTAC) is a compound object made up of other components. Each PTAC consists of an outdoor air mixer, direct expansion (DX) cooling coil, heating coil (gas, electric, hot water, or steam) and a supply air fan. PTACs can have draw through or blow through fan placement and can also be modeled by positioning the supply air fan between the outdoor air mixer and the DX cooling coil.
Note: Standard TRACE library members cannot be modified or deleted but they can be copied and edited.
Nominal Cooling Capacity
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Default: Auto Size box checked
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Typical Range: 7 to 19 Mbh
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: % Clg Capacity; W; kW; W/m2; W/ft2; tons; Btuh; MBh; tons/ft2; Btuh/ft2
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This checkbox indicates whether or not the capacity used for the selected cooling coil will be auto sized by the program or referenced from the user defined input.
Nominal Heating Capacity
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Default: Auto Size box checked
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Typical Range: 7 to 19 Mbh
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: % Htg Capacity; W; kW; W/m2; W/ft2; tons; Btuh; MBh; tons/ft2; Btuh/ft2
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This checkbox indicates whether or not the capacity used for the selected heating coil will be auto sized by the program or referenced from the user defined input.
Supply Fan
Supply Fan Placement
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Default: Blow through
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This selectable input field defines how the supply fan is arranged. There are two choices, Blow Through or Draw Through. The Blow Through choice indicates that the fan is located upstream of the coils. The Draw Through choice indicates that the fan is located downstream of the coils. These are the only configurations that are available and the HVAC system nodes used as inlets and outlet in the components must be arranged consistent with the flow path.
Cycling Mode
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Default: Cycling fan
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This field is used to determine how the unit fan is to be controlled. There are two possible choices:
1. Cycling Fan: The fan speed is chosen so that the unit capacity is greater than or equal to the heating / cooling load and the fan is cycled to match unit output with the load.
2. Continuous Fan: The fan speed is held constant to produce a fixed air flow rate whenever the unit is scheduled on.
Supply Fan Type
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Default: Constant Volume
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This is the type of supply fan that is associated with the library member. Two options are available: Constant or Variable Volume.
Supply Air Fan
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Default: Constant Volume Fan
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This input selection refers to the name of the fan library member that is used in this object.
Fan Full Load Energy Rate
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Default: 0.0002 kW/(cfm) ; Auto Size box is unchecked
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Typical Range: 0.0001 to 0.0004 kW/(cfm)
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: W; kW; W/(m3/sec); W/(m3/sec)-Pa; W/(cfm); W/(L/sec); W/(L/sec)-Pa; kW/(cfm); kW/(L/sec); kW/(cfm)-in H2O; kW/(L/sec)-Pa; W/(cfm)-in H2O; bhp
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This checkbox indicates whether or not the full load energy rate used for the selected fan will be auto sized by the program or referenced from the user defined input.
Pressure Rise
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Default: 4 inches H2O
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Typical Range: 0.25 to 5 inches H2O
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: in H2O; lb/ft2; psig; Pa; kPa; mm Hg; mm H2O; bar; in Hg; atm; mm CE; m CE; m H2O; mbar
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The value will be populated by default based on the fan library member selected. You can override this value and the units of measure.
Dead Band Airflow
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Default: Auto Size box checked
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Typical Range: N/A
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: m3/sec; cfm; cfm/ft2; (m3/s)/m2; % Clg Airflow; % Htg Airflow; L/s; m3/hr; (m3/hr)/m2
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This numeric field defines the supply air flow rate leaving the PTAC when neither cooling nor heating is required (i.e. the cooling and heating coils are not operating). This field is only used when the PTAC’s supply air fan operating mode schedule specifies continuous fan operation.
If the air conditioner’s supply air fan operating mode schedule specifies continuous fan operation and this value is set to zero or this field is left blank, then the model assumes that the supply air flow rate when no cooling/heating is needed is equal to the supply air flow rate when the cooling or heating coil was last operating (for cooling operation or heating operation).
Unitary Cooling
Unitary Cooling Type
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Default: Air-cooled
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This field specifies the type of DX cooling equipment that is to be modeled for this PTAC unit. Only one option is available: Air-Cooled.
Unitary Cooling
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Default: 20 to 75 Ton High Eff VAV Packaged VS RTU
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This field allows you to select the cooling coil library member that will be used for this PTAC equipment.
Unitary Cooling Design Airflow
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Default: Auto Size box checked
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Typical Range: 200 – 1200 cfm
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: m3/s; cfm; cfm/ft2; (m3/s)/m2; % Clg Airflow; cfm/ton; (m3/s)/(kW of Cooling Capacity); (m3/hr)/(kW of Cooling Capacity); (m3/s)/(W of Cooling Capacity); m3/hr ; m3/hr/m2; L/s; (L/s)(kW of Cooling Capacity)
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This input refers to the design cooling airflow value associated with the PTAC library member. This input can be used to scale the size of the coil as well.
Unitary Heating
Unitary Heating Type
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Default: Electric
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This field specifies the type of heating equipment to model for this PTAC. Four options are available to choose from: Electric, Gas, Steam, Water.
Unitary Heating
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Default: Electric Heating Coil
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Typical Range: N/A
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Min Max: N/A
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Units: N/A
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This field allows you to select the heating coil library member that will be used for this PTAC equipment.
Heating Design Airflow
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Default: Auto Size box checked
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Typical Range: 200 to 1200 cfm
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Min Max: 0 to 1,000,000,000,000,000 (this field cannot be left blank)
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Units: cm3/s; m3/s; cfm; cfm/ft2; (m3/s)/m2; % Htg Airflow; cfm/ton; (m3/s)/(kW); (m3/hr)/(kW); (m3/s)/(W); m3/hr ; m3/hr/m2
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This input refers to the design heating airflow value associated with the PTAC library member. This input can be used to scale the size of the coil as well.