Air Terminal
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A Air Terminal connects to a central air-handling unit, and it comes in various types, including variable air volume, variable air volume with a heating coil, constant air volume, and constant air volume with a heating coil.
Specify the Air Terminal Type, choosing from Variable Air Volume or Constant Air Volume. Control For Outdoor Air allows you to choose Yes or No. If Yes is selected, the minimum air flow rate for the air terminal is set with respect to the minimum ventilation rate required to meet zone ventilation requirements.
Specify the Control For Outdoor Air by choosing either Yes or No. If Yes is selected, the minimum air flow rate for the air terminal will be set with respect to the minimum ventilation rate required to meet the zone ventilation requirements.
Specify the Min. Airflow Input Method by choosing from Constant, Fixed Flow Rate, or Scheduled. If Constant is selected, the program utilizes the constant minimum air flow fraction entered in the following field to determine the minimum flow rate to the zone while the system is operating. This fraction is expressed as a ratio of the maximum flow rate. If a Fixed Flow Rate is chosen, the program uses the value for the minimum flow rate entered in the field named Fixed Minimum Air Flow Rate. On the other hand, if Scheduled is selected, the program obtains the minimum flow fraction from the schedule specified in the field called Minimum Air Flow Fraction Schedule Name. The default method is Constant, allowing for flexibility in determining the minimum flow rate based on your system requirements.
Specify the Constant Min. Air Flow Fraction, which determines the minimum flow rate to the zone while the system is operating, expressed as a fraction of the maximum air flow rate. Typically set to meet the minimum ventilation requirement for occupants, this fraction is crucial for proper system functioning.
Specify the Sizing Method, opting for Autosize or Manual. In the case of Autosize, the program will utilize its sizing routines, whereas Manual sizing demands completion of all numerical fields with valid entries for accurate sizing calculations.
Specify the Max. Air Flow Rate, representing the minimum flow rate to the zone during system operation, specified as a fixed minimum air flow rate in cubic meters per second. Typically, this rate is set to meet the minimum ventilation requirements for occupants.
Specify the Heating Coil Min. Water Flow Rate, usually zero for gas and electric coils. Set this value to the minimum design hot water or steam volumetric flow rate in cubic meters per second for the hot water or steam heating coil. Typically, it's set as a shut-off valve adjusted to zero. The steam volumetric flow rate is calculated at 100°C and 101325 Pa. If there's no reheat coil, leave this field blank.
Specify the Heating Coil Max. Water Flow Rate, also zero for gas and electric coils. Set this to the maximum design hot water or steam volumetric flow rate in cubic meters per second for the hot water or steam heating coil. This field is autosizable. Leave it blank if there's no reheat coil.
Specify the Max. Flow During Reheat, a fraction multiplied by the Maximum Air Flow Rate to determine the maximum volume flow rate in cubic meters per second allowed during reheat operation. This field is autosizeable and defaulted to autosize. If autosizeable is selected or the field is blank, the value is set to 0.002032 m³/s·m² multiplied by the zone floor area divided by the Maximum Air Flow Rate. This field and the following one are only used if Damper Heating Action is set to Reverse With Limits.
Specify the Damper Heating Action, choosing Normal action if you want the damper to stay at the minimum air flow rate during heating, gradually increasing the reheat coil's water flow to meet the heating load. Opt for Reverse or ReverseWithLimits (default) action if you prefer the unit to start with minimum air and hot water flow, gradually increasing the latter until it reaches the maximum or the user-specified maximum reheat air temperature, and then allowing the damper to open to meet the load. For Reverse, the damper can fully open, while for ReverseWithLimits, it only partially opens to a maximum flow rate set in the following fields. These options are applicable when the minimum air flow isn't adequate for the peak heating load, and note that for heating coil types other than hot-water coils, reverse action behaves the same as normal action, maintaining minimum air flow during heating.
Specify the maximum supply air temperature (degrees Celsius) leaving the reheat coil in a VAV terminal unit during heating operation to prevent unrealistic high temperatures in the supply air to the space. If left blank, the temperature may exceed practical limits.
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