Property
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Notes
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Inputs and Outputs
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Control connections for an auxiliary heating device (hot water coil or electric heater) and a circulating fan are also provided. If the VAV box includes these items, the microblock properties are used to assign the input number for the circulating fan. The fan input signal is normally passed directly to this input number and the htg % (dmpr) input is normally passed directly to the AUX HEAT output; however, during testing and balancing, the technician can control these outputs directly through the built-in testing and balancing routine. For more information on the built-in testing and balancing procedures, see the appropriate control module documentation.
The other outputs from this microblock are the actual flow reading (FLOW) and a signal for the damper open or close (FULL OPN, FULL CLS). The damper signals are only active when a control module with built-in actuator, such as a U341v+, is used. If any other control module is being used, these outputs will always be off.
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Simulation
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The Simulation section in the microblock dialog box allows you to define the conditions that will be used during an EIKON for WebCTRL simulation.
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Network Visible?
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When you set Network Visible? to Yes, the microblock's output is visible to third-party equipment.
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Name
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The microblock label used in the interface. You can use any characters (including spaces) in this field, except for the " character.
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Units
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The Units field has two parts, a scrolling list and a number field. If the unit of measure that you need is not available in the scrolling list, enter a BACnet number in the number field. Units can be read directly from the BACnet object but setting this property in the microblock reduces network traffic.
Units, abbreviations, and BACnet numbers
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Flow Loop
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The Flow Loop allows multiple instances of this microblock to be used in the same control program. If this is a typical single-duct VAV system, this field should be set to Primary. Dual-duct systems require two Airflow Control microblocks (one for each duct). The microblock that is controlling the primary cooling duct should have this field set to Primary. The microblock that is controlling the second duct, typically a heating or ventilating duct, should have this field set to Secondary.
NOTE Set the hardware configuration on the microblock Properties page. Set the airflow source on the control module driver Properties page.
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Flow Measurement Units
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The Flow Measurement Units field is for display and documentation purposes only. The sensor reading will be given in the same units used during the system calibration. If the flow calibration readings are entered in CFM, for example, the flow sensor will read in CFM. This field allows you to record what units were used and to display them on the Properties page.
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Cooling Max Airflow
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The Cooling Max Airflow field is the maximum airflow that will be provided to the zone when the VAV box is in a cooling mode. If the VAV air handling unit provides warm air when the system is in a warm-up mode, the Heating Max Airflow field is used as the maximum flow under these conditions. The Occupied Min Airflow and Unoccupied Min Airflow set the minimum flows as required for ventilation purposes. You may also set the Aux Heat min Airflow. These minimums apply to either heating or cooling airflow. (Typically, the unoccupied minimum airflow is set to zero, but special circumstances may require airflow even when the zone is unoccupied.)
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Damper Motor Travel Time
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The Damper Motor Travel Time property should be set to the total time required for the damper motor to travel from its full-closed to full-open position. The Direction field tells the flow control algorithm whether the motor turns clockwise or counter-clockwise to open the dampers.
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Supply Air for Heating During Warmup
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If the Use Supply Air for Heating During Warmup Mode field is set to yes, the flow control algorithm uses the htg % input to control the VAV dampers during the warm-up mode. If this field is set to no, the dampers will be controlled to provide the appropriate minimum occupied or unoccupied airflow to the zone during the warm-up period.
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Flow Input / Setpoint Fan Control, Damper Cycle Count
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The Flow Input (AI), Flow Setpoint (AO), Fan Control (BO) and Damper Cycle Count (AV) columns should match the settings for the points the data will come from. This includes existing Trend and Alarm settings.
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Editing Privilege
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Preset (the default Editing Privilege) indicates that each property in a microblock has an appropriate privilege assigned to it.
If you change the Editing Privilege, all the properties in that microblock are assigned to that one editing privilege, which is not always desirable.
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