| Property | Type | Description |
| AHU Mode Request | Enumerated | This property indicates the requested operating mode (a.k.a. Present Value) of the AHU member. This is what VAS would like its AHU member to do. Valid Range: 0 = Unoccupied 1 = Optimal Start 2 = Occupied 7 = Night Economize 8 = Night Heat Cool. |
| AHU: Ref | Apex Object Reference | This referencer specifies the object that serves as the air handler for the system, such as a DAC or MP580/581. |
| Air Flow Override | SNVT HVAC Override | This property is really a command that is sent to the BCU when the Apply button in the VAV Air Valve group is pressed. The VAV Air Valve group is found on the Overrides tab of the VAS editor. |
| Autocommissioning Cmd | Enumerated | This property is really a command that is sent to the BCU when the Apply button in the VAV Autocommissioning Sequence group is pressed. The VAV Autocommissioning Sequence group is found on the Overrides tab of the VAS editor. |
| Aux Heat Control Request | Boolean | This property indicates what VAS wants to do with its VAV members’ auxiliary heat. If the feature to allow VAV auxiliary heat at night is unchecked (which is done on the Setup tab), and "AHU Mode Request" is Unoccupied, Optimal Start, Night Economize, or Night Heat/Cool, this property will report Disabled. If the feature (to allow VAV auxiliary heat at night) is unchecked, and "AHU Mode Request" is Occupied, this property will report Auto. If the feature (to allow VAV auxiliary heat at night) is checked, this property will report Auto all the time. Valid Range: 0 = Disabled 1 = Auto |
| Aux Heat: Disable at Night | Boolean | This property is used to indicate to VAS whether or not you want VAS to disable its VAV members’ auxiliary heat at night. If yes, VAS will disable its VAV members’ auxiliary heat when the "AHU Mode Request" property indicates Unoccupied, Optimal Start, Night Economize, or Night Heat/Cool.
Default Value: No |
| Calibrate Initiate: Ref | Object Constant Boolean | This property indicates which value to communicate to the VAV members regarding calibration. When "Calibrate Initiate: Ref" toggles from 0 to 1, VAS will send a calibrate command to each VAV member. "Calibrate Initiate: Ref" must stay in each state for at least a minute to ensure VAS has enough time to detect each change of state.
Default Value: Normal |
| Common Space VAV Mode Request | Enumerated | This property indicates the requested operating mode (a.k.a. Present Value) of the Common Space VAVs. This is what VAS is telling its Common Space VAVs to do.
Valid Range: |
| Duct Press Opt: Enable | Boolean | This property is used to enable and disable duct pressure optimization.
Default Value: Enabled |
| Duct Press Opt: Interval Time | Unsigned Integer | This property dictates how often "Duct Press Opt: Setpt Request" can be adjusted.
Default Value: 15 minutes |
| Duct Press Opt: Interval Timer | Unsigned Integer | This timer determines when "Duct Press Opt: Setpt Request" can be adjusted. When it doesn’t equal 0, it can be thought of as the amount of time until the next possible adjustment of "Duct Press Opt: Setpt Request". |
| Duct Press Opt: Max Pos | Real | This is the maximum of the "Air Valve Position" properties from all of the VAVs specified in VAS’ "Member List" property that are not excluded from duct pressure optimization (refer to the Members tab in the editor). |
| Duct Press Opt: Max Pos Source | Apex Object Reference | This property indicates the VAV member associated with the "Duct Press Opt: Max Pos" property. |
| Duct Press Opt: Pos High Limit | Real | This property is the high limit of the air valve position deadband. At the end of a reset interval, if the position of the most-open air valve is greater than the high limit, the optimization program increases "Duct Press Opt: Setpt Request" by "Duct Press Opt: Setpt Reset Amt ".
The default high limit is 95%. A position of greater than 95% indicates that the VAV is providing the maximum airflow possible given the duct static pressure and that space temperature control of the zone may be lost. (One assumption regarding air valve position is that if the air valve position of the most-open VAV in the system is 100% open, there is not enough duct pressure to satisfy the instantaneous airflow requirements of that zone. Furthermore, if one zone is starved for air, others are likely to follow.) The high and low limit for the most-open air valve provide a control deadband. The default low limit of 85% and high limit of 95% create a deadband of 10%, which improves stability while satisfying the airflow requirements of the system in the most efficient manner. Default Value: 95% |
| Duct Press Opt: Pos Low Limit | Real | This property is the low limit of the air valve position deadband. At the end of a reset interval, if the position of the most-open air valve is less than the low limit, the optimization program decreases "Duct Press Opt: Setpt Request" by "Duct Press Opt: Setpt Reset Amt ".
The default low limit is 85%. An air-valve position of 85% or less in the most-open VAV indicates that there is enough pressure to satisfy the instantaneous airflow requirements of the zone. The high and low limit for the most-open air valve provide a control deadband. The default low limit of 85% and high limit of 95% create a deadband of 10%, which improves stability while satisfying the airflow requirements of the system in the most efficient manner. Default Value: 85% |
| Duct Press Opt: Setpt Default | Real | This property represents the default duct pressure setpoint for the VAV air system. The default duct pressure setpoint (a.k.a design duct pressure setpoint) is the duct pressure needed to achieve design airflow to the spaces at peak load conditions. The default duct pressure setpoint is determined during balancing.
The most important output of the VAS duct pressure optimization program is the requested duct pressure setpoint (the "Duct Press Opt: Setpt Request" property of the VAS object). The VAS sends this setpoint to its AHU member provided that you have referenced the "Duct Pressure Setpoint: Ref" property of the AHU member to the "Duct Press Opt: Setpt Request" property of the VAS. The optimization program can adjust the requested duct pressure setpoint by "Duct Press Opt: Setpt Reset Amt" at the end of each reset interval. The requested duct pressure setpoint is set equal to the default duct pressure setpoint when: 1. The status of the duct pressure optimizationprogram is any of the following: • Disabled by Operator 2. The status of the duct pressure optimization
Default Value: 2.00 in. w.g. (500 Pa) |
| Duct Press Opt: Setpt Max | Real | This property indicates the maximum static pressure setpoint that VAS can use in its duct pressure optimization program.
Default Value: 3.01 in. w.g. (750 Pa) |
| Duct Press Opt: Setpt Min | Real | This property indicates the minimum static pressure setpoint that the VAS can use in its duct pressure optimization program.
Default Value: 1.0 in. w.g. (250 Pa) |
| Duct Press Opt: Setpt Request | Real | This is the result calculated by the VAS Duct Pressure Optimization program. It is the property that should be referenced by the "Duct Pressure Setpoint: Ref" of the object specified by the "AHU: Ref". Both DAC and MP580/581 objects have a "Duct Pressure Setpoint: Ref" property. |
| Duct Press Opt: Setpt Reset Amt | Real | This property indicates how much of a reset will occur (if one is to occur) at the next reset interval.
Default Value: 0.1 in. w.g. (25 Pa) |
| Duct Press Opt: Status | Enumerated | This property indicates if the Duct Pressure Optimization program is active, disabled, or inactive and if it is disabled or inactive, why so. Valid Range: 0 = Active 1 = Disabled by Operator 2 = Inactive: No VAV Data 3 = Inactive: VAVs in Test 4 = Inactive: Max Heat 5 = Inactive: AHU Off 6 = Inactive: Air Valves Closed |
| Member List | Application Member | This is the list of the VAVs assigned to this LonTalk VAV Air System. |
| Object Identifier | BACnet Object ID | This property indicates the unique hexadecimal ID of this object. This ID is used internally to identify the object |
| Object Name | Character String | This property indicates the name of the object. |
| Object Type | Enumerated | This property indicates the object’s type (i.e. VAS LonTalk). |
| Security Class | Bit String | This property indicates the security classes to which the object is available. |
| Shutdown Time Delay | Unsigned Integer | You should think of this property as an indication of how long it takes for the fan in the air handler to go from full speed to full stop. When "AHU Mode Request" transitions to Unoccupied, VAS is going to delay its Common Space VAVs from going to the Unoccupied mode for this period of time so the air coming from the air handler’s fan (albeit diminishing) has someplace to escape.
Default Value: 5 Minutes |
| Space Temp: Average | Real | This property indicates the average space temperature of the VAV members that are not excluded from temperature calculations via the VAV Members grid. The VAV Members grid is found on the Members tab of the VAS editor. |
| Space Temp: Maximum | Real | This property indicates the maximum space temperature of the VAV members that are not excluded from temperature calculations via the VAV Members grid. The VAV Members grid is found on the Members tab of the VAS editor. |
| Space Temp: Maximum Source | Apex Object Reference | This property indicates the VAV member associated with the "Space Temp: Maximum" property. |
| Space Temp: Minimum | Real | This property indicates the minimum space temperature of the VAV members that are not excluded from temperature calculations via the VAV Members grid. The VAV Members grid is found on the Members tab of the VAS editor. |
| Space Temp: Minimum Source | Apex Object Reference | This property indicates the VAV member associated with the "Space Temp: Minimum" property. |
| Startup Time Delay | Unsigned Integer | You should think of this property as an indication of how long it takes the VAV controller to drive its air valve from its Unoccupied setpoint (full closed) to its Occupied setpoint (which could be full open). If the AHU and VAVs were allowed to go Occupied at the same time, and if the AHU could make more air than what the Common Space VAVs could concurrently pass, the ductwork could become over-pressurized. To prevent this from happening, VAS will delay its AHU from starting by this amount of time.
Default Value: 1 Minute |
| System Mode | Enumerated | This property indicates the active mode of the VAS. Valid Range: 0 = Off 1 = Air Handler Startup Delay 2 = On 3 = Common Space VAV Shutdown Delay |
| System Mode Timer | Unsigned Integer | This property indicates how many minutes are left in the Air Handler "Startup Time Delay" or the Common Space VAV "Shutdown Time Delay". |
| Update Tag | Unsigned Integer | Value indicating last edit change of this object. |
| Vent Opt: Enable | Boolean | This property indicates whether or not the ventilation optimization program is enabled. The ventilation optimization program manages the outdoor air intake system to meet ANSI/ASHRAE Standard 62-2001: Ventilation for Acceptable Indoor Air Quality. This standard specifies minimum ventilation rates and indoor air quality to minimize the potential for adverse health effects for occupants.
Default Value: Enabled |
| Vent Opt: Interval Time | Unsigned Integer | This property indicates how often in minutes "Vent Opt: OA Setpoint Corrected" is reset. The VAS waits two times the reset interval to calculate the corrected ventilation setpoint after the optimization program transitions to active. This allows the system to stabilize before the first calculation occurs.
Default Value: 15 Minutes |
| Vent Opt: Interval Timer | Unsigned Integer | This property indicates the time remaining until the next reset of "Vent Opt: OA Setpoint Corrected" is to occur. |
| Vent Opt: Max Vent Ratio | Real | This property indicates the maximum ventilation ratio of the VAV members that are not excluded from ventilation optimization via the VAV Members grid. The VAV Members grid is found on the Members tab of the VAS editor. For those familiar with ASHRAE Standard 62-2001 Equation 6-1, "Vent Opt: Max Vent Ratio" is Z. |
| Vent Opt: Max Vent Ratio Source | Apex Object Reference | This property indicates the VAV member associated with the "Vent Opt: Max Vent Ratio" property. |
| Vent Opt: OA Setpoint Corrected | Real | This property indicates the desired ventilation setpoint of the AHU. This is the property that the AHU should be referencing for its minimum outdoor airflow setpoint. For those familiar with ASHRAE Standard 62-2001 Equation 6-1, "Vent Opt: OA Setpoint Corrected" is Vot. |
| Vent Opt: OA Setpoint Default | Real | This property indicates the default ventilation setpoint for the VAV air system. (Don't confuse the AHUs default ventilation setpoint with the AHUs design ventilation setpoint. The AHUs design ventilation setpoint is the setpoint determined by the design engineer to supply the design ventilation airflow at peak load conditions.)
The most important output of the ventilation optimization program is "Vent Opt: OA Setpoint Corrected". The VAS sends this setpoint to its AHU member provided that you have referenced the "Outdoor Air Flow Stpt: Ref" property of the AHU member to the "Vent Opt: OA Setpoint Corrected" property of the VAS. "Vent Opt: OA Setpoint Corrected" is set equal to "Vent Opt: OA Setpoint Default" when:
Default Value: 0 cfm (0 l/sec) |
| Vent Opt: OA Setpoint Total | Real | This property is the summation of the "Ventilation Setpoint: Active" property in each VAV member that is not excluded from ventilation optimization via the VAV Members grid. The VAV Members grid is found on the Members tab of the VAS editor. For those familiar with ASHRAE Standard 62-2001 Equation 6-1, "Vent Opt: OA Setpoint Total" is Von. |
| Vent Opt: Status | Enumerated | This property indicates if the Ventilation Optimization program is active, inactive, or disabled and if it is disabled or inactive, why so. Valid Range: 0 = Active 1 = Disabled by Operator 2 = Inactive: No VAV Data 3 = Inactive: AHU Not Occupied 4 = Inactive: No Qualified VAVs |
| Vent Opt: VAV Airflow Gross | Real | This property is the summation of the "Airflow: Active" property in each VAV member. |
| Vent Opt: VAV Airflow Net | Real | This property is the summation of the "Airflow: Active" property in each VAV member that is not excluded from the ventilation optimization program via the VAV Members grid. The VAV Members grid is found on the Members tab of the VAS editor. For those familiar with ASHRAE Standard 62-2001 Equation 6-1, "Vent Opt: VAV Airflow Net" is Vst. |
| Ventilation Ratio Limit AHU: Ref | Object Constant Real | The AHU ventilation ratio limit is the maximum percentage of outdoor air (OA) the AHU can provide to the supply air stream. This limit is based on the capacity of the AHU and on the current weather (because only a certain amount of outdoor air can be conditioned at any given temperature).
AHUs are not designed to condition 100% outdoor air. They can typically condition roughly 25% outdoor air on a design day. The limit is a safeguard that prevents the AHU from trying to do more than it is capable of. For a normal day, the AHU ventilation ratio limit is typically 40–50%. The VAV ventilation ratio limit is 10–20% higher to account for re-circulated outside air (re-circulation credit). So a typical setup might be an AHU limit of 40% and a VAV ventilation ratio limit of 60%. For those familiar with ASHRAE Standard 62-2001 Equation 6-1, "Ventilation Ratio Limit AHU: Ref" is the high limit of Y. Default Value: 40% |
| Ventilation Ratio Limit VAV: Ref | Object Constant Real |
This property indicates the ventilation ratio limit for each VAV box in the VAV air system. The ventilation ratio of the Tracer VV550 controller is the percentage of outdoor air needed in the air stream to satisfy the current ventilation requirements. The ventilation ratio limit is used as a referencer (Ventilation Ratio Limit VAV: Ref) from the VAS to determine the "Ventilation Ratio Limit: Tracer" property of every VAV member so that all VAVs adhere to the same restriction. The Tracer ventilation ratio limit is the maximum percentage of outdoor air the system can deliver to the VAV box. The Tracer VV550 uses this value in two ways:
Default Value: 60% |
| Water Valve Override | SNVT HVAC Override | This property is really a command that is sent to the BCU when the Apply button in the VAV Water Valve group is pressed. The VAV Water Valve group is found on the Overrides tab of the VAS editor. |