### Pressure Dependent Airflow Control The information below provides a FULL description of this microblock and all of its properties. What information you see and what you can do with it depends on your license and the application you are in, and in some cases, a controller's driver version. This microblock is compatible only with Carrier controllers.
Microblock family | I/O Point microblocks
Icon and symbol |
What it does | Calculates and maintains the desired damper position in a pressure dependent zone. Controls AUX reheat operation and fan operation in a fan powered box. Its inputs, outputs, and properties interface with the control algorithms built into other controllers. The algorithm ensures that zone airflow stays above the specified minimum for zone indoor air quality standards. Enables testing and balancing through the WebCTRL® interface or through a stand-alone utility. Controls the damper and other key zone operations, such as the fan (FAN) and auxiliary heat (AUX HEAT), during commissioning.
Click for details below How it works Inputs and outputs Properties Simulation Tips and tricks BACnet object property addresses
#### How it works The algorithm calculates the desired damper position (setpoint) based on the microblock’s current operational mode (TERMINAL MODE), zone temperature requirements, air source mode (AHU MODE) and TERMINAL TYPE. When in heating or cooling mode, the calculated damper position is a function of the COOLING % or HEATING % input to the microblock. Using the configured values for minimum and maximum damper positions as 0% and 100% respectively, the actual calculated damper setpoint is scaled to the range determined by the configured min and max damper positions based on the following formula. Damper Setpoint = ((% Damper Request) * (Max. Damper Position – Min. Damper Position)) + Min. Damper Position. For instance, for a configured min damper = 0% and a max damper = 100%, in a cooling mode, a COOLING % input value of 50% (damper request) would result in a calculated damper setpoint of 50%. For a configured min damper = 10% and max damper = 80%, a COOLING % input of 50% (damper request) would result in a calculated damper position of 45%. NOTE When the VAV HEATING input = Yes, the damper setpoint calculation uses the Heating % value as the % Damper Request. When the VAV HEATING input = No, the damper setpoint calculation uses the AUXHEAT % value as the % Damper Request. Once the desired damper position is calculated, the microblock’s DAMPER POS output is used to position the damper accordingly. The damper sends position feedback information to the microblock to provide accurate movement of the damper to its calculated setpoint. The following table shows the damper setpoint and heat enable/disable state for all associated AHU MODES, TERMINAL MODES, and zone temperature requirements for each terminal type:
Air Source (AHU) Mode | Temperature Control Requirement | Terminal Type | Aux Heat | Terminal Mode | Damper Control (Damper Setpoint used) | Heat Control | Fan Control
Off | None | All | N/A | Off | Hold Damper Position (N/A) | Disable | Disable
Cooling | All | N/A | Off | Hold Damper Position (N/A) | Disable | Disable
Heating | Single Duct | N/A | Off | Hold Damper Position (N/A) | Disable | Disable
Series or Parallel Fan | No | Off | Hold Damper Position (N/A) | Disable | Disable
Series Fan | Yes | Heat | Hold Damper Position (N/A) | Enable | Enable
Parallel Fan | Yes | Heat | Close Damper (Heat) | Enable | Enable
Cooling, FreeCool | None | Single Duct | N/A | Cool | Cool minimum | Disable | Disable
Series Fan | N/A | Cool | Cool minimum | Disable | Enable
Parallel Fan | N/A | Cool | Cool minimum | Disable | Disable
Cooling | Single Duct | N/A | Cool | Modulate Damper Position between Min and Max (Cool) | Disable | Disable
Series Fan | N/A | Cool | Modulate Damper Position between Min and Max (Cool) | Disable | Enable
Parallel Fan | N/A | Cool | Modulate Damper Position between Min and Max (Cool) | Disable | Disable
Heating | Single Duct, Parallel Fan | No | Heat | Minimum Damper Position (Cool) | Disable | Disable
Series Fan | No | Heat | Minimum Damper Position (Cool) | Disable | Enable
Single Duct | Yes | ReHeat | Reheat Damper Position | Enable | Disable
Series or Parallel Fan | Yes | Heat | Minimum Damper Position (Cool) | Enable | Enable
Vent | None | Single Duct or Parallel Fan | N/A | Vent | Vent Position | Disable | Disable
Series Fan | N/A | Vent | Vent Position | Disable | Enable
Heat, Warmup | None | Single Duct, Parallel Fan | N/A | Heat | Minimum Damper Position (Heat) | Disable | Disable
Series Fan | N/A | Heat | Minimum Damper Position (Heat) | Disable | Enable
Cooling | Single Duct, Parallel Fan | N/A | Heat | Minimum Damper Position (Heat) | Disable | Disable
Series Fan | N/A | Heat | Minimum Damper Position (Heat) | Disable | Enable
Heating | Single Duct | No | Heat | Modulate Damper Position between Min and Max (Heat) | Disable | Disable
Single Duct | Yes | Heat | Modulate Damper Position between Min and Max (Heat) | Enable | Disable
Series or Parallel Fan | No | Heat | Modulate Damper Position between Min and Max (Heat) | Disable | Enable
Series or Parallel Fan | Yes | Heat | Modulate Damper Position between Min and Max (Heat) | Enable | Enable
Pressure | None | Single Duct, Parallel Fan | N/A | Pressurize | Maximum Damper Position (Cool) | Disable | Disable
Series Fan | N/A | Pressurize | Maximum Damper Position (Cool) | Disable | Enable
Cooling | Single Duct, Parallel Fan | N/A | Pressurize | Maximum Damper Position (Cool) | Disable | Disable
Series Fan | N/A | Pressurize | Maximum Damper Position (Cool) | Disable | Enable
Heating | Single Duct, Parallel Fan | No | Pressurize | Maximum Damper Position (Cool) | Disable | Disable
Series Fan | No | Pressurize | Maximum Damper Position (Cool) | Disable | Enable
Single Duct, Parallel Fan | Yes | Pressurize | Maximum Damper Position (Cool) | Enable | Disable
Series Fan | Yes | Pressurize | Maximum Damper Position (Cool) | Enable | Enable
Evac | All | All | N/A | Evac | Close Damper | Disable | Disable
#### Inputs and outputs Inputs
Cooling % | Cooling called for (%). Connect to a direct-acting controller such as the Zone Controller microblock's CLG% output.
Heating % | Heating called for (%). Connect to a reverse-acting controller such as the Zone Controller microblock's HTG% output.
RH % | Cooling for Dehumidification called for (%). The microblock compares this value to the COOLING % and IAQ % inputs and selects the greatest value.
IAQ % | Airflow for IAQ called for (%). The microblock compares this value to the COOLING % and RH % inputs and selects the greatest value.
AHU Mode | Analog value that represents the current mode of the air source.
Terminal Type | Analog value that represents the type of terminal control used by the microblock: single duct, series fan, or parallel fan terminal.
Heat Type | Analog value that represents the type of Aux Heat used by the microblock: two position, modulating, staged electric, ducted or non-ducted.
VAV Heating | Binary value. When VAV HEATING = YES, the heating damper position is a function of the HEATING % input. When VAV HEATING = NO, the heating damper position is a function of the AUXHEAT (%) input.
Fan | Fan start/stop signal. Usually passed directly to the Fan output, unless controlled by the Airflow Test and Balance Utility for testing and balancing.
Aux Heat Auxiliary Heat | Required Auxiliary Heat %. Usually passed directly to the Aux Heat output, unless controlled by the Airflow Test and Balance Utility for testing and balancing.
Outputs
Fan | Fan start/stop signal. Usually passed directly from the Fan input, unless controlled by the Airflow Test and Balance Utility for testing and balancing.
Aux Heat Auxiliary Heat | Signal to turn on the box's auxiliary heat. Usually passed directly from the Aux Heat input, unless controlled by the Airflow Test and Balance Utility for testing, and balancing.
Terminal Mode | Analog value that represents the current mode of the air terminal: Off Heat Warmup Vent N/A Cool Dehumidification Reheat Pressure Evac N/A Zone IAQ Zone Test and Balance
Airflow Mode | Analog value that represents the current control state of the damper: Max cooling, Min heating, etc. This is maintenance data that can be used by the Test and Balance software.
Heat Enable | Binary value that represents the current commanded state of the Aux Heat control.
Damper Pos Damper Position | (0–100%). Analog value that represents the current commanded position (setpoint) of the damper. For External damper types, connect to the analog output or floating motor output that controls the damper actuator.
#### Properties TIPS Alt+click any value in the WebCTRL® or Field Assistant interface to view property details, including its editing privilege and expression (location path) for use on graphics. You can right-click some properties in the EIKON® Property Editor and select Make editable or Make read-only to determine that property's functionality in your system.
Display Name | The microblock label used in the interface. You can use any characters (including spaces) in this field, except for the " character.
Reference Name RefName | Use the default reference name unless you want a more descriptive name for graphics or network links. Limitations: lower case only limited to 40 characters cannot begin with a number must be unique within a control program
Description | (optional) A BACnet-visible microblock description.
Editing Privilege | Preset - Each microblock property has an appropriate privilege or role assigned to it. You can use Global Modify in the WebCTRL® interface to find out what the actual privilege is. CAUTION If you change the Editing Privilege from Preset, the privilege you select will be used for all properties of this microblock, which is not always desirable.
Flow Measurement Units | The unit of measurement of the microblock's flow value. This will be displayed on the Test and Balance utility and WebCTRL® and Field Assistant Test and Balance section on the microblock pop-up Details tab.
Hardware Configuration
Damper Motor Travel Time | The time (seconds) the damper motor takes to travel from its fully open to its fully closed position.
Direction: CW = | Close - Turn the damper motor clockwise to close the damper. Open - Turn the damper motor clockwise to open the damper. NOTE Applies to integrated actuators only.
Damper Positions
Cooling Min | The minimum specified damper position for the cooling mode (HEAT MODE input is off).
Cooling Max | The maximum specified damper position for the cooling mode (HEAT MODE input is off).
Reheat Min | The minimum damper position specified to ensure adequate airflow over a box's auxiliary heating coil. Applies when the AUX HEAT input is greater than zero. Type 0 if the box does not have an auxiliary heating coil or if the box contains a fan that ensures sufficient flow across the coil.
Heating Min | The minimum specified damper position for the heating or warm-up mode (HEAT MODE input is on).
Heating Max | The maximum damper position specified for a heating or warm-up mode (HEAT MODE input is on). Typically used if the air handling unit supplies warm air to heat the zone.
Vent Position | The specified damper position when the air terminal is in Vent mode.
Property Page Text
Show Property Page Text | Check to show this microblock's value on the equipment's Properties page.
Property Page Text | You can edit the microblock description that appears on the Properties page. See "Editing Properties page text using special characters" and "Formatting a microblock property" in EIKON® Help.
BACnet Configuration
Object Instance | Auto-assign - A BACnet Object ID is assigned by the system. Use specific value - (0–3999999) Assign a number that is unique within the controller.
BACnet
Reference Name | Use the default reference name unless you want a more descriptive name for graphics or network links. Limitations: lower case only limited to 40 characters cannot begin with a number must be unique within a control program
Description | (optional) A BACnet-visible microblock description.
Network Visible | Check to allow other BACnet equipment to read or change the microblock's present value.
Object Instance | Auto-assign - A BACnet Object ID is assigned by the system. Use specific value - (0–3999999) Assign a number that is unique within the controller.
#### Simulation Define the value(s) the microblock will use when you simulate the control program.
#### Tips and tricks BACnet properties The Pressure Dependent Airflow microblock is a proprietary BACnet object. If you make this object Network Visible, you can address a BACnet Analog Network Input or BACnet Analog Network Output microblock to access many of its configuration and control properties in other control programs. See BACnet object property addresses below.
#### BACnet object property addresses The Pressure Dependent Airflow Control microblock is a proprietary BACnet object (object type 769). The format for a BACnet address is bacnet://device/object/property@priority. EXAMPLE To set up a microblock to read the Cooling Output (%) from the first Airflow Control microblock in the same controller, use the following address. `bacnet://this/769:1/4512` In the above address, 769:1 indicates the first instance of a Pressure Dependent Airflow Control microblock in the controller.
BACnet property identifier # | BACnet property identifier | Description | Read/ Write
4501 | PD_MIN_COOL_POSITION | Configured Min Cool Damper Position %. | R/W
4502 | PD_MAX_COOL_POSITION | Configured Max cool Damper Position %. | R/W
4503 | PD_MIN_REHEAT_POSITION | Configured Min Reheat Damper Position %. | R/W
4504 | PD_MIN_HEAT_POSITION | Configured Min Heat Damper Position %. | R/W
4505 | PD_MAX_HEAT_POSITION | Configured Max Heat Damper Position %. | R/W
4506 | PD_VENT_POSITION | Configured Vent Damper Position %. | R/W
4507 | PD_REHEAT_LOCK | Reheat Lock value %. | R/W
4508 | PD_DAMPE_LOCK | Damper Lock value % | R/W
4509 | PD_AUTO_ZERO | Indicates completion of Auto Zero for Damper calibration. | R/W
4510 | PD_TAB_MODE | Current mode of the Test and Balance program. | R/W
4156 | APPLICATION INSTANCE | The Linkage application instance used in this microblock. | R/W
4511 | PD_USE-SUPPLY_AIR | Use VAV Heating | R
4512 | PD_COOLING | Cooling % required. | R
4513 | PD_HEATING | Heating % required. | R
4514 | PD_REHEAT | Reheat % required. | R
4515 | PD_DAMPER | Damper % required. | R
4516 | PD_RH | RH % required. | R
4517 | PD_IAQ | IAQ % required. | R
4518 | PD_AHU_MODE | Current AHU Mode. | R
4519 | PD_TERMINAL_TYPE | Terminal Type. | R
4520 | PD_HEAT_TYPE | Heat Type. | R
4521 | PD_TERMINAL_MODE | Current Terminal Mode. | R
4522 | PD_AIR_FLOW_MODE | Current PD Airflow Mode. | R
4523 | PD_HEAT_ENABLE | Heat Enable commanded state - on, off. | R
4525 | PD_LOCK_FLAGS | Binary lock bits whether to apply locks. Include one of the following index numbers in the address field: 4530(4) Holds the damper in its current position. 4530(5) Locks the fan to the Fan Lock State property value. 4530(6) Locks the damper to the Damper Position Lock Value property. 4530(7) Locks the aux heat to the Aux Heat Percentage Lock Value property. 4530(8) Locks the flow setpoint to the flow Setpoint Lock Value property. NOTE 4530(0) creates a "Write access denied" error message. For example, bacnet://this/769:1/4530(4) | R/W
4527 | PD_DAMP_CONFIG | Damper config - internal, external, stroke time, direction. | R
4528 | PD_MOVES_TODAY | Number of damper movements today. | R
4529 | PD_MOVES_YESTERDAY | Number of damper movements yesterday. | R
4530 | PD_FAN_LOCK | Fan lock value - on or off. | R/W
4531 | PD_FAN_OUTPT | Fan output status. | R
4532 | PD_PROP_STAT_FLAG | BACnet status flags. | R
4533 | PD_TAB_TECH_NAME | Test and Balance technician name. | R/W
4534 | PD_TAB_ORG_NAME | Test and Balance Company name. | R/W
4535 | PD_LAST_TAB_DATE | Last Test and Balance Date. | R/W
4536 | PD_DISPLAY_NAME | Microblock Display Name. | R/W
4537 | PD_OWN_PRG_OBJ_ID | Object ID for program containing this instance. | R
4538 | PD_OVR_FLAGS | Unsigned - Status flags of property overrides in effect. | R
4539 | PD_MIN_COOL_POSITION_OVR | Real - Volatile override for Min Cool Position. | R/W
4540 | PD_MAX_COOL_POSITION_OVR | Real - Volatile override for Max Cool Position. | R/W
4541 | PD_MIN_REHEAT_POSITION_OVR | Real - Volatile override for Min Reheat Position. | R/W
4542 | PD_MIN_HEAT_POSITION_OVR | Real - Volatile override for Min Heat Position. | R/W
4543 | PD_MAX_HEAT_POSITION_OVR | Real - Volatile override for Max Heat Position. | R/W
4544 | PD_VENT_POSITION_OVR | Real - Volatile override for Vent Position. | R/W
4545 | PD_TAB__PARS_SEAL | BACnet DateTime - volatile - used to detect writes by external test and balance software. | R/W
4546 | PD_LOCK_FLAGS_BOOL | Boolean array of lock flags for damper, fan and aux heat. | R
4547 | PD_PROP_STAT_FLAGS_BOOL | Boolean array of BACnet status flags. | R
4548 | PD_BPD_VERSION | Microblock version number. | R