[AhuPltMod21] Plant operating mode determination for air handling unit, for on/off fans
Program block, name / node subtype: [AhuPltMod21] Plant operating mode determination for air handling unit, for on/off fans
Library hierarchy: Ventilation and air conditioning equipment
Family: AhuPltMod
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*SttUpAlmHdl21a in controllers with system version < 1.5 |
Configurator
Program blocks are stored in the library without I/Os. Use the auto-create and auto-connect functions to create I/Os and/or to connect them to the interface blocks, e.g., R_A, CMD_B. Alternatively, take the I/Os from the folder containing the predefined I/Os in the library and/or from the plant and connect them to the interface blocks.
Determines the plant operating mode by considering various possible sources (e.g., scheduler, manual operation, room unit).
For plants with 1-speed or controlled fans.
Possible operating modes
Operating mode | Description |
|---|---|
Off | All aggregates are off (dampers are closed, fans are off, coils are off, control components are off). |
On | All aggregates are on (dampers are opened, fans are running, coils are on, control components are on). |
On, Full speed | N/A |
Night cooling | Some aggregates are on (dampers are opened, fans are running, coils are off, control components are off except for the logic for night cooling). |
Smoke extraction by supply air | Some aggregates are on (dampers, fans, coils, and control elements in the supply part are on and control elements in the extract part are off). All outputs are commanded with higher priority. Startup purge of the heating coil is inactive. |
Smoke extraction by exhaust air | Some aggregates are on (dampers, fans, coils, and control elements in the supply part are off and the dampers and the fan in the extract part are on). All outputs are commanded with higher priority. |
Smoke extraction purge | All aggregates are on (dampers are opened, fans are running, coils are on, control components are on). All outputs are commanded with higher priority. Startup purge of the heating coil is inactive. |
The operating mode is shown on BACnet with a multistate calculated value "Present operating mode" with the states "Off" and "On".
A parameter in the program is preset to prevent the plant from running. This is useful for testing data points. It must be switched off to start the plant.
"Startup function and alarm handling" controls the startup behavior of the plant after power-on. There is a delay after startup, "DlySttUp", of about 50 seconds. Do not change this delay. Change the delay, "DlyOn", so that it is different for each plant. This ensures that plants start one after another and do not overload the electrical system. There is also a collection and aggregation of all faults and alarms from the plant. If a local alarm lamp and/or reset button is required, an alternative can be selected.
This program block has the following optional functions:
Option: Fire and smoke extraction evaluation (3xAI)
Reads the status of a fire detection contact and from the optional contacts for smoke extraction with supply air and smoke extraction with exhaust air (EvlFireSmext21).
Option: Fire damper test
Initiates a fire damper test with a software button or scheduler (FdpTst21). When the fire damper test starts, it stops the plant. First, it sends a command to open the dampers. Then, after a specific time, it sends a command to close the dampers.
The evaluation of the fire damper test takes place in the fire damper groups. FdpGrp21 and FdpGrp22 have an optional interface, the "Fire damper test", and test evaluation logic, and a value object that display the result of the test.
Option: Night Cooling
Enables a "Night cooling" operation mode if the following conditions are met (NgtC21):
- The plant is off.
- The "Night cooling" is enabled by its own scheduler.
- The outside temperature is not too low.
- The difference between the room temperature and the outside temperature is high enough.
- The room temperature is not below the heating setpoint.
Stops the plant and the "Night cooling" operation mode if any of the above conditions are not met.
Option: External off
Interface that can be connected to a program logic for shutting down the plant.
Option: External on
An interface that can be connected to a program logic for switching on the plant.
It is prepared for AutoConnect to "AhuReq" in SplyAir21. For coordination with DRA, instantiate SplyAir21 in the air handling unit plant.
Option: Operating mode switch (1xMI=2xBI)
Reads the state of an operating mode switch, normally at the front of the electrical panel, and has the states "Auto", "Off", and "On".
Option: Operation indication (1xBO)
Commands a lamp (usually green) that turns on if the plant is running or that blinks if a switching operation is in progress.
Option: Request from room operator unit
A binary simple process value that can be read/written from the device chart of a room unit. It can switch on the plant.
Option: Room temperature sustained operation
Switches the plant on if the room temperature falls below a "Room temperature setpoint sustained mode" (normally far below the heating setpoint with a value of, e.g., 12 °C) and switches it off with a hysteresis of, e.g., 2 K.
Option: Scheduler
Scheduler of type MSCHED with the states "Off" and "On" that switches the plant off and on.
Even with two states only, this is a multistate scheduler (not binary) that can be extended more easily if the project requires it.
Option: Smoke detector (1xBI)
Reads the state of one or two smoke detectors (serially connected) and switches off the plant.
Option: Smoke detector maintenance (1xBI)
Reads the state of the maintenance indication contact of one or two smoke detectors.
Option: Timer button (1xBI)
Reads the state of a timer button and switches the plant on for a specified time (adjustable in the program).
Name | Description | Type | Alarm / Notification class | Trend / Type |
|---|---|---|---|---|
PrOpMod | Present operating mode | MCalcVal: Multistate calculated value | No | Yes, 4 |
RsnPrOpMod | Reason for present operating mode | MCalcVal: Multistate calculated value | No | Yes, 4 |
OpModMan | Manual operating mode selection | MCnfVal: Multistate configuration value | No | Yes, 4 |
SttUpAlmHdl | Startup function and alarm handling | [SttUpAlmHdl22a] Startup & alarm handling, acknowledge & reset, 3 priorities | N/A | N/A |
Name | Description | Type | Alarm / Notification class | Trend / Type |
|---|---|---|---|---|
EvlFireSmext | Fire and smoke extraction evaluation | N/A | N/A | |
FdpTst | Fire damper test | N/A | N/A | |
OpModSwi | Operating mode switch | MI: Multistate input | No | Yes, 4 |
Sched | Scheduler | MSchedule: Multistate scheduler | No | No |
OpInd | Operation indication | BO: Binary output | No | Yes |
NgtC | Night cooling | [NgtC21] Night cooling, based on the operating mode in the rooms and temperature values | N/A | N/A |
SmkDet | Smoke detector | BI: Binary input | Yes, 4 | No |
SmkDetMntn | Smoke detector maintenance | BI: Binary input | Yes, 8 | No |
SpTRSstdMod | Room temperature setpoint sustained mode | ACnfVal: Analog configuration value | No | No |
TmrBtn | Timer button | BI: Binary input | No | Yes, 4 |
Description |
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Request from room operator unit |
External on |
External off |