• Device Discovery and COV in BACnet

    One of the main features of the BACnet protocol is a service called device discovery. This service allows the Building Automation System (BAS) operator to poll the networked devices for their identifying information, operational status, and values. Devices are identified by their device object name and unique instance number (ObjectID). A device name is optional, while the ObjectID serves for the controls to identify devices. Unlike all other object types, each device may contain only one Device object. The instance number of this Device object must be field-configurable so that it may be assigned a unique instance number among all of the Device objects of all of the devices on a given BACnet internetwork.

    Additionally, a field may exist for the location in the building or on the network. These can also be recorded in programming notes and do not necessarily reside on the module. A password is another feature that may exist but is not critical to function.

    When setting up the Energy Valve for BACnet communications, either BACnet MS/TP or BACnet IP must be chosen based on the desired BACnet network topology. In addition to this setting, the Energy Valve must be assigned a unique Instance ID. Using BACnet MS/TP, the user must choose the appropriate baud rate and MAC address. It is advisable, but not necessary, to set the Max Master to that of the BAS network on which the EV is being installed. Using BACnet IP, the user will have to assign a UDP port. This port should default to 47808 but must match the port used by the BAS system. Entering a device name that describes the EV location is also a good practice.

    After device discovery is performed, the next task is integrating object data to exchange and report information between devices. There is a lot of information, and values don't frequently change in many cases. Most BASs' monitor data object values by continuous polling, which wastes network bandwidth by increasing network traffic. Change Of Value (COV) schemes are one way to mitigate this traffic. A COV involves the client subscribing to the server device containing the value of interest and specifying the change amount. After the subscription is accepted, the server device monitors the object's value. The server issues a COV notification if the value has changed by more than the defined increment amount since the last reported value. Only values that exceed the defined COV increment get reported, saving network bandwidth by decreasing traffic.

    Mind Mapping Design Thinking Infographic Graph

    The Belimo Energy Valve™ supports up to six active BACnet COV data subscriptions, in which the client subscribes for notifications from the server with a lifetime of 1… 28'800 seconds. Below is a list of available object values for COV subscription.

    BACnet Object Description

    Object Name

    Object Type
    [Instance]

    Description Comment Status_Flags

    Values

    COV Increment

    Access

    Device

    Device [Inst.Nr]

     

    0… 4'194'302
    Default: 1

    W

    RelPos

    AI[1]

    Relative Position in %
    Overridden = true, if the gear is disengaged

    0...100

    0.01...100
    Default: 1

    R

    SpAnalog

    AI[6]

    If SetpointSource MV[122] is not 1: Analog then Out_Of_Service is TRUE
    Overridden = true, if forced control (bus, tool and analog forced control) is active

    0...100

    0.01...100
    Default: 1

     

    Sens1Active_Volt

    AI[20]

    Sensor 1 as Voltage in V
    If Sens1Type MV[220] is not 2: Active then Out_Of_Service is TRUE

    0...15

    0.01...15
    Default: 1

    R

    Sens1Passive_ Ohm

    AI[21]

    Sensor 1 as Resistor in Ohm
    If Sens1Type MV[220] is not 4: Passive then Out_Of_Service is TRUE

    0.1... 1'000'000

    0.1... 1'000'000
    Default: 1

    R

    T1_UnitSel

    AI[22]

    Temperature 1 (remote) in selected unit
    Unit can be selected with object MV[127]

    -20…120

    0.01…252
    Default: 1

    R

    T2_UnitSel

    AI[23]

    Temperature 2 (Flow Body) in selected unit
    Unit can be selected with object MV[127]

    -20…120

    0.01…252
    Default: 1

    R

    SpRel

    AO[1]

    Setpoint Relative in %
    The set point is related to either the position, the flow (of V'min, Vmax) or the power (of Pmax).
    See also MV[90], MV[94], MV[100], MV[110]
    Overridden = true, if forced control (bus MV[1], tool and analog forced control) is active

    0...100
    Default: 0

    0.01…100
    Default: 1

    C

    RelFlow

    AV[10]

    Relative Flow in %

    0…150

    0.01…150
    Default: 1

    R

    SpAbsFlow_ UnitSel

    AV [17]

    Setpoint Absolute Flow in selected unit
    Unit can be selected with object MV[123]
    Overridden = true, if forced control (bus, tool and analog forced control) is active

    0…1,5*Vnom

    0…1,5*Vnom

    R

    AbsFlow_UnitSel

    AV[19]

    Absolute Flow in selected unit
    Unit can be selected with object   MV[123]

    0…1,5*Vnom

    0…1,5*Vnom

    R

    Sens1Temp_ UnitSel

    AV [20]

    Sensor 1 as Temperature in selected unit
    Unit can be selected with object MV[127]
    If Sens1PassiveType MV[221] is 1: None or Sens1Type MV[220] is not 3: Passive then Out_Of_Service is TRUE

    -20…248

    0.01...252
    Default: 1

    R

    DeltaT_UnitSel

    AV[22]

    Delta Temperature in selected unit
    Unit can be selected with object MV[128]

    0...140

    0.01…810
    Default: 1

    R

    RelPower

    AV[40]

    Relative Power in %

    0...300

    0.01…300
    Default: 1

    R

    CoolingPower_ UnitSel

    AV[45]

    Cooling Power in selected unit
    Unit can be selected with object MV[124]

    0… 74'150'000

    0.1… 73'361'050
    Default: 1

    R

    HeatingPower_ UnitSel

    AV[46]

    Heating Power in selected unit
    Unit can be selected with object MV[124]

    0… 74'150'000

    0.1… 73'361'050
    Default: 1

    R

    CoolingEnergy_ UnitSel

    AV[47]

    Cooling Energy in selected unit
    Unit can be selected with object MV[125]. See also MV[200]

    0… 2'147'483'641

    1…1.35E12
    Default: 1

    R

    HeatingEnergy_ UnitSel

    AV[48]

    Heating Energy in selected unit
    Unit can be selected with object MV[125]. See also MV[200]

    0… 2'147'483'641

    1…1.35E12
    Default: 1

    R

    VolumeDecimal_ UnitSel

    AV[50]

    Decimal Number of the Volume_m3 Object
    Resolution of 0.01m3 of the Object PIV[50]. See also MV[200]

    0.01-0.99

    0.01-0.99
    Default: 0.1

    R

    Volume_UnitSel

    AV[52]

    Accumulated Volume in selected unit
    Unit can be selected with object MV[126]. See also MV[200]

    0… 2'147'483'641

    1…4.2E10
    Default: 1

    R

    GlycolConcentration

    AV[60]

    Glycol concentration in %
    Measured value or override value in settings

    0…100

    0.01…100
    Default: 1

    R

    Vmin

    AV[90]

    Minimum Flow Limit in %

    0…100

    0.01…100
    Default: 1

    W

    Vmin_UnitSel

    AV[93]

    Minimum Flow Limit in selected unit
    Unit can be selected with object MV[123]

    0… 360'000

    0… 360'000
    Default: 1

    W

    BACnet Object Description

    Object Name

    Object Type
    [Instance]

    Description Comment Status_Flags

    Values

    COV Increment

    Access

    Vmax

    AV[94]

    Maximum Flow Limit in %

    0…100

    0.01…100
    Default: 1

    W

    Vmax_UnitSel

    AV[97]

    Maximum Flow Limit in selected unit Unit can be selected with object MV[123]

    0… 360'000

    0… 360'000
    Default: 1

    W

    Vnom_UnitSel R

    AV[100]

    Nominal Flow in selected unit
    Unit can be selected with object MV[123]

    0… 360'000

    0… 360'000
    Default: 1

    R

    Pmax

    AV[110]

    Maximum Power Limit in %

    0…100

    0.01…100
    Default: 1

    W

    Pmax_UnitSel

    AV[113]

    Maximum Power Limit in selected unit
    Unit can be selected with object MV[124]

    0... 74'150'000

    0.01… 73'361'050
    Default: 1

    W

    Pnom_ UnitSel

    AV[116]

    Nominal Power in selected unit
    Unit can be selected with object MV[124]

    0… 21'500

    0.01… 73'361'050
    Default: 1

    R

    SpDeltaT_UnitSel

    AV[120]

    Setpoint Delta Temperature in selected unit
    Unit can be selected with object MV[128]

    0…99

    0.01…99
    Default: 1

    W

    SpAbsFlowDeltaT_ UnitSel

    AV[127]

    Setpoint Absolute Flow at Delta T in selected unit
    Unit can be selected with object MV[123]

    0… 360'000

    0… 360'000
    Default: 1

    W

    BusWatchdog

    AV[130]

    Timeout for Bus Watchdog in s
    Non functional. Reserved for future extension

    0…3600
    Default: 0

    0.01…120
    Default: 1

    W

    ErrorState

    AV[140]

    Error State
    No communication to actuator: Communication with actuator not possible.
    Gear disengagement: Gear disengaged button is pressed Actuator cannot move: Mechanical overload due to blocked valve, etc.
    (only available for EV..R+KBAC)
    Reverse flow: Reverse flow is detected
    Flow setpoint not reached: Setpoint cannot be reached within 15 min during flow control
    Flow actual exceeds flow nominal:   Actual flow exceeds the designed nominal flow
    Flow measurement error: Air in the system, error occurred during flow measurement
    Remote temperature not OK: No connection to external temperature sensor
    Flow body temperature not OK: Error with embedded temperature sensor
    Communication to sensor interrupted:   Internal communication to flow sensor interrupted
    Freeze warning: Measured temperature & glycol concentration indicate that grease ice can build up
    Glycol detected: Glycol was detected in a MID application Power setpoint not reached: Setpoint cannot be reached within 15 min during power control

    Bit   0: No communication to actuator
    Bit 1: Gear disengaged Bit 2: Actuator cannot move
    Bit 3: Reverse flow
    Bit 4: Flow setpoint not reached
    Bit 5: Flow with closed valve
    Bit 6: Flow actual exceeds flow nominal
    Bit 7: Flow measurement error
    Bit 8: Remote temperature not OK Bit 9:   Flow body temperature not OK
    Bit10: Communication to Sensor interrupted Bit11: Freeze warning Bit12: Glycol detected
    Bit13: Power setpoint not reached
    Bit14: not used Bit15: not used

    1… 16'383
    Default: 1

    R

    Refer to the Energy Valve Technical Documentation for the energy valve setup instructions.

    Back to Blog