SEQ_DIR:
Function block SEQ_DIR (FB476) helps interconnect control blocks in programmable sequence, i.e. the desired function can be assigend at any place in the sequence. The block is used for Cooling/Dehumidification according to the direction of control action (direct).
Function
CTR blocks are interconnected between the pins of block PID_CTR and on block SEQ_DIR. ReadCnf (Read Configuration) is used to define the sequence.
Basics
Multiple PID controllers are interconnected in a sequence (based on load, modulating sequence switching) for temperature control, humidity control, and eventually other types of control.
A portion of the controller can be responsible for heating or humidification, the other portion for cooling or dehumidification. Each of these controllers command a specific plant element including radiators, heating coils, fan, with the sequence being selectable over BACnet.
In the control program, the controllers for heating or humidification, and the controllers for cooling or dehumidification are grouped to improve understanding and increase flexibility.
The interconnection of the Heating function is marked in red in the figure.
Block
- A pin group is reserved for interconnecting multiple links.
- The Sequence order is determined by a number.
Cooling: SEQLINK_DIRECT (SEQ_DIR)
SeqCnctIn= actual sequence number
Heating: SEQLINK_REVERSE (SEQ_REV)
SeqCnctIn= actual sequence number
The element is taken out of the sequence if multiple SeqNr pins have the same number and an error state [ErrSta] is outputted.
Inputs
Pin | E | O | Description |
SeqCnctIn | pa | – | Input sequence connection |
SeqNr1...8 | pa | – | Sequence number 1...8 Sequence number input value |
ToHi1...8 | pa | – | To higher neighbor 1...8 Log input value |
ToLo1...8 | pa | – | To lower neighbor 1...8 Log input value |
Outputs
Pin | E | O | Description | |
SeqCnctOut | a | – | Output sequence connection | |
FmHi1...8 | a | – | To higher neighbor 1...8 | |
FmLo1...8 | a | – | From lower neighbor 1...8 | |
ErrSta | a | – | Fault state. Ouput value Enumeration | |
1 (Yes). | Error occurred | |||
0 (No) | No error has occurred | |||
ErrSeqNr | a | – | Error sequence number Ouput value Enumeration | |
Pin description
Input values
Pin | Description | Data type | Value | Unit | Min. | Max. |
EN | Release | Boolean | 0 | – | 0 | 1 |
SeqCnctIn | Sequence connection input | Record | – | – | – | – |
SeqNr1...8 | Sequence number X | Integer | 0 | – | 0 | 8 |
ToHi1...8 | To higher neighbor. | Record | – | – | – | – |
ToLo1...8 | From lower neighbor X | Record | – | – | – | – |
Output values
Pin | Description | Data type | Value | Unit | Min. | Max. |
ENO | Enable output | Boolean | 0 | – | 0 | 1 |
SeqCnctOut | Sequence connection output | Record | – | – | – | – |
FmHi1...8 | From higher neighbor. | Record | – | – | – | – |
FmLo1...8 | From lower neighbor | Record | – | – | – | – |
ErrSta | Fault state. | Enum | 1 | – | 1 | 3 |
ErrSeqNr | Error sequence number | Enum | 1 | – | 1 | 9 |
Use
The block is used to interconnect control blocks in the cooling/dehumidification sector.
Process response
Standard (see General rules and information).
Troubleshooting
Possible errors include
- Controller not wired or ToHi and ToLo on SEQLINK is set to default:
- SeqNr 0 and unique ---> ok
- SeqNr 0 and multiple ---> ok
- SeqNr ≠ 0 and unique ---> ok
- SeqNr ≠ 0 and multiple ---> error
- Controller wired
- SeqNr 0 and unique ---> ok
- SeqNr 0 and multiple ---> ok
- SeqNr ≠ 0 and unique ---> ok
- SeqNr ≠ 0 and multiple ---> error
Online
Two SeqNr with the same number ---> Take this element out of the sequence (how?) and output an ErSta
New numbers apply immediately, not only after a restart.
Offline
New SeqLink is cascaded by mistake ---> No reaction
SeqLink for Cool is used for heating setpoint
Standard (see General rules and information).