User Manual

Control concept
Control concept and control blocks
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Structure control functions
In this way, complex control and monitoring functions of a plant can be logically subdivided to allow for
clear assignment of the function unit or the real element of the plant. The higher-level control concentrates
on the control and monitoring of the overall plant, while the sub-control function units assume internal
control and monitoring of the given elements for the function unit.
Standardization of control functions
Moreover, plant security and available was increased through standardized control and monitoring
functions which would result in considerable expense using conventional methods.
Standardized control and monitoring functions:
● Unambiguous selection of operating mode
● Uniform fault-related shutdown
● Comprehensive status monitoring
● Switching sequence for ventilation systems
● Output stage control for heat generating plant
● Reporting of local intervention
● Avoidance of unnecessary attempts at switching
● Prevention of inadmissible switching operations
● Protection of plant by preventing switch-on or switch-off
Blocks bound by the control concept
Function Block name Task in the control concept
Prioritization of influencing
variables
ENSEL_BO
ENSEL_MS
Collect information for the selection of the resulting plant operating mode. All
superposed information are processed by priority resulting in the plant being
turned on or off, e.g., smoke extraction switch, frost protection, scheduler
program.
The blocks are primarily used on the hierarchy level plant/partial plant, but
may also be reasonably used, e.g., in aggregates.
Command control CMD_CTL Superposed control block for sequence control. The block ensures that
individual plant aggregates are switched on or off sequentially in a certain
order. The block monitors aggregates and can send alarms. It is optimized for
controlling air handling plants, but can be used for other applications. The
block is used on the hierarchy level plant/partial plant.
Power control PWR_CTL Superposed control block for power control. The block is used for control and
monitoring of the performance of a number of energy producers (multiple
boiler systems, refrigeration machines). Depending on the request power
demand, energy produces are switch on or off in stages. PWR_CTL is
optimized for controlling heating and refrigeration plants. The block is used on
the hierarchy level plant/partial plant.
I/O blocks with control
functionality
BO
MO
AO
Output blocks implemented per BACnet standard and therefore including a
priority mechanism (priority array) that is well suited for control tasks. The
priority array [PrioArr] be used through data flow interconnections and BACnet
commanding. Moreover, the block integrate the following control functionality:
- Motor control (pump, burner, etc.), one- to four-speed [BO, MO]
- Fan control, one- to four-speed [BO, MO]
Value blocks with control
functionality
BVAL
MVAL
AVAL
Value objects or value blocks are implemented per BACnet standard and
therefore includes output blocks via the priority mechanism. These blocks are
referred to as data points that can communicate within the system with the
I/O modules via BACnet. These blocks are primarily used as the
communication interface between superposed control [CMD_CTL, PWR_CTL]
and the aggregates.
Rotation block ROT_8 The Rotation block switches the operating mode on and off for a maximum of
eight functional units in accordance with a selected mode of rotation
(sequence or hours run). The change of operating mode is based on demand,
hours run, occurrence of a fault or manual intervention (override).
The block is used to process the functional units (e.g., aggregates or
components) as a function of run-time or faults. These blocks are used, e.g.,
for double pumps, that are changed over based on runtime.