User Manual

Logical I/O blocks
General functions
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238 | 353 CM110664en_07
For each change at the output [PrVal] from OFF to Stage n or from Stage n to
OFF, the entry for priority 6 is set up as follows:
If the minimum ON-time [TiOnMin] or OFF-time [TiOffMin] is greater than 0:
1. Priority 6 adopts the new present value [PrVal].
2. Priority 6 is set to active.
3. The timer for the minimum on-time or off-time is started.
4. After expiry of [TiOnMin] or [TiOffMin], priority 6 is set to inactive.
If the minimum switch-times [TiOnMin] / [TiOffMin] are set to 0, no action is
taken.
● The functions described above are supported only by the BO, MO, BVAL
and MVAL blocks.
● With multistage switch commands, the monitoring periods are enabled only
when switching from OFF to Stage n or from Stage n to OFF. When
switching from one stage to another (e.g., Stage 1 to Stage 2), the timer
times are not enabled.
● However, any timer times already running will continue to run.
● Unnecessary on/off switching operations can be prevented by activating
minimum switch-on or switch-off times.
● Activating switch-on or switch-off delays ensures that run-on time delays
are maintained.
In order for a given value to be included in the evaluation of [PrioArr], its
information bit must be set.
The following applies to priority 1,4,7 and 15 (data flow connection): The
relevant information bit is set via pins [EnSfty], [EnCrit], [EnSwi] and [EnPgm].
The following applies to priority 2, 5, 8, 14 and 16 (BACnet command system):
When a given value is commanded via BACnet, the value concerned is entered
in the [PrioArr] and the associated information bit is set automatically.
The following applies to priority level 6: Both the value and the information bit
are handled by the block concerned.
Prio Meaning Use Access via
1 Safety value (life safety)
Reserved for the initiation of safety
functions (1 = highest priority).
If priority 1 or 2 becomes the
determining value for [PrVal], then the
value concerned is transmitted
immediately to the [PrVal] output. It is
not subject to the delay times defined
for priority 6.
Local safety function, e.g.:
- Fire
- EMERGENCY OFF
- Service switch
- Gas alarm
- Thermal package
Data flow interconnection via pins:
[ValSfty] and [EnSfty].
Normally, [ValSfty] is a constant and
[EnSfty] can be enabled/disabled.
2 Higher-level safety function, e.g.:
- Smoke extraction
BACnet command system.
Access via the CMD_CTL block.
3 Not used in Desigo.
4 Critical value (plant protection)
Reserved for monitoring critical plant
states.
If priority 4 or 5 becomes the
determining value for [PrVal], then the
value concerned is transmitted
immediately to the [PrVal] output. It is
not subject to the delay times defined
for priority 6.
Local monitoring of critical plant states,
e.g.:
- Frost protection (protection from
excess cooling)
- Interlock of aggregates
- Icing protection
Data flow interconnection via pins:
[ValCrit] und [EnCrit].
Normally, [ValCrit] is a constant and
[EnCrit] is enabled/disabled.
5 Higher-level monitoring of critical plant
states:
- Frost in ventilation system (close
dampers, stop fans, switch pump on and
open valve)
BACnet command system.
Access via the CMD_CTL block.
The minimum on/off
time
Constraints
Application
Information bit