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Siemens Building Technologies Basic documentation RVD240 CE1P2384en
HVAC Products 21 Locking signals 27.05.2004
21 Locking signals
21.1 Fundamentals
The following functions use locking signals and send them to the heat converters and
consumers:
• Minimum limitation of the boiler return temperature
• Protective boiler startup
• D.h.w. priority
With the heat exchanger and consumer controllers, it is possible to set on operating line
136 (gain of locking signal) to what degree they shall respond to a locking signal. This
gain of the locking signal is adjustable from 0 to 200 %.
For heat converters and consumers with 3-position control, following applies:
Setting operating line 136 Response
0 % Locking signals will be ignored
100 % Locking signals will be adopted 1-to-1
200 % Locking signals will be adopted 2 times
For consumers with 2-position control, following applies:
Setting operating line 136 Response
0 % Locking signals will be ignored
>0 % Locking signals will be adopted 1-to-1
There are 2 types of locking signals:
• Uncritical locking signals
• Critical locking signals
The response of the consumers / heat converters depends on the type of locking signal.
21.2 Critical locking signals
Critical locking signals are generated by the boiler controller with protective boiler
startup or during minimum limitation of the boiler return temperature, aimed at throttling
the consumers to get out of the crucial range more quickly.
If the boiler controller is in segment 0, the critical locking signal will sent to all heat con-
verters and consumers in the entire bus system.
If the boiler controller is in segment 1…14, it will only send the locking signal to all heat
converters and consumers in its own segment.
• Heat converters and consumers with 3-position control reduce their control setpoint
depending on the magnitude of the locking signal and the setting "Gain of locking
signal". The pump will not be deactivated
• Consumers with 2-position control deactivate the pump at a defined locking signal
value if the setting "Gain of locking signal" >0 %. The switch-off point depends on the
setting "Gain of locking signal"
The RVD240 cannot generate critical locking signals since it is not a boiler controller.
Plant type x–4 is the only consumer that never responds to critical locking signals.
21.3 Uncritical locking signals
21.3.1 General
Uncritical locking signals are generated in connection with the d.h.w. priority (absolute
and shifting) and only act on the heating circuits. The following locking signals exist:
• "Controller-internal locking signals"
• "Locking signals from the data bus (LPB)"
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