User Manual

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Siemens Universal controllers RMU710B, RMU720B, RMU730B CE1P3150en
Building Technologies Heat demand 03.10.2011
The adjustable value prevents entire plants from being switched on (e.g. heat
generation plant), even in the case of the smallest heat demand. Switching on (that
is, routing as a bus signal, or to outputs Q, d, Y, a) takes place only when the set
limit value "Limit value request on" is exceeded.
[%]
On
Off
3123D10en
Limit value
req off
Limit value
req on
To adapt the control system to the plant, the control action of the flow temperature
can be set to the setpoint shifts in 3 steps (slow, medium, fast) using the following
setting:
Setting "Request evaluation" is used to determine if the max value or the average
of the requests is to be used.
 When using the maximum setting, the flow temperature is readjusted so that the
valve position for the consumer with the greatest heat demand is 90%
 When using the average setting, the flow temperature is readjusted so that the
valve positions of the 4 largest consumers are 90% on average
Note: This setting does not ensure that all consumers are covered. It makes
certain, however, that an individual consumer cannot force the flow temperature
to high levels (e.g. because a window was left open)
25.4.1 Internal heat demand
The "heat demand relay" signal is available as well as an internal signal on
output (
d). The demand as a digital value can be further handled by a logic
block, etc., for example, to switch on a pump when a heat demand was sent.
"Limit value request on"
Control action
Evaluation of request
Purpose and function