Delay Heat Request - Siemens LMS14 User Manual

Delay heat request

Building Technologies Division
6.5.10 Delay heat request
Line no.
HC1 HC2 HC3
746 1046 1346
Certain types of heating systems use heating circuit valves in place of heating circuit
pumps as actuating elements. Such valves are sometimes characterized by relatively
long changeover times. As a result, the heat source/burner might reach its operating
position before the heating circuit valve has opened, meaning that the produced heat
cannot be drawn by the heating circuit.
Parameter Delay heat request (746, 1046, 1346) can be used to delay the heat request
from the heating circuit to the heat source, thus ensuring that the actuating element
releases the heating circuit before the heat source reaches its operating position.
Note!
It should be taken into account that the system pump/heating circuit pump will be
switched on in the case of a forced signal due to...
• recooling of the DHW storage tank,
• excess heat discharge by the solid fuel boiler,
• excess heat discharge via input H1/H2/EX2.
If the system pump is installed downstream from the buffer storage tank, it will also
be switched on in the case of a forced signal due to recooling of the buffer storage
tank.
The delayed heat request is inactive in these cases so that the system pump is
activated before the heating circuit is released by a heating circuit valve.
Note!
If the application requires function Overtemp prot pump circuit (820, 1120, 1420), it
must be made certain that the heating circuit's slow-acting actuating element (valve)
meets the requirements.
Note!
If parameter Delay heat request (746, 1046, 1346) is set to a value >0 and DHW
Charging priority (1639) is set to Absolute, that heating circuit's actuating element
continues to be controlled.
This means that DHW charging priority Absolute will not be considered for this valve
circuit and – depending on the function of boiler pump Q1 and the type of hydraulic
system (e.g. charging pump) – both heating circuit and DHW are being served
simultaneously.
But function Overtemperature protection continues to be active for this heating circuit,
provided it is parameterized.
User Manual LMS14...
6 The settings in detail
Operating line
Delay heat request t
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CC1U7471en
07.05.2014