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Siemens Basic Documentation RVP360 CE1P2546en
Building Technologies 13 Function block: Setpoint return temperature limitation 2017-07-24
13 Function block: Setpoint return tem-
perature limitation
On this function block, the setpoint for minimum limitation of the return temperature
or the constant value for shifting maximum limitation of the return temperature can
be adjusted.
13.1 Operating line
Line Function, parameter Factory setting
(range)
Unit Heating
circuit
101 Setpoint return temperature limitation, constant value
--- (--- / 0...140) °C –
13.2 Description
The setpoint for minimum limitation of the return temperature can be set on operat-
ing line 101.
The function can be deactivated by entering ---, which means that the return tem-
perature will not be limited.
13.3 Minimum limitation of return temperature
Wherever required, this function block provides minimum limitation of the boiler
return temperature. This applies to …
plant type 4 - x: “Space heating with mixing valve”,
plant types 5 - x and 6 - x: “Space heating with mixing valve
and precontrol with boiler”
Minimum limitation of the return temperature prevents boiler corrosion due to
flue gas condensation.
13.3.1 Type of sensor
Suitable are Siemens sensors operating with a sensing element LG-Ni1000.
The sensor is to be installed in the return.
With plant type 4 - x, the return temperature signal can also be forwarded via LPB.
In interconnected plants, only 1 return temperature sensor per segment may be
connected.
13.3.2 Mode of operation
If the return temperature falls below the set minimum limit value, the temperature
differential of minimum limit value and actual value is integrated. From this, a criti-
cal locking signal is generated and forwarded to the connected consumers. This
causes the loads to reduce their setpoints, aimed at consuming less energy.
If the return temperature returns to a level above the minimum limit value, the inte-
gral is reduced, resulting in a reduction of the critical locking signal. The connected
consumers increase their setpoints again.