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Siemens Building Technologies Basic Documentation RVD230 CE1P2383en
HVAC Products 4 Acquisition of measured values 27.05.2004
temperature or the differential temperature limitation function has been activated.
In that case, the controller’s LCD shows Er.
If maximum limitation of the secondary return temperature is activated (by making an
entry on operating line 177; lowering to the primary limit value), no error message will
be generated on purpose.
4.9 Secondary return temperature (B7 and B71)
4.9.1 Measurement
The primary and the secondary return temperatures (heating circuit, d.h.w. circuit,
common, precontrolled) are acquired at B71.
This measured value is required for maximum limitation of the secondary return tem-
perature and for limiting the temperature differential.
4.9.2 Types of sensors
The following types of sensors can be used:
• All types of sensors from Siemens with a sensing element LG-Ni 1000. Suited for
d.h.w. applications is the immersion temperature sensor QAE2… . Its range of use is
0…130 °C
• Commercially available immersion temperature sensors with a sensing element Pt 500
The range of use of all types is 0…140 °C; but the Pt sensors are suited for medium
temperatures up to 180 °C.
The controller automatically identifies the type of sensor used.
4.9.3 Handling faults
In the event of a faulty secondary return temperature sensor (short-circuit or open-
circuit), an error message will be generated when maximum limitation of the primary
and secondary return temperature or the differential temperature limitation function has
been activated.
In that case, the controller’s LCD shows Er.
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