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Siemens Building Technologies Basic documentation RVD240 CE1P2384en
HVAC Products 4 Acquisition of measured values 27.05.2004
4.7.3 Handling faults
• When used as a storage tank temperature sensor:
In the event of a short-circuit or open-circuit, the controller first attempts to use the
second sensor. If no second sensor is available, an error message will be delivered
• When used as a secondary return temperature sensor:
If there is a short-circuit in the measuring circuit, an appropriate error message will
be delivered
4.8 Return temperature (B7, B71 and B72)
4.8.1 Measurement
Depending on the type of plant, the return temperature (both primary and secondary) is
fed to input B7, B71 or B72.
With plant types no. 2–x and 3–x, the primary return temperature at input B7 is passed
on via LPB; with plant types no. 0–x, it is input B72.
4.8.2 Types of sensors
The following types of sensors can be used:
• All types of sensors from HVAC Products with a sensing element LG-Ni 1000. Suited
for d.h.w. applications is the immersion temperature sensor QAE2... . Its sensing
range is 0...130 °C
• Commercially available immersion temperature sensors with a sensing element
Pt 500
The sensing range of all types is 0...180 °C.
The controller automatically identifies the type of sensor used.
4.8.3 Handling faults
In the event of a faulty primary return temperature sensor (short-circuit or open-circuit),
an error message will be delivered when the maximum limitation of the primary return
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 delivered on purpose
In the event of a faulty secondary return temperature sensor (short-circuit or open-
circuit), an error message will be delivered when the 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.
Primary return tempera-
ture sensor
Secondary return tem-
perature sensor
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