Siemens RVS41.813 - Overview of Setpoint and Control Sensor Selection

Required sensors:
To enable the controller to put the heat pump into operation
without control of a buffer
or combi storage tank, at least the return temperature sensor (B71) and the relevant
source temperature sensor must be installed. In the case of air-to-water heat pumps,
the evaporator sensor (B84) is required also.
Line no. Operating line
2840 Switching diff return temp
If the return temperature exceeds the setpoint by half the switching differential, the heat
pump will be switched off; if it falls below the setpoint by half the switching differential,
the controller will put the heat pump into operation.
Sw
itching differential
return temperature
If the return temperature setpoint drops belo
w 30 °C, the switching differential is
reduced in a way that the switch-on point approaches the setpoint. With a return
temperature setpoint of 20 °C, the switch-on point is identical with the return
temperature setpoint.
2840
T
OFF
ON
Ta
20°C
30°C
TRLw
OFF Switch-off point
ON Switch-on point
2840 Switching differential return
temperature
Ta Outside temperature
T Temperature of heat pump return
TRLw Return temperature setpoint
The calculatio
n of the return temperature setpoint is explained on operating line 5810
("Differential HC at OT –10 °C").
The function i
s not active when heat compensation is switched on.
Overview of setpoint and control sensor selection
Various factors determine which sensor is used to control to which setpoint. The
following table provides an overview on plant configurations and the sensors used to
control to which setpoint. Requirement is always a valid heat demand to the heat pump.
Response in case of faults is not considered here and not all listed cases may
represent reasonable plant configurations.
Compressor K1/K2
Electric immersion heater
K25/K26
Storage
dmd
1)
B21 B71 B10 BZ
5)
5810
Sensors Setpoint SD
2)
Sensors Setpoint SD
2)
No - - -
Off (fault 138)
Off
No - - ok
Off (fault 138)
B10 T
Vw
1°K
No - Ok - B71 T
Rw
±BZ/2 B71 T
Rw
±BZ/2
= 0 B71 T
Rw
±BZ/2 No - Ok ok
> 0
B71 T
Rw
±BZ/2
B10 T
Vw
1°K
No ok - -
Off (fault 138)
B21 T
Vw
1°K
No ok - ok
Off (fault 138) B21
T
Vw
1°K
= 0 B71 T
Rw
±BZ/2 No ok Ok -
> 0
B71 T
Rw
±BZ/2
B21 T
Vw
1°K
= 0 B71 T
Rw
±BZ/2 No ok Ok ok
> 0
B71 T
Rw
±BZ/2
B21 T
Vw
1°K
Yes - - - On
3)
On
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Siemens Switzerland Ltd User manual RVS61.843, RVS41.813 CE1U2355en_02
HVAC Products 6 The settings in detail 28. September 2009