Setpoint not reached on time:
Setpoint reached on time:
2863
2862
2862
Tx
Tw
0
S1
1
SD
0
S2
1
2862
2862
T
t
t
T
TW
Flow or return temperature setpoint
Tx
Actual value of flow or return temperature
SD
Switching differential
S1
Compressor stage 1
S2
Compressor stage 2
2862
Locking time stage 2
2863
Release integral stage 2
T
Temperature
t
Time
In the case of flow temperature control, the controller uses the flow temperature for
calculating the release and the reset integral. When control is based on the return, the
return temperature is used for making the calculation.
To ensure correct switching on of the second stage with storage tank charging (buffer
or DHW storage tank), a flow temperature sensor must be connected. If that sensor is
missing, the controller makes the calculation with a backup value of 0 °C.
If there is excess heat, the controller generates an integral. As soon as the set value for
the integral is reached, release of the second stage is withdrawn and the first stage
switched off. If the temperature returns to a level below the switch-on point, the first
compressor is switched on again.
Reset integral stage 2
SD
Tx
Tw
0
S1
1
0
S2
1
2864
T
t
TW
Flow or return temperature setpoint
Tx
Actual value of flow or return
temperature
SD
Switching differential
S1
Heat pump stage 1
S2
Heat pump stage 2
2864 Reset integral stage 2
T
Temperature
t
Time
If both stages together deliver too much heat, the second stage is immediately switched
off when the switch-off point or, latest, the reduced maximum switch-off temperature is
reached (2844 and 2845).
Automatic changeover of the compressors ensures that both compressors operate
pretty much the same number of hours.
Compr sequence
changeover
If the difference of operating hours between the first and the second compressor
exceeds the limit (h) set here, the order of startup changes as soon as both
compressors are switched off. This means that compressor 1 becomes compressor 2,
and vice versa. The current compressor sequence appears on operating line 8446.
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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