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Siemens
Basic Documentation RVP360
CE1P2546en
Building Technologies
18 Function block: Solar d.h.w.
2017-07-24
18.3.6 Storage tank recooling
After overtemperature protection for the collector has been active, function "Stor-
age tank recooling" discharges the d.h.w. storage tank to bring it down to a lower
temperature level.
Storage tank recooling is effected via the collector’s surface. For that, the collector
pump is activated, thus transferring heat from the d.h.w. storage tank to the collec-
tor to be emitted to the environment via the collector’s surface.
The recooling setpoint (TRk) is set to a fixed 80 °C. The switching differential for
recooling (SD
ON
) corresponds to the value of the switch-on differential (operating
line 201) of charging control, but is limited to a minimum of 3 K for recooling.
1 K
1 K
25
4
1
D
10
ON
OFF
2 K
TRk
SD
ON
Temperature differential ON
ON/OFF
Collector pump
TRk
Recooling setpoint
T
Temperature
TSp
Storage tank temperature
t
Time
TKol
Collector temperature
If the storage tank temperature lies at least 2 K above the recooling setpoint and
by at least the temperature differential ON above the collector temperature, the
collector pump is activated:
TSp > TRk + 2 K and TSp > TKol + SD
ON
If the collector temperature rises to a level of 2 K below the storage tank tem-
perature, the collector pump is deactivated:
TKol > TSp – 2 K
If the storage tank temperature reaches a level of 1 K above the recooling
setpoint, the function is ended:
TSp < TRk + 1 K