STIEBEL ELTRON SOM 7 PLUS Bedienung Und Installation Seite 49

2.8.26 Option, drainback
Note
A drainback system requires additional components, for example a container to catch the heat transfer medium. Only enable the drainback
option if all required components have been installed correctly.
The drainback option is only available for systems with one cylinder and one collector array (system type 1, 2, 3, 8 and 9).
In a drainback system, the heat transfer medium is pumped into a container during times when the collector is not able to operate. The drainback
option triggers the filling of the collector, as soon as solar heating begins.
ODB: Option, drainback
Setting range: OFF / ON
Factory setting: OFF
tDTO: Period, start condition
Setting range: 1 ... 100 s
Factory setting: 60 s
tFLL: Filling time
Setting range: 1 ... 30 min
Factory setting: 5 min
tSTB: Stabilisation time
Setting range:
1.0 ... 15.0 min
Factory setting: 2 min.
OBST: Booster function
Setting range: OFF / ON
Factory setting: OFF
If the drainback option has been selected, the pump operates for the time set
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under tFLL at 100% speed and pumps the heat transfer medium from the con-
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tainer into the collector circuit (solar thermal system). After the filling time tFLL
has expired, the pump speed will be reduced to the value selected under nMN.
The shutdown conditions are ignored for the stabilisation period that you can
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select under tSTB. This ensures that the system is not shut down prematurely.
Parameter tDTO enables a period to be determined during which the start con-
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ditions must be met continuously.
Parameters tDTO, tFLL and tSTB must be set following the selection of the drain-
back option.
Starting the drainback option automatically changes the temperature diffe-
rential parameters DT O , DT F and DT S. In addition, the setting range and the
default value for the collector temperature limit EM are changed.
After selecting the drainback option, the cooling functions OCC, OSYC and OSTC
as well as the frost protection function OCF are no longer available. If one of
these functions was previously enabled, it will be disabled by the drainback
function and will also not be reinstated at the end of drainback.
The function OBST starts a second pump during filling. This function is only
available in drainback mode with system type 1.
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