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[Solar] function block ETAtouch controller
If one of the described conditions is not met (for
example, if the buffer is currently being charged
by the boiler), there is no reason to feed the solar
charge to the upper buffer coil. Therefore, the solar
charge is directed into the lower coil in order to charge
this area. If all conditions are once again met, charging
is switched to the upper coil.
The only exception to this is when solar power
increases while charging the lower buffer coil.
Then, once the minimum time (factory setting 20 min.)
passes, charging will switch to the upper coil, although
the conditions are not met.
6.7.4 Solar heating system with external
heat exchanger
Solar heating system with external heat exchanger
The control principle is the same as in a solar heating
system with just one tank, see chapter 6.7.1 "
Solar
heating system with one tank".
The speed of the collector pump also controls the
adjustable temperature difference [Target collector
diff.] between the collector and the tank.
Fig. 6-59: Solar heating system with external heat exchanger
connected to buffer
In addition, a variable speed secondary pump is
available for the heat exchanger. Through speed
adjustment, it attempts to adapt the temperature
difference between collector and secondary flow (see
chart 78 °C - 74°C = 4 °C) to the temperature
difference between the return of the solar heating
system and the tank (49 °C - 45 °C = 4 °C).
Fig. 6-60: Regulation principle
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