DrainSet MTDC and DrainSet LTDC Completely pre-assembled, pre-wired and pre-configured Drain-Back Station.

  • Drain-Back Box with a volume up to 40l (depending on collector size 30-40m²)
  • TDC controller incl. 3 Temperature sensors
  • Safety valve 6 bar with pressure gauge
  • Filling and flushing unit DN20 incl. connections and fill and drain valve
  • Modular extension for big systems possible
  • High-efficiency solar pump (WILO Yonos Para ST 25 /13 PWM, height up to 13m).
  • The height indications refer to water as the heat transfer medium. If glycol is used to fill the drain-back system, the delivery head of the pump is reduced by about 2-3 meters.



Idle mode of solar system
In idle mode, the heat transfer medium is in the Drain-Back Box. The collectors are empty.


Solar system in operation
Under solar exposure, the system is set into operation by the TDC controller and the whole solar circuit / collectors are filled will maximum pump speed. Once in regular operation, the pump operates with reduced and continuously optimised speed to save energy.


Storage fully loaded
When the storage is fully heated up or if the solar collectors are no longer warmer than the storage, the pump is automatically switched off. The heat transfer medium flows back from the collectors into the Drain-Box system without vaporising. Therefore, any overheating of stagnant solar systems is effectively prevented.

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PC Simulation

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Where to buy

Find your national SOREL contact person or the nearest SOREL retailer