Patent ID: 7192518

Claim:
A liquid circuit comprising a liquid storage vessel, a liquid pump, a consumer device, a filter element disposed in a filter housing, said filter element dividing the liquid circuit into an unfiltered liquid side and a filtered liquid side, and a controller with a temperature detection unit for determining the temperature of a liquid in the liquid circuit, wherein said temperature detection unit is arranged on the unfiltered side of the filter element between the liquid storage vessel and the filter element and detects the temperature of the unfiltered fluid on the unfiltered side of the liquid circuit; wherein said filter element and said controller are integrated into a common liquid filter system comprising a housing having an unfiltered liquid inlet communicating with the unfiltered liquid side of the filter element, a filtered liquid outlet communicating with the filtered liquid side of the filter element, a liquid return which communicates with the controller, and a liquid outlet which communicates with the controller which directs liquid flow to the liquid outlet under all temperature conditions; said liquid storage vessel being connected to the unfiltered liquid inlet by an unfiltered liquid line; said filtered liquid outlet being connected to the consumer device by a filtered liquid line; said consumer device being connected to the liquid return by a liquid return line, and said liquid outlet being connected to the storage vessel by a liquid drain line; and wherein said controller comprises a valve for returning a portion of the excess liquid not needed by the consumer device to the unfiltered side of the filter element via a connection line under low temperature conditions.