Control device for an engine-independent heater, heating system, and method for controlling an engine-independent heater

A heating system especially for motor vehicles, having:

• a heat transfer medium circuit that is filled with a liquid heat transfer medium that is capable of absorbing thermal energy, transporting it further, and outputting it again at a predetermined location, and
• a heater, having
• an engine-independent heat source for heating a liquid heat transfer medium located in a heat transfer medium circuit,
• a temperature sensor for detecting a current temperature of the heat transfer medium in the surroundings of an outlet at which the heat transfer medium exits the heater, and
• a control device for controlling a heating capacity of the heater by reducing a heating capacity of the heater when a current temperature gradient ((dT/dt)Ist) of the heat transfer medium is equal to or greater than a temperature gradient threshold value ((dT/dt)schwell), wherein the control device repeatedly recalculates the temperature gradient threshold value ((dT/dt)schwell) dynamically as a function of a temperature difference (Δθ=θsoll−θIst) between a target temperature (θsoll) of the heat transfer medium that is to be achieved and a current heat transfer medium temperature (θsoll), wherein the temperature gradient threshold value ((dT/dt)schwell) rises with increasing temperature difference Δθ=θsoll−θIst.

A method for controlling an engine-independent heater that heats a liquid heat transfer medium of a heat transfer medium circuit especially for motor vehicles, the method having a control device that performs the following steps:

• determining a current temperature gradient ((dT/dt)Ist) of the heat transfer medium,
• determining a temperature gradient threshold value ((dT/dt)schwell), wherein the current temperature gradient ((dT/dt)Ist) is repeatedly recalculated from heat transfer medium temperatures (θIst) measured at different times,
• comparing the current temperature gradient ((dT/dt)Ist) with the temperature gradient threshold value ((dT/dt)schwell), and
• reducing a heating capacity of the heater when the current temperature gradient ((dT/dt)Ist) is equal to or greater than the temperature gradient threshold value ((dT/dt)schwell), and wherein the temperature gradient threshold value ((dT/dt)schwell is repeatedly recalculated dynamically and as a function of a temperature difference (Δθ=θsoll−θIst) between a target temperature (θsoll) of the heat transfer medium that is to be achieved where the heat transfer medium temperature is measured and the current heat transfer medium temperature (θIst).