In oil tanks, which are placed outdoor, the temperature of the fuel oil can drop to a level, which causes the leaching of paraffin. This can even occur at a temperature of about +5°C. These "flocculations" can result a blocking of the fuel oil filter. The heating system fails and the maintenance costs can be considerably high. To avoid "flocculating", bamaheat® has developed a easy and cost-efficient possibility. The oil tank is tempered at the suction area by self-limiting heating cable. Thereby the heating cable FB-OL-26 leads via a PG gland into the fuel tank cap and out again. The oil tank inside heater is supplied as a building kit and consists accordingly to the appropriate tank size of heating cable, interconnection technology, coupling set and assembly instruction. A thermostat for switching the system on and off in dependence on the ambient temperature is required additionally.