The EF and SE pumps are equipped with motors cooled by the surrounding pumped medium. In order for the motors to be adequately cooled, the EF and SE pumps must always be completely submerged in the pumped medium during operation. For applications where this is not possible, the fill level must never fall below half the height of the pump.
The KP and AP pumps, on the other hand, have motors that are cooled from the inside by the pumped medium flowing through the pump. For this reason, during operation these pumps need not be submerged in the pumped medium, such that shallow pumping down to a level of 3 cm is possible.