400 V 12/24 V The HP cooler series are designed for the optimal cooling of hydraulic and lubricating oils and are used in all areas of industry. The NNK series is available with 3 x 400 V E motors, the HP series with 12 V, 24 V, 3 x 400 V E motors and with hydraulic motors. The optimum utilisation of the ventilator used was tested in the wind channel. The HP series is based on 12 cooler sizes which enable the best cooler for the individually required cooling service to be designed. The oil coolers are soldered aluminium coolers with very high heat transfer between oil and cooling air. This extraordinarily high heat transfer arises through the soldering of a special turbulator and a high-performance lamella with a large surface.