The present invention attempts to provide a hard coating which has excellent hardness and lubricity. A pump is conveniently provided with the distribution module for zone heating and a mixing valve may be further provided for adjusting the temperature of potable water heated within the heat exchanger. A pusher arm is provided for each of the compartments. Naturally, the narrow interruption is created by masking it from dopant implantation when realizing the perimetral high voltage ring extension region.