A low clearance alarm bumper apparatus includes a bumper that can be suspended adjacent a doorway and below the level of the header for activating an alarm circuit upon being tilted in response to an impact, such as when a forklift carrying a tall load approaches the doorway. The cascade hot water heater may perform a heat exchange between the first refrigerant and a second refrigerant. Further, the probe layer has a probe at the ABS which has a decreasing width from its top to its bottom to provide a trapezoidal shape which minimizes side writing due to skew of the probe at outermost and innermost circular tracks of a rotating magnetic disk. The amount of the adhesive agent injected with respect to each of the through holes is controlled so as to be fixed.