The BHW100 sensor has a target molded into the plastic enclosure (opposite the side with the Maretron label). The target should be exposed so that when the water rises above the middle of the target, the BHW100 will indicate high water by illuminating the red LED and sending a signal to the Maretron Switch Indicator Module (SIM100).

The BHW100 is mounted to a vertical wall in the bilge with the label pointed in towards the wall and the target facing outward into the bilge. The BHW100 always act immediately to rising water. However, there can be some delay to receding water while the water evaporates off the face of the BHW100. Here are some tips to make the BHW100 act quickly to receding water:

1) Mount the BHW100 to a vertical wall in the horizontally direction as shown in the attached instruction sheet. This helps water quickly run off the BHW100.

2)  Cover the mounting screws and metal mounting sleeves with some silicon. Water bridging between the target and mounting screws makes the BHW100 think it’s still under water. Eventually the water evaporates and the BHW100 shuts off but if you prevent the un-evaporated water from bridging between the target and screws, you will get the BHW100 to react much quicker to the receding water.