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OT Can Concrete + High Humidity Set Off High Water Alarm?

D107 Member Posts: 1,852
edited September 2019 in THE MAIN WALL
The other day our flood alert went off but there was no water anywhere. The unit is a floor sensor with four screws contacting the floor--rising water would create conduction between the screws and set off alarm. We have two separate sensors in different locations working off of one wall box which connects to main panel. I narrowed it down to the sensor next to the boiler. I had screwed it tightly down onto the cement floor; when I loosened the screw, the alarm finally went off. Aside from a bad connection at the wall box, it seems that the humid day and the tight adhesion to the floor caused the alarm. Doesn't really seem possible to me as from what I've read concrete is not a good conductor at all.


  • Jamie Hall
    Jamie Hall Member Posts: 23,441
    Dry concrete is a poor conductor. Wet or damp concrete... can be a very good conductor indeed. I can easily see cool concrete plus high humidity being damp enough.

    Which, parenthetically here, is why working on energized electrical switchgear while standing on damp concrete is not a good idea...
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • ratio
    ratio Member Posts: 3,652
    If the surface of the concrete was below the dew point, condensation could be the issue as well.