NS146 NCC National Controls Corp Liquid Level Board
By switching a program wire from position A to B, the user can select either pump down (Mode A) or pump up (Mode B) logic.
In Mode A, pump down, the load is de-energized until the liquid reaches the high probe. When liquid touches the high probe, the load is activated until the level drops below the low probe.
In Mode B, pump up, the load is energized until the liquid reaches the high probe. When liquid reaches the high probe, the load is de-activated until the level drops below the low probe.
If the tank is non-conductive, a third (common) probe must be installed at a level where it will always be submerged,