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Lead/Lag Rotation ladder logic

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Our commercial property  resides over an underground spring (varying water level and  flood water  in-rush flow).  We have a three tier basement where you walk down to the basements first tier then down three steps to the middle tier then down another three steps to the bottom tier.

Some months, the sump basin maybe bone dry, but like right now, its coming in at a rate of 360 GPM!!  (when we lost electric power one year for 4 days, we top out at 12FT of flood water in our basement)     :  ( 

The original existing sum well (3ft diameter x 2ft deep) is way undersized for todays increased flood water volume.  I've increased my "sump storage capacity" by allowing the bottom tier to now flood. This now gives me approximately a 2K gallon storage area before I have to start the pumps. This provides a good pump dwell time (pump/sleep).



I'm pondering the approach to take in formulating  the ladder logic that will handle the pump lead/lag and rotation.

My current code now resolves the two required things ..... the number of pumps requested  (max. four ... by the measured water level) and the number of pumps available  (in AUTO mode ..... out of the four pumps).

I'm thinking that to advance the pump lead/lag pump assignment after any pump down cycle is completed, is to set this up in a shift register to do this.  This register would have to carry and shift maybe just one pump request or up to four depending on the flood level.

I would have to  also test and set an alarm flag should any time the "pump requests "exceed "pump  availability

Any sample code clips to this type of functionality would be helpful to get me started!




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