This is not a complete nor even a good setup, but may help guide your thinking.

Abstract away all you can.

Create FBs/FCs/DBs to manage your sump, pumps, level, and actions as well as calibration for the level sensor to provide inch & feet values from the current level value, plus some way to ignore noise - otherwise you might get some short-term swirling action which short-cycles both pumps.

Sump DB might have actual level tags like "current level (inch)", "current level (feet)", and setpoints "desired level (inch)", desired level (feet)" .. and other level setpoints as noted in your specifications.

LeadingPump DB might have tags like isPumpNumber (1 .. number of pumps), upNextPump (1 .. number of pumps) - the tag would read like this: "LeadingPump".isPumpNumber

LaggingPump DB might have tags like "isPumpNumber" and arrLaggingPumps = array [1..# pumps] where the array is sorted with 1 representing the next pump to call up as required, 2 being the next pump to call up if leading & lagging pumps are not sufficient, OverloadAlarm - and associated OverloadAlarmDelay - would activate when there were not enough lagging pumps to meet the setpoint requirements after OverloadAlarmDelay time has passed below setpoint and all available lagging pumps were activated

Then you create action FCs to monitor and create actions based on the various DB tags.

CurrentState DB:

  LeadingPumpNumber : Int

  LaggingPumpNumber : Int

  arrLaggingPumps : array[1..number_of_pumps] of Int

Once the problem is abstracted away from the IW / QW / I#.# and Q#.#, you can configure the FBs/FCs to operate the pumps.

You can have FCs named things like:

CalibrateLevelSensor(IN: raw_sensor_data, OUT1: level_inch, OUT2: level_feet, IN: raw_at_zero, raw_at_max, feet_at_max, OUT3: done / error / status)

UpdateSetpoints(IN: Enable - bool; all those setpoints with good names which you provide from an HMI or SCADA or however you update them; OUT: those setpoints which are then transferred to Sump DB when Enable input becomes true.

ManageSumpLevel(IN: Enable; all those setpoints in the Sump DB, LeadingPump.isPumpNumber, arrLaggingPumps)

UpdateLeadingLaggingPumps( ) which calls UpdateLeadingPump( ) and UpdateLaggingPump( ) when Enable input is true

I think you can see a better solution already, but these hopefully make  you think about it differently so that you can work it out.

Also, there are existing application examples for sump level control.  A quick online search should yield algorithms and maybe even sample applications, and of course, some useful general purpose library functions - like calibration - which is controlled tag scaling.

acclark

Hi,

I am currently working on a project to have 2 sump pumps alternate after each time the system turns on to expel water/fluid in a sump pump. This is ultimately what I would like the system to do: The lead pump will be turned on when the ultrasonic sensor registers a certain predefined setpoint (like 2 feet from the bottom of the well) and the lag pump will turn on if the lead pump cannot keep up with the water entering the sump pump (ie 4 feet from the bottom of the well). There is also 2 mechanical floats, one for turning off the pumps when the water is 6" off of the bottom of the well (so that the pumps do not run dry) and then the high float will keep both pumps on until the low float registers a low water level. One the water is cleared from the sump pump the next time the system is engaged the lead and lag pumps will switch.

I am using TIA V14 with a s7-1200 controller with an AI 8x13 bit expansion pack connected to a TP700 comfort HMI.

I think the way to go would to be using a counter and math functions to designate which pump is lead and which pump is the lag for each cycle. But open to any solution for this. 

I'm still learning when it comes to PLC programming so any help would be much appreciated.

Attached is the program I have so far, which tbh is really basic just not sure how to proceed at this point.

Thanks,

Andrew