Rockfordpi (Customer) asked a question.

March 19, 2021 at 8:22 PM
How to setup PLC to turn pump off when tank full and on when tank nears empty also turn off pump when there is no water flow (dry well, frozen pipe, leakage, etc) and back on after a delay for well to recover

I have a 3 phase well pump controlled by a Toshiba H3 Drive. I have a 3000 gallon storage tank. I have a float switch which turns pump on via drive at lower water mark and off when full. All this works fine with just the drive. I want to be able to turn off the pump on a no flow situation.

 

I could simply directly switch off the drive on a now-flow situation, but this particular drive does not all me to setup long timers (more than a few seconds) to allow the pump to delay until water flow and try to come back on after a dry well condition.

 

I generally understand the drive inputs and want to use the PLC to control the drive, no relays needed.

 

I have a click PLC CO-01DD2-D. I generally understand what a PLC does, logic, switches, conditions, etc. I have also read a lot and watched a lot of videos. Where I am lacking most is in the nuts and bolts of the wiring and relating the ladder logic back to the switches.

 

Currently my PLC has 24v to PLC power source. I also have a jumper from the negative on power source to C0 and a jumper from + to v1. I don't have a flow switch yet, but I can test with a simple toggle switch.

 

I have the software installed and can read and write projects to and from PLC.

 

My questions. how and from where is the float switch powered or how do I wire the float switch?

 

How do I implement the timer in ladder logic to wait 30 seconds before it checks for a no flow situation on pump startup and to delay for 2 hours when it detects a no flow situation while pump is running?

 

(I know I could do same thing by measuring pump amps, but the drive does not have the timer feature to re-start and sometimes the amps on the pump is squirrely because I am on the far far right of the pump curve and there could also be an electro-mechanical problem and the pump is 200' deep and I don't plan to pull it until it fails. )

  • 6 answers
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  • Garry (Customer)

    Hi Rockfordpi

    Here is the wiring for the CPU unit you have.

    Click plc wiringThis was taken from the following manual.

    https://cdn.automationdirect.com/static/manuals/c0userm/c0userm.pdf

    If you were to wire your float switch to X1 then it would replace the contact switch shown in the picture.

     

    Do you have any of the logic already in your program?

    Can you send us your code?

    Thanks,

    Garry

     

    https://accautomation.ca/click-plc-timers-and-counters/

     

    https://accautomation.ca/series/click-plc/

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    • Rockfordpi (Customer)

      Thanks for your reply Gary. I am slowly getting there.

       

      So, one side of my float switch goes to X1, to where do I wire the other side?

       

      All of the what appears to be 24v power supplies in the diagram above confuse me. When connecting to the drive I just connect 2 two terminals, no external power supply involved (I had to read the manual three times to understand that, LOL) and I am having a hard time switching from that frame of reference.

       

      I do not have any logic in the program yet, but I have thought through it and conceptually I know what I want/need to do. It is just a matter of converting that logic to ladder logic and wiring the switches to match it. I think that part may be easier once I can figure out to setup the switches

      Expand Post

  • Rockfordpi (Customer)

    OK, I got the water level switch to work. Not sure this is the correct way, but I connected one side of the switch to V1 and the other side to X1. Got my program to turn on Y1 when the X1 switch is closed. Y1 will be the output that activates the drive to start pumping.

     

    Now, I need to modify the program to add a timer. I need the timer to wait 15 seconds and check and see if X2 is on. X2 will be the flow switch indicating water is flowing. If no water is flowing I need to turn off Y1.

     

    Next I need to periodically check X2 to be sure water is still flowing. If now water flowing, I need to turn off y1 for 1 hour and restart the program. I also need to turn off y1 when tank is full (x1 is off)

     

    I could write this as a computer program using a procedural language in about 5 minutes. Still struggling to convert that to ladder logic and make the physical switches match.

     

    Expand Post

  • Rockfordpi (Customer)

    Thanks Gary, this is exactly what I need! The syntax for ladder logic was bogging me down.

 

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