2 Alternating pressure pumps Lag/Lead/Standby

[1010101]

I/O drawing. I tried to make it like the example you posted Lancie.

 

[Lancie1]

Sorry I did not get back sooner. You probably turned it in but here are a few corrections:

On your Rung 0, remember that the pressure switch that your instructor described "opens at 25% pressure". That means it is going to be closed, then opens. So you want an instruction that is "0" or off until that pressure switch input goes from closed (1 or ON) to open (0 or OFF). That means your instruction must return a result that is always OPPOSITE of the pressure switch so use a XIO (neumonic: O means Opposite). Right now you have a XIC I:1/4. Change the XIC instruction (appears as --||---) to a XIO (---|/|---).

On your drawings you only have to show the 4 modules and the input devices and output devices, but not the power supply. You can delete the power supply. Also, your modules may be 120 volt devices, not 24 VDC. It depends on which modules are being used. At one time you mentioned 1756-IA16 (for 120 volt AC inputs) and 1756-OA16 (for 120 volt AC Outputs). If that is what is connected to your lab PLC, then you must show the voltage as that and also show the correct voltage connections to your Input and Output modules.

Your Stop pushbutton should be shown with a Normally Closed contact. Your Start buttons are okay. Your Selector Switch contacts should be shown like this: |----o-||-o----, or this |----o/ o----.

Your Pump Contactor Relays should be the relay COIL, not a contact. In other words, the PLC Output must turn on or energize a relay coil, which in turn will operate a contact (not shown) that energized the pump motor starter. A relay coil is traditionaly shown like a circle with a relay number inside :------{R1}----|. Your light symbol is okay, but if you want it to be clearer, draw 4 short diagonal "rays" extended outward from the circle to represent light.