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Hey guys just wondering if anyone has ever built a VFD for a well pump using a pressure transmitter and a Allen Bradley drive. Maybe this isn’t even possible. Just curious. Thanks
 
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B

Bobster

This is a bog standard design, depends on what you want the pressure transmitter to control.
 

Spoon

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As above. Isn't it just a case of the transmitter being an input for the Allen Bradley PLC and an output being the 'Start' signal for the VFD?
Or do you want different controls?
 
B

Bobster

@Rob, you are up early mate...
I'm not in the UK timezone.

The OP dependent on what he wants to do, could connect the sensor direct to the drive without the need of a PLC and use the drives inbuilt PID or basic logic functions.

It's a really common set up for pumping systems/LEV systems.
 

Spoon

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I'm not in the UK timezone.

The OP dependent on what he wants to do, could connect the sensor direct to the drive without the need of a PLC and use the drives inbuilt PID or basic logic functions.

It's a really common set up for pumping systems/LEV systems.
True mate. That's why I asked if he wanted different controls
 
B

Bobster

Just to keep the pressure at 60 psi
Easy, just get a VFD with an analog input that matches the output from your pressure transmitter, and that is capable of built in PID control.

How big a drive are you planning on using kW wise?

The Powerflex 7xx seiries would have all the capability. However, if it is a small VFD it may be cheaper to use a small programmable relay to run the PID loop.
 
B

Bobster

Just noticed you're a plumber.

This is a simple job, but above even a "standard electrician"

You'll also have to take into account your local codes. An the system will most likely, dependent on where you are in Canada be (UL) C-UL compliant
 

Spoon

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Just out of interest @Ganelmatt can you tell us more about what you need this for. I'm just curious as if this is something you are designing then you may have over engineered it a bit.
I'm presuming the VFD is cause the motor is 3 phase and you only have single phase? I can't see a need for variable speed of the motor.
Is the motor existing or are you purchasing one?
 
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  • #12
What VFD are you thinking of using?
As above, why not feed the signal from the sensor directly into the drive? Why the Allen Bradley PLC?
It’s a Allen bradly drive I have, just wasn’t sure if there’s setting in the drive to say run and keep the pressure sensor reading 60
 

Spoon

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It’s a Allen bradly drive I have, just wasn’t sure if there’s setting in the drive to say run and keep the pressure sensor reading 60
That makes it more clear. The VFD is Allen Bradley and there is no PLC.
 

Spoon

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So tell us what you are trying to do, in more detail.
Why are you using a VFD?
Is the pump motor an existing motor?
 
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  • #16
So tell us what you are trying to do, in more detail.
Why are you using a VFD?
Is the pump motor an existing motor?
I want to convert my current pump to a constant pressure pump with a vfd. I work at a wastewater plant and we have VFDs on everything so I was hoping to do the same to my well pump. I have a basic understanding on how it works, but just unsure of how to wire it up. I bought a Allen Bradley VFD that is for single phase 240v. I want it to work that when the pressure drops the pump comes on and ramps up and down with the demand
 

Spoon

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What can you tell us about your well pump motor?
Any chance of a pic of the information plate.
Wastewater plants most prob use VFD's as the motors are variable speed. I can't see a plant not having 3 phase.
Depending on your motor you may not need a VFD and just start/stop the motor via a contactor operated by your sensor.
What sensor do you have? (or are looking at)
 
  • Thread Starter Thread Starter
  • #18
What can you tell us about your well pump motor?
Any chance of a pic of the information plate.
Wastewater plants most prob use VFD's as the motors are variable speed. I can't see a plant not having 3 phase.
Depending on your motor you may not need a VFD and just start/stop the motor via a contactor operated by your sensor.
What sensor do you have? (or are looking at)
I’m just looking, possible a 4-20 mv sensor
 

darkwood

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You can set drives up to search for a optimal feedback voltage/current that is user selectable, I would incorporate a pot' for either trimming and/or setting the pressure value, the VFD will then increase or decrease the speed of the pump until that pressure is realised as it looks for the voltage you set.
Although this can be easily set up as a basic program, you may find it gets more complex as you may need to change a few more complex parameters if the drive has them to ensure you don't end up with the drive going into cyclic hunting which will see the pressure rise and fall like a wave diagram, you can limit this sometimes with the pressure sensor choice (integral delays etc) as well as (if included) making changes to parameters in the drive.
 
  • Thread Starter Thread Starter
  • #20
You can set drives up to search for a optimal feedback voltage/current that is user selectable, I would incorporate a pot' for either trimming and/or setting the pressure value, the VFD will then increase or decrease the speed of the pump until that pressure is realised as it looks for the voltage you set.
Although this can be easily set up as a basic program, you may find it gets more complex as you may need to change a few more complex parameters if the drive has them to ensure you don't end up with the drive going into cyclic hunting which will see the pressure rise and fall like a wave diagram, you can limit this sometimes with the pressure sensor choice (integral delays etc) as well as (if included) making changes to parameters in the drive.
What is a “pot”?
 
B

Bobster

It could be that you only require to run the motor at a fixed speed to produce your 60psi constant pressure, however, if the process is variable and it needs to tune itself. THe higher end Rockwell drives have built in PID functions that can use the 4-20mA signal from the pressure transmitter to ajust it's own speed accordingly.
 
  • Thread Starter Thread Starter
  • #23
It could be that you only require to run the motor at a fixed speed to produce your 60psi constant pressure, however, if the process is variable and it needs to tune itself. THe higher end Rockwell drives have built in PID functions that can use the 4-20mA signal from the pressure transmitter to ajust it's own speed accordingly.
I’m want to use a Allen Bradley 22-A4P2N113 Powerfex
 
B

Bobster

That particular model doesnt have PID capabilities.

I would install it, an using the dial on the front, see if a 60psi constant pressure is feasible without PID control.

If it isnt, then an Allen Bradley 820 plc will be the cheapest way to introduce PID control. An the software for it is free.
 
  • Thread Starter Thread Starter
  • #25
That particular model doesnt have PID capabilities.

I would install it, an using the dial on the front, see if a 60psi constant pressure is feasible without PID control.

If it isnt, then an Allen Bradley 820 plc will be the cheapest way to introduce PID control. An the software for it is free.
Ok thanks for all the help. Appreciate it
 
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