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Old March 18th, 2005, 04:21 PM   #1
BoxerBrats
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Red face Analog Output follow up

OK I started a thread on how to do analog outputs on a DirectSoft program to control a VFD driving a well pump.

The basics is we have 3 pumps the first is a 5 HP jockey pump comes on first.

If it can not handle the load then we bring on the second pump (60 HP) controlled by a VFD. When this comes on we drop out the jockey pump.

When it is running at 60 HRZ and still not handle the water demand then we bring on the 3rd pump (60 HP) wich is across the line start. At this time we ramp th e VFD down to 30 HTZ and increase/decrease speed to maintain the water demand.

Unill we reach the set point then remove the 3rd pump, and then the 2nd pump.

I have attached my program, with hopes of getting some input back. Since this is the first Analog program I have done, and trying to avoid any unexpected mistakes.

Thanks
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File Type: zip DP Rancho.zip (5.7 KB, 50 views)
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Old March 18th, 2005, 09:14 PM   #2
BoxerBrats
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OK lPDF file

OK try uploading it to a PDF file

Let me know if this works better
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File Type: pdf Rancho.pdf (45.3 KB, 82 views)
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Old March 18th, 2005, 09:44 PM   #3
elevmike
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Boxer,

Tip 1..Your 1st rung should be a sub called by the "first scan" contact. Place the sub containing all the presets and constants below the end statement. This will have a dramatic impact on the scan time.
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Old March 19th, 2005, 05:54 AM   #4
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confused

Ok litle confused, if I plce the rung with constants below the end rung. Wont the scan miss all this?
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Old March 19th, 2005, 07:13 AM   #5
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Read the book

Hi BoxBratts
Quote:
Ok litle confused
If you will go to the top of the page Click on Learn PLCs and read what`s there. It will take away alot of confusion. If you don`t you are just going to get bits and pieces and you will still be confused. I looked at your program and it look`s like you have a good understanding of relay logix all you need is to understand plcs. If your going to be your companies programmer you might as well diggin and start reading. If you don`t there is alot of people on here you are not going to understand when they answer your questions.
Quote:
Ok litle confused, if I plce the rung with constants below the end rung. Wont the scan miss all this?
The first scan won`t and that`s all that matters.

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Old March 19th, 2005, 08:28 AM   #6
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Ok Boxer,


Download this and check it out..
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File Type: zip RanchoV2.zip (6.2 KB, 24 views)
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Old March 19th, 2005, 09:26 AM   #7
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ok thanks for all the help... really appreciate this
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Old March 19th, 2005, 09:39 AM   #8
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Ok a quick question, my boss is under the impression that we will need a flow meter in this project, so even if we have a flow, but the pressure has been reached the pump keeps running. He is worried that we will have pump short cycling.

I put in a 2 minute time delay so when pressure is reached and VFD is at minumun 30 hrtz and maintains for 2 minutes. This should prevent any short cycling

Oh and forgot to metion it feeds a 300 gallon storage tank. Wich provides water for lawns in a gated community

So is it posible I am not seeing the whole picture?
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Old March 19th, 2005, 10:01 AM   #9
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How deep is this well? The reason I ask is that the tank seems undersized relative to the motors.

For example, 100 feet of water equates to a pressure of about 43 PSI. 60 HP at 43 PSI equates to over 2000 GPM. Now that's without factoring in the efficiency of the pump, but it looks like you could fill that storage tank pretty fast.
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Old March 19th, 2005, 10:26 AM   #10
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i can honestly say, I am sure of the size of tank, only seen pictures of it. I know the tank was put in by a reputable well company
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Old March 19th, 2005, 10:30 AM   #11
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This seems like a lot of work & $$$ for such a simple project..I may be missing something, but it seems that a simple level transducer in the tank may provide for all of your needs. The level sensor could provide for your flow rate, (how fast the tank is filling), and for the acutal level in the tank. You might also want to place a level switch in the well so that if/when the well runs dry you'd stop the pump and wait for recovery. Rather tne a VFD, consider a soft start, (less expensive and complicated).

Question: Is there another pump to run the sprinklers? Or are you counting on tank pressure?
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Old March 19th, 2005, 10:36 AM   #12
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counting on tank pressure


The pump draw from a well fed by a pond


They are under the impression by using the vfd and pressure transducer, to increase / decrease pump speed will save money on electric bill. Out here in california electricity has become a prime concern.
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Old March 19th, 2005, 10:46 AM   #13
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Quote:
Originally Posted by BoxerBrats
counting on tank pressure


The pump draw from a well fed by a pond


They are under the impression by using the vfd and pressure transducer, to increase / decrease pump speed will save money on electric bill. Out here in california electricity has become a prime concern.
Is this a raised water tank? By pressure are you refering to static head (water tower), or pressure caused by pressurization during the filling?

Either way I dont thing the VFD is going to save money on juce. However it will give you better control over the pressure issue.
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Last edited by elevmike; March 19th, 2005 at 10:50 AM.
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Old March 19th, 2005, 10:50 AM   #14
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using pressure caused pressurizing the tank from the pumps
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Old March 19th, 2005, 11:47 AM   #15
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Also another question, If using subroutines like your example. Now if I wanted to add a operator interface would I want to put the pressure set ect in the firt routine, or have it set where it scans it on every scan?
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