Messages

1

Irrigation / Re: Ag Irrigation pump work

« on: March 02, 2015, 01:19:24 PM »

Wow, thanks for the info! 

Oddly enough, I have another well that was put in place by the same well drillers and I believe they used a CSV at that location.  The well is smaller, but there is a 5gal pressure tank at the head and I turn it on just by opening the valve.  I've always wondered how important it is to open/close that valve really, really slow?   

On my other well (40 HP and VFD) I need about 170 PSI at the well head to move water up the hill and into my storage tank.  If I turn the VFD up to 60 Hz the pump will extract nearly 200 GPM from the well (3" well manifold, 4" main line going the distance).  Is there a CSV large enough to handle this flow and pressure? 

It seems to me that choking down the pressure at the well head to reduce the flow would cause a large spike in pressure between the pump and the 'choking down' point, but from reading what you've written and other things I am going to reconsider!

Thank you for the helpful and money saving information!  Next time my VFD fails I'm going to change course.

2

Irrigation / Re: Ag Irrigation pump work

« on: March 02, 2015, 09:49:28 AM »

Hi Cary,

Thank you for the informational reply.  So these pumps have some sort of internal pressure sensor turns the pump on or off depending on the position of the downstream sprinkler valve?  Also, would a Grundfos CM10-1 in 3 phase be better/more efficient than the gator?  I've got 3 phase power (that I have pulled 1500 ft!!) so I think a 3 phase pump would be more efficient?  Due to the length of the pull, wire size is also important...I need to keep an eye on amps. (no more than 10a on a 3 phase, not sure how many amps would be lost in a step down transformer)

Seeing as how the flow of this irrigation block will never vary, I can understand why a VFD is totally unnecessary.  I'm still trying to figure out how I would get by without it on my big pump though.  By adjusting the Hz I can get the pressure to exactly where I need it without over pressurizing the system and (I assume?) wasting energy. 

I'm going to be drilling another well in a few months and I can imagine the well drillers will want to use another VFD.  This project will be slightly different, however, in the sense that this well will only be used to fill a 30,000 gal storage tank.  I can see how it would be best to just pump at one set rate into this tank instead of having all of the complicatedness of a VFD.  Does the soft start/stop and other pump saving computer tricks that come with a VFD make it useful?  Better to use the smallest wire available down the borehole to cause startup voltage drop as a soft start mechanism?

In regards to my existing VFD setup...I had this well installed in 2012 and have already replaced TWO VFD controllers.  All of the sudden they make a big scary sound when I turn the power on and blow all of the fuses.  Only solution is to replace the whole thing.  Luckily they've been under warranty.   

Thanks for the help, this has definitely changed my mind about the almighty VFD!

3

Irrigation / Ag Irrigation pump work

« on: March 01, 2015, 06:07:35 PM »

Howdy,

Great forum here...lots of things I should know more about.

I'm currently in the midst of a project here on the farm.  I've currently got a well that sits about 200 feet in a valley below my farm.  I pump from this well with a 40HP motor on a VFD up to the trees at a rate of about 150 GPM @170 PSI.  For lots of reasons, I'm having a big tank installed at the top of the property that I will use as storage and also for ease of irrigation management.  As luck would have it, there are nearly 200 trees around this tank that are irrigated with micro sprinklers (.16 GPM each) that will not have sufficient head pressure from the elevation difference of the tank.  For these trees, I will need a booster pump.  Something in the 40 GPM / 40 PSI range.

I spoke with my well driller/pump guys and they admitted that the smallest pump setup they deal with would be overkill for this small of a flow, but it could be done.  This is would be a 'wet well' on a 3 Phase VFD.  Talked about other options, but they really like the wet well pumps due in no small part to their significantly longer warranty period vs above ground pumps.  Total estimated bill, $6k.  I've been looking around trying to find another way.  Looked at Grundfos CM / CME pumps.  Even the CME with the VFD setup was 2500 or so, which looked a whole lot better than $6K.  Even better still is the Grundfos CM-10.  Really simple pump that I think just turns itself on and off with a pressure switch.  Which brings me to this site and my question...If I have my tank plumbed directly to the pump plumbed to a Hunter irrigation control valve, would I be served well with a CSV?  I anticipate controlling this irrigation block by simply directing the hunter sprinkler valve to open, having the pump turn on and then shutting the valve when the time is up.  Is this a decent and practical way of doing this? 

What are your thoughts about the CM pump? 

Thanks in advance...

Matt