Large Irrigation system

[trivard71]

I recently built a new house on 3 acres, and installed a 20 zone irrigation system.
I have a 1 hp pump in my well.
The pressure switch is 40-60 psi.
Needless to say the pump cycles a lot during irrigation.
Will a Cycle Stop Valve void the warranty on my pump?
There is 100 psi poly pipe coming into the house from the well where I would need to install the CS valve. Can that handle the back pressure?
Which CS valve would you recommend?

Thanks.

[TKB4]

since cary hasn't responded yet I will give it a stab.  No, the Cycle Stop Valve will not void the warranty on your pump.  If the pipe you have now handles the pressure ok (which it apparently does ) then it will handle the back pressure from cycle stop valve.  Remember the pressure still won't go higher than your high cutoff pressure of you pressure switch so about 60 psi in the pipe downstream of the pressure switch.  For a 1 hp pump the CSV125-1 would be my choice and psi of 50 or so.  You could also get the CSV1a if you want to adjust the pressure as low as 15lbs I believe but I would only get this one if putting in new tank pressure switch etc just due to extra cost.

I would suggest however,  that if you use the irrigation a lot and don't need a high pressure for that you could use two CYCLE stop valves and systems with lower pressure going to the irrigation system to save energy.

[Cary Austin]

Sorry I missed this.  Than TKB4!

[EPStutes]

Cary,

Good morning.  I am also in the process of setting up a large sprinkler system.

My zones rates will range from 10gpm to 28 gpm assuming a 50-75 psi output pressure from the CSV

Pump is a Franklin 25JS3S4-PE and the pump and topsides rate/pressures are shown in the attached table.

The well company installed a CSV1A with a 20gal tank.  Am I figuring the CSV output pressures as shown in my table correctly?  Is this the best setup for my application?

Thanks,

Eric Stutes

[Cary Austin]

Looks correct. So, even with a 50' water level and a back pressure of 195 PSI, setting the CSV for 50 PSI leaves 145 PSI differential pressure.  150 PSI is max differential we recommend for the CSV1A, so setting it higher decreases the differential and gives you more pressure at the sprinklers.

[EPStutes]

Thanks for the quick response. 

I was planning to set the stop pressure to 80psi which is the recommended max operating pressure of the sprinkler control valves.

[Cary Austin]

With a 60/80 pressure switch setting the CSV can be set to maintain 70 PSI constant.  That decreases the differential pressure to about 125 PSI, which is perfect for the CSV1A.

[EPStutes]

Cary,

Sorry, I may not understand the way a CSV works correctly

Assuming an 60 psi header pressure, my individual zone rates range from 13 - 29gpm based on the number of heads in each zone.

How should I determine the DP of the CSV-1A correctly based on the flowrate and CSV inlet pressure?

I was just referencing the attached CSV Reduced Pressure Fall Off Chart based on the flowrate.  Do I need to add the friction DP to that also?

And how does changing the setpoint impact the pressure reduction chart?

[Cary Austin]

29 GPM is really too much for a 1-25 GPM CSV1A.  But if the pump is large enough you can squirt that much water through it.  Reduced pressure falloff is how much higher you have to set the CSV pressure at 3 GPM flow to get what you want at 29 GPM flow.  With 30 PSI of falloff the CSV would need to be set at 90 PSI (using a 80/100 pressure switch) to get 60 PSI at 29 GPM flow for the big zones.  There will also be more than 30 PSI friction loss, which means the pump must be able to do 29 GPM at 90 PSI to get 29 GPM at 60 PSI out of the CSV1A.

The CSV125 or the CSV3A2T would be much better for a 29 GPM zone/pump as they do not have reduced pressure falloff, and are larger valves with much less friction loss at 29 GPM flow.

If you can split up the zones and make them all smaller than 20 GPM the CSV1A will work fine.

[EPStutes]

Carl,

Thanks again for your input.  I tweaked the head counts in each zone.

Do these rate look more inline with the CSV1A sweet spot?

[Cary Austin]

I don't understand your "CSV outlet pressure".  With the CSV set at 60 PSI the outlet pressure should always be 60 PSI or less.  How much less depends on friction loss and reduced pressure falloff for the amount of water being used at the time.  With a large enough pump to make up for the friction loss you can push as much as 33 GPM though the CSV1A.  The outlet pressure of the CSV starts at 60 PSI, then is reduced by the reduced pressure falloff amount depending on the flow rate.

As long as the pump doesn't cycle off and you can live with the pressure at the sprinklers the CSV1A is fine.  But all those numbers would be a moot point when using the CSV3A2T as the CSV outlet pressure would be at 60 PSI regardless of the flow rate because there is no reduced pressure falloff.  Then the CSV3A2T is large enough that there is only about 3 PSI of friction loss possible.  Even the CSV12560-1 would work much better with that size pump. 

A CSV that is too small for the pump is like trying to suck a golf ball through a garden hose. It just ain't big enough. Lol!

[EPStutes]

Thanks for pointing out that the CSV did not look right. 

Correction Made:  I had GPM and PSI swapped in my CSV friction calculation

So for a rate of 25.9GPM

CSV friction loss = 17.0 psi
CSV reduced pressure falloff = 14.8psi

152.76psi Pump Pressure (@25gpm) - 43.35psi Riser Head Pressure (100ft) - 7.97psi Riser Friction loss (1-1/4" ID @25gpm) - 31.81psi CSV DP(@25gpm) = 70psi CSV Outlet Pressure

Is that right?

I just want to confirm if the CSV-1A is best for my setup or if I need to go back to my well contractor to change it out.  My target is for a flow at the Pump sweet spot of 22-28gpm which seems to be right for the CSV-1A.

[Cary Austin]

"152.76psi Pump Pressure (@25gpm) - 43.35psi Riser Head Pressure (100ft) - 7.97psi Riser Friction loss (1-1/4" ID @25gpm) - 31.81psi CSV DP(@25gpm) = 70psi CSV Outlet Pressure"

OK, I take it from the above statement that the "riser head" is the depth to water in the well.  I also assume from the 25JS3S4 model number and the graph showing zero flow at 500' of head that this is the 3HP version?  I will attach a curve.

If you are using 25 GPM that pump can produce 350' of head.  Since it is 100' to water in the well, the CSV at the surface will see 250' of head or a back pressure of 108 PSI.  Because the pump can build 108 PSI you can loose 38 PSI to friction loss and still have 70 PSI outlet of the CSV.  However, with the CSV1A set at 70 PSI while using 3 GPM, the 15 PSI reduced pressure at 25 GPM will cause only 55 PSI to come out of the CSV1A.  You can adjust the CSV1A up to make up for the reduced pressure falloff, but not the friction loss.  By setting the CSV1A at 85 PSI while using 3 GPM and a 75/95 pressure switch setting, it will deliver 70 PSI out let at 25 GPM while the inlet side of the CSV is at 108 PSI from the friction loss.

Next thing is if that is a 3HP pump it really needs a minimum of 3 GPM to stay cool.  The regular CSV1A as a 1 GPM minimum for 2HP and smaller motors.  We can make it into a CSV1A-3GPM, which will have a 3 GPM minimum to keep the motor cool, which is also the rate of tank fill after all taps are closed.  At 3 GPM that pump builds 500' of head, which is the same as 216 PSI.  216 PSI would then be the max pressure the pipe in the well will see.  But you would loose 43 PSI of that as the water travels up the 100' from the static level in the well.  That means the pipe at the surface before the CSV and the inlet or back pressure to the CSV will be 173 PSI. 

This is all very possible with what you have.  But with that size pump and 100' to water the CSV3A2T would make a lot of difference.  With this 2" valve there would be no reduced pressure fall off and every zone from 3 GPM to the max the pump can produce would be at a constant 70 PSI as that is the setting of the CSV3A2T.  The inlet pressure to this valve would still vary according to how much water is being used.  The inlet pressure to the CSV would be 173 PSI when using 3 GPM and 108 PSI when using 25 GPM.  But there is only 3 PSI of friction loss which will allow you to use larger zones up to about 30 GPM before you start losing any pressure on the outlet of the CSV.

It would be great if you ran it with the CSV1A for a while then switched to the CSV3A2T.  It would be easy to document the difference and night and day to see.  Working less than 15-20 GPM with the CSV1A you are not getting into the maximums for that 1" valve.  But anything higher than 20 GPM is pushing it for the CSV1A.

The CSV3A2T is a 2" valve that uses the CSV1A as the pilot control.  If you do switch it out you will have a spare pilot for the CSV3A2T.  Being pilot operated and a larger 2" valve is what lets the CSV3A2T have so much better flow characteristics than the 1" direct acting CSV1A by itself.

Thanks for making me explain all that as some of this stuff needs to be written down, not just in my head.  Lol.

[EPStutes]

Wow!

Thanks for all the details.  This is a new well that has been installed and not commissioned yet.  I will call the wells company and discuss swapping out the CSV-1A with the CSV3A2T as you recommended.  Your explanation will be a big help in that effort.

Hopefully I will not have any any more questions.

Thanks again,

Regards,

Eric Stutes

[Cary Austin]

Here if you need help or have more questions.