Is this just another case of ‘pump too small’?

[jphalin]

What am I trying to accomplish:

Trying to achieve 20-25 GPM at a constant pressure of 50 so I can design a sprinkler system layout with confidence that I have the right amount of heads and pressure.

What is happening:

I am testing with a frost free hydrant as I am trying to understand my optimal GPM/PSI settings as part of the design for the sprinkler system.

-if I open the frost free full open, I get 30 GPM @ 40 PSI after much adjusting of the system.
 if I crank down the adjusting bolt on the CSV1A, I can get to 42 PSI max but the rapid recycle is occurring when I turn the water off with less than 5 seconds on the Cycle Sensor setting so I have to ease back on the bolt to resolve this. Seems strange since I understood that only 1 GPM was supposed to fill the pressure tank, but maybe I don’t understand the relationship between the adjustment bolt and how the pressure tank is filled.

- if I reduce the flow from the frost free (partially close the handle) to 20 GPM I can be around 48 PSI.

- if I reduce the flow from the frost free to 15 GPM, I can maintain 55 PSI which I think I have the valve adjusted to currently.

Here is my setup:

- 2100 gallon cistern with Goulds 25GS15422C 230V 1 1/2HP 25GPM pump
- CSV1A
- CS1PH1-2HP230V CYCLE SENSOR
- 4 gallon pressure tank set to 35 PSI
- Pressure switch Set to 45/65 (changed this from 40/60 trying to work around rapid recycle issue)
- no elevation change but test frost-free hydrant is about 125’ away. 1 ¼” poly line to ¾” hydrant.


Questions:

-   Do you have a sense of what this pump should be able to produce GPM/PSI wise given no elevation change? Is this just another case of the pump being too small to provide the needed pressure? It is close at 20 GPM but I bought this pump a long time ago when I understood even less and just installed it now.
-   I am wondering if this issue with the rapid recycle is expected as I tighten the adjustment bolt? Or is there a problem with the valve or the pressure tank causing this?
-   Are there any additional setup recommendations to optimize this setup?

Thanks for any advice!

[Cary Austin]

You should have plenty of pump to do what you want.  If you want 20 GPM at 50 PSI, you need to set the CSV1A at 60 PSI while running 3 GPM and turn the pressure switch up to 50/70.  Also need to increase the air charge in the tank from 35 to 45 and turn up the pressure relief valve.

The CSV only starts filling the tank when the pressure is higher than the CSV set pressure.  With the CSV set at 60 you will have 50 at 20 GPM and the tank will fill from 60 to 70 at 1 GPM rate.

[jphalin]

Right on! When I adjusted the pressure tank air pressure and pressure switch range per you suggestion, the issue with the 'rapid cycle' went away and I was able to adjust up the CSV valve to hit my goal.

Thanks again!

[Cary Austin]

Yeah the CSV always has to be set lower than the off setting of the pressure switch.  Glad you are happy!