Max psi for SQFlex pump (and a 1.5" long barb fitting?)

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Evan Byrne

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Hey all,

I am going to be installing a SQFlex 30-SQF-160 to run a solar irrigation system on my farm. I am going to be installing a CSV with it to reduce the cycling and I'm trying to figure out the maximum pressure my pump can build to properly size my poly pipe (200psi vs 250psi), and the CSV itself (some models top out at 150psi max inlet, some are 400psi). The pump curves provided for the SQF series are completely different than the standard pump curves. I'm not sure how to calculate the maximum pressure this pump can build. The literature states a maximum ambient pressure of 217psi, but that is also listed for all the SQF pumps, I believe that means max head of ~500ft.

My well is 200ft deep with water at 30ft. A Kw conversion would put this pump at roughly 3.2HP
Does anyone know how to calculate the maximum pressure this pump can build based on the pump curve? I have attached it.

Bonus question: Does anyone know of a 1-1/2" Stainless Long Barb/NPT fitting? There are great ones available for 1" and 1-1/4" but this pump discharges 1-1/2" and I'm trying to keep my friction loss at a minimum so I'd prefer to hang it on 1-1/2" poly. Is 2 hose clamps on a 5 barb short fitting ok? Would you trust it?
 

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Reach4

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CSV is only for centrifugal pumps. The SQFlex 30-SQF-160 may be centrifugal, but you would want to check. This causes me to think that pump is very probably centrifugal.
"Seven pump models can deliver from 2 gpm at 600 feet to 65 gpm at 20 feet of head with a 1 kilowatt solar array or less. Helical rotor pumps (models 3, 6 and 11) for high head applications and centrifugal pumps for low head applications assure a pump that is efficient for any use."

It is the one up top that takes the greater force.

https://www.winsupplyinc.com/boshart/_/A-05564189
https://www.supplyhouse.com/Boshart-BMAXL-150NL-1-1-2-MPT-x-Insert-Male-Adapter-Extra-Long-Lead-Free
 
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Evan Byrne

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CSV is only for centrifugal pumps. The SQFlex 30-SQF-160 may be centrifugal, but you would want to check. This causes me to think that pump is very probably centrifugal.
"Seven pump models can deliver from 2 gpm at 600 feet to 65 gpm at 20 feet of head with a 1 kilowatt solar array or less. Helical rotor pumps (models 3, 6 and 11) for high head applications and centrifugal pumps for low head applications assure a pump that is efficient for any use."

It is the one up top that takes the greater force.

https://www.winsupplyinc.com/boshart/_/A-05564189
https://www.supplyhouse.com/Boshart-BMAXL-150NL-1-1-2-MPT-x-Insert-Male-Adapter-Extra-Long-Lead-Free

Good call on the centrifugal vs helical, I have been warned about this. I remember Cary's comment about pressure tanks taking off like a missile from a helical that just keeps building pressure. I am virtually certain that the 30-sqf-160 is centrifugal. The Helical pumps have a very different looking curve, almost straight lines instead of curves, and typically high head and low flow. This is a 40GPM pump at 63ft of head, thats why I chose it for a drip irrigation system on my farm.

Thanks for the barb links! I had been looking for stainless with no luck. Is there any issue with using brass to stainless threaded connections? Any risk of galvanic corrosion?
 

Reach4

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No. CTS pipe is copper tubing sized, and will not go onto the barbs.

You want SIDR pipe to fit onto barbs.
 

Valveman

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The larger SQF pumps are centrifugal and work fine with a CSV. Those curves are hard to read. I think this is the correct curve. It looks like 262' is max head, which is only 113 PSI. It looks like it will do 40 GPM from 66'. But how deep is the water in that 200' deep well. If you only need 15 PSI (34') for the drip, that only leaves enough pump left for a water level of 32'. I would think the water in your 200' deep well is deeper than 32', but maybe not. If that pump will do what you want the CSV125 will work fine with that pump.



30SQF160jpeg.jpg
 

Evan Byrne

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Hi Cary, Thanks for your reply. My water level is around 30ft, but accounting for some pressure loss I was aiming for somewhere in the middle of those curves. Something like 120ft of head and 40gpm. As I read it, the pump will still produce around 16gpm at 262' of head, so I don't believe that meets the traditional meaning of maximum head does it? I will email Grundfos and see if they can provide some clarification. I have a CSVS-125-3 ready to go but I want to make sure I'm not going to be exceeding the 150psi limit, or something higher and risk blowing my poly and losing this $2800 pump down the hole.
 

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I looked at the curve for the 30SQE170. It shows 260' max head, so I think the 160 will be about the same. But I would make Grundfos verify that. You shouldn't need the -3 in the CSV125. The higher the differential pressure the more the minimum flow though the CSV. With a 40/60 pressure switch and a pump that builds 260' of head max, the -1 CSV should flow about 1 GPM minimum and the -3 will flow about 3 GPM minimum. The -3 won't hurt anything but will allow the pump to cycle when using a 2.5 GPM shower or anything smaller than 3 GPM.
 

Evan Byrne

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I looked at the curve for the 30SQE170. It shows 260' max head, so I think the 160 will be about the same. But I would make Grundfos verify that. You shouldn't need the -3 in the CSV125. The higher the differential pressure the more the minimum flow though the CSV. With a 40/60 pressure switch and a pump that builds 260' of head max, the -1 CSV should flow about 1 GPM minimum and the -3 will flow about 3 GPM minimum. The -3 won't hurt anything but will allow the pump to cycle when using a 2.5 GPM shower or anything smaller than 3 GPM.

I called Grundfos and even one of their engineers wasn't able to tell me the exact max pressure based on the SQF curve. I did get clarification that according to the curve, if the pump was at 262ft of head it would be making 17gpm. I also got clarification that it is indeed Centrifugal. I'm still nervous to install this thing without knowing the maximum pressure it can build because I could either blow a barb fitting, burst the poly or damage my CSV125. It's going to be used to irrigate a farm and flows below 20gpm will be rare.
 
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