Constant pressure pump issues

[Mac1122]

I have a constant pressure pump that is set to deliver 50psi in the house and works fine. It also has my irrigation system on it and when I turn on any zone 4 heads at a total of 12 gpm the pressure at the tank is only 30 psi. When the pump contractor tied the irrigation system in it is right at where the line comes in from the well but am I wrong in thinking it shouldn’t matter with this type of system? My pump is a Myers 20gpm with a 1-1/2 hp motor and a Franklin sub drive 75

 

[Valveman]

If the pumping level in the well is 230', then 12 GPM at 30 PSI is all a 20 GPM, 1 1/2HP pump can do. If your water level is less than 230'. the pressure should be higher. Either your water level is 230' or the pump is not doing as much as it should. I have seen subdrive systems with the irrigation taken off at the well head like that and the pump would pulse as the water is being let out prior to the pressure sensor/switch. Just the first of many problems you will probably have with that VFD type system. Of course if you used a CSV for constant pressure instead of a VFD your pump system might last 30 years, and most pump guys don't like that, which is why they prefer VFD's.

 

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[Mac1122]

If the pumping level in the well is 230', then 12 GPM at 30 PSI is all a 20 GPM, 1 1/2HP pump can do. If your water level is less than 230'. the pressure should be higher. Either your water level is 230' or the pump is not doing as much as it should. I have seen subdrive systems with the irrigation taken off at the well head like that and the pump would pulse as the water is being let out prior to the pressure sensor/switch. Just the first of many problems you will probably have with that VFD type system. Of course if you used a CSV for constant pressure instead of a VFD your pump system might last 30 years, and most pump guys don't like that, which is why they prefer VFD's.

I am only 30 foot to the bottom of the well. Would it help if I was after the pressure switch or not. Water level is 17 feet

 

[Valveman]

I have seen those things cause the pressure to fluctuate when water is teed off prior to the sensor/switch. However, it doesn't say anywhere in the instructions that you cannot do that. The only thing I see is in the trouble shooting guide. It says if the pressure fluctuates when using a branch prior to the pressure sensor to flip DIP switch #4 to the "on" position. But there are lots of possible problems with those things. If I only sell a Cycle Stop Valve on systems where they have had problems with a VFD, it adds up to a lot of CSV's.

 

[Midriller]

I would assume the well is not keeping up with the pump. A 1-1/2 H.p 20 GPM pump is vastly over sized for the system. Kick your irrigation system on and put your ear to the well head. If you hear a sucking sound it is drawing down. It may or may not have a draw down seal. a 30' well and a 17' static means you only have a 13' water column. the well would have to produce A TON of water to keep up with the 30 gpm that pump is producing in this system. This would be the case regardless of VFD or CSV A sub drive uses a micro switch and does not matter where you tap in. A Grundfos Cu- 301 uses a Transducer and would require the water to pass by it for proper operation.

 

[Mac1122]

I have seen those things cause the pressure to fluctuate when water is teed off prior to the sensor/switch. However, it doesn't say anywhere in the instructions that you cannot do that. The only thing I see is in the trouble shooting guide. It says if the pressure fluctuates when using a branch prior to the pressure sensor to flip DIP switch #4 to the "on" position. But there are lots of possible problems with those things. If I only sell a Cycle Stop Valve on systems where they have had problems with a VFD, it adds up to a lot of CSV's.

I would assume the well is not keeping up with the pump. A 1-1/2 H.p 20 GPM pump is vastly over sized for the system. Kick your irrigation system on and put your ear to the well head. If you hear a sucking sound it is drawing down. It may or may not have a draw down seal. a 30' well and a 17' static means you only have a 13' water column. the well would have to produce A TON of water to keep up with the 30 gpm that pump is producing in this system. This would be the case regardless of VFD or CSV A sub drive uses a micro switch and does not matter where you tap in. A Grundfos Cu- 301 uses a Transducer and would require the water to pass by it for proper operation.

It does have a draw down seal.

 

[Mac1122]

It does have a draw down seal.

When the irrigation is on there are only 4 heads running at 3GPM per head.

 

[Mac1122]

It does have a draw down seal.

Also what is the cut on pressure of a constant pressure pump. Mine seem to come on as soon as you open a faucet and stops within seconds after you close it

 

[Valveman]

Those switches on a Subdrive only have 1 PSI between on and off. They will come on as soon as you crack open a faucet, and will go off almost as soon as the faucet is closed. That isn't a good thing as you are not able to use any water from any size tank, but that is just the way they work.

 

[Valveman]

When the irrigation is on there are only 4 heads running at 3GPM per head.

From 30' deep, a 1.5HP, 20 GPM pump should be able to put out 25 GPM at 50 PSI. Since your irrigation only uses 12 GPM, either the pump or well is not putting out that much water. If it is a well problem, the low amp safety in the VFD controller should be shutting off the pump. But 12 GPM at 30 PSI is certainly not right. You paid big money for that VFD system, make them get it right.

 

[Midriller]

Replace the well, Draw down seals are band aids for bullet wounds. The pump installer should have caught this while test pumping over the top, but i agree, hopefully a reputable company will stand behind the work.

 

[Mac1122]

I would assume the well is not keeping up with the pump. A 1-1/2 H.p 20 GPM pump is vastly over sized for the system. Kick your irrigation system on and put your ear to the well head. If you hear a sucking sound it is drawing down. It may or may not have a draw down seal. a 30' well and a 17' static means you only have a 13' water column. the well would have to produce A TON of water to keep up with the 30 gpm that pump is producing in this system. This would be the case regardless of VFD or CSV A sub drive uses a micro switch and does not matter where you tap in. A Grundfos Cu- 301 uses a Transducer and would require the water to pass by it for proper operation.

If the well wasnt keeping up with the pump would I hear air in the sprinkler as they are running?

 

[Mac1122]

I talked to a well guy and he said no real way to test the pump. Of course he wants to put a new pump in and see if that works. Kind of an expensive troubleshooting method. Any ideas would help.

 

[Valveman]

Any good pump man would know how to test the pump. Of course it can be tested. Has that thing even lasted long enough to be out of warranty? Sounds like you need to find a good pump man. And no you probably won't see air in the sprinklers. The pump should shut down if it is pumping air.

 

[Mac1122]

Look at this well spec sheet when installed and yes it is from 2006 so past warranty

 

[Mac1122]

 

[Valveman]

Thirteen years is about 3 or 4 times the length of time those Variable Speed Pumps usually last. The way Subdrives work I would expect an impeller or three has broken loose from the shaft, and that pump just isn't doing what it should. The pump can easily be tested, especially once you get it out of the well. But even if it test good I would get a new one, as it has been tortured for 13 years from the VFD controller. A regular constant speed pump, especially when installed with a CSV should last 20-30 years, which is why they had rather sell you one of those VFD type pumps.

 

[Mac1122]

Thirteen years is about 3 or 4 times the length of time those Variable Speed Pumps usually last. The way Subdrives work I would expect an impeller or three has broken loose from the shaft, and that pump just isn't doing what it should. The pump can easily be tested, especially once you get it out of the well. But even if it test good I would get a new one, as it has been tortured for 13 years from the VFD controller. A regular constant speed pump, especially when installed with a CSV should last 20-30 years, which is why they had rather sell you one of those VFD type pumps.

Does it look like my water levels are ok based on the numbers

 

[Valveman]

I don't know that water levels matter with a draw down seal? I would think if the well is not producing enough it would act like a restriction to the suction side of the pump, but the water level would not change. The pump could be tested in a barrel, bucket, kid pool, etc., then you would know if it is the well or the pump not producing as it should.

 

[Mac1122]

If I change things up and go with a CSV where then do i tap the output to the irrigation system, before or after the CSV