pressure issue with well

[DonC]

Hi,

Our well pump is @ 350'. We have a 2hp grunfos 3 phase pump. The controller and pressure tank are approximately 200' from the well in a small shed. This shed has a manifold with the line from the well, 2 outside hydrants, a line to the house and a 1/2" line to our trailer parked outside the shed, and a pressure tank attached to it. The pressure tank looks to be about 30 gallons. There is a pressure sensor on the manifold that goes to the controller. All pipe is 1.25 except the line to the trailer which is 1/2"
The line to the house is about 100' long where it is stepped down to 1".
Our controller shows the pressure maximum is 62psi and the lowest I've seen it is about 54psi. The controller is a Pentair Intellidrive constant pressure controller.

What we have discovered is that in the house running even a single 1/2" cold water line for a few minutes, our pressure suddenly drops. After a minute or so it comes back up.
I'm wondering if we should install a second pressure tank in the house or perhaps a booster pump. Or perhaps adjusting the settings on the pump controller. I'm thinking the pressure drop we are seeing is because of the length of the line from the shed to the house and the delay in recharging the pressure tank from the well.

We also have a 5th wheel trailer connected to the main manifold where the pressure tank is and we've never seen a pressure drop in the trailer. The trailer is fed with a 1/2" line. We've been living in the trailer for 2 years while we build the house. We've also used sprinklers attached to the hydrants and never noticed a pressure drop on those either.

The main floor in our house is approximately 12' above the level of the main water line from the shed.

The guy who installed it all is no longer here so I can't ask him questions about how it should be working or why it's doing what we are seeing.

thanks
Don

 

[Valveman]

Sorry for your problem. That Pentair Intelidrive controller is a VFD, which varies the speed to the motor. There are so many parameters to set and things that can go wrong with a computerized VFD controller that 99% of the time that is where the problem lies. 62 PSI constant should be so strong you don't even need soap in the shower or to wash your hands. You will lose 5 PSI going up the 12' elevation, and should still have a strong constant 57 PSI at the upper floor. You need to observe the pressure gauge when the low pressure event is happening. If the gauge shows 62 PSI no matter what, you have a restriction after the gauge somewhere. But if the gauge drops low and stay low for a minute, the parameters in the drive are shutting it down. There is a minimum flow that is needed to keep the pump running on a VFD. If the 1/2" faucet doesn't let out enough water to keep the motor cool, the drive will shut it down, make it wait a minute, then restart the pump. Same thing if the motor is drawing an overload.

Like I said, the problem is usually the VFD. They are made to make lots of money for the pump manufactures and they have to be expensive and unreliable to make that happen. The sooner you get rid of the VFD the sooner your problems will go away. This is just the first of many other problems that will arise from using a VFD. BUT, you have a three phase motor and probably wire that is too small for a single phase motor. This is how they cut the cost of the first install and lock you into continually replacing the expensive VFD controller.

To make it a RELIABLE and long lasting constant pressure system you will need to get rid of the VFD controller, replace the three phase motor with a normal single phase motor, and install larger wire if needed. Then adding a Cycle Stop Valve as comes in the PK1A kit will deliver the strong constant pressure you want, even at lower flow rates than the VFD, without all the expense and problems caused by using a computer to vary the speed of the pump.

Edit; BTW a booster pump or extra pressure tank will not help and only make the problems worse.