Pressure pump problem

[Doug Chaney]

I bought this rural home recently and the pressure pump bothers me a whole lot. The thing cuts on off when no one is running water! EVEN if I close the ball valve to the house it might cut on and off...which makes no sense to me ...what is it trying to pressurize back through the pump? Is the backflow device in the wrong place? Bad transducer? I don't get it. One problem that makes it all utterly confusing for me is that it is a 3 phase motor even though I don't actually HAVE 3phase! It is an Aquavar 3AS20 controller, powering/controlling a THREE PHASE pump motor (2hp itt goulds pump motor assembly) Is that setup supposed to use less electricity than if I had conventional single phase motor controlled via a mechanical pressure switch?? I am thinking I would love to replace the entire setup with something I understand and feel able to work with? Do I even need 2 hp? We are a retire couple living in this 2300 square foot home. I do not understand the terminology involved with sizing a pressure pump. We are on a common well for several homes, the water tank is on my property just above the level of our home.... plenty of water available but no pressure without pressure pump...it just trickles out of faucet with the thing off. I would love to have someone recommend what I should do...should I keep this system? If so what can I do so it is not running all the time when no water is running! Should the backflow be on the inlet side of the pump? Because this one is on the other side...

 

[Reach4]

Do I understand that the pressure pump supplies water to 3 homes? If you had room, I wonder if would make sense to have two systems giving redundancy. If you want/need to work on one, you switch to the other...

 

[Sponsor]

 

[Valveman]

Where to start? The Aquavar is a VFD that converts your single phase power to three phase power, because the VFD needs a three phase motor to work with. This kind of locks you into staying with a VFD type system (on purpose) unless you want to change the motor. I just helped another guy with a bad VFD and he was able to purchase a complete new single phase pump/motor/control for less than a new VFD.


With a normal speed pump/motor you either need to add a couple two/three pressure tanks or use a Cycle Stop Valve and maybe an 80 gallon pressure tank, since you have a 3HP and multiple houses on this system. The CSV holds a constant pressure the same way the VFD and pressure transducer does, just without varying the speed of the motor and all the electronics and VFD stuff that goes with varying the speed.


The pressure in the system as it is should not decrease unless water is being released somewhere. If you have the valve to the houses off, the only place water can go is back through the pump, which would be the check valve not working. Check valve before or after the pump is not important in your case, but a working check is.


Next possibility is that the VFD and transducer do not have any pressure differential. If the VFD is set to maintain say 60 PSI. Some may start the pump at 59.5 and turn it off at 60.5 PSI. With only 1 PSI between on and off you don’t have to release much water (quart) for the pump to have to start again, no matter where the water is being released. Some VFD’s will let you program a bandwidth or “sleep mode”, that lets the pump go to sleep at 60 PSI, and wake up at 50 PSI. The 10 PSI between on and off will let you use some water from a pressure tank for a while, depending on how large a tank you have. (80 gallon tank = 15 gallons of water/ 40 gallon tank has 7 gallons)


VFD’s are all electronic, vary the speed and need a three phase motor (usually), are susceptible to temperature and weather, electrical issues and lightning, cooling fan problems, etc.. Even little things can be problems like needing a special check valve to work with the erratic flow from a VFD.


A CSV will deliver constant pressure from a normal single phase pump/motor. It uses a regular mechanical pressure switch, usually best with 20 PSI between on and off like 50/70. Then the CSV would be set to hold 60 PSI, and you wouldn’t know the difference in pressure between the CSV and a VFD controlled pump. Except that you wouldn’t have to worry about it with the CSV like you are now. The CSV is simple and mechanical, and has no electronics. The simpler the pump and controls, the more likely water will flow out when you open a faucet.

And you don't need redundancy if you have a dependable pump system to start with. Most redundant pumps on CSV systems have to be exercised regularly, as they are never used.