Year-long nightmare

[Cfyfe3199]

Hello all, have been lurking for answers to some of my problems and I've picked up some great info so far, so thank you for that.

I moved into my house in June 2017. On a "mountain," tons and tons of HARD rock. They had a hell of a time hammering out the foundation. Drilled well, 650', original well report stated a 6GPM flow.
My original setup was a 2HP 3-phase motor/pump set at 500'. In the control box, i have a Schneider Electric model ATV312HU15M2 drive which supplies power to the motor. 60/40 pressure switch with a pressure tank (cant remember the size, but its not that big.)

So, we had problems with running out of water. I don't irrigate, wash cars, anything that would be considered wasteful. Well pump would shut off on low pressure, we let it sit overnight, and would have some more water in the morning, only to run out again very quickly.
So we added some cisterns in the basement. 3/300 gallon tanks (900 total). The well pump fills the cisterns by use of a float switch, but it is not wired directly into the drive. What we did was add a solenoid valve after the pressure tank. Float switch would lower, open the solenoid valve, pump would turn on once pressure dropped, and fill until the float switch told the solenoid vale to close, pressure would build up to 60psi and the pump would ramp down. This worked for a few months until I noticed the pump shutting down on low pressure.

Next attempt was to lower the pump, with hopes that the additional storage in the well plus the cisterns would be enough. This proved to be untrue. We lowered the pump to 640', only the have the same low pressure after a week or so. I verified water levels in the well by using an Eno Science well sounder.

My recharge rate had dropped to 0.05GPM
No, not half a gallon a minute.
1/20th of a GPM. Completely unsustainable. I've gotten by with hauling water in an IBC tank from my parents house across town (on city water) and filling my cisterns every few days.

At this point I bit the bullet and gambled with drilling deeper. The drillers went from 650' to 905'. They hit new rock formations, which is promising, and claim the well now makes 10GPM which is more than i ever hoped for.

Here's my question. I still want to use my cisterns, but I do not want my 3-phase pump motor to operate on pressure anymore. I have to keep adjusting the ball valve to restrict some of the water flow so the pump doesnt shut down on low pressure. It seems like more of a temporary fix.

How can I get this 3-phase variable speed pump to operate with just the float switch alone?
What kind of safeties can i use for a low-water situation?
Am I better off switching to a single phase setup with a cycle-stop?

I am not worried about pumping from the cistern to the house, that setup is working perfectly (DAB E.SYBOX)

Thanks for any and all help, let me know if any more info is needed.

 

[Texas Wellman]

Nobody on this board likes drives. If it was mine I would definitely go with a standard single phase set-up. However, if your well truly makes 10 GPM that is plenty of water to use without the extra complexity that the cisterns add. I realize you may be gun shy due to the last fiasco but you can always add the cistern set-up later.

The best option would be to size a pump and depth setting so that the pump could never "outrun" the well. In other words, if you have a "10 gallon per minute pump" once the water level reaches a certain depth (drawdown) the output of the pump drops down to less than 10 GPM. In fact most 10 GPM pumps will easily pump much more than 10 GPM depending on the head.

I really believe all your problems stem from the fact that your previous well was mostly a dry hole and if you truly have at least 10 GPM or even 1 GPM most of your problems will be solved. Also, since your old pump ran dry a lot, I would go ahead and replace it as well.

As far as the cycle stop valve goes what size tank do you have now?

 

[Sponsor]

 

[Reach4]

I am not a pro. To fill a cistern from water that could be 885 ft down, a 5 gpm 2 hp pump would probably be a good choice. Your existing pump may not have the lifting ability from deep if it was a 10 gpm pump or maybe even a 7 gpm pump.

I have also seen a 3-phase inverter to produce 60 hz 3-phase suggested, which is what you are asking about. I don't find the posts at this point, however. That would be controlled by a float switch through a 2-pole relay probably.

I am not a pro.

 

[Boycedrilling]

In your circumstance the Altivair 312 series drive is being used as a phase converter, rather than to vary the speed of the pump. Your submersible Pump is being turned on and off by the pressure switch. It could just as easily be turned on and off by a float switch.

With 3 phase output from the Altivair, the electrical load is spread evenly between the three current carrying conductors. #10 wire is sufficient for a total length of up to 910 feet. If you were to eliminate Altivair, you would need to replace the motor with a single phase motor, AND all the wire from the reservior with #6 wire.

On your original installation, the added cost of the drive, reduced the size of the wire needed, at a cost savings of one thousand to fifteen hundred dollars. If you were to change to a single phase motor now, you would be looking at four to five thousand dollars in materials.

Will a motor last as long on a drive as a conventional system? Probably not. I’ve got domestic pumps that I installed 25 years ago that are still running fine, as long as the pressure tank precharge is checked annually. I don’t know of any pressure tanks that will hold their precharge for over 20 years.

I’ve replaced a motor that was 4 years old and a pump end that was 3 years old,both on drives in the last two weeks. Neither was the fault of the drive. Both had leaks and were running continuously at minimum speed. On a conventional system both probably would have also failed from constant cycling, because of the leaks.

On domestic pump systems, my preference is to install a conventional pressure tank system. If they irrigate their yard , I prefer to install a cycle stop system. However there are circumstances where a drive is the correct choice.

I’m getting ready to install a 150 hp lineshaft turbine for a farmer. The power company gave approval for a size 5 across the line starter. However a soft start panel is only five hundred dollars more and gives a lot more protection. A drive for this pump would have been around twelve thousand dollars additional.

 

[Texas Wellman]

Boyce has given you some excellent advice. Experience counts.

 

[Boycedrilling]

Since you have a drive now, you can “detune” the pump. By lowering the maximum hertz you will reduce the gallons per minute that the pump will produce.

 

[Cfyfe3199]

Wow, thanks a lot for the help guys.

In your circumstance the Altivair 312 series drive is being used as a phase converter, rather than to vary the speed of the pump. Your submersible Pump is being turned on and off by the pressure switch. It could just as easily be turned on and off by a float switch

That’s where I get hung up on exactly how to do that. It’s a 120V float switch. Do I wire it into where the pressure transducer is now?
Are you familiar with the drive I have?

Since you have a drive now, you can “detune” the pump. By lowering the maximum hertz you will reduce the gallons per minute that the pump will produce.

Would also love to do this, but having trouble making sense of the drive. It’s not very user friendly.

 

[Valveman]

You should be able to wire a float switch to the same terminals and do away with the pressure switch. Then you just set the max htz for the rate you want to fill the cistern.

That smaller wire and three phase motor locks a lot of people into keeping and putting up with the problems of a VFD.

 

[Boycedrilling]

No I have never used the Altivair drives. You can download a manual. Google is your friend, use it.

What I’ve found is that programming variable frequency drives is like learning computer languages. My first computer class in college was Fortran using punch cards. Then we learned Cobal. Basic was the 3 or 4th programming language we learned. I don’t even know what the computer languages being used these days are, and luckily I don’t need to know.

Every brand drive has a different programming “language” and ideosyncracies. Some are easier that others, that is one of the things that I like about Danfoss drives. They program in plain English. That is the drive that is used in the Pentair Intellidrive. I have also used Hitachi and ABB drives. However I prefer Yaskawa drives on installations over 5 horsepower. They are not particularly easy to program, but I have great support from My distributor, and have learned to navigate their programming system. I almost refuse to use any thing else, just because it’s too much work to learn how to program a different brand. I can also program a Yaskawa from my laptop and save all the modified parameters in a file on my laptop.

The Altivair manual will instruct you on how to turn the drive on and off using the float switch. I did this once on a 10 hp sump pump, only we used the float switch to change the speed of the pump. If the water level rose the pump would run at full speed till the water level dropped. Then the pump would run at a slower speed still pumping water. Why did we do this ? The farmer had a,ready wired in a float switch to turn the pump on and off. It was 400 feet to the sump from the control panel. An ultrasonic transducer to monitor the water level costs close to a thousand dollars, and needs shielded control wire. By using the drive and the float switch, we were able to maintain the water level in the sump to les than a one foot fluctuation.

The manual will also instruct you on how to set the maximum hertz. You might find that you only want to run your pump at say 54 hertz maximum instead of the normal 60 hertz.

 

[Cfyfe3199]

Thanks a ton for all advice. Will try a few things and report back. I'm assuming the drive just needs a closed contact between the 2 terminals to signal "on" so i'll try a light switch and see what happens.

I've been looking into the FE SubDrive 20, anybody have any concerns with it? I basically like it because of the built-in underload protection and more simple configuration options.

Will a pumpsaver be useful in my application?

 

[Valveman]

"Built-in underload and pumpsaver do the same things. You don't need both.

I have customers using the Cycle Sensor for underload protection with a drive that doesn't have that feature. Seems to work OK.

A light switch or the float switch should work on those two terminals.

You already have a DAB and a Schnider VFD. Why would you want third problem like the Subdrive? Drives will save you some money on wire for a deep set submersible, but they usually cost you more than you save in the long run. Your DAB maybe "working perfectly" now, but give it a few years and you will be looking for an alternative.

 

[Cfyfe3199]

"Built-in underload and pumpsaver do the same things. You don't need both.

I have customers using the Cycle Sensor for underload protection with a drive that doesn't have that feature. Seems to work OK.

A light switch or the float switch should work on those two terminals.

You already have a DAB and a Schnider VFD. Why would you want third problem like the Subdrive? Drives will save you some money on wire for a deep set submersible, but they usually cost you more than you save in the long run. Your DAB maybe "working perfectly" now, but give it a few years and you will be looking for an alternative.

Well I would be swapping the VFD for the SubDrive, so no I wouldn’t be using all 3 at once.

Although I haven’t dug into the motor protection too far yet, from what I understand a PumpSaver is only good for single phase motors.

Will look into the Cycle Sensor

 

[Valveman]

The Sub Drive is just another brand of VFD, and in my opinion it is one of the worst ones. You have single phase before the VFD and three phase after. You would need to use a single phase Cycle Sensor on the inlet side before the VFD. And you would still be able to use the Cycle Sensor after you switch back to a normal single phase motor and do away with the VFD.

 

[Cfyfe3199]

The Sub Drive is just another brand of VFD, and in my opinion it is one of the worst ones. You have single phase before the VFD and three phase after. You would need to use a single phase Cycle Sensor on the inlet side before the VFD. And you would still be able to use the Cycle Sensor after you switch back to a normal single phase motor and do away with the VFD.

Great, will do that. Thanks again for your help, finally making sense of a lot of things thanks to you gentlemen.