Slowing down oversized well pump?

Help Support Plumbing Forums:

OverThere

New Member
Joined
Jun 8, 2021
Messages
3
Reaction score
1
Location
NC
I have a well with no known information. My best guess is it is relatively shallow, and only produces around 5gpm. On the other hand I think I have a 2hp sump pump (uses 1550 watts running) and that can push out over 13gpm, quickly draining the well.

Obviously my pump is oversized, and I want to reduce the max output in case somebody leaves the water running. I do not need more than 5gpm. Also, I only have a 20 gallon pressure tank with 4.4 gallons of draw down (30/60 PSI) and it fills up in less than 20 seconds causing excessive cycling.

1. Can I use a low cost VFD to slow the existing pump down to a more reasonable rate? I can get a 3hp rated VFD on Amazon for about a hundred bucks.
2. Should I use a valve instead to choke down the flow of the pump?
3. Can I/should I increase the pressure to hold more in the tank?

Which option would be easier on the pump? I feel like if I used a VFD to reduce the power of the pump, the motor will last longer than a valve causing higher back pressure. Am I wrong? I don't want to spend the extra money for a constant pressure system, just want the pump to more closely match the actual yield.
 

Valveman

Pump Controls Tech
Professional
Lifetime Supporter
Joined
Jan 6, 2010
Messages
927
Reaction score
217
Location
,Lubbock, Texas
A sump pump is different than a submersible pump? It is probably a single phase motor. They do make single phase VFD's now if you really want to get stuck with an expensive Tar Baby? Even a cheap VFD will cost you plenty in other ways because it shortens the life of the pump and causes many other problem. A 5 GPM Dole valve would be a simple choice. However, this limits you to 5 GPM max. Even though a well only makes 5 GPM, there is usually quite a bit of water stored in the well (from pump to static level). This allows you to use more water than 5 GPM for short periods of time to meet peak demands.

It is usually best not to restrict or slow down the pump, just protect it from running dry. Using a Cycle Sensor, which is a dry well protection device, if you do leave a hose on and pump the well dry, it will shut the pump off and protect it. But this way you are not limited to 5 GPM total, as you will need more than that for short burst.

 

OverThere

New Member
Joined
Jun 8, 2021
Messages
3
Reaction score
1
Location
NC
Shortens the life of the pump? Are you even aware what a VFD is? A VFD not only provides a soft start, it simply slows the motor down so it isn't 2hp any longer. Why would that harm anything? It should increase the life significantly. It's like a fancy dimmer switch for motors.

On the other hand a valve simply forces high pressure to do the same thing and make the pump work against the valve. Why would that not be bad for the pump?

The cycle sensor would do absolutely nothing to solve this problem - like I said the pressure tank is undersized and the pump is oversized. It has to cycle frequently the way it is currently setup or it wouldn't work at all. I am going to add an additional pressure tank, but still not enough for this size of pump.

There is no reason I would need more than 5gpm plus whatever is in the pressure tank (that's two showers at once) but if I did I would simply go turn up the VFD. I do not use water for irrigation. Would a single phase VFD not be like having a digital-adjustable dole valve? How would that "harm" anything? Seems like the perfect solution. I need to be clear - I am not talking about a fancy variable pressure system, just a cheap VFD that slows down the motor to a set level that more closely matches the well yield. My well is shallow and only 6" so it doesn't store a ton of water.

The "best" thing to do would be to install an appropriately sized smaller pump, but I don't want to do that when I already have one that works down the hole. Whoever installed the pump used the wrong size, probably the same guy that didn't bother to mark the depth or yield measurements.
 
Last edited:

Valveman

Pump Controls Tech
Professional
Lifetime Supporter
Joined
Jan 6, 2010
Messages
927
Reaction score
217
Location
,Lubbock, Texas
Lol! Your misunderstanding of how pumps work is very common. VFD sales people don't even have to work at it, because most people falsely believe slowing a pump down is good for it. On the other hand, most people falsely believe restricting the flow of a pump with a valve will make it work harder, when both of those things are the opposite of the truth. It is not an easy thing to explain. I have an entire web page dedicated to explaining it, and even that is way over most people's heads, even for engineers and installers. You can find the technical information here. VFD Does Not Save Energy – Cycle Stop Valves, Inc and here CSV vs VFD – Cycle Stop Valves, Inc

I will give you a couple of examples.

Cheap VFD's are not good because they don't have the filters needed to keep a VFD from pulsing 2000 volt spikes to a 230 volt motor. Even more expensive VFD's that have filters, can only reduce the voltage spikes a little. VFD's also need to be adjustable enough to program the parameters that will make a submersible motor survive the abuse of varying the speed. Soft starts are not good for a submersible motor as the thrust bearing doesn't get the hydroplane and lubricating effect until the pump is up to 50% speed. 50% of full speed must be achieved in less than 1 second to prevent bearing damage. Every component in a pump/motor has a mechanical frequency which will cause it to vibrate. Going from zero hertz to max hertz means the pump is at some times going through the mechanical frequency of every component in the pump or motor. And yes those things will shorten the life of the pump, not lengthen it, no matter what the marketing people say. The VFD itself uses extra energy. Any line or load filters causes it to lose even more energy. I could go on, as you will see if you go through the multiple articles I have written on this subject in the last 30 years.

Now, why you think this and the reason so many VFD companies get away with what they are doing, is because centrifugal pumps are counter intuitive. They work just the opposite of what our brains say is logical. Unlike a piston or gear pump, a centrifugal pump uses less energy, runs cooler, and last longer when the flow is restricted with a valve, which also eliminates the cycling. But a simple and inexpensive valve like the CSV that replaces VFD's, larger pressure tanks, etc, and really does make pumps last longer is a disruptive product to the industry. The things you see advertised the most are what companies make the most money on, which is just the opposite of what is best for the consumer. The things they don't want you to know about, like the CSV, would be bad for business. Yeah, I always thought, "If you build a better mousetrap". But it doesn't work that way in this age of planned obsolescence, which means marketing the heck out of cheaply built, short lived, expensive, and non-repairable products of all kinds. I digress!

Your pressure tank idea will not work as pressure tanks are empty by the time the pump comes on. Then you would be limited to the 5 GPM the pump is restricted, slowed down, or sized to produce. Using two 3 GPM showers at the same time when the pump is sized or slowed down to 5 GPM would result in really low pressure, making it necessary to run around in the shower just to get wet. Lol!

The Cycle Sensor, even working with a Cycle Stop Valve, would let your pump supply two showers at 6 GPM, or even four showers at 12 GPM for as long as the water stored in the well will last. If you run two or four showers for too long, the Cycle Sensor will shut the pump off and display DRY. You can set the restart delay for 10 minutes or hours, to let the well replenish before the Cycle Sensor automatically restarts the pump. Then, because you have a 12 GPM pump, the CSV will keep the pump from cycling when using anything less. So, when using only one 3 GPM shower or sprinkler, the CSV will keep a strong constant 50 PSI to the shower or sprinkler and not let the pump cycle at all, even if you are in the shower or run the sprinkler for a month.
 
Last edited:

Valveman

Pump Controls Tech
Professional
Lifetime Supporter
Joined
Jan 6, 2010
Messages
927
Reaction score
217
Location
,Lubbock, Texas
Here we go again.
Lol! Sorry! To be such a simple valve the CSV has a complicated explanation. And there is no quick and easy way to explain all the problems with VFD's. You would think I could just copy/paste my responses after all these years. But I still like to give a reply to the way the questions are asked. "Dimmer switch" would take me another page or two. :rolleyes:
 

OverThere

New Member
Joined
Jun 8, 2021
Messages
3
Reaction score
1
Location
NC
LOL! I can see this website is nothing but an infomercial for the CSV scam. Most people don't like those, I'm one of them. Not interested in any CSV products, they increase the pressure far above the rating of the pipe on the pump...

You clearly don't understand how a VFD works. I'm not talking about a fancy pressure regulated system or anything a "salesman" said. I found your ranting webpage about how nobody wants you to sell your product because you think it is "disruptive"...and that is hilarious. Your product is garbage, I'll post somewhere else that is actually useful.

And you're totally ignoring the actual problem, which is the well doesn't produce enough water.

Laughably stupid. If your product was any good you wouldn't be slinging it on bad internet forums.
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
933
Reaction score
308
Location
Iowa
LOL! I can see this website is nothing but an infomercial for the CSV scam. Most people don't like those, I'm one of them. Not interested in any CSV products, they increase the pressure far above the rating of the pipe on the pump...

You clearly don't understand how a VFD works. I'm not talking about a fancy pressure regulated system or anything a "salesman" said. I found your ranting webpage about how nobody wants you to sell your product because you think it is "disruptive"...and that is hilarious. Your product is garbage, I'll post somewhere else that is actually useful.

And you're totally ignoring the actual problem, which is the well doesn't produce enough water.

Laughably stupid. If your product was any good you wouldn't be slinging it on bad internet forums.
This guy is a gem. A valve can't increase the pressure on a system.
 

GReynolds929

Professional
Professional
Joined
Jun 16, 2018
Messages
172
Reaction score
113
Location
WA
LOL! I can see this website is nothing but an infomercial for the CSV scam. Most people don't like those, I'm one of them. Not interested in any CSV products, they increase the pressure far above the rating of the pipe on the pump...

You clearly don't understand how a VFD works. I'm not talking about a fancy pressure regulated system or anything a "salesman" said. I found your ranting webpage about how nobody wants you to sell your product because you think it is "disruptive"...and that is hilarious. Your product is garbage, I'll post somewhere else that is actually useful.

And you're totally ignoring the actual problem, which is the well doesn't produce enough water.

Laughably stupid. If your product was any good you wouldn't be slinging it on bad internet forums.
Hahaha, priceless. Proceeds to join a “bad forum” to ask for help and then immediately proceeds to insult everyone who replies while demonstrating his own ignorance and stupidity. Welcome troll....
 

Valveman

Pump Controls Tech
Professional
Lifetime Supporter
Joined
Jan 6, 2010
Messages
927
Reaction score
217
Location
,Lubbock, Texas
I don't hold it against him. I was expecting something similar. Once someone has drank the VFD Koolaid their brains are permanently altered. They have been convinced water will flow uphill and no amount of logic or explanation is going to change their mind. I have been hearing the same thing since 1993. However, having been doing this for almost 30 years, there are now over a million CSV's working, doing a better job and making pumps last much longer than the VFD or large pressure tank the CSV replaced. But people don't like to be corrected. They lash out at me all the time no matter how nicely I try to explain it. If they don't listen and end up buying a VFD, I figure they get what they deserve. People who have already been through the problems I list with VFD's have just the opposite reaction. "The CSV is great! Why didn't someone explain the problems of VFD's to me a couple of years and several thousand dollars ago?" Then they realize they just answered their own question. :rolleyes:
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
933
Reaction score
308
Location
Iowa
The sad part is he came here for advise (or I guess maybe not) and encountered an expert to give him advise. He was so willing to clutch his Wikipedia inspired theory that he will now walk a worse path. You see that alot. Someone does some research online and then goes to a forum to have their plan confirmed. There are a lot of people who think the internet and 2 weeks of research account for actual expertise.
 

SHEPLMBR

not a Junior Member anymore!
Sponsor
Joined
Mar 9, 2016
Messages
1,339
Reaction score
429
Location
Augusta WV
Shortens the life of the pump? Are you even aware what a VFD is? A VFD not only provides a soft start, it simply slows the motor down so it isn't 2hp any longer. Why would that harm anything? It should increase the life significantly. It's like a fancy dimmer switch for motors.

On the other hand a valve simply forces high pressure to do the same thing and make the pump work against the valve. Why would that not be bad for the pump?

The cycle sensor would do absolutely nothing to solve this problem - like I said the pressure tank is undersized and the pump is oversized. It has to cycle frequently the way it is currently setup or it wouldn't work at all. I am going to add an additional pressure tank, but still not enough for this size of pump.

There is no reason I would need more than 5gpm plus whatever is in the pressure tank (that's two showers at once) but if I did I would simply go turn up the VFD. I do not use water for irrigation. Would a single phase VFD not be like having a digital-adjustable dole valve? How would that "harm" anything? Seems like the perfect solution. I need to be clear - I am not talking about a fancy variable pressure system, just a cheap VFD that slows down the motor to a set level that more closely matches the well yield. My well is shallow and only 6" so it doesn't store a ton of water.

The "best" thing to do would be to install an appropriately sized smaller pump, but I don't want to do that when I already have one that works down the hole. Whoever installed the pump used the wrong size, probably the same guy that didn't bother to mark the depth or yield measurements.
the fact that you say you are using a ump pump is probably what is causing confusion.,
 

Valveman

Pump Controls Tech
Professional
Lifetime Supporter
Joined
Jan 6, 2010
Messages
927
Reaction score
217
Location
,Lubbock, Texas
The sad part is he came here for advise (or I guess maybe not) and encountered an expert to give him advise. He was so willing to clutch his Wikipedia inspired theory that he will now walk a worse path. You see that alot. Someone does some research online and then goes to a forum to have their plan confirmed. There are a lot of people who think the internet and 2 weeks of research account for actual expertise.
But if they are willing to learn, at least they have the Internet. In the past you just had to take what the local pump man said you needed. And if you have a good pump man that is a good idea. Problem is there are very few good pump guys anymore. Most are just parts swappers, and keep swapping parts until it works and the bill is high. I have learned I will never get the majority of people using Cycle Stop Valves. But I get everyone of them that is willing to educate themselves on how pumps and controls really work. The difference is "willing to learn" compared to "just want everyone to confirm how smart my idea is".
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
933
Reaction score
308
Location
Iowa
I don't know if it's my background in hydronics, but the csv just makes intuitive sense to me. I think it may be the electrical training also.

I think your right, people don't really know how electrical and mechanical devices actually work.
 

Valveman

Pump Controls Tech
Professional
Lifetime Supporter
Joined
Jan 6, 2010
Messages
927
Reaction score
217
Location
,Lubbock, Texas
I don't know if it's my background in hydronics, but the csv just makes intuitive sense to me. I think it may be the electrical training also.

I think your right, people don't really know how electrical and mechanical devices actually work.
It wasn't intuitive to me, and its not to most people. I would have sworn on my life that restricting the flow with a valve will make a pump work harder, not easier. My only saving grace was I was in the pump business and could test it and see it everyday on every pump, and I did until it finally sunk in.

I also thought using a VFD to slow the pump down would save energy. I could see the amps reduce when the flow and RPM was reduced, and that made perfect sense to me. It took me a long time and another smart engineer to explain it to me, before I finally understood the VFD is just reducing the amps to spin the motor. A VFD actually causes the power used to pump the water to actually increase, not decrease. I did a lot of math and looking at pump curves before I understood it.

So, I certainly understand why many people don't understand pumps, valves, and VFD's. I have been learning something new about pumps everyday for over fifty years. What I don't understand is people with closed minds who don't want to learn something new and beneficial?
 

JG plumbing

Well-Known Member
Joined
Mar 26, 2021
Messages
933
Reaction score
308
Location
Iowa
The part about it using less amps wasn't intuitive,then you think less water being lifted and it clicks. Or did for me anyway.
 
Top