Do you know how to choose the right VFD domestic water booster pump?

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Valveman

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I hope everyone has some pop corn and a comfy chair for the show. It would be nice if out of all those engineers at Yaskawa if at least one of them was a mechanical engineer, not just all electrical engineers. A good mechanical engineer would know that VFD's DO NOT SAVE ENERGY!

A VFD takes energy to run like any computer, and its a BIG computer. The best VFD in the world can only be 95% to 97% efficient at the most. That means a VFD adds 3% to 5% energy cost before the pump is even considered. Plus like any computer, a VFD uses energy even when the pump is off, because the VFD is not. Take the most efficient pump in the world and control it with a VFD, and you have just made that pump 5% less efficient and use more energy, even at full flow and best efficiency point.

Then anytime less flow is needed, and the VFD reduces the RPM of the pump, you are getting fewer gallons per KW not more. On constant pressure applications, which is nearly every domestic and fresh water pump system, a VFD can increase the cost of energy per gallon by up to 500%.

there have only been four failures. Three were due to water leakage from above which was not covered and the fourth was installed in a hot room during the summer with heaters on and no explanation was offered to why it failed.

One other way in which VFD waste energy is that they need cooling. New York maybe cool enough that air conditioning is not necessary, as long as they are not installed indoors. But anywhere in the south an air conditioned room or at least an air conditioned cabinet to put the VFD in is necessary. Without a cooler installed, the electronics in a VFD produce so much heat it will trip itself off on overheat. And nobody even calculates how much energy is used to keep the room or cabinet cool. One VFD user in Can Cun Mexico told me the air conditioners for the VFD's use more energy than the pump system itself, but it does get hot in Can Cun.

I don't believe VFD's are a bad choice for every application. They work great with positive displacement pumps, escalators, conveyor belts, and such. I have one on a hydraulic pump for a plastic injection machine that is wonderful. But I have a window unit air conditioner duct into the VFD cabinet, or it trips out on overheat. With a positive displacement pump a VFD can save energy, just not with regular centrifugal pumps that we all use to pump water. But the fact that VFD's will save energy on select uses like my hydraulic pump, people think they save energy on any system, and that is far from the truth.

In New York City, variable speed domestic water booster systems are not only ideal to have but they are now part of the electrical code in order to save electricity.

"I am with the government, and I am here to help you." LOL All government officials want you to think they are making life better for all of us, to justify their jobs. In reality they make codes that increase cost and decrease dependability, because they know not what they are doing. So called "green buildings" that are supposedly designed to be more efficient, are showing higher energy costs than the regular old buildings across the street. This is because engineers spec VFD's for the pump system, thinking the reduced RPM and lower amperage the pump is drawing will save energy. They don't understand that even though the VFD makes the pump/motor draw lower amps, the pump has to run a lot longer time to supply the water needed. A VFD can reduce the amp draw of a pump/motor by up to 50%. But when running at 50% of max load, the pump has to run 24 hours per day to supply the water instead of just 3 hours a day. Doing some simple math, one can deduce that running a pump at 50% energy load should cut the electric bill in half. However, running the pump at reduced speed and 50% load, means it has to run 8 times longer to supply the water needed. In this way a VFD decreases the energy needed to spin the pump/motor, while increasing the energy cost per gallon produced by 400%-500%.

Looking at what pump companies are pushing these days, you can tell they make a lot more money selling VFD's than they ever did selling pumps. And making more money is what all this hype is about, not saving energy. "Saving energy" is the carrot they use to con people into purchasing a VFD. "Saving energy" is a con, because it is not true. There is nothing more efficient than a standard full speed pump running at it best efficiency point, using across the line power. Anytime a VFD reduces the speed, the energy consumption goes up not down.

"But it is in the code, so it must save energy." The code needs to be re-written by someone who knows how to read a pump curve, not by someone making up stuff to justify their job. Again, VFD's DO NOT SAVE ENERGY!
 
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Valveman

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And what do you think the odds were that that professional still works for the company eight years later, and what are the odds that the required cable that fit the computer and fits the PLC is still around somewhere when you have trouble?

I think 8 years is a little optimistic about how long a VFD will last. But that is telling and kind of the point. A regular dumb pump with a non-VFD control should last 30 years. In that same length of time they will get to sell you at least 4 VFD's, and replace the VFD damaged pump/motor at least once or twice. Like I said, as long as people fall for the VFD hype, they get to sell you at least 4 times as much equipment to keep your water flowing.

A VFD is a microprocessor based pulse width modulator. It is a computer, similar to the one on your desk top. Finding cables that fit, or any replacement parts for a computer just a few years old is impossible. There is no repair on a VFD. They simply want you to throw it away and purchase a new one when they fail. They no longer even make parts to repair a 4 year old computer, as newer VFD's were introduced, trying to solve some of the problems inherent in the older VFD models.

I don't bash VFD's because I sell a competing product, I bash VFD's because I know exactly how they work, or more precisely how they don't work. I studied electrical engineering, and started using VFD's before the 90's. Every 18 moths to two years since then, they have come up with a new model VFD to try and solve the problems with the older models, making the 2 year old VFD's obsolete. This is planned obsolescence at its finest, and the average person is falling for it hook, line, and sinker. The main problem is, mother nature or the laws of physics will never let them solve the problems of VFD control. They are getting better at Band Aiding the problems, but they can't be solved. There are inherent problems with changing the frequency and varying the pumps speed that will never be solved.

That is why I make a competing product that mimics the control of a VFD system, without varying the pumps speed. When you understand that the horsepower or energy use of a pump decreases when restricting the flow with a valve the same way the energy use drops when varying the pumps speed, it makes perfect sense. This is just the natural way all centrifugal type pumps work, but is so counter intuitive that most engineers don't understand it, especially electrical engineers. The anger I see from these people when explaining how pumps really work is incredible. Their anger doesn't intimidate me. I want to see a pump curve that proves me wrong, or they are just wasting my time being angry.

Running a pump larger than needed for the demand is wasting energy anyway you control it. The best way to save energy on a large system is to use multiple pumps of different sizes. That way you can turn on the pump closet to the size of the demand required. A VFD or a CSV can round the corners between the different demand rates and allow the system to switch on or off the right size pump for the load demanded. But it is having multiple size pumps to meet multiple different demands that will save energy, not the VFD.
 

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Do you know we need to consider some important points before making a choice of a domestic water booster pump for our homes? Let's have a look at an expert's advice on this at the following link:

How to Choose the Right VFD Domestic Water Booster System for You

My competitors laugh at me for spending $800.00 on a 5 hp drive. Instead, they use a cheap drive which costs less than $150.00.

Like all computers, VFD's have come way down in price over the years. The last 5hp drive I sold in 1992 was over $10,000.00. And that was in 1992 dollars. I think homeowners will be interested to know that contractors are only paying $150 to $800 for those drives today, as they are charging the homeowners $800 to $2000 plus installation. Can you see the dollar signs that drive the sales of VFD yet? Sell someone a dumb pump with a CSV for control, and you will not get another penny from that customer for 20-30 years. Sell someone a VFD, and you get to replace the $2000 VFD every 8 years at the most, and replace the VFD destroyed pump at least once or twice in the same 20-30 years.
 

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I invite you to come to my shop where I will show you a 50 gallon drum of water connected with good drives but dumb PLCs.

Connecting a pump to a 50 gallon drum is how they incorrectly show energy savings from a VFD. There is no lift when connected to a 50 gallon drum like there is when lifting from a 50' or 500' water well. They will just vary the flow with a valve and show how the VFD slows the pump down to 1/12th of full speed and is only using a fraction as much energy. However, one Achilles heel of the VFD is that centrifugal pumps lose head by the square of the speed. When lifting from a well, and/or producing 50 PSI constant to the house, the pump cannot be slowed by more than 10% or 20% and still build the pressure needed. But a crafty VFD salesperson will use a drum to make you think a 10HP pump can be slowed down to a 1HP load. In reality a 10 HP can only be slowed to about 5HP load and still push water out the faucet. Then an even more stark reality, is when a VFD is reducing a 10HP pump to draw only a 5HP load, the pump is only putting out about 1HP worth of water. Simple math makes this show a 500% increase in energy consumption when using a VFD.
 

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When I called Yaskawa, I discovered there were 15-20 degreed engineers that were available. Since making that decision, I have sold over 800 drives.

I agree Yaskawa makes one of the best drives. But that is because they have so many adjustments possible, compared to the plug and play cheaper drives that have basically no adjustments. All these adjustments are necessary because every pump system is different. Minimum hertz, ramp up an down speeds, underload, overload, pressure set points, and many other adjustments must be made properly for the system to work. Finding an installer with enough knowledge to set these parameters, and also knows enough about pumps to understand what those parameters are, is almost impossible. Even all those VFD engineers can't do it. They may know all there is to know about VFD's, but if they really understood pumps, they would know a VFD is not even necessary to get reduced energy consumption from a pump.

VFD engineers do not understand the natural horsepower reducing capabilities of a regular dumb pump. Pump engineers do not understand the complicated "magical properties" of a VFD. For the few of us who have studied both, it is obvious that a VFD is just trying to trick a pump into doing something it already does naturally without a VFD.

800 drives with only 4 failures would be good if that was over 30 years. But I am guessing that was in less than 10 years, as that is about how long those type VFD's have been available. I see this company has only been in business for 14 years, so it can't be longer than that.
 

Valveman

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“Pumps are dumb, the way you control them isn’t. It is smart and getting smarter.”

Expensive and complicated are usually just the opposite of "smart". "Smart is getting the longest lasting and best pump control possible at the lowest price. Even though a CSV maybe just a "dumb valve", it is still much "smarter" than a VFD.
 

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The next thing that happens is these companies get angry and say "valves burn energy and a VFD save energy". They will claim the backpressure or low flow from a CSV will destroy the pump. Some will even claim the pump company will not warranty a pump with a CSV, as in this ongoing thread here.

https://terrylove.com/forums/index.php?threads/cycle-stop-valve-voided-my-well-pump-warranty.79108/

The lengths these companies will go to and the things they will say to keep people from getting a CSV to make their pump last longer and cost less is amazing and unbelievable. I offer plenty of facts and pump curves to prove what I say. All I get in return are insults, as any pump curve proves without a doubt that VFD'S DO NOT SAVE ENERGY!
 
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