Is a VFD Constant Pressure System worth the $$$?
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- เผยแพร่เมื่อ 15 มิ.ย. 2024
- Is a VFD Constant Pressure Pump System Worth It?
Cost Comparison Video: • Cost Comparison: VFD v...
Just to specify, in this video I will be specifically talking about submersible well pump systems that use variable speed drives to achieve constant pressure in residential systems.
Short answer, Maybe. But most likely Not.
Are VFD’s more efficient? No, not even close. A pump is much less efficient at slower speeds as well as outside the recommended operating range. Most in home applications require less than 2 to 3 gpm and thus would be very inefficient. A conventional pump system runs 1 to 2 minutes generally at its most efficient point to refill the pressure tank. In most low flows using a standard size tank, you can run 20 to 25 gallons between pump cycles.
So what about cost of installation? Generally a little higher than conventional.
Constant water pressure is one of the major reasons that people get excited about VFD’s but this can easily be accomplished by inexpensive mechanical means. Cycle guards, cycle stop valves, even pressure regulating valves can be used. It is worth pointing out that a VFD will provide constant pressure at greater efficiency than a mechanical option.
So after all that what does a VFD really do that’s good?
...
The main benefit is cycle protection at the expense of efficiency.
Provides constant pressure BUT mechanical valves can do this also.
Protects the motor from a variety of situations that could damage it. BUT motor protection devices are inexpensive compared to VFD’s
Potential for longer motor life due to soft start capabilities and the overall higher reliability generally found in 3 phase motors.
Compact.
So when is it a good time to consider a VFD?
Wide range of flow (Small agriculture, small community systems)
Exceptionally deep wells or great distance from electrical source (wire size, but wire doesn’t wear out like electronics) Make sure you consult the manufacturers limits on wire length per drive.
Situations where space for sufficient pressure tanks is not available
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Hands down the best explanation of well pumps comes from this gentleman. Thank you.
Our pleasure!
I couldn't be happier with my constant pressure system. My homes 1986 well pump gave out in 2013 on a holiday weekend just after I purchased the house. The only system the guy had on his truck ready for install was a VFD. It's great being able to water the grass, wash laundry and take a shower at the same time with no noticeable difference in pressure. The electronics, gage, and small pressure tank are wall mounted so there is no giant pressure tank, taking up floor space and collecting spiderwebs. I can easily change the pressure on the system if I want, at the push of a button. Previously I would have to get on the floor and use a screw drive to adjust the mechanical pressure switch. I was also able to have a larger capacity pump installed with out worrying about over cycling the pump. Not to mention it plays nice with my 7200 watt portable backup generate that I normally spend 1-2 days a year running on. I would probably have trouble running the whole house on a generator that small if I was running a standard pump.
This was nine years ago, but the price difference for a conventional system with 1/2 hp pump VS VFD with a 3/4 hp pump was 40% more for the VFD. About $1,300 more at that point in time.
How about the whining noise that keeps mice away from my house. I consider that a plus. But I agree with you. Awesome
Very good information. Thank you for it. Although I kept thinking you were going to refer to the board behind you!
Thank you for this video. My wife and I are building a new house. We will have limited space, leaving us with the problem of housing our pump equipment. The well driller suggested we use a constant pressure system. Since I knew nothing about these systems, your video was most helpful. 👍👍
Thanks for the kind words! :)
Very helpful. Thanks for the video. All the best from down under.
Great video. I still have no idea which one to go with. So many variables.
I wound up buying my pentek intellidrive surge protectors from Worst (great prices and excellent customer service). Yes, more $ but soooooo worth it. Best money ever spent on our home.
Very informative. Thx for the great info!
Glad it was helpful!
Thank you very much for all the videos about well systems.
Questions: I just bought a house, it has a well system for 20 years. Should I replace the new well's pump or let it runs until it dies then replace the new pump.
Thanks
This was so helpful! My pressure tank is toast and I was considering a VFD system for a farm application, with 3 houses on it. Is there complications with having the pressure controller in one of the houses? Will pressure tanks be needed in the others?
Thank you for this video! I bought a house with a well last year, and today the pressure tank (in my utility room next to the water heater) started leaking a bit. Found 2-3 cups of water on the floor, called the plumber who's worked on the house before and knows the system. He's described both types, but this really helps me understand better. Thankfully my well is 100+ feet deep and produces a good quantity of water. I've never had pressure problems, and am on irrigation April15-Sept15 for outdoor watering. The WellXtrol pressure tank has been here since the house was built 25 years ago, so I'm sure it need to be replaced. Don't think I need the VFD system - another tank will do just fine, and much less expensive....especially since I'm in the middle of a kitchen remodel.
Glad you found our video useful!
This is a really thorough and informative video. Thanks for putting it together. My parents have an open loop geothermal system...I'd like to know if you've got any thoughts on setting one of those up for the best efficiency as it demands water 24/7 about 8 months a year.
I do not know much about geothermal systems since that is not my area of expertise. I know it can something be difficult to find a pump if the water temp is too high. Cooling would be my major concern and a possible reason to use a VFD on an over-sized motor to have better control of motor temp.
Thanks for the video Chris. Same situation here with an open loop geothermal system. My water tank is leaking and the plummer offers a constant pressure drive system. The 1HP well pump has been faithful for 30 years. It sits in 38'F water and works hard only during winter; 6 months long here in Quebec city. Your video confirmed my decision to keep the old system and replace the 25 gal draw down tank. I have the space. Also, during grid outages, I run a generator which would surely have bad effects on the variable drive electronics fragility.
good video, explains a lot to me. Had a well guy out and he suggested one. My issue is NO pressure at the faucet / tub. Have 58 PSI at the well, 38 PSI at the pressure tank, 4to 5 minutes a gallon at the bathtub. Just purchased the house last fall, been an interesting experience. No I don't have a whole house filter since that seems to be the first statement made. Peace
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Good call. A normal pump and a large pressure vessel.
We are going about 450 feet down. We are looking at Grudfos well pump 3hp and Grundfos Twins. We could be supplying 3 homes. We will have a 2500 gallon storage tank so that the well pump will only cycle to "top up". House distances vary from 150 feet to about 300 feet from the pump house. The feeds to each home will be 1.5" tom2". Feeds will be relatively straight. We are going to add a power line filter right at the Twin electrical feed point grounded to the pump house UFER system. Though the Grundfos data based on the Twin selected lines shows me 35-45 GPM at 60PSI can be obtained, I'm not too concerned since the usual water demand in homes comes in small "spurts" during a given day. All homes have agreed to leave land as pasture land and irrigation will be flower beds, etc so that no home would be using the well quite disproportionately. My GC has noted problems with VFDs in short life span and suggest constant pressure via a CSV system which I understand does put unusually high back pressure on the pump. Since the conventionals do spin the motor at constant speed, the GC claims longer life for the booster system and lower cost to install. I'm thinking the Grundfos Twins are their own a small package with no external pressure tank thus creating a simpler system to install. The Grundfos folks I have spoken have noted very high reliability with the Twins. I understand the cost of the Twins but the ability to have 2 pumps operating in a cascading manner seems much better....this is the beauty of the cascading ability, each pump will come on at some point to share the demand but at equal but lower speeds. Also the Twins VFDs are blue toothed so they "talk" to each other so I could read the data on my smart phone, forward to Grundfos and they can tweak it, send it to me and I can upload the new parameters per Grundfos engineering. The Twin setup seems like light years ahead technically speaking versus the CSV approach. We of course can raise the pressure of the Twins to compensate for pressure drops since in reality flow rates in homes during any time of the days are pretty low. Even with 3 homes I believe the Twins can easily handle the job. Comments ?
Cycle Stops do drop amperage per demand so technically it can regulate motor efficiency
“Soft start” sounds like a big selling point for systems that might need to run during an outage on battery. But sensitivity to surges and harmonics suggest standard non-inverter backup generators could damage the controls.
And the efficiency question: how long will he battery run it?
I am thinking of installing a open loop geothermal heat pump 5 ton that will have a water requirement of up to 10 gallons per minute when system is running and have been advised to install a VFD. asking if you have any opinion on this? If i do not do this, they are stating i may need a 100 gallon pressure tank to handle strong pulls on really hot days or really cold days. I have 22 gallons a minute supply rating and my house is 2300 sq ft. 2 bathrooms and only 2 people living most of the time.
Two bedroom home with two adults, small bathroom in a detached garage. No need for a VFD system? What if I put my yard sprinklers on the well as well? Still no VFD? Maybe another type using a control stop valve instead? Thoughts?
I have been debating a vfd well pump for about a month now. We have a big house and the water travels a good distance once it gets inside. We recently swaoped the pressure switch out and it works, the lump kicks on and off but as soon as a zecond water source is turned on and i mean immediately the water pressure DISSAPEARS.....does this sound like a pressure tank issue or? I was debating vfd to eliminate this issue
Very good video. Thanks for mentioning Cycle Stop Valves. You make the statement that with a CSV the pump is always spinning at full RPM. However, you fail to mention that the horsepower or amps will naturally decrease as the CSV reduces the flow rate. Full speed does not mean full amps. The amps of a constant speed pump will vary with the flow rate almost the same as if you were varying the speed. I also disagree that VFD's increase the life of pumps/motors. The voltage spikes and harmonic content of the power from a VFD are just as bad if not worse than the torque and inrush current from an across the line start.
Thanks for the comments. At full speed a conventional pump operating at its best efficiency point, generally the middle of the pump curve is at its most efficient which is maybe 60 something percent efficient. When the pump moves away from that best efficiency point, gallons per kilowatt is hugely impacted. Using a CSV can easily cause a pump to run at or near dead head during low flow and this is extremely inefficient, I would speculate 30% or possibly less Also worth mentioning is using a CSV can push a pump to operate in a down thrust position depending on sizing considerations and pump selection, this no doubt kills multi stage pumps. Which is why pump selection is critical with a CSV. VFD's offer more flexibility in this category. So the gallons per kilowatt hour is impacted. On most residential systems the scale is so small that it is negligible but very much existent. Due to VFD soft starting capabilities, motors will no doubt have a better opportunity to last longer, no doubt in my mind. This is one of the main and most important features of VFD's especially as the size of the system scales up.
@@chrisworst8353 I don’t think pump selection is critical with a CSV. Pump selection is critical for efficiency period. A 10HP cannot be efficient at a 2HP load, no matter how you control the pump. Gallons per kilowatt are hugely affected with a VFD as well. Using a VFD can easily cause a pump to run at or near dead head during low flow and this is extremely inefficient. The whole concept of the CSV is that it can never completely close, so it can never deadhead the pump. Proper calibration of a VFD is required or it could easily deadhead the pump, running below the frequency that will produce the static head. Multi-stage pumps just require a little more cooing flow, and the increased backpressure from the multiple stages automatically increases the minimum flow through the CSV to accommodate. Submersibles with the downthrust load on a Kingsbury type thrust bearing will last longer with increased downthrust, than if allowed to slowly ramp up to 30hz, where there is no hydroplane effect lubricating the thrust pads. Efficiency or Horsepower is all on the pump curve. Because horsepower also goes down with increased backpressure, many times there is very little difference in the kilowatts per gallon between CSV and a VFD. A VFD can be used on a multitude of devices. The CSV only works when pumping fairly cool, clean water at a constant pressure. But for cool water delivered at a constant pressure there are two ways to skin that cat, and the cat gets skinned about the same either way. Lol
@@cyclestopvalves8380 I did specify at or near dead head, either one is detrimental to down-thrust and pump wear. VFD's can also in some specific instances operate near dead head but that relates directly to the variables of pump selection and well depth and static water level in relation to the pump curve. A CSV regardless during low flow will be at or near dead head regardless of other equipment selections. Not knocking CSV's here, I like them for a wide range of applications. Just clarifying further differences in operation where certain instances one may be better suited than the other.
@@chrisworst8353 Deadhead is when the pump is not moving any water. Close to deadhead is when there is not enough flow to keep the pump and motor cool. The CSV can never completely close. It always allows enough flow to keep the pump/motor cool. So, the pump can never be at or near dead head with a CSV, and there is not enough down thrust to be detrimental to the motor thrust bearing. As long as the thrust bearing is good, floating stack impellers do not touch the diffuser to cause any wear.
@@cyclestopvalves8380 CSV is a DC pump. So you have a transformer that cleans up the power. This is the same technology that is used on inverter hvac and refrigerators.
@Chris Worst, so constant psi is achieved by a pressure transducer's output being fed back to the VFD's control? Is that right?
Would a vfd be better for backwashing media filters? Can a vfd be converted from a two pipe jet pump ?
I really appreciate you do this kind of video. I have a problem with my submersible pump. I just got a new well drill and connected to my Pressure tank. The water pressure build up to 60psi and cut off fine. but when a valve is open the pressure drains down zero and shut off the pump. so we cannot use the water. I tried to prime it by opening the drainage pipe little bit and have it run for a while but it's fully open, the pressure will drop to zero and shutdown the pump. Is there anything wrong with my system? this is a fairly new system, unfortunately, it is out of the country and no one has any idea of how it works. Would you happen to have any idea what could be causing the pressure to drop to zero?
Why is the pump shutting down? Do you have a low-pressure cutout switch installed? Like the one in this video: th-cam.com/video/ROvZpwHV9Ho/w-d-xo.html
Nice video - thanks for the information. Kind of what I was thinking anyway.
We are replacing a 30 year old pump - > 500 ft down. It is still running but the wires to it > 1000 ft away have a open circuit problem (likely water ingress) which stopped the system.
Wanted to at least fully consider the VFD pump system. But not necessary or useful in our installation.
So the long wires - inductive and resistive load - this creates a soft start situation. And here the well pump just fills a 1500 gallon tank (keeping it at its max fill level) - with an additional 2500 gallon tank being added (2nd will be plumbed for rain catchment as well - if ever needed - we get ALOT a rain here in pacific northwest). Pump is either pumping full out or is off. Then a separate pump (pressure pump) pulls water from the tank into a 200 gallon pressure tank - the pressure pump just runs until it hits the max pressure we have it set to, and comes on again when the minimum pressure limit is reached as the bladder in the constant pressure tank shrinks down. So its the pressure tank which determines the actual pressure output in this system, and not the well pump. So constant pressure is useless in this application.
Although I like VFD for driving machines -- may be converting one machining system to 3 Ph motor & VFD likely early next year. But these allows running at lots of speeds and under different load conditions.
But for this well the only benefit seems the use of smaller wire sizing - I mean the old pump is over 30 years old and still going.
Yet since we have to wait for the well company on replacing the innards (pump, wire and water pipe) of our well, we have to put in large wires now to use the existing pump until they can come out. Ours requires 2-2-2-4 wire (using Aluminum) which will be about $2500 for 1200 feet - this is mainly because when our predecessors put the well in - the down wire used was a measley #10 wire - and drops significant voltage in the 500 foot depth. When we have the new pump put in we'll go for larger wire size to decrease losses to assure it always has sufficient voltage.
With the current 2 ph system - I am running both the well pump and presssure pump from our inverter which is driven from a battery bank from the solor panels - but I can readily pull my generator out to the well head and drive the well pump to fill our tanks. (exactly what I am doing now while we wait on wiring).
I can also normally (when wiring is not inop) connect the generator in the from the tank house here at the house, if our solar system croaked. Or connect the generator to charge the batteries - if the inverter still working. So there are many options with driving a conventional pump.
With the VFD: (1) you would not be able to directly drive the well pump from a generator or normal inverter, (2) VFD is a single point of failure - you would want to have a backup VFD in case it went out; (3) the whole issue with surges and harmonics with VFD seems another can of worms when one is hacking power together to get their next cup of water.
QUESTION ---
Interestingly regarding wire size and efficiency the well person I talked with said that reducing the wire losses to the pump would not increase efficiency of the system. Seems counterintuitive.
I understand the pump is set to run at a fixed RPM - so it sorta makes sense. I would expect that the higher voltage reaching the pump would seem to at least increase motor torque, and perhaps prevent it from lugging down and heating up with premature shortened life - but that's an issue I think of more with gas powered devices designed to develop their power at higher RPM. If the RPM is fixed - well it seems odd that it would make no difference - but then although I'm an electronic engineer I haven't spent any time looking at power profiles for well pumps (I was in to computer design) - so perhaps it only needs to have just sufficient voltage to run, and power is lost one way or the other...
So I'd be interested in this aspect of "efficiency" if anyone knows more about it on a regular AC motor.
Do VFD pumps have lower startup current?
Hi,is a bigger tank better and helps getting a better constant pressure
Tnx
Great Video. Thank you for the explanations.
Glad it was helpful!
Can anyone tell me what the difference between VFD and SQE?
I irrigate about an acre with a 2hp submersible and it takes every ounce of pump it can put out and from 170 ft of depth. I'm thinking about going to 5 hp vfd. Thoughts?
Give us a call and we can help you select the best pump for the job: 855.329.4519
Does the recommendation change if using a storage tank with a booster pump? The conventional well pump just fills the tank. Constant pressure on the booster sure is desirable.
The same principles would still apply, but for some, the cost is worth it.
in CPS system, do you still need relief valve? since it is constant, pressure is not abrupt pump stoppage and surge.
Yes, you still need one. There is still the possibility of the pressure sensor failing and the pump over-pressurizing the system.
Problem: I have a 160 gal storage tank with distilled water which we use for university laboratories. The water is plumbed through 3 floors at all our labs and works by gravity. There are at least 50 faucets. a few months ago, we had a leak. I checked all the faucets 3 times as well as the shut off values and for the life of me I can't find it. As a result, and if I forget to fill the tank, it empties out overnight and I have to go from lab to lab to get all the air out of the lines. Needless to say, this is a royal pain in the ass and, try as I may, I can't get all the air out. If I were to install a variable speed pump right below the water tank, can it be used to force the air out of the water lines when faucets are opened?
Please give our techs a call to discuss: 855.329.4519
What about if a family has a 9 bathroom house. A 35 gpm shower and 30 gpm irrigation zones and he wants to be able to run the irrigation alone, or at the same time he showers in his 35gpm and somebody can shower in his 6 gpm shower and run a zone. He also wants a zone to be able to run alone. As low of flows as 13 gpm on drip tubing. He also doesnt want big tanks in his lawn or garage.
Well then he gets a 5 or 7.5 hp with a 50js or 75js with a crazy expensive vfd and just doesn’t complain when he has to call the local pump company for maintenance every few months lol
@@davidmartens7253 what if I put him in a 5hp 90 gpm with a vfd and he just called me out to change the filters it's a 3r cabinet and it's the first maintenance he has had in 7 years?
Hi,
Can I keep the same size of pressure tank in case I want to upgrade from conventional to vfd system.
Yes, your pressure tank should be large enough since the VFD requires a much smaller one.
What is your opinion on cycle stop valves?
what if i want my pump at ground level ?
Hi,
Can I install a prv in addition to vfd??
No, there would be no use in doing that.
That was a lot of information for a "maybe."
The goal was to allow you to come to your own conclusion based on your own specific application. If you still have questions give us a call: 855.329.4519
I would also say if you got a 600 hp turbine and your running multiple circles. One circle has made its pass and shuts down. The desired flow is reduced by 1200gpm. You do the math. You can put a csv on it and your burning 650 amps still while getting 35% less water. Or you can overpressure and blow up a center pivot. Or you can run a drive and it scales back to 45hz. Thats a 25% reduction in freq and volts and 57.9% reduction in power usage thats a amp draw of 274 vs 650. If you run a derated pump end. So you can speed up to 80 hz. Its a misconcention thats a kets say 7.5hp notor for a 3hp pump end. However if you were gonna put a 7.5hp 90 pump and motor in. Which you can do and run up to 60hz like normal. However a 3hp 90 gpm on a 7.5hp at 80 hz will produce a better curve than a straight 7.5hp motor + pump
If you choose the right pump it will have a natural horsepower drop of about 50% without reducing the speed. So the 650 amps would be reduced to about 325 amps with a Cycle Stop Valve or CSV. It is a misconception to think the amps stay the same just because the speed is constant. All good centrifugal pumps will have a horsepower curve that naturally drops as the flow rate is reduced or restricted with a valve, without varying the speed. It is rare for a VFD to reduce the horsepower enough to justify the expense of a VFD over a CSV.
@@cyclestopvalves8380 , very interesting. I'm fascinated by the amp draw change depending on load; recently I installed a HiBlow pond pump. When I cover the end, of the air output, I see an amp drop. When I release the end (of the air hose), the amp draw INCREASES. This seems the reverse of what I expected. Based on that information, it makes sense that a booster would operate much the same way; when the draw is reduced (through restriction), the amp draw would also drop. It's an area of electricity that I am new to. Looking at buying a new booster pump (multistage, single phase). So your information is VERY helpful. I think it is a very misunderstood area, which is why I want to know more.
If I have a traditional system (water tank, traditional pump, 85 gallon pressure tank, 40-60 switch)... what do I have to buy to switch to VFD or constant pressure?
The best for no service calls etc and get benefits of soft starts and automatic cutoff that the VFD systems provide is get a pump that is well matched to needs and get a pump such as the grundfus SQ ones that have soft start and low water automatic cutoff. If you want you can get the Grundfus SQE or similar VFD pump then when controller goes out install a Cycle Stop Valve and don't repair the controller.
When the controller goes out, don't repair it? Are you just wiring in 3 phase directly through your pressure switch? Interesting idea
@@lucascoulton No just wire as usual without the $300 plus controller the SQE will then act as an SQ pump. The Cycle Stop Valve is what would keep a constant pressure with variable volume demands
My newly installed VFD is very loud. Sounds like a small hotel hair dryer with changing speeds throughout the house.
I challenge your statements on costs, particularly insofar as a new well and infrastructure. A VFD system allows the use of 3-phase motors, which are more efficient and which allow smaller cable diameters. The savings on hundreds of feet of cable alone can be massive. In Canada we are allowed only a 3% voltage drop and thus cable gauge is a big factor. On bedrock or low producing wells, the costs of pump controllers, a dry well protector (pump tec) and a large pressure tank easily exceed the cost of a VFD. As a business that services well pumping systems, I love conventional systems with their pressure switches, capacitors, relays and large tanks... their failures are a good source of income, but I prefer the reliability and happy customers, so we only install VFDs with new systems, and getting rid of a bulky tank is a big selling point for existing systems.
Challenge accepted. I will soon create a video using 3 separate well examples. You are welcome to provide me the well specs such as depth and recovery as well as operating pressure and flow requirements. If I do not hear from you before the end of this week I will just select 3 random wells on my own. I will show in depth energy consumption and reliability factors including run time, etc.
Check out the new video: th-cam.com/video/Wi2Y8ppZtlo/w-d-xo.html
In EU max 4%.
No new Taxis hydrostatics heating and cooling systems like yesterday
Oh no 🤦♂️
lol. you're literally the worst!! j/k. thanks for the video! :) (i couldn't resist)
With a capital W! :p
Can you add a soft start to an exciting well?, like your videos