Still reading ... from a VFD owner

[garnish]

First, let me provide a bit of background.  We bought our place about 8 years ago with a 60/40psi 60gal pressure tank and a Franklin Electric pump controller (capacitors and contacts).  I didn't like how water pressure varied and we were renovating the entire house while living in it on weekends. So I went into the Pump store and they sold me on a Monodrive to run the pump (that had been down-hole for, my estimate, 25 years).  I was happy to get rid of the big 60gal tank and reduce my pumping footprint to a small amount of wall-space.  I'm not an engineer but I play one on weekends and a VFD made intuitive sense to me.  For 4 years we ran the pump that way and it was awesome.  I even ran an A/C coil in my furnace plenum but pumped well water through it because the water comes out of the ground at 6degC in these parts.  The coil was a 1/4" ID so flow rate was small but the VFD ran it fine.  Some months, the thing ran continuously because we have a lot of south facing windows and the place heats up real good.  The well is 10gpm and I was monitoring the head by tracking current draw on the pump (the higher the current draw, the lower the head, I wanted to see whether I was drawing the well down close to the pump.  Turns out I wasn't, even with irrigation and regular household use).  Suddenly after about 4 years, the well failed.  The drive started pumping black silt and the Monodrive kept shutting down the pump because it was plugged.  The well guy came out and it turns out he's the same guy who drilled the well 35 years ago and as far as he knew, that was the original pump that was in there.  Turns out the steel casing collapsed into the well and he tried to retrieve the pump but after a few hours, it was clear it wasn't coming out.  So we abandoned that well and drilled a new one about 50' away.  He dropped in a new 3/4" hp pump and hooked it up to the Monodrive.  He's not a VFD fan but wasn't able to explain why; just that he'd seen controller problems in the field.

That was about 4 years ago.  2 years ago we ditched the hillbilly swamp cooler and bought a real A/C unit but are doing a lot more spray irrigation now.  The new pump has run flawlessly for 4 years of regular use with some irrigation. 

Last night we had a terrific light show outside.  A couple hours of lightning and cracking thunder.  Then at 9:00PM I noticed we had no water.  I checked the Monodrive and it was reporting an under-voltage condition.  I buzzed out the line and it was a nice solid 240VAC.  I checked the cooling fan and it ran nicely at 9v. I cycled the Monodrive a few times and it kept reporting the same condition. I threw my oscilloscope on the incoming power and it looked clean.  I decided to start googling and came upon this site.  While reading the site, I heard the shower turn on as my teenager decided to have a "shower" (yeah, yeah)... I looked at the Monodrive and it was all happy as though nothing happened.  I concluded that something was going on down the line from the lightning storm giving us crappy power that I wasn't able to see on my scope.

I do embedded firmware for a living so my day job has me closer to being an electrical engineer than anything else, but in my hobby time, I tend towards the mechanical.

Now this morning, I'm digesting the contents of this site and I'm somewhat skeptical as I am with all new things.  I'll buy into something if it makes intuitive sense.  I immediately understand how a centrifugal pump uses less energy with greater back-presssure, that's just intuitive to me.  Unfortunately, from what I know about centrifugal pumps, when there's excessive back pressure, running outside of BEP, they begin to cavitate.  I know that cavitation is what will prematurely destroy a centrifugal pump and that's also intuitive to me.  So it would seem that a CSV would cause a pump to cavitate which is not what you want.  That's the biggest thing I can't resolve in my mind.

Around here, electricity is fairly cheap so I'm not super concerned about saving electricity.  I just want to have a nice shower and that's the biggest reason I have a constant pressure setup.  I've got to be honest, reading the content of this site, the wording is very "snake oil" even though I completely understand the principal behind the CSV and it makes perfect sense.  But when I start reading articles with lots of unbacked assertions and possible falsehoods, I lose interest and increase my skepticism.  Because of this verbiage, I'm not inclined towards replacing my VFD with a CSV.  It seems like the site is trying too hard to sell something that should be self-evident if it was truly better.

Examples (new account, I'm not allowed to post links):

1) The power-consumption-cycle-stop-valve-vs-large-hydro-tank page is doing payback calculations on 1200GPM pumps.  I'm thinking the average acreage owner doesn't have a 1200GPM well and I'm not convinced this stuff scales down linearly to 10GPM.  Based on current measurements I've taken from my system while it's running, there is definitely less power consumption when the pump is spinning slower (though it's tough to correlate because I don't know what's happening with the water level inside the casing).

2) One of Cary's posts in the forum, he asserts "The only restriction that will hurt a pump is one that make the water heat up." and I don't think that's true for a centrifugal pump, as above.  A restriction causes cavitation which will hurt a pump.   Overheating should be the least of your concerns with a submerged pump in the bottom of a hole full of 6degC water that is constantly moving while the motor is spinning.

3) The internal memo from Grundfos makes a lot of sense.  I don't see it as a 'sales tactic' and in fact raises some good points that are not adequately (in my mind) refuted in the response posted above the letter. In fact, in the response is the sentence "Many studies have also proven that VFD's do not save energy and shortens the life of pumps and motors" but in fact, there is only one 'study' in the links that attempts to explain this but it is a power point slide that is missing the corresponding speech that would expand on the points.  The rest of the links are all expired (404).  So the response reads (to me) like FUD.   If there are 'lots of studies', they should be easy to find and the links shouldn't disappear.

4) The "Letters from Pump & Motor Manufacturers" page section attributes the same letter (Kevin Price of Sun-Star Electric, Inc) to two different sources.  (Hitachi and Centri-Pro Sub Motors as well).  That might have been an oversight.

5) The page "csv-vs-vfd-power-factor-and-kw" appears to show that a VFD actually does use less energy than a pump controlled by a CSV.  Again, I don't care about energy savings but it does suggest there is some truth to the VFD manufacturers claims in direct conflict to the unbacked response to the Grundfos letter.

Again, I'm not inherently skewed towards VFD and I only have one horse in this race.  I do agree that sometimes simpler is better; in fact I own a 1972 Toyota as well as a 2015 Ford.  The '72 Toyota is way easier to fix than the 2015 Ford and is several orders of magnitude simpler.  Unfortunately, the '72 is a hobby vehicle because, in just about every way, the 2015 Ford is superior and day to day, I prefer to drive the Ford. 

The two biggest things I can't resolve in my mind are:

1) Pump cavitation.  How is this not a problem when controlling a pump with a CSV?

2) The CSV site says over and over that I will be replacing my pump every 2-3 years.  In stark contrast to this, I have now run 2 pumps for 4 years with no problems that can be attributed to the VFD.  In fact, the first pump was at least 25 years and possibly 35 years old, and it ran fine for an additional 4 years on a VFD so I have trouble believing that a VFD is hard on a pump.  The previous owners of this home warned us the pump was likely in need of replacement as they had never had it replaced since they had the well drilled.  I'm willing to concede that they may be mis-remembering but at least it was probably 25 years old.  In fact, the VFD might have saved that pump because it detected a problem and shut down the pump.  We'll never know since it's now at the bottom of the old well.


On to the financial... I paid $1100CAD for my Monodrive setup which included the controller, manifold, pressure switch and 1gal pressure tank.  If the controller itself fails, maybe it costs $800CAD to replace.  Just an estimate.

To replace the Monodrive with a CSV setup including a monitor is about $255+$365 so about $600USD plus shipping, so about the same as replacing my Monodrive when it fails.

Since I haven't seen any empirical evidence that pump life is shortened by the VFD, the buy proposition is simplicity.

But I can still be convinced.

[Cary Austin]

LOL garnish!  I have tried a hundred different ways in over 25 years to explain how a CSV works.  As you can see to be such a simple valve it has a complicated explanation.  You won't hear anything good about the CSV from any of the pump manufacturers and very few pump installers.  That is because we were blacklisted in 1994 by all the big pump manufacturers.  Not because the CSV causes cavitation, damages the pump in anyway, or even increases energy costs. Just the opposite, because the CSV makes pumps last longer and use smaller pressure tanks, which is disruptive if you make your living selling pumps and tanks.  "Domestic" priced and size VFD's were introduced in the market in 1999, to have something that could compete with the constant pressure performance of the CSV, without shooting the manufacturers planned obsolescence in the foot.

If you look at what all the pump manufacturers are pushing, which is obviously VFD's, then you know what they make the most money selling.  What makes manufactures and installers the most, also cost the consumer the most.  25-35 years is the average life of a regular pump and pressure tank system that isn't allowed to cycle too much, while 4-10 years is a long time for a VFD pump system to last.  But they make VFD's sound really good, and a lot of people fall for it 3-4 times before they realize there has got to be a better way, which is the CSV.

A CSV can never close completely, therefore it can never deadhead the pump or cause cavitation.  All the CSV does is make the pump think it is in a deeper well when you need/use less water.  Looking at a pump curve you can see any pump will produce max flow of water from a shallow well and as little as 1 GPM from a deep well.  It is only a 25 GPM pump when the water level is shallow, it is a 1 GPM pump when the water level is deep.  And as you already know, the pump/motor draws lower amps, makes less heat, and will last longer running 1 GPM at low amps, as compared to making 25 GPM and drawing high amps and making max heat.

I wish I had a nickle for every time someone said "to good to be true", "snake oil" in the last quarter of a century.  But if you read any of the reviews from the hundreds of customers nice enough to post pictures and tell their stories, you will see it works as advertised.  I think I am going to quit trying to explain it and just post the reviews.   

See some of the reviews here.
https://cyclestopvalves.com/collections/frontpage/products/custom-pk1a-pside-kick-kit

[garnish]

The conspiracy theory stuff doesn't particularly interest me, just the technical.

As such, I guess I don't understand your statement:

A CSV can never close completely, therefore it can never deadhead the pump or cause cavitation.

...when there are lots of sites that describe discharge cavitation when operating against a restriction at rates far below BEP, for example:

https: //blog.craneengineering.net/what-is-pump-cavitation   (I can't post links so I've added a space in the preceding link to fool the parser).

When a pump's discharge pressure is extremely high, or runs at less than 10% of its best efficiency point (BEP), discharge cavitation occurs. The high discharge pressure makes it difficult for the fluid to flow out of the pump, so it circulates inside the pump. Liquid flows between the impeller and the housing at very high velocity, causing a vacuum at the housing wall and the formation of bubbles.

So are you saying that the CSV's are calibrated for each particular well and pump to ensure the pump does not run far enough below BEP so as to cause cavitation?  It would seem that would be something more important to put on your site than the many conspiracy articles.

[Cary Austin]

It is in every video or article in our web page.  The CSV cannot close completely.  The bypass in the CSV is designed to allow sufficient flow to keep the pump/motor cool.  Cavitation happens when you restrict the suction of a pump, which we do not.  Restricting the discharge of a pump can cause re-circulation within the pump, but as long as the water doesn't heat up from re-circulating, it doesn't cause any damage.  In 25 years and close to a million pumps there has never been a pump harmed by a CSV. Quite the opposite as a matter of fact, the CSV always increases pump life.

Your the one bringing up conspiracy theories, saying it is too good to be true and calling it "snake oil".  The fact that pump companies don't like CSV's is the best reason to use them.  The best way to figure out how something works is to try it, or listen to someone who has.  Did you not read a few of the hundreds of reviews saying they are glad they didn't listen to the pump man because this works great?

People would still be using a horse and buggy if they listened to the manufacturers saying how dangerous an un-reliable those new fangled automobiles were.  If you try a CSV and don't like it, send it home for a refund.  Never got one back in 25 years.

[garnish]

Cavitation happens when you restrict the suction of a pump, which we do not.

I specifically said "Discharge Cavitation".  I pasted a link and pasted text from the link that specifically addresses discharge cavitation.  At no time did I say anything about restricting the suction.

Restricting the discharge of a pump can cause re-circulation within the pump, but as long as the water doesn't heat up from re-circulating, it doesn't cause any damage.

That's not true.  Restricting the discharge of a pump can cause cavitation as explained in the link I included in the post to which you are responding.  Last night I spoke with a mechanical engineer who specs pumps and knows more about this subject than you and I can ever hope to know. He agrees with me.  Unless you design the bypass according to the pump curve of a specific pump, you can get discharge cavitation.  The bypass you have designed might be right for some pumps and wrong for others.

I read some reviews.  I don't care about reviews.  Reviews are from people who may not understand how this stuff works or may not have run the product long enough to know whether the product is causing damage.  The more I learn about CSV's (which is really just a pressure control valve, not some curious new invention), the less I trust that it will not damage my pump.   I don't need to read reviews because I have no doubt that a pressure control valve works great, when spec'd properly against my pump curve.  It's even possible that your pressure control valves will work great with my pump.  But you have not convinced me that your pressure control valves will not damage my pump because you don't know what kind of pump I have nor do you know what the pump curve looks like for my pump (and neither do I, actually).

If pump manufacturers could find a more profitable way to control pumps, then they would do so because it would give them a competitive advantage over their competition.  I don't believe they are all conspiring against you.

My VFD has not eaten any pumps in 8 years in stark contrast to your claims.

Thank you for trying to address my concerns.  I will stick with my VFD.

[Cary Austin]

Ahh a VFD person.  I should have known you already drank the Cool Aid.  Pump manufactures want you to think discharge cavitation is a problem with a CSV, that way they get to sell you their most profitable item, which is the VFD.  If you got more than 5 years out of a VFD system you are just more lucky than everybody else.  Over 25 years and hundreds of thousands of CSV's in service without a single pump damaged proves pumps can take a lot lower flow rates than the manufacturers want you to believe.  Sure cavitation can eat a pump like that, IF you restrict the flow enough the water gets hot.  The whole point of the CSV is to bypass enough to keep the pump cool.  Cool water doesn't cause problems like that. 

Open impellers and impellers trimmed to be a long distance from the cut water vane could cause cavitations at low flow rates.  But closed impellers with a tight fit around the wear ring/impeller hub don't have that problem.  So you are correct that not every pump can work at such low flows.  But the normal submersibles, jets, turbines, and centrifugal pumps that are used for most fresh water applications don't have a problem.

If your pump shows cavitation damage from a properly installed CSV, I would pay you double the cost of a new pump and labor.  So prove to me a CSV can cause cavitation like that if you can.  Never seen it in 25 years.  I don't expect you or your so called expert to prove me wrong now.

It is very common for VFD people to try and prove me wrong.  They just haven't been able to do so in 25 years so far.

[Cary Austin]

Here is a picture of a 25 GPM impeller and diffuser that worked with a CSV for 12 years.  Notice it still looks like new.  There is absolutely no damage.  I just took it apart after 12 years to see what it looked like. 

Pump companies have always tried to tell me cavitation would be a problem.  When I first started I would run a 50 HP submersible at 5 GPM for 6 months straight, then take it apart and inspect.  Or a 100HP centrifugal at 3 GPM for months, same thing.  I even have a little sub running a test for 17 years without ever shutting off and it is still running fine.  None of these pump show any damage.  You circulate enough to get the water hot and it is a different story, but with cool water there is no problem with pumps at low flow rates.

If what you are saying was true, I would have gone bankrupt replacing all those failed pumps for the last 25 years.

[Cary Austin]

This is typical of someone who fell for the VFD hype to try and convince me the CSV won't work.  Sure the idea of a VFD is intuitive, but pumps are counter intuitive.  Reducing the RPM of a pump with a VFD will cause more energy to be used per gallon produced.  Restricting a regular full speed pump with a valve will cause the amps to drop the same way slowing the pump down with a VFD will do.  Everybody thinks restricting a pump with a valve will make the pump work harder, and slowing it down with a VFD will make it work easier.  Both of those things are intuitive, but wrong.  The counter intuitive nature of a centrifugal pump makes it easy to understand why garnish and others get so confused.

Then they listen to so-called pump experts telling them cavitation at low flow will destroy their pump, which is also not true.  They tried to tell me the same things 30 years ago.  But having been raised in a pump and drilling business with thousands and thousands of pumps under my belt, I just never saw that happen.  So I did tests on all kinds of pumps myself years ago.  I have pictures of impellers and things to prove the CSV does not cause cavitation damage as some people try to say will happen.  The trick is having a large enough bypass in the CSV to keep the water cool.  If the water heats up or you are pumping hot water to start with, cavitation damage is a problem.  Again, in 25 years and hundreds of thousands of test cases, there has never been a single pump failure attributed to a CSV.  A CSV always makes pumps last longer, it does not shorten the pumps life.

If non-existent cavitation is the worst they can say about a Cycle Stop Valve, there is nothing to worry about.  I should list the many, many problems associated with VFD control, but you can already find that is many of my articles and videos.  It takes pages and pages to write up all the problems with VFD's, and the one thing they claim is a problem with a CSV is not a real problem.  Deciding between a CSV and a VFD should be an easy choice for those who haven't already drank the VFD Cool Aid and are no longer able to make intelligent decisions.

The reason some people aren't interested in the conspiracy theory is because they already fell for it, and don't want to be proven wrong.  Also it is real easy to overheat a submersible pump even though it is submerged under nice cool water.  Just cut the flow to less than 2/10's of a GPM and the nice cool water in the pump will begin to boil, then you will see damage like is in the pictures of cavitation in the link. Keep the water cool like a CSV does, and it will never hurt the pump.