Messages

1

Frequently Asked Questions / Re: Question about my new CSV

« on: April 29, 2015, 04:05:03 PM »

Looks like you are going to need to pull the pump.

2

Frequently Asked Questions / Affinity Laws and CSV vs VFD.

« on: April 28, 2015, 09:21:39 PM »

I found this article very helpful in understanding pump curves.

Hope the link and this quote is allowed;

http://www.pump-magazine.com/pump_magazine/pump_articles/article_44/article_44.htm
Observations:

For friction-dominated systems (long pipes, flow transfer cases) VFD saves a very substantial amount of energy, and operates pumps reliably due to close proximity to BEP flow (100% in example shown)

Tried to fix link, added below.  Cary

Tried to fix link, added below.  Cary
For static-dominated systems (injection against constant pressure, lifting against constant head) the energy savings are substantially less, and the pump operates, surprisingly, substantially off-BEP position, not significantly different from a valved flow control case

For cases where both systems are present, an in-between scenario would result

So, in a average residential single household situation. The $2-$4 (I figured pump on a total of 3 hours a day) you would save in electricity per month would never pay the additional cost of the VFD over the VFD's lifespan.

Hope that helps someone else.

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Frequently Asked Questions / Re: Written Expalnation of How a CSV Works

« on: April 28, 2015, 02:28:46 PM »

Thanks again for your highly knowledgeable replies. It has taken me a lot of thinking these last few days to realize you have the CSV setup for maximum effectiveness for the vast majority of people/uses.

I can see in a few situations (rare) were adjusting the tank size and bypass rate might help tweak out whaterever performance characteristic you want.

With all that. It seems using a quality pump with the CSV is extremely important. As in the pump needs to have a good power/flow curve that saves energy with lower that rated flow.

For a residential booster. application max 16-18gpm, do you reccomend any specific brand/model pumps?

I should be in Ohio soon and there is a good chance I will end up in a property with a well. Starting off I will just use whatever is there. If there is not already a CSV, that will get installed first. Then I want to get a whole house RO setup installed with whatever needed prefiltration/storage tanks, etc.

Now I'll really show my ignorance, I would think with 20+ years of "in the field" experience/reputation, that a CSV would be the default setup for any house with some kind of water pump. 20+ years gives it enough time for word of mouth to get around and for most of the counter misinformation to be debunked. This does not seem to be the case, those stupid VFD's seem to be the default. Is it really just money driven by the pump manufacturers? I would hope that 20+ years would overcome that.

Thanks again, I'll be a site lurker now. When I get around to my whole house RO.... I'll have some more questions (maybe see you on Terry's).

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Frequently Asked Questions / Re: Written Expalnation of How a CSV Works

« on: April 27, 2015, 10:07:13 PM »

Holy cow?!!?!?!? Just noticed;

Cycle Stop Valves, Inc.
10221 CR 6900
Lubbock, Texas 79407

I am in Midland (not for long). If I make it back up that way, I offer to buy you lunch. Don't worry, I am just a normal OCD engineer.

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Frequently Asked Questions / Re: Written Expalnation of How a CSV Works

« on: April 27, 2015, 10:04:32 PM »

I take offense to that.  I try very hard to be accurate and not to be the least bit misleading.  But that is exactly what many others are doing, so I understand your mistrust.

I apologize. After reading much more from your site. I don't believe you have ever been intentionally misleading on this site.

I love to be questioned and challenged on this subject.  But please ask the questions and let me reply before accusing me of misleading.

Examples coming up that I believe are misleading.

Transient pressure waves created from starting and stopping a pump at maximum flow is what causes water hammer.  These waves travel from 3,000 to 8,000 feet per second.  A pressure tank tries to catch these waves after they happen.  This is too little and too late to stop water hammer.  It is kind of like trying to catch a bullet with your teeth.  Plus the tank is on a tee and at a right angle from the direction of flow.  Transient pressure waves don’t like taking a 90 degree turn when they are doing 5,000fps.

A CSV can make a pump start and stop at 1 GPM.  The check valve is only open the width of a piece of paper when the pump shuts off.  Without the pump surging on startup or the check valve slamming on shut down, there is no water hammer to “catch”.

First example. Everything you state is accurate. I am not trying to play semantics, but I believe your case is overstated. "Hammer arrester's'" are fairly cheap and work well. Even the pressure tank helps. The bottom line is that "water hammer" is a problem that usually can be cheaply dealt with. Still a plus for the CSV.

If you only use 300 gallons per day and you have a huge tank (119 gal) that holds 30 gallons of water, then yes your pump would only cycle 10 times per day.   But those 10 starts will be at locked rotor amperage.  And those 10 stops will be abruptly after the pump has been running for some time at full service factor load.

Both of those things create more heat in the motor than when the pump is started and runs at reduced amperage as it does with a CSV.  The CSV basically de-rates the motor load enough that it would be safe pumping hot water.  So when de-rated as such and pumping cool water, less run and off time is needed for motor cooling.  A pump/motor can also survive many more cycles because of the mechanical soft start/soft stop of a CSV than when starting and stopping at full speed, amperage, and heat production.

Second example. Will 10 start/stop cycles everyday shorten a pumps life expectancy (considering many are rated for over 100 start/stop cycles a day) ?
This will depend upon the pump, but how much do they get "de-rated". From the pump charts I have seen, a maximum of 50% some pumps very little. So now you can have the situation where the pump is pushing out 25% of full water capacity using 50% of the full rated current. So half the heat production with one quarter of the cooling. How is this good? I expect this is not an important factor as long as the pump stays off long enough to cool down. 2,3,4,5 minutes... I don't know.

It seems like a non-issue until you have experienced constant pressure.  With a large pressure tank and a 50/70 pressure switch you are getting an average of 60 PSI.  That means the pressure dropping to 50 and increasing to 70 over and over is a normal operation.  Pressure is always better when the pump is on and the pressure is increasing than when the pump is off and you are just getting what a little air can push out of the tank.

You may never notice and just think these pressure swings are normal for county living. But the first time you experience a shower a for as long as you want at a constant and steady 60 PSI, you will say you no longer even need soap in the shower as the water pressure just blast the dirt off.  Then your friends from the city will have to come to your house to experience showers with better than city water pressure. 

I am a city boy (not for much longer). I have no experience with fluctuation in water pressure. My guess is that a slow change between 70psi to 50psi then back to 70 would not be noticed by me. With a tank that has a 10%+ daily use draw down capacity, this change in pressure would be slow. My reasoning for this is that the main place I would notice it is in the shower, since I have those freaking stupid 2.5gpm energy/water saver shower heads, the pressure wouldn't even be noticed. The same amount of water would be coming out regardless of pressure between 50-70.

OK let’s talk about the “space”.  How much per square foot does it cost to build a house and how many square feet does it take to install a large pressure tank?  Then how much does it cost to heat 300 gallons of water from well temperature to room temp every day?

Good point.

I'll give you credit (as in the facts/information show you are correct), for residential applications (haven't thought of commercial or industrial), everything considered, your CSV with smaller pressure tank will 99%+ of the time be the way to go. As an mental exercise. I am thinking where the "tipping points" in water consumption usage patterns where a faster tank refill and larger tank would be more effective.

I am now thinking a CSV with a pressure tank that has a draw down capacity of around 3 times the refill bypass. I should setup some spreadsheet to perform all the what-ifs for this situation. From a design perspective... would it be better to size a house system starting with how many times you want to cycle a day (this perspective could be used for CSV or no CSV and large pressure tank designs)?

Is the following statement technically accurate?

The nature of how a CSV works; you are lowing the maximum usable pressure capacity of the pump. You are lowering the total energy efficiency of the pump (vs large pressure tanks or VFD) in trade of getting more constant water pressure.

I believe the above statement is technically correct, but misleading. 

I am not just having fun with you, I do plan on putting a CSV in my next house (soon, I am moving). I just need to figure out if it is worth it to go with a bigger pressure tank and/or larger bypass (to fill the pressure tank).

Hope you have a good day and thanks for the intellectual exercise (even thou I failed)!

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Frequently Asked Questions / Re: Written Expalnation of How a CSV Works

« on: April 27, 2015, 04:09:27 PM »

Brain fart. Scratch the idea of multiple pumps with a large pressure tank. That would never be more effective than a single pump on a large pressure tank.

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Frequently Asked Questions / Re: Written Expalnation of How a CSV Works

« on: April 27, 2015, 02:52:03 PM »

Thank you for the quick reply and the link, there is some information/ideas in that link I was looking for.

To try and eliminate misunderstandings with my thinking, a couple of points I'd like to make. These are my current opinions/guesses and can/will change as I learn more.

1)  Your statements on this website are 95%+ spot on (that my research confirms). The remaining few percent are technically accurate but misleading. Honestly, this is annoying. OK, this is highly subjective and can mostly be just me.

2) I respect that you have an ingenious device that can work very well for many people. In my familly, the way we learn is by questioning and sometimes challenging the knowledgeable person. In no way is this meant to be personally insulting, please don't take it as such.

Now some questions.

1) A CSV will very effectivly stop "water hammer". Won't any pressure tank in-line also do this? Is it that the CSV in combination with a pressure tank works better? How would you quantify this?

2) How reliable has the CSV been? Is there a suggested maintenance schedule? Does the CSV have a 10,20,30 year expected lifespan?

3) A major advantage to a CSV is reducing water pump start/stop cycles. If you have a larger pressure tank, won't this accomplish the same thing.? As an expamle, if a house uses an average of 300 gallons a day and you have a pressure tank with a 30 gallon draw-down, the maximum start/stop cycles will be 10 per day. Does a CSV have any start/stop cycle advantages over a large (10%+ of daily use) tank?

My current thinking;

1) A residential CSV with small pressure tank is only slightly cheaper than a large pressure tank (119/30 gallon). Both being $400-$600 with the large tank on average about $100 more than the CSV setup.

2) Energy efficiency is better with the large pressure tank system. This will vary between 5% and 20%. This one is complex and I don't ever see it making a $100 difference per year on the electrical bills (single household)

3) A slow pressure swing because of a large pressure tank between 50-70 or 60-80 seems a non-issue. No experience here, just a guess. Anyone else care to comment?

4) Given the space for a larger pressure tank and slightly higher initial cost with slightly lower electrical costs. A large pressure tank seems to be the overall better way to go. This is given that a correctly sized pump is used, which is true in either case.

I am now looking at the cost effectiveness of a dual pump large pressure tank residential system. A ~6 GPM pump to handle normal useage and a 12gpm pump to handle hi usage. Maybe it would be better to use two 6gpm pumps at the same time verses turning off smaller pump when demand turns on large pump. Hmmmm, interesting.

Thanks for reading my rambling, and please (anyone) post your thoughts.

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Frequently Asked Questions / Re: Written Expalnation of How a CSV Works

« on: April 26, 2015, 10:17:41 PM »

The counter intuitive part of the CSV is that the motor amps drop when the flow from the pump is restricted with a valve, the same way the amps drop when the motor is slowed down with a complicated, computerized, expensive, short lived Variable Speed Drive (VFD or VSD).

Many people think that choking a pump back with a valve makes the amps go up and the pump to work harder, while slowing the motor speed would make the pumps work easier.  In fact just the opposite is true.  Choking the flow from a pump reduces the amp draw and makes the pumps work easier, while reducing the speed with a VFD is very hard on the pump/motor.

If you find a pump man or engineer who understands this, you have found a good one.  If they think a CSV is hard on a pump and a VFD saves energy and makes pumps last longer, they don't know their butt from a hole in the ground, so find a new pump man or engineer.

At first I was going to call your BS. Then, having a touch of OCD.... I researched the power draw of centrifugal  pumps. You are correct in your statements about power being less with lower flow.

Then I was wondering why I was thinking that restrictioning the flow would make the pump use more power. The only reason I came up with is that I was thinking about a positive displacement pump that will draw more power as you restrict the flow (is. Pressure goes up to maintain constant flow requiring more power).

So I am guessing that others are thinking about how a positive displacement pump works verses how the centrifugal pump works.

With that said, reducing flow by half on a centrifugal pump does not reduce power in half. I am thinking about figuring out the energy effectiveness of the CSV verses no CSV with a huge pressure storage tank with large drawdown (in the hundreds of gallon range). Granted, you lose the constant pressure of CSV... But then a pressure swing between 60-80 shouldn't be that annoying. I know the huge storage tank would have to be more energy efficient (just a little). But then, how long would the little energy savings take to pay for the huge tank. Am guessing about one persons lifetime. Then add that the tank won't last that long , makes having a huge tank pointless (system lifetime costwise).

You have any thoughts on the direction of my thinking?