Air in Water Lines Only first thing in the Morning

[Twowaxhack]

If I owned Gould’s and my head engineer didn’t know that a centrifugal pumps amps would be reduced as its flow is choked off, would be terminated immediately.

It’s well known by engineers that deal with centrifugal pumps that amps are reduced when flow is reduced.

https://www.google.com/search?q=a centrifugal pumps output relationship to amp draw

 

[Ferdinand]

The motor is not running slower. It’s just not having to move as much water being restricted so the load is actually decreased on the motor even though it’s spinning at the same RPM.
Cray cray huh ?

Hurts my head for sure.

But as you can see for the CSV to be such a simple valve it has a complicated explanation. "Counter intuitive" is the key word.
[...] The valve just makes the pump think the well is deeper so it can't pump as much water. All pumps work on a curve. At low pressure they produce a lot of water and pull max amps. At high pressure, like in a deeper well, they produce less water and draw lower amps.
[...] To make this an even longer post and blow your mind some more, the pump actually speeds up when the flow is "choked" off with a valve.
[...] I have been trying for almost 30 years now and it is impossible to explain a counter intuitive property in a short post.

Thank you so much for your patience in writing your long description and the video. And thanks to the moderators for their leniency in allowing us to hijack this thread.

One moment it's all crystal clear in my head, then the next moment I'm baffled again. It's like one of these illusions where one person will insist they only ever see the witch, whereas another can see only the pretty girl, and some are lucky enough to be able to flip back and forth at will between seeing either one.



It makes perfect sense that at some given volume of flow the pump can only lift water to a particular head height. To provide more flow and/or lift water to a greater height will require more power. Moving to different points on the curves, less flow rate means the pump's power is instead available to lift a smaller amount of water higher. Or, in the opposite direction, the pump can move more water but lift it less high. More height requires more pressure, which is a squared function i.e. lbs per square inch, whereas more volume flow is a cubic function i.e cubic inches. So the power required is much more sensitive to volume changes than it is to pressure changes.

Restricting the flow via the CSV increases the back pressure, i.e. increases the head height while choking the flow rate. More head height, more power required. Less flow rate, less power required. But power increased for more pressure is a squared function, while the power decreased for volume is cubic, so overall there is less power required when the flow rate is choked.

Can you give a few more details how this pump's efficiency is calculated, as shown at 1:25 in your video?


For each of the rpm traces shown, it looks like a maximum efficiency of ~65% is achieved at about 220 gpm flow rate.

Using the 3450 rpm line, that pump can raise a column of water up to about 310 ft and hold it there with zero flow exiting out of the top of the pipe, while burning up 12hp just to hold that height. This is like waiting at a traffic light with your car's engine running, i.e. it's burning gas going nowhere, so zero percent efficiency.

At the far right end of the lines the pump is running at max horsepower to deliver its largest volume of flow rate, but the height capability has dropped way down.

At peak efficiency it's pumping to its largest combined volume x height / horsepower capability? What's the formula being used to calculate that efficiency.

 

[Valveman]

It’s well known by engineers that deal with centrifugal pumps that amps are reduced when flow is reduced.

https://www.google.com/search?q=a centrifugal pumps output relationship to amp draw

You would think so right? But I swear 95% of engineers think the amps go up and the pump works harder when the flow is restricted with a valve. There are a few who understand, but I think 5% maybe generous. The fact that the amps go down when the flow from a pump is "choked" or "throttled" with a valve is not intuitive. It doesn't make sense. Only the engineers who can get out of that box of having to make sense of everything will understand it. Many even get angry and call me all kinds of names. Here is a comment from such an engineer. I edited out the most ugly parts to make it PG. Lol!

"To Whom it May Concern
Ignorance truly is bliss. Your website demonstrates you have a very rudimentary understanding of pumping technology and fluid mechanics, I'm going to send it to my engineering buddies so they get a good laugh. I'm a licensed professional engineer and also a Certified Energy Manager through AEE. If it were worth my time I could easily show you how putting a flow restriction device on a pump wastes energy. It is probably the first thing you learn in engineering. You aren't the first good-ole-boy I've seen making ridiculous claims. You can't say a technology is wrong because you've seen it implemented on the wrong applications. I don't think you have the knowledge or credentials to back up what you are saying. I read most of the drivel on your site and am appalled it is even legal for you to do so.

Regards,
Licensed Professional Engineer and Certified Energy Manager through AEE"

 

[Valveman]

Hurts my head for sure.



Thank you so much for your patience in writing your long description and the video. And thanks to the moderators for their leniency in allowing us to hijack this thread.

One moment it's all crystal clear in my head, then the next moment I'm baffled again. It's like one of these illusions where one person will insist they only ever see the witch, whereas another can see only the pretty girl, and some are lucky enough to be able to flip back and forth at will between seeing either one.

View attachment 29338

It makes perfect sense that at some given volume of flow the pump can only lift water to a particular head height. To provide more flow and/or lift water to a greater height will require more power. Moving to different points on the curves, less flow rate means the pump's power is instead available to lift a smaller amount of water higher. Or, in the opposite direction, the pump can move more water but lift it less high. More height requires more pressure, which is a squared function i.e. lbs per square inch, whereas more volume flow is a cubic function i.e cubic inches. So the power required is much more sensitive to volume changes than it is to pressure changes.

Restricting the flow via the CSV increases the back pressure, i.e. increases the head height while choking the flow rate. More head height, more power required. Less flow rate, less power required. But power increased for more pressure is a squared function, while the power decreased for volume is cubic, so overall there is less power required when the flow rate is choked.

Can you give a few more details how this pump's efficiency is calculated, as shown at 1:25 in your video?
View attachment 29339

For each of the rpm traces shown, it looks like a maximum efficiency of ~65% is achieved at about 220 gpm flow rate.

Using the 3450 rpm line, that pump can raise a column of water up to about 310 ft and hold it there with zero flow exiting out of the top of the pipe, while burning up 12hp just to hold that height. This is like waiting at a traffic light with your car's engine running, i.e. it's burning gas going nowhere, so zero percent efficiency.

At the far right end of the lines the pump is running at max horsepower to deliver its largest volume of flow rate, but the height capability has dropped way down.

At peak efficiency it's pumping to its largest combined volume x height / horsepower capability? What's the formula being used to calculate that efficiency.

You can back out of the Brake Horse Power formula to get efficiency if needed. But I usually get my efficiency numbers from the pump curve like you did.

The standard BHP formula is flow X head X 100 divided by 3960 X Efficiency.

https://cyclestopvalves.com/pages/pump-horsepower-characteristics

 

[Twowaxhack]

I would say 5% is not an accurate number If asked if a centrifugal pump would pull more amps or less when pumping under restriction vs full open outlet.

I’m going to ask a few and see what their answer is.

 

[Valveman]

Great! Yeah ask them. First ask them if a VFD saves energy. When they say yes, ask if throttling with a valve saves energy. They will say heck no a valve burns energy. Then ask about the amps going down on a centrifugal pump when restricted with a valve. Some will say yes. Then ask how it is burning energy when restricting with a valve causes the amps to drop almost as much as a VFD. I love to see the perplexed look on their faces when they think about that. Most will double down on their stupidity and swear a valve still burns energy anyway. Very few think they still have something new to learn. But those that do will say they never thought about it like that and will have to go back and look at some pump curves.

 

[Twowaxhack]

Great! Yeah ask them. First ask them if a VFD saves energy. When they say yes, ask if throttling with a valve saves energy. They will say heck no a valve burns energy. Then ask about the amps going down on a centrifugal pump when restricted with a valve. Some will say yes. Then ask how it is burning energy when restricting with a valve causes the amps to drop almost as much as a VFD. I love to see the perplexed look on their faces when they think about that. Most will double down on their stupidity and swear a valve still burns energy anyway. Very few think they still have something new to learn. But those that do will say they never thought about it like that and will have to go back and look at some pump curves.

Sounds like fun. I will for sure let you know how it goes.

 

[JG plumbing]

Doubling down on stupidity. Hmm. Never heard of that. Lol

 

[Ferdinand]

I'm sure I'll be suitably embarrassed when the really simple answer is explained to me.

Most will double down on their stupidity and swear a valve still burns energy anyway. Very few think they still have something new to learn. But those that do will say they never thought about it like that and will have to go back and look at some pump curves.

Well, colour me suitably embarrassed.

 

[rsoto]

Did you stuff Taco Bell down the garbage disposal? I get like that in the morning when I eat mexican food the night before

 

[PerplexedPlumber]

Hmm. If it does that to your garbage disposal, what happens to your internal plumbing? (please, no graphic answers, just a rhetorical question)

Nevermind - that's what you intended!

 

[Valveman]

Doubling down on stupidity. Hmm. Never heard of that. Lol

Sorry! Been making this argument for more than 30 years and my filter for being polite is worn thin. Lol. I wish I had some of the conversations with engineers recorded. I do keep the emails and comments in a file. But here is a good one from a driller who was getting coached by the engineer at the pump company.

 

[JG plumbing]

Sorry! Been making this argument for more than 30 years and my filter for being polite is worn thin. Lol. I wish I had some of the conversations with engineers recorded. I do keep the emails and comments in a file. But here is a good one from a driller who was getting coached by the engineer at the pump company.

I love the argument of "been doing this (incorrectly) for X number of years."