IntelliFlo VSF Optimal Efficiency

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nsgoldberg

nsgoldberg

Member
Oct 3, 2020
10
Southern California, Lake Mathews
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Finished putting our pool in last month, being an engineer I like the data available from the VSF. Wondered what the most efficient setup was for the pool, so using the speed, flow, and power readings from the ScreenLogic app on the PC, I made a psedu-efficiency curve. Note that this only applies to my pool, the head loss on another pool will be different. I simply took the flow rate and divided it by power draw to determine the efficiency curve.

The flow rate went to zero at 1400 rpm, so that's the minimum in the experiment. Not that it matters, at 1700 rpm the flow is 25 GPM, which is the minimum flow rate for the IC40 chlorinator. Actually, the IC40 spec says 25±5 gpm, so to be on the safe side I consider 30gpm to be the minimum, which correlates to 1800 rpm and 311W. For my pool this correlates to a 9 hour turnover, but I'm running it 11 hours a day, as my home solar covers it. During the winter, I'll drop that down to 9 hours.

Just thought I'd share, if you have a VSF it's an easy way to determine your most effective/efficient speed. Only takes 15 minutes or so to do.
 

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I would not put much stock in "turnover" as that is not needed, but you are spot on in trying to find the minimum rpms for your IC40 to work. The other thing to look at is the minimum speed for your skimmer weir doors to stay open and effectively skim the pool. I suspect it will skim just fine at 1700 RPMs, but it is worth checking out.

The other thing to watch out for is how your IC40 works with a dirty vs clean filter. After backwashing I can get by with running mine at 1200 RPMs, but as it gets dirtier I need to bump it up to 1300 or 1400 rpms to keep the flow light happy. Usually once I hit 1400 I know it is time to backwash again.
 
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mknauss said:
Yikes. Why is that? Is the vac you have suction side?
Click to expand...
Yes, but for consistency of measurement, I closed the diverter valve to pull from the skimmer and drains only. I was a bit surprised to see it drop off so quickly as well.
I cleaned the DE filter at 30 days last week (new pool), so that shouldn't be an issue.
 
JJ_Tex said:
I would not put much stock in "turnover" as that is not needed, but you are spot on in trying to find the minimum rpms for your IC40 to work. The other thing to look at is the minimum speed for your skimmer weir doors to stay open and effectively skim the pool. I suspect it will skim just fine at 1700 RPMs, but it is worth checking out.

The other thing to watch out for is how your IC40 works with a dirty vs clean filter. After backwashing I can get by with running mine at 1200 RPMs, but as it gets dirtier I need to bump it up to 1300 or 1400 rpms to keep the flow light happy. Usually once I hit 1400 I know it is time to backwash again.
Click to expand...
We have a pool cover on the pool at all times except when using the pool. So I'm not sure how much skimming is taking place.
Good point on the dirty/clean filter for the IC40, I'll keep an eye on that.
 
Are you using a real flow meter or the mathematically created data from the Intelliflo?
 
mknauss said:
Then all you need to run the pump for is to create chlorine. You can likely reduce pump run time dramatically.
Click to expand...
Good to know. I've been using test strips but just ordered the K-2006C and K-1766 so I can have a more accurate picture of the water health as I make changes.
 
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nsgoldberg said:
From the IntelliFlo (ScreenLogic on PC). I had assumed it had a mechanical flow meter in there. Is that not the case?
Click to expand...
No. It is created by some algorithm. I would not count on its accuracy.

In reality, most of us ignore flow rate. Does not really matter. Just use RPM. When your flow switch on the IC closes, that is your minimum RPM to run.
 
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mknauss said:
No. It is created by some algorithm. I would not count on its accuracy.

In reality, most of us ignore flow rate. Does not really matter. Just use RPM. When your flow switch on the IC closes, that is your minimum RPM to run.
Click to expand...
Good to know. I had assumed there was a mechanical flow meter in there. That's kind of misleading. Thanks for the info!
 
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This shows the operating range for flow control in the gray shaded area.

The pump uses the power to estimate the flow at a specific rpm.

Intelliflo VSF Performance Curve.png
full
 
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This is your approximate system curve plotted on the pump performance curve.

The system curve is approximately y=0.0138x^2, where y is the feet of head and x is the flow in gpm.
InkedIntelliflo VSF Performance Curve_LI 333.jpg
1626459585065.png

y=0.0138x^2, x from 0 to 100 - Wolfram|Alpha

Wolfram|Alpha brings expert-level knowledge and capabilities to the broadest possible range of people—spanning all professions and education levels.
www.wolframalpha.com www.wolframalpha.com
 
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25 gpm should be about 9 feet of head, but the curve is not always perfect.

Things like check valves can make the curve somewhat erratic.

At 9 feet of head, the speed should be about 1,125 rpm, but it might be higher if you have check valves in the system.

1626460138758.png
 
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@nsgoldberg
I recently had the same concerns regarding both the flow numbers as well as the power numbers being reported by my VSF.
I also had the same discussion more or less regarding what I believed to be erroneous data being reported by my pump.
@mknauss and @JamesW both helped me to kind of confirm that the VSF flow numbers were based on power and head loss algorithms etc., and not some flow meter inside the pump.
This was also somewhat confirmed by an engineer that I spoke with at h2flow Controls. He reported that he had discussions with Pentair engineers at a past trade show and those engineers basically admitted same.

If you care to read more about my own particular findings regarding both power and flow numbers from my VSF, you can see that discussion here.

IntelliFlo Numbers Confusing.

Ran across something the other day with my IntelliFlo pump that I can't figure out. At 700RPM, the pump reports using 35 watts and indicates 0 GPM (well, that's not right coz water is coming out of the returns but whatever). That's not my issue really. At 600RPM, the pump reports using 46...
www.troublefreepool.com www.troublefreepool.com

I used a FlowVis Digital Flow Meter to help me see what the "more accurate" flow numbers were and a digital display AC Power Meter to get more accurate power readings. I performed a confirmation "bucket" test to back up the flow numbers that I was seeing from the FlowVis Digital. I did discover that the numbers reported by the VSF are more inaccurate at lower RPMs.

Thanks...
r.
 
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Thanks for the info. Good stuff in that experiment MyAZPool. I might put my Fluke clamp meter on the pump line and see what my power readings are.

I still find it odd that I get a reading of zero flow at 1400 rpm and you don't hit that until 800. Your pool is larger than mine. I have a spa, maybe that's the difference?
 
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nsgoldberg said:
Thanks for the info. Good stuff in that experiment MyAZPool. I might put my Fluke clamp meter on the pump line and see what my power readings are.

I still find it odd that I get a reading of zero flow at 1400 rpm and you don't hit that until 800. Your pool is larger than mine. I have a spa, maybe that's the difference?
Click to expand...
I noticed that too and I really don't have a good explanation on why that is. :scratch:
Thanks...
 

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