Intelliflo VF flow rate for good skimmer function

urban-farmerJune 2, 2011

I just installed a Pentair IntelliFlo VF variable speed pump. I have it set for one turn of a 25,000 gal pool in an 8 hour period. I start the filter cycle with Feature 3 set at 75 GPM for 1 hr. That gives me about 48.8 GPM for the remaining 7 hours of filter cycle.

I get modestly acceptable surface movement and skimmer suction at 75 GPM, and almost no movement at 48.8 GPM. Pentair tells me that these flow settings are way too high and that 30-35 GPM should provide me with good skimmer function.

I ran a number of tests with Pentair tech support guy on the phone. He thinks my skimmer line is either partially blocked, or the 3-way valve is not fully opening the skimmer line. Seems to me that would just require a higher pump speed to develop the set flow rate to overcome the additional pressure drop. I wasn't convinced the Pentair guy knew what he was talking about.

I replaced a single speed 2 HP Whisperflow. That pump really pushed the surface and the skimmer worked great. To replicate the surface movement using the VF, using the VF manual function, I determined my 2 HP pump was probably putting out about 120-130 GPM; VF is incredibly loud at these flow rates and uses about 25% more energy than my 2 HP.

Pool is 32x16, one skimmer on the middle of 32' side, bottom drain, and 4 return jets. The 3-way valve is set for about 80% skimmer and 20% bottom drain.

What flow rate do you need for good surface cleaning and skimmer function? Any ideas on what's wrong?


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Every pool is different but many people find that low flow rates don't work well with skimming so I would go by your own experience. No one, not even a Pentair tech can tell you what speed will work well with your specific pool. It dependends on too many factors so trial and error will work best. So I would say that there is nothing wrong and you are just experiencing what many others have as well. Higher flow rates work better for skimming.

On low speed, my pump puts out about 35 GPM and skimming is minimal at best but that is because I have two skimmers and a main drain so flow is split between them so I can't really expect skimming to be all that great.

Some POs have found that they can run on lower speeds most of the time but for the majority of users, it seems that most need to run at higher speeds for at least part of the cycle.

    Bookmark   June 3, 2011 at 11:36AM
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urban you have the ability to valve the suction lines to the pump so that low speed settings only pull water from the skimmer and not the main drain...this will direct more flow through the skimmer at lower speeds allowing better skimming action at reduced pump speeds.

You're correct..keep that VF pump on lower speeds when at all possible...variable speed pumps use lots of energy at higher speeds due to wasted heat from the drive and other factors.

If you still can't get the skimming action that you once had and are not happy with the energy consumption with the VF at higher speed....I would recommend a 2 speed pump instead. The 2 speed will use only slightly more energy at low speed and considerably less energy at high speed allowing good skimming action at reduced energy cost.

Hope this helps.

    Bookmark   June 3, 2011 at 1:19PM
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The Intelliflo can match the high speed flow rate of any two speed pump and still use less energy so why would you ever replace an Intelliflo with a two speed pump as long as it is running?

    Bookmark   June 3, 2011 at 5:32PM
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Thanks for the input. I flushed the skimmer line and all was clear. I developed power curve for my pool by running at varying flow rates. I decided to use 75 GPM (1400 w, 2700 RPM) for 1 hr at the beginning of the cycle to clear the surface. Then remaining 6 hrs runs at 57-59 GPM (1000 w, 2100 RPM). Original 2 HP pump pulled 2000 w, so savings will be about 45%.

    Bookmark   June 10, 2011 at 1:29PM
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The Intelliflo efficiency peaks around 1000 RPM so why not use 1000 RPM for 12 hrs instead of 2100 RPM for 6 hrs? You should come out ahead.

    Bookmark   June 10, 2011 at 1:51PM
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You're correct, at 1000 RPM flow rate is 30 GPM @ 250w. It would save another 25%, but surface movement and skimmer suction is non-existent. So when the pool is uncovered, I've decided I'm willing to pay a bit extra to keep the surface clean. When the pool is covered, the lower flow rate makes a lot of sense. Thanks.

    Bookmark   June 10, 2011 at 8:28PM
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This may start a big debate But if it were me I would trash the 3-way valve unless you have automation and install good quality ball valves for better control. I hate those things!!! J.M.O.

    Bookmark   June 12, 2011 at 7:36AM
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