pentair intelliflo effeciancy

[Suley]

Hello all!

Can someone please tell me at what rpm is pentair intelliflo variable speed most efficient?

I have 2" plumbing all around.

Thanks!

 

[SWpisces]

I have read on this forum that 1000 rpm seems to be the most efficient....that being said, variables are abundant. We have our VS 3050 set @ 1200 rpm's for 12 hours. Has worked out well so far. This is our first year with the pool so still finding the "sweet" spots for most things. May decrease the pump time and see what happens. When we put in the robotic cleaner we use speed 3 to run it. Only put the cleaner in once a week as we have an automatic cover.

 

[mas985]

Which version of the Intelliflo do you have? With the NEW VS and VF, they will give you the watts in the output screen. To determine the best efficiency maximize RPM/Watts for the VS and maximize GPM/Watts for the VF. For most setups, this happens around 1000 RPM plus or minus.

 

[Suley]

Thanks Mark!

I will do that and see what it comes out to... I think i have intellifo variable speed as it displays in watts. The manual whic came with the pump says variable speed and VS- AU.

Can you please tell me how to determine for sure which pump i have?

Thanks again!

 

[JasonLion]

The VF allows you to set the pump speed in either RPM or GPM. The older VS-3050 has a simpler display that only shows RPM and doesn't have any timers. The newer VS-AU won't do GPM, but otherwise is just like a VF, with timers and the ability to display watts.

 

[jbuckley21]

I just installed the intelliflo vf and have it running 24hrs to turn once on ~40k size pool. It is doing 27gpm at ~2 and change rpm and 430watts.

Thinking about backing it down to 12 hours, but to turn once it will jack up the gpm and watts.

not sure that helps, but thats where I am at.

 

[Suley]

Hey Mark!

I am trying to use your spreadsheet to determine the flow.

My pump data:
850 rpm - 102 watts
1000 rpm - 124 watts

Then according to the sheet, I am pumping 20gpm at both speeds?

A bit confused... am i reading the sheet WattsTable right? If yes, I spend more electricity at 1000 rpm and get the same flow?

Thanks!

 

[JasonLion]

I'm not an expert on Mark's spreadsheet, but if I remember correctly it helps to get calibration data for the flow rate at two widely separated speeds. So try running at 2000 RPM and plug that number into the spreadsheet and see if you get different results.

 

[mas985]

The WattsTable is kind of hard to read/interpolate for low speed. The curves are very flat so a small change in watts give a larger change in GPM. Using the Watts2GPM worksheet, I get the following:

850 RPM, 102 watts, 15.66 GPM, 5.28' of head, 9.21 gallons/watt-hr

1000 RPM, 124 watts, 19.88 GPM, 7.19' of head, 9.62 gallons/watt-hr

 

[Suley]

Thanks!

I am trying to determine the flow rate in my system and toying with the idea of installing a flow meter....

Any guidance whether it is a good idea to install it? i was reading on the forum that flow meters are not too accurate at low flow rates to the extent of being off by 10gpm... So i turned to Mark's spreadsheets...

Any ideas how to get a decently accurate flow rate?

Thanks!

 

[mas985]

Flow meters have their issues one of which is the range of measurement. You can get one for the lower end of measurement but you will still end up with a +/- 10% of full scale accuracy. The second issue is you need a long straight section of pipe to get accuracy (14xD) . Many pads don't have this.

Another method to improve accuracy is to get a suction gauge but even then, the measurements have to be done at higher speeds and then scaled for lower speeds since it is difficult to measure pressure and suction in lower ranges.

So short answer is that there really isn't a good cost effective way to measure low flow rates. There are much more expensive flow meters that have accuracy over a wide range of flow rates. The Watts2GPM spreadsheet should get you within a few percent of actual values so it shouldn't be all that worse than a flow meter at low flow rates.

I reality, you shouldn't need all that much accuracy anyway. The efficiency metric of gallons/watt-hr is fairly flat in the optimal range so a little error won't hurt the bottom line much.

 

[Suley]

Aha! No flow meter then! :-D

Another question about the spreadsheet... how much should i worry about difference in the piping from mine to your model which was used to develop the spreadsheet?

Thanks!

 

[Suley]

Mark,

I was looking at my readings and comparing them with your calculations for 850 and 1000 rpm.

My readings from the pressure gauge on the filter are much lower than your calculation... Any ideas? or is it the static head and dynamic head issue?

My readings:

850 rpm - 2.3 ft head
1000 rpm - 4.15 ft head

I read the gauge in Psi and converted the readings into ft of head. Having a different pressure value will effect the flow rate wont it?

Thanks!

 

[mas985]

Your second to the last post question:

The model used is basically a pump model and is valid for any plumbing system. For a specific plumbing system and RPM value, there is only one value of GPM and Watts that the model produces. This why knowledge of the actual plumbing system is not required. Three equations and four variables are used in the model:

Pump Watts = Fw(RPM, GPM) - Determined from CEC data
Pump Head = Fh(GPM) - Determined from CEC or published head curve data
Plumbing Head = Fh'(GPM) - Generally unknown and is an output

Each spreadsheet uses the above equations to turn known inputs to the unknown outputs:

Watts2GPM
Inputs: RPM, Watts
Outputs: GPM, Head, Plumbing Curve

Head2GPM
Inputs: RPM, PSI, Suction
Outputs: GPM, Head, Watts, Plumbing Curve

PSI2GPM (Cost# sheets as well)
Inputs: RPM, PSI, Suction plumbing description
Outputs: GPM, Head, Watts, Plumbing Curve

All of the sheets require RPM as an input since this is always known. Also, all of the sheets calculate the plumbing system curve which is unique to each plumbing system and is generally not known.

Your last post question:

First, the filter pressure only gives you an indication of return head not total head. You need a suction measurement to get that. Second, the elevation of the pump/filter will affect the filter pressure and needs to be taken into account. Third, low flow rates generate low pressure and pressure/vacuum gauges lose accuracy at the low end of scale much like the flow meters. Most pressure gauges have a 1 PSI accuracy so if it reads 1 PSI, it could be anywhere from 0-2 PSI.

What was the actual filter pressure on the gauge (not feet of head)?

Also, what is the elevation of the pump relative to the water level?

 

[Suley]

Filter pressure:

850 rpm - 1 PSI
1000 rpm - 1.8 PSI

The pump is at the most 2 feet above the water's surface.

 

[mas985]

So for 850 RPM, the calculated return static and dynamic head at pump level would be:

Return Head = 1 PSI * 2.31 + 3' = 5.31' (3' is for the height of the filter gauge above the pump)

But given the accuracy of the pressure gauge it could be anywhere from 3' to 7.6'. The model calculates 5.3' of TOTAL head which is consistent with the return head and accuracy.

For 1000 RPM, the calculated return static and dynamic head at pump level would be:

Head = 1.8 PSI * 2.31 + 3' = 7.2'

But again, the accuracy of the gauge puts it in a range of 4.8' to 9.5' which is again consistent with the model total head of 7.2'.

But again, I don't recommend using the pressure gauge for measurements at low speed because the error is so large. However, if you have a higher speed pressure ~20 PSI, we can then use the PSI2GPM sheet to calibrate for the plumbing curve at high speed, and then use the other columns to determine the flow rate for low speed to see how much of a difference there might be from the wattage model. You only need the filter pressure and a good idea of the suction side plumbing (diameter and run lengths). This model uses approximations for the suction side losses so isn't as accurate as the other models but at least it gives you a second data point. Also, this method does not work very well if you have spring loaded check valves.

 

[Suley]

Thanks again!

I plugged in my numbers in watts2GPM and found something really interesting...

At 900 rpm my flow rate is 24.70! So:

850 rpm - 15.66 GPM - 102 Watts
900 rpm - 24.70 GPM - 115 Watts
1000 rpm - 16.08 GPM - 120 Watts

This seems like too good to be true at 900 rpm! Guess what i am thinking.... run pump at 900 rpm for 16 hours a day!

 

[mas985]

You posted before that 1000 RPM was 124 watts. Has that now changed?

Also, you have to take into account that the wattage readout has error as well and can only read to 1 Watt level. I asked Pentair once how accurate the readout was and they said "pretty good". Not worth much but it is important to understand that the model is very sensitive to errors at low RPM but unfortunately, that is also where the most measurement error occurs.

If we assume that the 1000 RPM @ 124 watts is correct, and the plumbing curve is a constant, then the other RPM values should be:

1000 RPM, 124 watts, 19.88 GPM
900 RPM, 109 watts, 17.65 GPM
850 RPM, 103 watts, 16.97 GPM

850 RPM is only 1 watt different that what the pump reported so that is certainly within error bounds. For 900 RPM, the wattage error would be around 6 watts which is only about 5% error so that isn't bad either. So with the model error, and the error in Wattage reporting, 5% is probably not too bad but the real problem is that it makes for strange results occasionally.

This is why I usually suggest a full calibration at high PSI/RPM and then scale the GPM by the RPM ratios. For most systems this works fairly well except those with spring loaded check valves where the plumbing curve does not remain constant.

 

[Suley]

This is why I usually suggest a full calibration at high PSI/RPM and then scale the GPM by the RPM ratios.

How do i do that?

I just got home and looked at the readings again... it is giving 120 watts for 1000 rpm. I did change the return valve and suction valve positions since i took the earlier readings. I am directing 30% suction to the spa and 90% to the pool now ...returning 50% to both spa and pool each as against no suction or return to spa like i found the pool when i brought the house.

I am sure this has changed everything....

So how do i do a full scale calibration? Does water temperature got to do anything with the watts? water was in mid 60s when i took those readings and now it is 78F today.

 

[mas985]

Valve settings will change power draw noticeably. Water temperature theoretically changes the friction loss in plumbing but it is such a small change that you probably would not notice the difference.

As for the calibration, run the pump at a higher speed. Target 2600 RPM and report back the PSI and the wattage reported.

Also, describe your suction side plumbing for me. Distance from pool to pad, pipe diameter and the number of full suction runs.