# Thread: RPM to GPM estimates for VS-SVRS?

1. ## RPM to GPM estimates for VS-SVRS?

Does anyone know where I can find this?

Thanks.

- Jeff

2. ## Re: RPM to GPM estimates for VS-SVRS?

We would need way more information to guess at that. The flow rate at any given speed depends on the "dynamic head", essentially the water resistance, of you your plumbing system. That in turn depend on almost every detail of how your pool is plumbed (and can be complex to figure out ).

3. ## Re: RPM to GPM estimates for VS-SVRS?

I found the head vs. RPM chart - and I need to get a vacuum gauge to figure out the TDH...

Thanks.

- Jeff

4. ## Re: RPM to GPM estimates for VS-SVRS?

Originally Posted by JasonLion
We would need way more information to guess at that. The flow rate at any given speed depends on the "dynamic head", essentially the water resistance, of you your plumbing system. That in turn depend on almost every detail of how your pool is plumbed (and can be complex to figure out ).
Jason I would be interested in a rough chart. I do understand that it would be very complex to figure out as every pool's plumbing is different but how accurate does one need to be? A rough chart would be close enough plus or minus a deviation, am I correct? I am sure mas985 would be able to put together something

5. ## Re: RPM to GPM estimates for VS-SVRS?

I put together this spreadsheet some time ago. It uses the energy readout of the pump and RPM levels to determine GPM. There is a direct relationship between the three for the Intelliflo. If you know two, you can determine the third.

6. ## Re: RPM to GPM estimates for VS-SVRS?

If I've done this right, here is the head/GPM/RPM curve...

7. ## Re: RPM to GPM estimates for VS-SVRS?

Originally Posted by mas985
I put together this spreadsheet some time ago. It uses the energy readout of the pump and RPM levels to determine GPM. There is a direct relationship between the three for the Intelliflo. If you know two, you can determine the third.
Thank you! This rocks!

8. ## Re: RPM to GPM estimates for VS-SVRS?

No Problem.

For the method I used in the spreadsheet, knowledge of head is not required. You only need to know RPM and Watts both of which the Intelliflo displays. Funny thing is that it would have been so easy for Pentair to also display GPM as they do in the VF. They could have just disabled the capability to set GPM for the VS.

9. ## Re: RPM to GPM estimates for VS-SVRS?

Originally Posted by mas985
No Problem.

For the method I used in the spreadsheet, knowledge of head is not required. You only need to know RPM and Watts both of which the Intelliflo displays. Funny thing is that it would have been so easy for Pentair to also display GPM as they do in the VF. They could have just disabled the capability to set GPM for the VS.
So - what you're saying is, there really isn't a "flow-meter" per-se in the the VF, as much as there is a calculation done internally by the pump's controller/computer between power and RPM that derives/approximates flow?

10. ## Re: RPM to GPM estimates for VS-SVRS?

Yes, except that is a flow meter, so yes there is a flow meter, it just works differently from what you might expect.

11. ## Re: RPM to GPM estimates for VS-SVRS?

Right, much like a TDS meter doesn't really measure TDS. It measures conductivity, in fact current, which is then calibrated to a specific TDS. There are probably dozens of examples of indirect meters or measurements. As long as the relationships hold, they are still fairly accurate.

Also, I updated the spreadsheet to include the head as an ouput on the calc sheet as well as a separate head table.

Keep in mind though, that I did a first order approximation to both the power and head curves so they are close to actual values but not exact. However, it should be good enough for what most people are looking for.

12. ## Re: RPM to GPM estimates for VS-SVRS?

Well, now I'm feelin kinda ripped off that it's just a SW thing - they took out of the VS and put in the VF.

13. ## Re: RPM to GPM estimates for VS-SVRS?

It isn't just software, the VF also has a much fancier display, more buttons, more memory, and a more accurate clock. The principal is more or less the same, much of the price difference is in the software (just not all of the difference).

14. ## Re: RPM to GPM estimates for VS-SVRS?

OK. Trying to use this spreadsheet but the results don't make sense.

I ran my new VS-3050 pump with 2 settings and two knowns, with an amp meter connected.

1400 rpm gave 234w. (.96a at 244V)
3450 rpm gave 1708w. (7a at 244V)

I plugged these into your spreadsheet and I got 32.4GPM at 1400rpm and 20.44GPM at 3450rpm.
Makes no sense, since it seems at least the pool is pushing a lot more water with the 3450rpm setting. I didn't enter any calibration fields, etc. into your spreadsheet. Maybe you can shed some light on this?

15. ## Re: RPM to GPM estimates for VS-SVRS?

For most plumbing at 3450 RPM, you should be getting something close to 3 kw or twice what you are seeing so I think something is wrong with the wattage you are using. What is the wattage reading from the Intelliflo output display? Amp meters on a VFD pump can give some bizzare readouts so I wouldn't use that. Use the Intelliflo display.

16. ## Re: RPM to GPM estimates for VS-SVRS?

I have a VS, not a VF - so have no display on the unit. I made an error. 7amps was 3110rpm (setting 4, which I thought was 3450). 9.5amps for 3450rpm.

So 32.40gpm for 1400rpm (13.29 head)
and 69.24gpm for 3450rpm (84.82 head)

I didn't expect my flow to be so high (32.4gpm) for 1400rpm. Do you think these flow estimates are spot on?

The erroneous #s I plugged in before didn't make sense, so made the curve spit a nonsensical #.

What is confusing to me (common sense wise) is that as wattage increases for the same RPM, head *decreases*. I always thought that longer runs with more resistance (more head) would make the pump work harder at any RPM level, thus increasing the wattage. And thus head should increase. Maybe you can correct my misunderstanding of basic fluid dynamics.

Just to give you an idea of my pool plumbing run (to see if it makes sense with these readings), my equipment is about 60 feet of pool pipe away from the pool. In the middle of that run there is a 5 foot rise and a five foot drop. [to make the pipes accessable for needed repair] The suction side is 2" and the return side is 1-1/2". I have a cartridge filter on the return side that I believe has flow limits of 70gpm.

I have a sperry digisnap dsa-500 amp meter that provided me with these real readings.

Interesting also to discover my voltage was 244v (my in house circuits are 122v).

17. ## Re: RPM to GPM estimates for VS-SVRS?

That pump curve is light. According to my books, the VS-3050 @ 55 feet of head is pushing over 140 GPM. The need for big pipes is apparent.At 85 ft, it's about 85 GPM. Both are at 3450 rpm and 3000 watts.

@ 300 watts @ 12 ft. of head it's 40 GPM

Remember, head loss drops in a given pipe as velocity drops due to less friction.

Scott

18. ## Re: RPM to GPM estimates for VS-SVRS?

Sorry, Pentair shows the VS-SVRS as having a display so I assumed they all did. Anyway, my concern with an amp meter is that the RMS current assumes a sinewave and while they do a lot of filtering on the input current, it can still have some artifacts which throw off the measurement. However, it sounds like you have a high end meter so it probably does a better job of measurement.

As for the validity of the calculation, this is a first order approximation so it won't be exact but if I had to guess, I would say the error is probably less than 10% and may be as good as 5% but the error is compounded if the amp reading is off. The numbers you are seeing would be indicative of 1 1/2" return plumbing, in other words, high head loss. What is the filter pressure at each of the readings?

19. ## Re: RPM to GPM estimates for VS-SVRS?

Originally Posted by PoolGuyNJ
That pump curve is light. According to my books, the VS-3050 @ 55 feet of head is pushing over 140 GPM. The need for big pipes is apparent.At 85 ft, it's about 85 GPM. Both are at 3450 rpm and 3000 watts.

@ 300 watts @ 12 ft. of head it's 40 GPM

Remember, head loss drops in a given pipe as velocity drops due to less friction.

Scott
I used the CEC measurement data and not the published head curves so there will be some slight differences. If you want to use published head curves, you can plug in your own numbers on the calibrate sheet in the head curve section.

20. ## Re: RPM to GPM estimates for VS-SVRS?

It is a \$50 home depot multimeter, so I'm not sure about high end. So I wonder too... but the readings are done on the input side at the mechanical timer. (both legs of wire have the same reading)

As far as PSI readings: 1400rpm 5PSI, 3110 RPM 24PSI, 3450RPM 30PSI.
Probably would make sense to have an interim reading to construct a nicer curve (2300?), so if you want I can do that.

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