The pump performance curve shows the shaded region between 20 GPM and 140 GPM as the "Operating Range for Flow Control", which indicates that they feel anything in this range should be accurate to within their tolerance.
IntellifloXF VSF will not pump more than 83 GPM even with low Total Head in 3" pipes
- Thread starter jcoop1
- Start date
I have numbers. Short story is that the Watts, Total Dynamic Head from the System PSI, and GPM shown on the pump display are very different than the Watts measured at the electrical panel, Total Dynamic Head from InHG/PSI measured at the suction and return drain plug, and GPM measured with a Blue White flow meter. The external Watts measurement, InHG/PSI, and flow meter GPM are all consistent the expected Total Dynamic Head of my plumbing and what I expected the pump to be capable of doing. The big question is why were the values displayed by the pump so wrong.
Here's the long story - I drilled a hole to correctly mount the Blue White flow meter in the last section of horizontal PVC pipe. The pipe wasn't long enough for the recommended horizontal distances to place the meter, but it was much better than me clamping it on the open end. It read 210 GPM when I had the pump running at 3450 RPM
The suction and pressure at the drain plugs were 16.5 in Hg and 8 PSI respectively:
I have a Sense Energy Monitoring system connected to my electrical panels and saw a drop of 3122 W from 12459 W to 9337 W consumption at the panel. I got these values by turning off the pump breaker while it was running to get the most accurate measurement (note that there are two pictures where I've moved the slider to show the total Watts consumed by my panels just before and after I shut the pump off)
I recalculated my total head for the pump I was running with the Pentair Total Dynamic Head calculator and got 37.49 ft total head at the 210 GPM that I observed on the flow meter.
Using the math I learned above, everything seems to roughly check out:
Total Dynamic Head from using pressure/vacuum gauges = 8 * 2.307 + 16.5 *1.13 = 37.101 ft
37.101 ft is pretty close to the 37.49 ft that I calculated from the plumbing
The 3122 W that I measured is pretty close to the 3200 W maximum and 210 GPM observed is pretty close to the ~225 GPM that the charts show the IntellifloXF VSF is capable of doing.
Everything is consistent.
Now to the pump readings:
79 GPM
2272 W
38 System PSI
The Watts is off, but I don't know if that's because of the difference @JamesW talked about measuring the single phase or 3 phase portion.
The System PSI of 38 would imply (38*2.31)=87.78 ft total dynamic head. That is WAY off from the empirical measurements with the pressure vacuum gauge and the expected value from the plumbing calculations, both of which were just over 37.
The 79 GPM is way off the expected and observed GPM of about 210 GPM, but it is somewhat consistent with the 38 System PSI shown on the pump.
I'm happy with the main conclusion that the the pump and the plumbing are providing the flow I had calculated ahead of time (slight pun), and are what I need for my water feature.
The big open questions are HOW does the IntelliflowXF VSF calculate System PSI and Flow (from RPM, Watts, its known curves, etc?); how does it measure Watts; and, why was it so off?
I'll point out again that I have two almost identical suction/pump/returns and both pumps were showing numbers consistent with each other but apparently way off from reality.
Here's the long story - I drilled a hole to correctly mount the Blue White flow meter in the last section of horizontal PVC pipe. The pipe wasn't long enough for the recommended horizontal distances to place the meter, but it was much better than me clamping it on the open end. It read 210 GPM when I had the pump running at 3450 RPM
The suction and pressure at the drain plugs were 16.5 in Hg and 8 PSI respectively:
I have a Sense Energy Monitoring system connected to my electrical panels and saw a drop of 3122 W from 12459 W to 9337 W consumption at the panel. I got these values by turning off the pump breaker while it was running to get the most accurate measurement (note that there are two pictures where I've moved the slider to show the total Watts consumed by my panels just before and after I shut the pump off)
I recalculated my total head for the pump I was running with the Pentair Total Dynamic Head calculator and got 37.49 ft total head at the 210 GPM that I observed on the flow meter.
Using the math I learned above, everything seems to roughly check out:
Total Dynamic Head from using pressure/vacuum gauges = 8 * 2.307 + 16.5 *1.13 = 37.101 ft
37.101 ft is pretty close to the 37.49 ft that I calculated from the plumbing
The 3122 W that I measured is pretty close to the 3200 W maximum and 210 GPM observed is pretty close to the ~225 GPM that the charts show the IntellifloXF VSF is capable of doing.
Everything is consistent.
Now to the pump readings:
79 GPM
2272 W
38 System PSI
The Watts is off, but I don't know if that's because of the difference @JamesW talked about measuring the single phase or 3 phase portion.
The System PSI of 38 would imply (38*2.31)=87.78 ft total dynamic head. That is WAY off from the empirical measurements with the pressure vacuum gauge and the expected value from the plumbing calculations, both of which were just over 37.
The 79 GPM is way off the expected and observed GPM of about 210 GPM, but it is somewhat consistent with the 38 System PSI shown on the pump.
I'm happy with the main conclusion that the the pump and the plumbing are providing the flow I had calculated ahead of time (slight pun), and are what I need for my water feature.
The big open questions are HOW does the IntelliflowXF VSF calculate System PSI and Flow (from RPM, Watts, its known curves, etc?); how does it measure Watts; and, why was it so off?
I'll point out again that I have two almost identical suction/pump/returns and both pumps were showing numbers consistent with each other but apparently way off from reality.
- May 3, 2007
- 18,088
- Pool Size
- 20000
- Surface
- Plaster
- Chlorine
- Salt Water Generator
- SWG Type
- Hayward Aqua Rite (T-15)
As was discussed above, once flow rates get above 140 GPM the display becomes inaccurate so I would just ignore what the display is telling you.
Comparing this to my theoretical head loss model, it seems pretty close. I had estimated a pump pressure of 8.5 PSI and suction of 14.7" hg. So not too far off.
Again, we discussed this in the posts above. For flow rates below 140 GPM, the Watts vs GPM is fairly linear so one can estimate GPM from RPM & Watts. I have emulated this calculation in a spreadsheet (see signature) but I suspect that Pentair uses a simple lookup table for the conversion.
As for measuring watts, I suspect they measure at the input to the pump drive since that also includes the power for the drive electronics and the most meaningful to the user. Also, in a VFD, the voltage delivered to the motor is calculated based upon the desired RPM and the PWM wave duty cycle is set appropriately to match that voltage. This is done to minimize the phase shift between the voltage and current sent to the motor (i.e. power factor close to 1). But to do this properly, they would also need to measure the current sent to the motor so that they can adjust the effect voltage to maximize the power factor. So they probably have the wattage available at both the input to the drive and the input to the motor. Technically, they could use either one to calculate GPM but again, only for flow rates below 140 GPM.