Variable flow pump.... HOW THEY SO SMAHT???

[CRUSH-IT!]

I can think of a number of ways to calculate flow for pump speed modulation.

1) pressure sensor on each side of the pump gives TDH and pump speed plotted against the pump curve gives flow.

2)Power consumption plotted against pump speed allows calculation of TDH and by extension Flow.

3) Each pump comes with a little genie that lives in the pump and sticks his toe in the water and adjusts pump speed accordingly.

4) something better than 1-3.

Anybody know?

 

[JamesW]

On page 44 there is a graph of Flow and Power vs. Flow.

https://www.horizonpoolsupply.com/_uls/resources/IntelliFlo_VF_Manual.pdf

So, they use the speed (RPM) and power to estimate flow.

The IntelliFlo does not have pressure sensors, but I think that pressure sensors would be better than the power usage method.

 

[CRUSH-IT!]

thank-you!!

 

[JamesW]

Note that at a constant speed, increasing the TDH reduces the power needed because the flow is reduced, which reduces the power used.

So, the power is graphed against the flow and not the TDH.

The power does increase with higher TDH if the flow is maintained by increasing the pump speed.

 

[CRUSH-IT!]

Thanks again! Im a bit surprised how hard I have found it to find complete pump curves for these pumps. that is, curves for more speed or flow levels. I would think the manufacturer must provide them

 

[CRUSH-IT!]

I understand that if pressure changes rapidly the pump will often downshift and upshift. I suspect this may be diagnostic. If you have power and speed and reduce speed to get a new power and speed in the same circuit configuration, you get a pair of simultaneous equations which can be solved to more accurately estimate flow and TDH. I suspect this gets them accurate enough for government work.

 

[JamesW]

It would be helpful to have a software program that can determine the power, RPM, TDH and flow when given two of the variables.

I'm sure that they probably have it, but getting it might not be easy.

They have a new metric called WEF which is supposed to help identify the efficiency of pumps, but it is completely worthless.

Being able to calculate the power usage at a given GPM and TDH would be helpful to determine the efficiency of one pump vs. another.

 

[CRUSH-IT!]

yep

 

[Ck28]

Pump affinity laws allow for the motor to run these calculations in the background. The drive has the pump curve plot points, most likely runs a test at full speed, 3450 rpm, measuring consumed power allows the system to determine flow, which determines pressure. It most likely has lookup tables for every power/ speed relationship and adjusts accordingly based upon the settings. Flow and pressure are essentially the same once the initial pump curve is establish during factory testing. I cannot seem to find efficiency curves for these pumps, so it is difficult to determine best efficiency point of operation. For maximum operational and energy efficiency you would want your operating point, system head curve crossing pump curve (at whatever operating speed), to be as close to BEP as possible.

 

[Homebrewale]

Use a FlowVis flowmeter.