WhisperFLo Looking At RPMs

[Sluwp]

The issue at lower flow rates is usually caused by spring loaded valve such as those in check valves and heater bypass valves. The valve opening is determined by the water velocity and the lower the velocity, the smaller the valve opening which changes the plumbing curve (i.e. moves it to the left or lower flow rates). But for most of the RPM values, Curve-A is sufficient.

The other problem is flow meters tend to get more inaccurate at lower flow rates as well and Blue-Whites are the worst. They have an accuracy specification as a percentage of full scale. But I would prefer to use the flow rate reported by the pump display as I believe it is more accurate than the Blue-White but the WF doesn't report flow rates.

Interesting. If those check valves are common that still something we should consider before saying to everyone the lower the better. And what if you have 5ft of static head loss ? The impact on the flow rate at 3450rpm might be 10-20%, the impact at 1000rpm might be 100%, 0 flow, 0 efficiency. Those theoretical plumbing curves don't account for that.

Run the pump at several speeds including the lowest possible and then we can curve fit to a cubic and see where the y-intercept ends up. This will confirm that the pump is reporting true power or only motor power.

If it's not public knowledge that pentair displayed watts don't match I may start a new thread.

 

[mas985]

What if you have 5ft of static head loss ? The impact on the flow rate at 3450rpm might be 10-20%, the impact at 1000rpm might be 100%, 0 flow, 0 efficiency. I feel like those plumbing curves don't account for that.

Offset plumbing curves actually can account for that but most pools do not have 5' of static head. Also, that only applies when water is returned at a different elevation like for a waterfall. With a suction port at or below water level and the returns at or below water level, there is no static head.

Here is the Whisperflo head curves with various plumbing curves that are offset by 5' of static head as an example:

 

[Sluwp]

Interesting, thanks ! I may create a new thread to talk about my case.

If it's not public knowledge that pentair displayed watts don't match I may start a new thread.

I just saw a video about a superflo and his external power meter was actually recording slightly less than what the pump was showing (but was close). I'll double check my setup.