| Union classes are exactly what I figured with you. I noticed you said the same thing I said in my original two posts on the issue, but surrounded with stuff that does not really apply to low head sequence pumps. So I guess if I was 'way off base' you must have been too....
My history is I grew up in Local 602, completed RSES in less than a year with 100% on all exams and went to GMU for EE. My grandfather was a Navy vet who fought on the USS New Orleans throughout all of the Pacific battles from Pearl to the peace ceremonies in China. He was a firecontrolman. My father and family worked in mechanical and controls contracts with Energy Management, who develops the equipment, automation and controls systems before it gets to the Navy ships. My father's company Cold Craft just finished a refrigeration refit in the White House he is very proud to have worked on. He is considered one the best mechanical and refrigeration experts in the world. We helped design Energy Management systems and integrate them into all types of applitcations, to give real world feedback prior to use on Naval ships and critical applications.
I worked as a troubleshooter for newly installed developmental systems in government and industrial settings and have worked on pumps and compressors larger than houses, several stories high, that have doors on them to go inside and work. I brought my younger brother into that industry and he now runs his own controls solutions company that integrates controls systems and equipment and handles high security databases and systems. We have worked to help develop Dunham Busch vane and centrifugal compressors, he was a DC area supervisor for Johnson Controls, and we did commercial and industrial refrigeration for decades. He works on projects for the Navy Yard, Homeland Security Dep Headquarters, NASA Research Center etc. They do alot of integration of Seimens, Johnson's Metasys, and other sytems and controllers, and get the HVAC and mechanical to work right while maintaining complete security on applications where it does not work when newly installed, it is already connected to the grid and the phone lines, and the engineers cannot figure out why and all their union trained techs 'fix' it, but it still doesn't work.
Most of what you wrote applies to some pumps in some circumstances, but not a sequence designed for low head. It is already in it's sweet spot with the outlet tube as are most pond pumps. They are not designed nearly the same as low noise sub pumps, which have far more durable bearings and less flexible impellers etc. Low noise and efficiency do not work together. Slippage will make the motor run quieter, but will also create fluctuations and cavitation that results in loading and unloading the motor rapidly and repeatedly. A large hp sub motor is designed to endure that like nothing. A fractional pond pump isn't, it will shorten it's life dramatically.
So for pond pump purposes what I said was 100% correct. For sub pumps what you said was half correct and half misapplied confusion from what appears to be an inerchange of terms and poor explanations from teachers resulting in crossing issues and terminology confusion. For instance, impeller efficiency and overall pump efficiency are related, but not the same thing. Locating noise causing issues and resolving them are not necessarily Energy Management or efficiency issues, but mission critical and application issues. If you get an impeller slipping 100% it still draws power. The curves you two spoke of do not always cross at the most efficient point, but most often do. Each pump(wet end) is different, and a sequence prefers low head and low restrictions. Other pumps are different. That is why you can find a 1/8 hp pump that moves 4500 gph and a 1/2 hp pump that moves 600 gph at much higher head tolerances. | 
06-16-2006
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