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[Reef head]

Very good read.
I'm not saying laws of physics have changed, but in the 16 and 1700's electricity didn't apply and more over not even close with a s/w fish tank.
PD pumps aka timing pumps will be the ones to increase heat and is used with high viscosity product ie sludge because of its shearing capabilities.
Back On To Centrifugal Pumps And motors. If you are running that motor at 60 hertz, that is it. No more no less. It will not be consuming any more or any less electricity, it is a fixed rate do to it NOT being a direct drive ie magnet. If you are using a barracuda pump you will see a load on a motor and consume more power. The little in sump pumps are all mag drive and not direct drive. Does is cost more with more head pressure with a direct drive? Yes.
What you are saying is a snail walked in to my mp40, will this increase electricity? No. If I turn up the vfd to run it faster will it consume more electricity? Yes.

 

[AZDesertRat]

Adding head is not increasing the load, you are missing the point. Adding head reduces flow and reduces the work required of the pump and in turn lessens the power consumption.

Yes electricity was scarce in the 1600-1700 time periods but we are talking about centrifugal force and fluid dynamics which do not necessarily need electricity.

As said before, these theories are extremely easy to demonstrate with a Kill A Watt or similar meter, it really works that way and is that easy.

Read the Affinity Laws and Bernoullis Theory and it wil make sense after you wade through all of it, there is no arguing with science.


If we use this analogy comparing pressure, flow and pipe diameter to volts, amps and resistance it makes more sense:
http://au.answers.yahoo.com/question/index?qid=20091115034034AA1Dqbz

When you increase the size of the discharge piping you decrease the resistance so pick up additional flow which equates to higher wattage or amperage even though the voltage has remained the same. Decrease the piping or add head and the work or amperage/watt go down along with the flow.


This article goes into more detail:
http://www.engineeringtoolbox.com/pumps-discharge-regulation-d_310.html

[h=4]Bypassing Flow[/h]The discharge capacity can be regulated by leading a part of the discharge flow back to the suction side of the pump. Bypassing the flow is energy inefficient since the energy to the pump is not reduced.

The article does have a small pump curve at the bottom showing power consumptions via adding head, bypassing flow and using a VFD or variable speed pump. Of course the VFD is the most efficient but is relatively new to our hobby and just now coming down in price where it is affordable to the masses like the new DC powered pumps. VFDs have been in use in municipal and industrial pumping applications for decades but they were and are still pretty expenive for smaller scale applications. I sold electric motores, motor control centers, pumps and Toshiba, Danfoss, Eaton Cutler Hammer and other VFDs for two years before coming back to my engineering/operations and maintenance position so am quite knowledgable on the subject.