Does increasing pipe size increase power requirements? 5

[danp129]

In regards to pool pumps, I was told that if I increased the pipe size from 1.25" to 1.5", my 1hp pump would draw more power because of the increased rate of flow. They backed up that claim with "head curves" from pool pump manufactures showing an increase in HP required for low-head, high-flow. It was my general understanding that reducing pipe friction would reduce power requirements, not increase them. My thoughts are that the reason for higher power draw at the higher flow rate on the mfg. curve chart is because there is higher friction. However, if the flow rate increases just because I reduced resistance to flow why would it draw more power when the RPM stays the same?

I am sorry if this is appears to be too basic of a question but it seems to go against logic. If they are correct, could somebody help a non-hydraulic engineer understand this?

For a background of what I've been told but haven't been convinced by, you can read this thread:

http://www.troublefreepool.com/new-pump-too-big-t57734.html

Note the graph below DOES NOT represent my single-speed 3450 RPM 1HP pool pump but is something I have been referred to, to visualize the increase in power draw.

Thank in advance for the engineering lesson!

 

[Artisi]

We can get it to 100 replies especially if we keep introducing new data which has nothing to do with the original question which had one word answer - yes.

It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)

 

[DubMac]

I'll do my part.

 

[BigInch]

It's always there, trip or not. After a trip, or any action that initiates a transient response, speed change, F/PCV setting, the intersection point just becomes a whole lot more dynamic than you're used to looking at, until it reaches steady state again.

Independent events are seldomly independent.

 

[Artisi]

H/Q curves, pipe diameters, axial flow pumps and a vast array of information has been introduced but nothing about the drive motor with exception of an earlier comment by myself. " ....... the likely change of input current will probably be unmeasurable or so insignificant not even worth the effort to measure. "

Looking at Baldor motor data as a reference and to satisfy my own curiosity, a 1hp 1ph motor at 50% load has a current draw of 5.3 amps, 75% is 5.8amp and 100% is 6.5 amp.
So, back to the question, a change of pipe diameter will / should / could / maybe result in an increase of power input however, in the case of the OP, how much extra current are we talking about - maybe 0.2 or 0.3 amps, so was it worth raising the issue other than from an academic aspect, it also and makes you wonder who "they" are, -- "They backed up that claim .."


It is a capital mistake to theorise before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts. (Sherlock Holmes - A Scandal in Bohemia.)