"Ed Anderson" <eanderson@carolina.rr.com> wrote
>
> Bill, is the second chart showing approx 0.175 HP required for 20 gph
flow?
> and given a 50% efficiency for an electric motor the actually HP required
by
> an electric motor around 0.35 HP?  If so that is still within the ball
park
> of the EWP.

------------
Ed,
The curve shows that the power incorporated into the water *at 20 gpm and
15psi* is only .175 HP, i.e. that much power has been used to raise the
pressure and flow rate. However, *pumps* are not 100% efficient, so I
arbitrarily showed the plot for a 50% pump efficiency. Unfortunately, I have
no way of telling the efficiency of the pump, could be 50%, or more-or-less.

This just shows that the actual work needed to move the water around the
system is not huge, but it doesn't say anything about the power absorbed by
a belt-driven pump that is throttled. Power delivered to the pump can be
converted to heat (wasted) or work (pumping water). Overspeeding the pump
ensures that you get more heat at high rpm's.

Bill