Axolotl writes:

Andrew Burgess wrote in
:


No. The wattage is a maximum value. Throttling the output, for
example, will reduce the power draw.

I do not think this is true. Two elements, pressure and volume, influence
the power consumption of any pump. If you look at Mark's Standard
Handbook for Mechanical Engineers 14-22 thru 14-25 you will find the
formula for centrifugal pump output.

I looked for something like this on the web and was unsuccessful.
(I only own EE books ;-)

Stripped of its more complicated
bits the formula shows that the power required, p = Q*H, where p = power,
Q=volume and H = head. Throttling reduces the volume output but increases
the internal pressure. Essentially throttling the pump has the same
effect within the pump of increasing the head.

I cannot think of a refutation for this, so maybe I'm misremembering
the 'minimum power consumed at no output' thing.

Unless you've oversimplified and the relationship isn't linear? Aren't
head-flow curves non-linear?

I'm going to email my friend with the power meter right now and borrow
his meter and do some measurements...