Here is a table of the theoretical HP consumption to
raise water x amount of distance y gallons per minute.
The height of the water column is indistinguishable from psi so
the two are plotted together at the top of the table.

This is theory only. The actual HP required depends on the
efficiency of the pump. A check on page 198 McMaster
Carr tells us a 3450 RPM 1/3 HP 110V 2.5 amp motor with a
nice looking centrifugal pump will pump 10 gpm at a 37 foot
head. From our chart that is .11 HP so centrifugal pumps are
about 33% efficient so triple these HP numbers
in the table. That is not to say the centrifugal
pump is this inefficient throughout out the RPM range of a
pump mounted on an engine. This is just a spot efficiency check.

The HP to drive the pump ultimately must come from the engine.
An alternator is about 80% efficient and an electric motor is also about
80% efficient and a centrifugal pump is about 33% efficient
so we are looking at .8 x .8 x .33 for an overall efficiency for
the electric pump of 21% while that of the direct drive
pump is about 33% efficient.  Sounds like an electric car.

I uploaded my program on here so all you engineers can check
my calculations.

It will be interesting if Bill hooks up an ammeter to that
one HP table saw motor of his.

Paul Lamar

Ops. Minor error. Here is the corrected text.

And yet another attempt at formatting the table so it comes
through the internet un scathed.

Paul Lamar

C M Smith wrote:

The theoretical water horse power is imperial gallons per minute times the head in
feet times the specific gravity all divided by 33 000. The HP to drive the pump is
water HP times 100 divided by percentage efficiency. One US gallon is 0.8327 Imp
gallons. Taking a point on the pump curve of 30 US gal and 10 psi, and a SG of 1,
indicates the water HP as about 0.15 and say at an efficiency of 33% this is a
pump motor of about 0.5 HP

C M please spot check my table and see if it is correct.

Paul Lamar

OK I think I have found the bug. My data now correlates with C M's.
I was converting feet to psi incorrectly.

I have also added some comma delimiters so it will load in most spread sheets
to get a nicely formatted table.

Paul Lamar

Ops. One more thing. The typical pump efficiency is lower at 27% and not 33%
One mistake leads to another. I should go back to bed :-)

Please check this efficiency number with actual pump results.
Some on page 198 & 199 of the McMaster Carr catalog #105
 
Paul Lamar
 
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