To Water Well Journal: Response to Ed Butt's Second Article
In the response by Ed Butts to my last letter, January 2004 issue of WWJ, I
agree that Ed never states minimum required head is 200 feet. He does state that
the readers of this column are only concerned with water pumps, and his example
uses a pump capable of 200 feet of head. Only if our well "magically" changed
from 200 feet to 96 feet, could the speed be reduced from 3600 to 2500 RPM,
dropping the horse power from 7.5 HP to 2.5 HP. If our well stays at 200 feet, or
boosting over the mountain still requires 86 PSI, this pump could be slowed no
more than 300 RPM. The load would then only be reduced from 7.5 HP to 5.6 HP.
Using the Affinity Law without maintaining the TDH or lift required, is what
confuses people into thinking that a 7.5 HP pump can be slowed to a 2.5 HP load,
when it simply would no longer be able to even get water to the surface.
I would also like to mention that the problems with valves as described in part #1
of this series are, only associated with diaphragm type valves designed over 40
years ago. The problems with valves that were mentioned including speed control,
hunting, chatter, scouring, plugging, leakage, and motor cooling, are not present in
more recent non closing diaphragm valves. The fact that these valves can never
completely close is why there are no longer problems with speed control, hunting,
or chatter. The seat of these non closing valves is purposefully scoured to prevent
plugging and to allow enough leakage to adequately cool a submersible motor. By
the way, if a lock out feature is needed on a valve, simply cut off the adjustment
Using more modern non closing type valves, a good comparison could be made
between Control Valves and Variable Frequency Drives. A side by side comparison
should include power consumption, reaction times, pump vibration, motor cooling,
installation procedures, maintenance, life expectancy, and price. Joe Lanes article
from a previous month (Constant vs. Consistent Pressure) was set up as a side by
side comparison. Had Joe turned on a 5 GPM sprinkler or heat pump for 12 or 20
hours a day, his test would have been more true to real life.
I have also installed many thousands of pump systems using Valves, VFD's, and
enough tanks to fill a football stadium. I have had to learn many things the hard
way. Test results can be biased, and personal opinions may not be based on fact.
Companies or individuals can be commercially motivated to keep us from knowing
what really makes pumps last longer, how to use fewer and smaller tanks, or even
the best way to save energy. Installers should do their own side by side
comparisons by carefully experimenting with all the options, as they must
determine for themselves what is fact and what is hype.
Cycle Stop Valves Inc.