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Re: Slowing down a Quite One pump -- or - Free the Amps, Choke the water

Adam asked if he could put a dimmer switch on a Quiet One
pump to slow it down.

Generally, no, it might work for a while but it will ruin
the motor.

Actually, it depends on the kind of power control you use
but I wouldn't even try it.  Almost all of the dimmer will
cause the AC motor on the pump to burn out.  

Speed control of AC motors and pumps is more complicated
than than merely redcuing the voltage or restricting the
current with controllers designed for incandescent

Instead of finding a control designed for the motor, which
would be costly, use a throttle valve on the waterline
instead.  Centrifugal pumps can have their output
restricted by throttling down the flow with a valve, but
only on the output side of the centrifugal pump, never the
input side!

Throttling won't harm the pump.  It will cause a reduction
in dynamic head but an increase in static head and the net
result might be some energy savings, but probably not.  In
any event, it won't increase energy use.

Note: if you severly restrict the output, the impeller will
be mostly just spinning in the same water in the impeller
chamber and that can cause cavitation, which is noisy, bad
for the impeller, bearings, and motor -- but you're
unlikely to want to restrict the flow down to almost

If you restrict on the input side, cavitation is much
easier to cause at higher flow rates, so put the ball valve
only on the output side.

Btw, it's unclear whether Pentair, which acquired Lifegard
who makes the pump, is going to continue to manufacture the
Quiet One we've known and loved for several years.  It
appears a replacement line of pumps of various sizes, using
the same "Quiet One" name has been released -- none using
the rock solid German motor on the legacy Quiet One pump. 
The Pentair Aquatics web site is still under production. 
Pentair started as a defense manufacturer during the Viet
Nam war and afterwards, to fill in the financial gap caused
by peace acquired Delta and Port Cable tools, then later a
pool accessory company, and now Lifegard.  Strange
bedfellows but all with good motors.

Scott H.

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