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Re: Slowing down a Quite One pump

Adam wrote:

Someone gave me a Quiet One pump and boy is it quiet!  It's rated at
something like 1100GPH and I figure it' pushing close to 7-800 in my
filterless tank, which is only a 75.  Can anyone tell me if I can just put a
dimmer switch in its line to slow it down?  Will this reduce power
You CAN NOT slow down a pump using a dimmer switch. Running an AC motor on low voltage will cause it to overheat. Running AC motors on low voltage is one of the worst things that can be done to them.

To reduce the flow of the pump you need to install an adjustable valve of some sort in the OUTPUT of the pump. I like to use gate valves here since they allow an easy fine-tuning type of adjustment, but ball valves will also work well. The pump will use less power as you reduce the flow through it, and you can find out by how much by looking at a chart of the "pump curve" that plots head vs flow and power consumption. Your valve will in effect increase the head (back pressure) seen by the pump as you close the valve, which will move you along the pump curve decreasing flow. Note that shutting the flow off completely like this is not a good idea since the pump depends on some flow to cool the bearings, and in the case of direct-drive pumps the motor windings as well.

You can also get the old "Green Plug" units from Electronics Goldmine that can further reduce the electrical usage of the pump. They work best on lightly-loaded motors, so a pump with reduced flow will see a benefit. Chances are that with a small pump like a Quiet One the electrical savings with the green plug won't be enough to justify the cost of the green plug, even one purchased at surplus prices. Saving a few watts might save $1 a year and probably isn't worth the trouble, and the green plugs had a habit of failing in certain not-too-uncommon situations that was one of their downfalls.


***************************** Waveform Technology UNIX Systems Administrator