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Wattage Used When Restricting Pump Flow

H

HerbieK

NJRC Honorary Member
NJRC Member
At the July meeting, there was a discussion involving what happens to wattage used when restricting pump flow.

I hooked my Kill-A-Watt up to my chiller pump (Gen-X), which has a ball valve on the outflow side.

When I turned down the flow (closed the ball valve slightly), the wattage used decreased as I had expected.

This seems to be counter intuitive in that you would think the pump has to work harder to force the water through a restricted outlet.

The common knowledge that I have run across is that I would experience the lowering of wattage effect, which is what I saw.

I started out with the pump drawing 75 watts (the pump is rated at 110W). When I restricted the flow, it ran down to 65 watts.

I guess when pump wattage is rated, the pumps have zero restriction. With the ball valve fully opened, the restriction on the pump was such that the wattage was way off of the rated wattage.

The bottom line is this:

You can't count on the rated wattage in the spec sheet (which is a good thing). It all depends on how the pump is plumbed up, and the only way to tell how much wattage is used is to whip out the old Kill-A-Watt.

Herb
 
S

stcreef

Those findings will only pertain to non-pressure rated centrifugal pumps.

Also if you remove any plumbing on the output and test the wattage, you'll probably see close to the rating. Any additional plumbing is a restriction. Hence slowing the flow. Allowing the pump to work less, because its not creating pressure.
 
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