Magnetic pump question-restricting output and electrical consumption?

acroholic · Aug 6, 2009

Guys,
Lets say I have an Eheim 1262 submersible pump. Full throttle this pump uses 80 watts of electricity. I ball valve down the output to 60% or so. Is the pump still using 80 watts of electricity, or does watts used go down as you decrease the output?
Dave

acroholic · Aug 6, 2009

dawgdude;378217 wrote: From my understanding when you place backpressure on a pump you actually increase the amount of energy it pulls because of the resistance. There was a mag18 on one tank I saw that was turned down half way. The pump was HOT to the touch underwater and prior to that they couldnt figure out why their tank temp was rising with the lights and heater off. I would pick up a kill-a-watt and see for yourself though.

If this is the case, then that makes a heck of an argument to correctly size your pump to the task at hand.

I hooked up my new chiller, and I have been playing with flow rates thru it trying to decide if the manufacturer recommended rates are too fast or not. A slower rate increases dwell time and could cool the water down more, but a slower flow rate might not keep up with the volume of the system, etc.

I like to make things hard on myself!

acroholic · Aug 6, 2009

ares;378220 wrote: Ive read on external pump instructions that restricting output is reccomended(if needed) and that it reduces load and electric consumption.

baffles my mind how that works, but its what the instructions say, this was from, I think little giant.

I expect that submersible pumps would work the same.

Hehehe! Two knowledgable people (Brian and Charlie) saying the exact opposite. At least you two have an answer. More than I can say!
Dave

rockdog · Aug 6, 2009

By turning it down you are making the pump work harder. The extra force needed to push the water through a smaller opening will cause it to draw more power and increase heat. You could try it with a watt meter to verify... would be a fun test.

Jason

grouper therapy · Aug 6, 2009

Strictly depends on the pump. Some pumps operate at a lesser wattage draw when restricted on the output but there are limitations on that.The dolphin ampmaster series pumps can operate efficiently at 50% restriction. Some pumps(I think most) when restricted also reduce rpm's. If they did not then they would have a tendacy to overheat because they are at that point tring to force the same amount of water through a smaller opening. It takes less amps to tyrn the motot at lower rpm's. I hope this makes sense.

grouper therapy · Aug 6, 2009

Wish I had spell checked that one.

oldschool52 · Aug 6, 2009

I have always read that restricting the output on pumps is ok but not intake. This makes sense since restricting the out put has less water going through the housing with the impeller still turning full RPMs. Less water more friction more friction more heat - burn up pump. Now restricting output you still have max water in housing but impeller still turning max RPMs should cause pump to heat up abnormally. I know some say that when restricting they turn less RPMs but I do not know of any with sensing devices that would actually do this. You're talking more money and electronics and most of the pumps I've seen, especially Mag type pumps are simple elctro magnets. So theroretically if you try to restrict a pump it is working harder to do it's job and shold increase the power it uses. It would be interesting to actually measure this to be sure. I'm not a pump expert but a retired electrical engineer. Hope this makes some sense.

skriz · Aug 6, 2009

Easy answer. Bring it by the shop and let's test it with the kill-a-watt!

Fwiw, I know the Reeflo pumps will consume less energy when you restrict the intake (yes, intake). Not sure about the output.

jmaneyapanda · Aug 6, 2009

MAGNETIC drive impeelars will use less energy on restricted outputs. Direct drives will use more.

jmaneyapanda · Aug 6, 2009

They get hot. WHen throttling down the mag drives, you are causing the magnets to resist, and this will form heat. But, they get hot either way, that is a side effect of submersibles.

grouper therapy · Aug 6, 2009

jmaneyapanda;378330 wrote: MAGNETIC drive impeelars will use less energy on restricted outputs. Direct drives will use more.

incorrect

grouper therapy · Aug 6, 2009

Skriz;378313 wrote: Easy answer. Bring it by the shop and let's test it with the kill-a-watt!

Fwiw, I know the Reeflo pumps will consume less energy when you restrict the intake (yes, intake). Not sure about the output.

I tkink you also have to reduce the output as well

grouper therapy · Aug 6, 2009

oldschool52;378293 wrote: I have always read that restricting the output on pumps is ok but not intake. This makes sense since restricting the out put has less water going through the housing with the impeller still turning full RPMs. Less water more friction more friction more heat - burn up pump. Now restricting output you still have max water in housing but impeller still turning max RPMs should cause pump to heat up abnormally. I know some say that when restricting they turn less RPMs but I do not know of any with sensing devices that would actually do this. You're talking more money and electronics and most of the pumps I've seen, especially Mag type pumps are simple elctro magnets. So theroretically if you try to restrict a pump it is working harder to do it's job and shold increase the power it uses. It would be interesting to actually measure this to be sure. I'm not a pump expert but a retired electrical engineer. Hope this makes some sense.

I'll see if I can find my rpm gauge it will not work on a mag drive but i can show how it works on a direct drive since i have the dry end shaft to place it on.

grouper therapy · Aug 6, 2009

Q: My Dolphin Pump is too powerful for my system. Is there a way to decrease the amount of flow without harming the pump?
A: Ball valves should be installed right after the pump intake and discharge unions for easy pump removal, and for discharge control. Discharge flow may be valved back to any flow without pump damage. The more flow is lowered, the less amps the pump will draw.
Got this off their website. I installed 6 of their pumps and tested each with a multimeter and they are correct. Less amps same volts=less watts

grouper therapy · Aug 6, 2009

We hope you will find the following suggestions and comments regarding pump installation to be
helpful. We do not claim that any of these suggestions are the only way to accomplish your job,
but in general they will solve many of the commonly found problems and help you prevent many
others.
Please note that ReeFlo pumps are external pumps. Do not submerge!

1. 
Locate the pump as close to the source as possible. It is best to have your main (longest)
run of pipe on the discharge side of the pump. The pump is designed to push water, not pull it.
2. 

Always have your inlet pipe diameter equal to, or larger than, the discharge line. This helps
prevent cavitation.
3. 

Never run a pump dry. This may damage the mechanical seal and impeller. They are
designed to pump fluid, not air. Insure the pump is full of water before you turn it on, and that
it doesn’t out pump the supply.
4. 

If your pump is producing too much flow, you can reduce the flow by partially closing a
valve on the discharge line. Never restrict the inlet!!! Surprisingly, this will make the motor work
less and use less electricity!! This “valving back” simply causes the pump to operate further back
on its performance curve.
5. 

If your pump is not producing enough flow. The easiest step is to widen the line especially on
the intake. As illustrated on the chart the narrowness of the line has great bearing on “friction
loss”....think bar straw vs. regular straw.
6. 

If more flow is required than a single pump can produce, consider using two or more
pumps in parallel. This will double the flow. If more pressure is required consider using two
pumps in series (one feeding into the other). This will have the effect of doubling the pressure.
We have found that using two pumps instead of one larger pump uses an average of 30% less

From the reeflo website

grouper therapy · Aug 6, 2009

Acroholic;378214 wrote: Guys,
Lets say I have an Eheim 1262 submersible pump. Full throttle this pump uses 80 watts of electricity. I ball valve down the output to 60% or so. Is the pump still using 80 watts of electricity, or does watts used go down as you decrease the output?
Dave

To answer your ? Dave I am going to test some mag drives this weekend.

jeff_mcphail · Aug 6, 2009

Akopley;378353 wrote: My tank is 81 degrees at night...it has to either be the mag pump or my skimmer pump...I am leaning towards the mag since it is throttled back.

I would just put a tee and valve in the line just past the output of your pump.Then open the valve(plumbed back to your sump or in my case to my UV) to slow the flow to your display and recirculate it back to your sump. This should stop most of the restriction on your pump and allow some of the output water to be re-skimmed as well. :thumbs:

acroholic · Aug 6, 2009

grouper therapy;378386 wrote: To answer your ? Dave I am going to test some mag drives this weekend.

Sounds great. I got an offer to borrow a kill a watt, so I'll report back as well.
Dave

jmaneyapanda · Aug 6, 2009

grouper therapy;378367 wrote: incorrect

Care to elaborate? This what an engineer at Danner/Supreme told me.

grouper therapy · Aug 6, 2009

jmaneyapanda;378404 wrote: Care to elaborate? This what an engineer at Danner/Supreme told me.

Like I said not sure about the mag drive using more or less and I 'm sure if I were an engineer at Danner I would have said the same. That being said I personally challenged both dolphin and sequence (reeflo) that their pumps pull less amps at less outlet flow. I tested with two different multimeters one very nice one and one cheap one and both showed drops in amps being used as restriction on outlet side was increased.

Magnetic pump question-restricting output and electrical consumption?

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