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Old 02-10-2012, 06:19 PM   #1
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What Electric Motor For This Application?


I just got a little water pump intended to be driven by an electric drill, it says.

Pumps 1.8m3 per hour.

Would like to set up a little fountain with it. But don't fancy running my electric drill for 10 minutes non stop, never mind an hour or so.

Could someone please advise me on what kind of motor I should get for this kind of application?

Or would an electric drill really run the pump okay for an extended period?

I really know nothing about electric motors and their abilities or how you choose which one for which app.

If anyone could provide some basic guidelines for me it'd be good. Like I had to find another motor for my concrete mixer some time ago and I just didn't know where to start. Got one and its fine but I really don't even know, offhand, what I got and certainly don't know what makes it suitable for the job where another one wouldn't be.

All I know is: they burn out and I don't want to burn out my drills.

I do have, for instance, that old concrete mixer motor. It would get hot and fail that's why I changed it - but maybe it'd be okay for this application? I can match up the revs I guess, somehow.

But, see, I don't understand the first thing. Is it okay to run a motor like that without any appreciable load for an hour or so?

I've googled around and found plenty of hits but they're all about the theory of electromagnetism and construction of motors and whatnot.. nothing seems to clearly and succinctly set me straight on that fundamental question:

what motor for this application? what factors do I use to determine this?

regards,

ab
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Old 02-10-2012, 06:25 PM   #2
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What Electric Motor For This Application?


hp = [GPM x (Head in feet)]/(39.56 x efficiency in percent)

Grainger well pump/motor efficiencies seem to go between 20% and 70%, small being less efficient.
My pond pump has about 1% of the elec. energy into it actually going into raising the water so the "wires-to-water" eff. is 1%. I guess this means the No Load Amps is 99% of the Full Load Amps.

Put the formula in Excel because you will be doing a lot of tweaking with the numbers.

Last edited by Yoyizit; 02-10-2012 at 06:29 PM.
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Old 02-10-2012, 06:47 PM   #3
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What Electric Motor For This Application?


Have you looked at small fountain pumps? Run the tubing to the top of the waterfall, drop the pump in the pit and plug in.
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Old 02-10-2012, 07:26 PM   #4
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What Electric Motor For This Application?


Quote:
Originally Posted by Yoyizit View Post
hp = [GPM x (Head in feet)]/(39.56 x efficiency in percent)

Grainger well pump/motor efficiencies seem to go between 20% and 70%, small being less efficient.
My pond pump has about 1% of the elec. energy into it actually going into raising the water so the "wires-to-water" eff. is 1%. I guess this means the No Load Amps is 99% of the Full Load Amps.

Put the formula in Excel because you will be doing a lot of tweaking with the numbers.
Yoyizit .,

Reread the OP part and this is not a standard engish stuff this is UK due the wording so I know it is UK due few keyword give away.,

But for metric verison it should be simauir but just change the GPM and head in feet to metric then ya should smack right on the spot.

Merci,
Marc
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Old 02-10-2012, 07:34 PM   #5
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What Electric Motor For This Application?


Thanks guys. I'll find the answers googling 'fountain pumps'. I didn't know that's where they were hiding. I went googling for 'pumps' and 'electric motors' and stuff and didn't get anywhere.

Now I find a wealth of stuff under 'fountain pumps' such as http://www.fountainpumpandsupply.com..._table.htm#rio

I can find something to buy there and I can find the specs of the motors they use there to give me some clues. And I can just bloody well try, too, can't I?

Thanks for setting me on the right road.

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Old 02-10-2012, 07:43 PM   #6
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What Electric Motor For This Application?


And the Rio 1400 at 3' comes in at 10% efficient. Time to replace my pump.
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Old 02-10-2012, 07:52 PM   #7
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What Electric Motor For This Application?


Those tiny pumps you hook up to a drill are less then useless. Toss it in the trash and buy a fountain pump. Northern Tool has some cheap ones.
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Old 02-10-2012, 08:15 PM   #8
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What Electric Motor For This Application?


They look like good products to me but the Australian distributors are ripping us off I suspect.... jacking the price up...

And some don't seem to be here. That Rio 2100 at 25W and an 8ft head for 692 gallons/hour seems perfect to me but I can't find it in Aus. and any competitors don't seem to be able to match the capacity/price.

I'll keep looking...

And I'll try what I've got... Though the big old motor is obviously overkill, I'd say... and before I even try it I expect the electric drill will overheat and collapse with an hour of this work...


But why?

The electric drill is rated 450W. Rio's motor is rated 25W.... The electric drill should find it almost a no load situation, shouldn't it?

I'm in Australia, guys. Speaka da English but use da Metric... but have atavistic memories of Imperial....

edit:

Just saw your post, Joe. Less than useless? Well I better start using it straight away and find out what you mean... Instead of keeping it on hand and having it crap out on me when I want it... thanks for the tip...

Thanks for the formula Yoyizit. If I've got it right and I have say 10% efficiency and the pump does 1800 litres/hr and I want, say, a 6ft head then:

1800 litres/hr = 30 litres/minute = 7.925gal/min

So: 7.925 x 6/ 39.56 x 10

= 0.12 hp.

= 89.48Watts

And that's the power of the motor I require?

So my electric drill at 450W is nearly 5 x more than required.

That's how it works?

Good to know. If I've got it right.

And you're saying there's some motors (or motor/pump combines?) only make 1% efficiency? Ker-ripes...

Last edited by abrogard; 02-10-2012 at 10:24 PM.
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Old 02-11-2012, 09:29 AM   #9
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What Electric Motor For This Application?


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Originally Posted by abrogard View Post
They look like good products to me but the Australian distributors are ripping us off I suspect.... jacking the price up...

And some don't seem to be here. That Rio 2100 at 25W and an 8ft head for 692 gallons/hour seems perfect to me but I can't find it in Aus. and any competitors don't seem to be able to match the capacity/price.

I'll keep looking...

And I'll try what I've got... Though the big old motor is obviously overkill, I'd say... and before I even try it I expect the electric drill will overheat and collapse with an hour of this work...


But why?

The electric drill is rated 450W. Rio's motor is rated 25W.... The electric drill should find it almost a no load situation, shouldn't it?

I'm in Australia, guys. Speaka da English but use da Metric... but have atavistic memories of Imperial....

edit:

Just saw your post, Joe. Less than useless? Well I better start using it straight away and find out what you mean... Instead of keeping it on hand and having it crap out on me when I want it... thanks for the tip...

Thanks for the formula Yoyizit. If I've got it right and I have say 10% efficiency and the pump does 1800 litres/hr and I want, say, a 6ft head then:

1800 litres/hr = 30 litres/minute = 7.925gal/min

So: 7.925 x 6/ 39.56 x 10

= 0.12 hp.

= 89.48Watts

And that's the power of the motor I require?

So my electric drill at 450W is nearly 5 x more than required.

That's how it works?

Good to know. If I've got it right.

And you're saying there's some motors (or motor/pump combines?) only make 1% efficiency? Ker-ripes...
Actually, in the cold light of morning, I realize I have made a mistake. Sorry.

The pump hp formula is correct but the watts into a motor need to be multiplied by the motor efficiency to get the hp out of the motor. Small motors are very inefficient.
So for 90 W into a 50% eff. motor you'd get 45W out which is 45/746 = 0.06 hp.

If you only have the volts and amps into a motor you also need to know the power factor in order to get the watts and this is also pretty low for a small motor.

I doubt the drill motor is designed for continuous operation so it may fail soon.

Last edited by Yoyizit; 02-11-2012 at 09:32 AM.
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