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watts for hp

09/30/2007 6:53 AM

I need to power a 1 HP electric pump with 120 volts. Will a 1000 watt generator do this?

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#1

Re: watts for hp

09/30/2007 7:25 AM

No one will give a strait answer on kw to hp conversion

mainly because there are too many variables .

the fact is 1 kw =1000 watts = 1.25 hp max

But it depends if the motor is under load at starting time

I start a 125 hp motor with a 100kw gen I step start the motor app.65 hp at a time with minimal load , there after I start and run a 50 hp and run them in unison so it's all about starting load .

If you can start that pump and then get pumping it will work if its going to pump as soon as it starts who knows ? Maybe go to a 2000 watt to be sure or if you already have it give it a shot the worst that will happen is it won't start the motor or pop the breaker

I have seen people actually use a pony motor to assist starting to reduce load and even hand push the belt to initiate start obviously unscientific and dangerous but it works with what is available .

Remember it's all about the variables molasses or water will pump at different rates ,hot or cold I hope this sheds some light .

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#2

Re: watts for hp

09/30/2007 3:53 PM

In theory yes. I see 3 problems, however. First, almost all low power generators have a very low duty cycle. Second, the start current on the motor could easily exceed the 8.3A your generator provides. Third, if you try to start with a locked rotor, the magic smoke will escape from your generator. I personally would use perhaps a 1800W generator with a darn fast fuse/breaker for intermittent duty and 4000 W for anything over 50% duty cycle.

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#3

Re: watts for hp

10/01/2007 6:18 AM

It depends how close the pump is to its 1hp-rated duty point.

  • If it's a centrifugal pump and doing very little work despite its 1hp rating, then, almost certainly.
  • If it's operating close to its maximum duty point then the question must look at how fast it is being run up to speed. It's possible the generator will survive the drop in volts while it accelerates.

Field trials?

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#4

Re: watts for hp

10/01/2007 9:35 AM

Given that the maximum hp available from a 1 KW generator is 1.25 hp and the starting load for the pump could exceed that, a trial of the pump in an unloaded condition would be desirable. Can you run the pump on a 110 AC line and use an ammeter to test it's starting load and define the actual power requirements, then spec out the generator accordingly?

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#5

Re: watts for hp

10/01/2007 1:53 PM

motors used on centrifugal pumps are commonly referred to as a variable torque application, due to the fact that the motor does not feel the load right at start up. As the motor RPM builds the pump begins to move the water thus increasing the load on the motor. now some centrifugal pump such as self priming will run at a fairly steady current draw as the water pressure builds due to the fact that some of the water is being recirculated within the pump. However a pump that is not self priming known simply as centrifugal will feel a dramatic increase in current draw as the pressure builds to a point where the pump can no longer move the water at which point the current draw will fall to a near no load current.

Motors used on Positive displacement pumps, most commonly used in hydraulic application are considered NON variable torque applications require full load right at start up.

in either case most single phase 110 volt pump motors are equipped with a starting capacitor which helps to lower the starting current.

Long story short I would say yes you can use the 1 KW generator for your pump.

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#6

Re: watts for hp

10/01/2007 2:56 PM

helloo

our friend have a 1 kw generator and 1 hp pump can we help him to operate the pump we do not knew exactly and i think he do not knew if the pump will ork in full load or not ,

as u see all wanted to tell u theioriticaly yes but in fact no coz the atarting current and if the motor will be full load or not but i have avery simple soultion

u can use a A CLOSED manual valve in the internal of the pump and starting the motor till it take it is max RPM ten begain to OPEN the manual valve little by little till it is maximum then u will discover if u will use the valve every time u open the pump or the load realy not high soo 1000 watt is enough (tamorak@yahoo.com)

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#7

Re: watts for hp

10/01/2007 4:45 PM

Thanks to everyone for all of the good input. Yes I need to do some trials. The work continues.

Rustyh2o

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agua_doc (1); dthomas16 (1); PWSlack (1); rustyh2o (1); tamorak (1); traditional (1); TVP45 (1)

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