Emergency generator for well pump

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  #1  
Old 01-23-07, 07:04 PM
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Emergency generator for well pump

I would like to buy an emergency generator with the capacity to run our well pump just to fill the pressure tank a couple of times a day. For this short pump run I would shut down all other electrical devices. It's a 3/4 hp submerged pump that runs on a 240V circuit. What are the minimum generator specs I would need?
 
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  #2  
Old 01-23-07, 07:14 PM
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I think I might try your question in the electrical forum. They may need to know how many amps the pump draws.
 
  #3  
Old 01-23-07, 08:27 PM
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Post moved to our electrical forum where our experts can set you straight.
 
  #4  
Old 01-23-07, 09:04 PM
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HI GREG.

donrmurray:
I think your standard 5KW would be fine. Personaly I would go no less.

Your pump only runs as needed.So you can plan it.
At this wattage you can have other items available, and draw back when needed.
 
  #5  
Old 01-24-07, 03:45 AM
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5000 watt is plenty to run the well, a furnace, refrigerator, some lights, small tv, and even make coffee.. I have a 4400 watt gen. and do all that with no problems at all..
 
  #6  
Old 01-24-07, 05:00 AM
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Well pumps have a a very high start up current. I have heard horror stories (and some are posted on this site) from people who spent lots of money on a generator and could not run their well. I do not think that 5000 watts is enough to run yours.
 
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Old 01-24-07, 01:24 PM
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Capacitor start pump motor?
 
  #8  
Old 01-24-07, 03:36 PM
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running wattage is likely between800 and 1300 W..however start up may be much higher...most gen. allow (like a breaker) for a short burst of draw (like a dead short for an instant) if you have doubts..why not rent the gen you are thinking of buying and try it on start up a few times to see how it handles it
 
  #9  
Old 01-24-07, 08:25 PM
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5kw- works fine with mine. Even with the lights on. It stalled once. I need a tune up. The electronics scare me,thats all.
 
  #10  
Old 01-25-07, 07:05 AM
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I have a 5500W (I think like 6500 surge) and I leave the well pump circuit turned off on the transfer switch. When we need to fill the pressure tank, I turn off all the other circuits and turn that one on by itself. My gen is just barely enough to run the well like that.
 
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Old 01-25-07, 07:19 AM
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What do you have, a 10 hp well pump? If it drags down a 5500 watt gen, there must be a problem.. I have a submersible well pump, and 4400 watt gen, and it never drags down.. Even with a TV, lights, and a coffee pot on..
 
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Old 01-25-07, 07:43 AM
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Well pumps have a a very high start up current. I have heard horror stories (and some are posted on this site) from people who spent lots of money on a generator and could not run their well.

Generally speaking, a portable generator is not enough for most well pumps.
 
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Old 01-25-07, 08:26 AM
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I saw your previous post racraft.. No need to repeat it..
I'm just saying my 4400 watts runs the entire house without dragging down..
I have a 5" well, and the pump never has a problem starting..
 
  #14  
Old 01-26-07, 09:12 AM
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This issue is critically dependant upon the characteristics of the well pump and the generator.

Different pumps and motors will have different starting current requirements. You can even get electronically controlled well pumps with variable speed drives that don't require any more current to start than their normal full load current. Some pumps will require 6x or more their normal full load current during the brief instant when they are first starting up.

Generators will similarly have different capabilities for dealing with sudden current demands. Remember that the generator itself is a spinning flywheel, and can thus supply much more than its rated power output for a brief time. But if you ask too much of the generator, it will stall the engine that is spinning it.

You are going to need to find out the specific details of your system in order to make an informed decision.

-Jon
 
  #15  
Old 01-26-07, 11:08 AM
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I'm trying to contact the guy that drilled our well to get more info on the motor. All I remember is that it's a 3/4 hp motor which was considered adequate for a residence well of that depth (208').
 
  #16  
Old 01-26-07, 11:14 AM
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I'm with billie_boy, I suggest that you borrow or rent the generator you plan to buy (or one very similar) and see if it works.

When I lived in Massachusetts, a 5000 watt generator would not work on my well pump. I don;t know the motor size, but I had a 280 foot deep well.
 
  #17  
Old 01-26-07, 06:07 PM
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donrmurray,

If your submersible is single phase you will have a relay/capacitor box located either in the house or at the well head.
The information on the motor should be there, if not the relay box might be able to be matched up to a particular pump motor.
On one maker's line of submersible pumps I checked the current draw of a few of the 3/4 hp models.
A 3/4 hp pump at 220 volts and depending on the gpm would draw between 5.4 and 8.0 amps which should work well with a 5 kw generator.

My story is that a 5 kw Coleman can operate my 3/4 hp 115 volt 10.8 amp septic pump.

You can see by the different experiences people have that trying a rental might be a good idea.
How you will go about changing your wiring to allow the gen to be connected to the pump will be another concern.
 
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Old 01-26-07, 07:14 PM
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Mine, 3/4 HP-220V-12 GPM- 150' + 50' to the house.
Exacts, I don't know (I was at work when they put the new one in).

My 5KW works fine, with fridge and lights. I still worry about the electronics with the fluctuation in voltage. But a rental is a good idea.
 
  #19  
Old 01-27-07, 08:43 AM
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FYI. The pump breaker is a 20A 240V setup. Does this indicate that the B&S 5550 generator that produces 30A at 240 would work fine? I understand that breakers can handle startup surges at higher amps, but the generator is supposed to do that also.
 
  #20  
Old 01-27-07, 11:18 AM
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You should be fine.
 
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