Running a well pump with a generator

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Old 12-01-13, 10:24 PM
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Running a well pump with a generator

I need to figure out whether our generator will run our well pump. The generator is a Honda EX4500S. At 240 volts, it's rated at 16.7 amps. It's rated output is 4.0 kVA with maximum output 4.5 kVA.

The pump is a Flint and Walling 1.5 HP and the specs list these amperages:

Yellow wire: 11.5 amps
Black wire: 11 amps
Red wire: 1.3 amps
The locked rotor amps in the specs are 52 amps

However, the results of a test with a clamp on amp meter were:
*
Yellow wire: 10 amps on startup surge/8.75 amps running
Black wire: 10 amps on startup surge/8.5 amps running
Red wire: 2 or 3 amps on startup surge/1 amp running
*
Based on the measured amps on startup surge of 10 times 240 volts = 2400 watts, it would seem that the generator would be large enough. Is that right? At first I thought the generator would need to handle 52 amps (the locked rotor amps), but from what I've read, locked rotor amps are the max amps if the rotor is literally locked/won't move. The actual surge in a normal startup would be much less.

Does it make sense that the measured startup surge amps are so much lower than the locked rotor amps and is it safe to use the measured number? Do you think this generator will run the pump?
 
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Old 12-01-13, 10:30 PM
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Welcome to the forums.

The Honda generators are pretty good at starting motor loads. You should be ok.
It would probably be a good idea to try it now before relying on the generator in a blackout.
 
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Old 12-02-13, 12:52 AM
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Generator for well pump

As mentioned your generator appears to be large enough for the load you have listed. With respect to the starting amps, a well-pump does not move much water until it reaches about half speed and unless your well is quite deep your start-up will most likely be lower than locked rotor. The only other consideration with respect to a generators capacity would be elevation. If you live at a high elevation you should check you generator specification for adjustment.
 
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Old 12-02-13, 08:02 PM
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Thanks for the help. The pump actually is quite deep - 700 feet - but we're near sea level. Is there any danger of damaging the pump if we try to start it with less amps than it needs for startup?
 
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Old 12-02-13, 08:13 PM
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If the voltage drops too low the amps drawn will go up putting a greater strain on the genset.
 
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Old 12-03-13, 09:48 PM
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Thanks. Do you think there would be any danger to the pump in trying to start it without enough generator power for the surge? I saw this:

-> Always start the generator before the motor is started and always stop the motor before the generator is shut down. The motor thrust bearing may be damaged if the generator is allowed to coast down with the motor running. This same condition occurs when the generator is allowed to run out of fuel.

It's a different situation than not having enough power to start the pump, but made me wonder if the pump could possibly be damaged.
 
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Old 12-03-13, 10:50 PM
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Well pump on generator

A submersible pump usually needs to get to half speed in two seconds to provide proper lubrication for the bearings. A generator needs to be up to speed prior to applying load. If you are only using a generator to operate the well pump and you are not manually operating the well, you need to set up your controls to allow for the time-delays needed.
 
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Old 12-04-13, 08:40 AM
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A generator should always be started and let run for a few minutes before connecting any load.
The load should be disconnected prior to shutting down the generator.

Sometimes you run out of gas..... usually it's not a catastrophe.
 
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