Generator Size - Well Pump

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VA123

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Hello, I need some assistance with proper portable generator sizing for my well pump. I am having a generator interlock installed with a 50 amp plug and my main concern is being able to power my well pump when I lose power. The pump is a Franklin 3/4hp two wire pump, model number 2445079004. The booklet that came with the pump seems to indicate I'll need at least 4,500 starting watts. I reached out to Franklin to confirm, and they provided the attached, which seems to indicate I'll need at least 9,400 starting watts? I have zero experience with generators, and I do not want to buy more generator than I need so I am hoping that anyone with experience on this front can either confirm that 9,400 starting watts is needed for this two wire pump setup or, if that sounds excessive, what size do you think would work?
 

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Fitter30

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Starting any motor is different from running amps. Starting is lock rotor amps/ watts starting from dead stop. Generators are rated at peak watts and running. I'm very rural have a 1/2 hp pump generator 7500 peak 6500 run. Also run a electric hot water heater, fridge,some lights, well pump ,ceiling fan, tv/ wifi and 5k window unit. Not at the same time. Heat lp decorative stove. Generator runs off lp so it puts out less watts. Window ac if we lose power can have a cool bedroom. Have a 500 gallon lp tank holds 80% 400 gallons. Been without power for two weeks in winter and were comfortable.
 

Reach4

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The Franklin AIM manual table 5 says that 4.5 KW is sufficient. It does not get into surge Watts or VA. It also says

Generators must be sized to deliver at least 65% of the rated voltage during starting to
ensure adequate starting torque.
 

VA123

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Okay thank you for the feedback. So what size generator would you all recommend I get to be able to run this thing?
 

Drick

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I have a 6500W running / 7500w peak generator and a 3/4 hp well pump. It can start the pump by itself no problem. It can also start the pump with the fridge, gas furnace, and some lighting already on as well, although its a close call and the light dimming on pump startup is very noticeable. If you want to be able to start and run the pump along with some lighting and other low amp draw loads I'd recommend not going below what I have. If all you care about is the pump I would say don't go below 5,500W just so you aren't bumping up against the generator's max rated output.
 

VA123

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I have a 6500W running / 7500w peak generator and a 3/4 hp well pump. It can start the pump by itself no problem. It can also start the pump with the fridge, gas furnace, and some lighting already on as well, although its a close call and the light dimming on pump startup is very noticeable. If you want to be able to start and run the pump along with some lighting and other low amp draw loads I'd recommend not going below what I have. If all you care about is the pump I would say don't go below 5,500W just so you aren't bumping up against the generator's max rated output.
Thank you for that info - do you have a 2 wire pump or do you have a 3 wire with the control box above ground somewhere? The starting requirements on the 2 wire pumps are supposedly much greater than the 3 wire.
 

VA123

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For anyone else wondering about generator sizing for their Franklin 2-wire well pump, I hope this helps: I spoke to Franklin tech support, and they advised the figures in the AIM are absolute bare minimum and the figures in the Franklin Aid document (attached to my first post) are what they recommend. Tech support stated the 2 wire pumps require quite a bit more power to start and do not like lower power scenarios. So, for my 3/4 hp two wire setup, they recommend a 9,400-watt generator, not as a bare minimum, but as a power level where there is no chance of running into issues.
 
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