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I would like to run a 240V well pump directly from a generator. The well pump has 4 wires: red, black, yellow, green (ground). The generator has a 240V outlet with 4 wires: ground (green), neutral, and two hots (between which is 240V).

Can someone tell me which wire I connect to which?

Thanks!
 

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The well pump requires a starter. It's not built into the pump motor because they require maintenance more often than the motor does, so the starter goes in a box in the wellhouse. You would feed the starter from the generator - you cannot run the pump directly without the starter.
 

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Discussion Starter #3
Thanks mpoulton!

I guess there was a reason I couldn't find any information on how to do this by searching on-line. That was exactly what I needed to know -- thanks!
 

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You need to be careful about sizing the generator you want to use. Starting current for something like a well pump can be 8 or 9 times the running current, albeit only for a short time. Even if a generator would technically run the pump, it wouldn't be able to start it. My well is nearly 1,000 feet deep, so my pump is quite large. The generator I'd need would far exceed what I'd need for the rest of the house. I could buy a whole lot of bottled water for what it would cost.
 

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You need to be careful about sizing the generator you want to use. Starting current for something like a well pump can be 8 or 9 times the running current, albeit only for a short time. Even if a generator would technically run the pump, it wouldn't be able to start it. My well is nearly 1,000 feet deep, so my pump is quite large. The generator I'd need would far exceed what I'd need for the rest of the house. I could buy a whole lot of bottled water for what it would cost.
As sort of a generalization, you need roughly 3000 watts of generator to start 1HP of well pump. This assumes that the gen is up to operating temperature and no other loads.

If the elevation is more than 2000' or so, you'll need an even larger gen. The output of a non-turbo gas engine decreases 3.5% per 1000' elevation.

It's fairly important that the gen actually be able to start the pump, Franklin (the largest manufacturer of submersible pump motors) requires that the motor be at least half speed within 3 seconds of starting. The reason is that the bearings are water lubricated and less than half speed doesn't provide enough lubrication.

Most gens have enough inertia to get the pump started quickly enough, but if it bogs down for more than 3 seconds, shut it off right away, and don't try to restart it until you're sure it'll start right up.

Rob
 
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