Running well pump off sub-panel


Old 08-05-10, 02:58 PM
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Running well pump off sub-panel


I'm new to this forum and don't really know much about electricity. I'm going to get an electrician to wire in a sub-panel and connect the wire for me however, I'm not sure what type of wire to run for what I need.

I am running about 3000ft of wire from an old farm house to the well pump, the pump is in the basement of a pump house which I would like to feed with enough power for:

- 3/4hp 120v jet pump for a 60ft well
- one electrical outlet for 150w lightbulb to heat the basement in winter
- one light socket with a 100w bulb

I am going to do the cost comparison with direct burial wire vs. regular wire with conduit but I was wondering what type of wire to use... any suggestions? I think I only need 1 phase but with it coming out of a sub panel I'm really not too sure

Old 08-05-10, 03:17 PM
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do you need to run 3 thousand feet or 3 hundred feet?
Old 08-05-10, 03:22 PM
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It is really not practical to run residential level voltage 3000'; a couple hundred is really the practical limit unless you're willing to spend a fortune on the wire. Longer distance requires a thicker and therefore more expensive wire. Just a quick calculation would put the wire size at #4/0 aluminum for a single 20A circuit which works out to about $5/ft just for the wire.

Another option would be to buy some used transformers from an electrical surplus supplier and run 480V out there. You would still need #2 aluminum wire which will be about $1.50/ft.

The best option is to have your power company install a primary and drop a service to this building.
Old 08-05-10, 04:03 PM
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With that long of a run, you will have to run 3 conductor for 240v, and you will have to seriously oversize the conductors to overcome voltage drop. The pump should be able to run on either 120 or 240v (most pump motors can). You will need to use MINIMUM of 2ga aluminum wire (much more cost effective than copper over that distance), assuming you will never draw more than the 5 amps the pump will require at 240v, to keep the voltage drop under 3%. Anything smaller will increase the voltage drop way beyond acceptable levels, and you will cause damage to the motor and/or burn the feeder cable.

That said, your most cost effective solution would probably be type UD (Underground Distribution) triplex cable. It's 3 underground rated conductors twisted together, very similar to the overhead drop to a house from the telephone pole. But even still, you're looking at over $4,000 just for the wire. Then there is the cost of trenching 2/3 of a mile. Depending on how deep the aquifer is, it might actually be cheaper to drill a new well closer to the house. I don't know.

How was the pump originally supplied? Is there a utility pole within closer proximity to the pump house? If so, look into running new service from there.
Old 08-05-10, 05:31 PM
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With that long of a run, you will have to run 3 conductor for 240v,
Matt your the pro but he has said he wants a light and some other things so unless he runs the pump on 120 he is going to need quadplex and running the pump on 120 ups the amperage and perhaps the wire size.

If he can't get a PoCo drop maybe a generator at the pump house and an elevated storage tank at the house. Storage tank high enough to provide pressure without an additional pump and large enough to provide two or three days water. Just run the generator to fill the storage tank.

But hopfully he meant 300 feet or can get a drop from the PoCo.

Last edited by ray2047; 08-05-10 at 06:42 PM.
Old 08-05-10, 06:01 PM
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You're absolutely right. I was thinking he could install a subpanel and sink a pair of ground rods at the pumphouse, but I forgot about the water pipe back to the house. That's a non conducting metallic path, therefore an isolated ground wire would be required as well..

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