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Goal Use one electrical cable to power lights and outlets through a conduit down a driveway where a light switch could turn power on/off to the lights, without turning power on/off to the outlets.

Details I have a driveway that is 350 feet with existing conduits between the 3 utility poles along it. I’d like to add a circuit for lights and a circuit for outlets to run between the poles.

I’ve done the calculations, and I’ll need an 8AUG wire to ensure the voltage drop off at the final outlet will be sufficient to power most things.

As we all know, electrical wiring is expensive, especially at that thick of a gauge. Initially I was thinking that I’d need 2x the amount of cable; 1 for the electrical and 1 for the lighting.

However, I was thinking that I could potentially use a 10/3 wire where the lights and light switch use the line from the traveler, and the outlets use the standard black line. That would allow me to turn the lights on and off with a switch, without turning off the outlets.

Questions

  1. would it work to use one cable for lights and electrical?
  2. is it safe to do it this way?
  3. anything else I should be considering for this project?

Update 1 Thank you all for the responses thus far. I want to clarify a few points based on the feedback.

The conduit is already in place, and runs from the house, under the driveway all the way to the first utility pole on the driveway. Then a separate conduit runs from utility pole 1 to utility pole 2. Then another from utility pole 2 to utility pole 3. All conduits are plastic and look to be 1/2 inch. All conduits are currently empty.

The utility poles along the driveway carry the power line and cable/telephone lines from the street.

I plan to use a new 15AMP circuit, but am open to suggestions otherwise.

For lighting, I’m planning on using standard outdoor LED lightning, nothing fancy. For outlets, I don’t plan to have anything using the outlets with any frequency, I just want power available down the driveway should I need to plug something in.

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    If you are running conduit, think WIRES in conduit, not CABLE. And if you think you need 8 AWG copper, you probably should use 2 or 4 or 6 AWG aluminum.
    – Ecnerwal
    Nov 26, 2023 at 17:11
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    What size and type/material are the conduits in question? What wires or cables, if any, are in them right now - what do those wires serve? What is the lighting load (watts or VA per fixture, number/location along the path of fixtures? What is the load of the thing you'll plug in at the end of the driveway that drives your load calculation for that? i.e. if this conduit has telephone or cable TV in it, you can't use it for 120/240 service.
    – Ecnerwal
    Nov 26, 2023 at 17:20
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    You start with how much power is needed at the end/along the length. That will tell what size wire you need. It sounds like you are thinking of only using 15 or 20 amp circuit.
    – crip659
    Nov 26, 2023 at 17:31
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    What do you want to use these outlets for? What are the utility poles for?
    – Huesmann
    Nov 26, 2023 at 17:33
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    existing conduits between the 3 utility poles along it ????? What is in that conduit now? What size is the conduit? Is it really yours or does it belong to the utility? Nov 26, 2023 at 21:10

2 Answers 2

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To address some of the question:

If you'll put street-light-style lights on the poles,

  • It's reasonable to feed them and the outlets together. You'll either need a third switched wire or you can use smart bulbs (if your wifi reaches far enough) or light-sensing switches at the poles. You can buy low wattage LED "stadium lights" for this purpose that draw so little current, your wire gauge calculations may improve.
  • For the farthest light, look into a utility-provided pole-mounted light. My utility will put one on their pole for a fixed monthly fee with no meter. If you can do that, and don't put an outlet at the far end, your problem becomes 230ft instead of 350ft.

If you use landscape lighting in the ground

  • Use 24V lighting. It's a lot easier to install and maintain, and it does need maintenance if it's near the driveway because it'll get damaged by vehicles frequently. Use LED lights that accept 12 to 24 volts, put a 15V transformer on each pole fed by your power feeder, and from the transformer use #12 cable and run it in shallow trenches (just slits) without conduit, outwards from the poles (not always away from the house).

For the outlets

Think carefully about the cost of running 300 feet of heavy wire, and whether the same money could be spent on battery- and gas- powered devices to replace whatever corded ones you plan to use along the driveway.

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    +1. But for the last part, definitely not gas - for a lot of reasons. But battery + solar could work very well. Nov 26, 2023 at 17:44
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    @manassehkatz-Moving2Codidact you're probably right about gas, but we don't know what OP needs to plug in. So for the answer I think the choice is theirs not mine.
    – jay613
    Nov 26, 2023 at 17:59
  • Thank you! Added complication in that the trees are very tall along my driveway so there’s not much sunlight. I’ve tried solar previously and it didn’t work. Regarding what I’d plug in, really it’s just to have power down there should I need to plug in Christmas lights or power a camera. No plans for anything heavy load.
    – Tim Dee
    Nov 26, 2023 at 21:26
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First, since you plan to do conduit, you'll be building the conduit empty and then pulling wires into it. You wouldn't use cable there; UF cable is very flat and requires an enormous conduit (e.g. 2" conduit for 6/3 UF, that's just bonkers). Since you are using individual wires, not only is that cheaper (price THWN wires), you get to size each wire to its task.

Note that due to an unfortunate coincidence, the ground needs to be the same size as the largest hot conductor.


If you're running separate hot wires for receptacles and lights, you will need to compute voltage drop independently for each. And it helps to compute voltage drop on the load that is actually on the wire, not what the circuit breaker says on the handle.

I expect you'll find something like #8 for the receptacles and #12 for the lights, unless you hate LEDs for some reason (and if you do, you better like copper).

They can share a neutral, and you'll need to compute voltage drop on the neutral for the combined load. Just ask the voltage drop calculator 3 times:

  • voltage drop on R (receptacle load) amps
  • voltage drop on L (lights) amps
  • voltage drop on R+L (both) amps

Remember 3.0000% is the wire salesman's suggestion, it's not written in stone. (though the wire salesman would certainly like you to think that it is). Power tools are built with an expectation that they'll be run on long extension cords, and voltage drop is much worse on those. Look at your tool nameplates and I bet they say stuff like 110V or 115V rated voltage. Now measure your actual supply. It's surely more than 120V.

"But how can the lights and receptacles be different sized wires?" Because you're laying conduit, you don't need to deal with choking a bulky cable down a conduit. Remember you must build the conduit empty, get it inspected if applicable, bury and tamp it, before pulling any wires in.

Now the price of THWN wire isn't terrible, but if the price becomes daunting, evaluate XHHW aluminum wire at 2 numerical sizes larger. Note that this requires tricky aluminum-rated splices. The ILSCO Mac Block connector might help, but you may find yourself in costly 3-port Polaris. That works against the favorable cost of the AL wire.

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    OP isn't talking about adding new conduit. Rather: existing conduits between the 3 utility poles along it. Which sounds a little odd. Nov 26, 2023 at 21:12
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    Thank you for those details, very helpful! In this case the conduits are already in place. I just need to pull the wires through.
    – Tim Dee
    Nov 26, 2023 at 21:27

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