# What gauge wire for long run



## EndTuition

I'm going to run 110v to the pier from the 200 Amp supply. It's about a 300 ft run. If I want 15 amps at the end, what size wire do I need to run ? Also thinking about running conduit (PVC) instead of UF. 

If there is a table somewhere online, I can look it up. Just don't know what to search for ?


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## RB II

google "wire ampacity" or just check out the link below

http://www.armstrongssupply.com/wire_chart.htm


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## sleepersilverado

What are you going to be running out there?

A voltage drop calculator shows #6 to have 15 amps at the end of the run allowing a 3.31%voltage drop.


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## EndTuition

Will be running LED pier and underwater lights. Want 15 Amps at 110 V.

Found a chart that said 10 AWG would go 550 feet, 12 would go 300.

Sound right ?


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## bassguitarman

EndTuition said:


> Will be running LED pier and underwater lights. Want 15 Amps at 110 V.
> 
> Found a chart that said 10 AWG would go 550 feet, 12 would go 300.
> 
> Sound right ?


I think your voltage drop will be too high. Try this calculator:

http://www.nooutage.com/vdrop.htm


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## sleepersilverado

I don't know the proper way to explain it where you will understand. Here is a list based on 5% or less voltage drop with 15 amps at the END of the circuit. 
#12 =115'
#10 =190'
#8 =289'
#6 =452'

Problem is you are comparing a branch circuit to a feeder. When it comes to distance voltage is your friend. Your only option is 120V so you must adapt with wire size.


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## carryyourbooks

here is the calculator i use.

http://www.southwire.com/support/voltage-drop-calculator.htm

based on 120v (more likely, this is your source voltage) @ 300 feet, needing 15 amps, you will need a #4 copper. btw, don't run uf. conduit is the only way to go.


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## sleepersilverado

carryyourbooks said:


> here is the calculator i use.
> 
> http://www.southwire.com/support/voltage-drop-calculator.htm
> 
> based on 120v (more likely, this is your source voltage) @ 300 feet, needing 15 amps, you will need a #4 copper. btw, don't run uf. conduit is the only way to go.


Carry you must have put it in as a 3% drop, I got #4 when I did it that way also.

I downloaded the southwire apps on my phone so I can use it in the field.


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## EndTuition

Thanks !


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## rew4

I'll go with carry on this one #4 will be a little more than you need (right now) but is is cheaper in the long run.


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## EndTuition

See attached...


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## LaddH

From the Southwire calculator

1 conductors per phase utilizing a #10 Copper conductor will limit the voltage drop to 7.87% or less when supplying 15.0 amps for 300 feet on a 120 volt system. 
For Engineering Information Only:
 30.0 Amps Rated ampacity of selected conductor 
 1.1417 Ohms Resistance (Ohms per 1000 feet) 
 0.05 Ohms Reactance (Ohms per 1000 feet) 
 12.0 volts maximum allowable voltage drop at 10% 
9.444. Actual voltage drop loss at 7.87% for the circuit 
 0.9 Power Factor

Go with # 10 , you can live with the 8% voltage drop since it is a lighting load.(check the lighting specs)You will have 110 volts at the end of the run if you start out with 120 volts. #4 is 3 to 4 times as expensive as # 10 and the conduit will have to be larger adding more cost. 
I do not see how it will end up cheaper in the long run to install # 4 unless you are sure you will need more power. in the future.
# 4 would probably be nice but you would not being doing it yourself if you weren't concerned about cost.


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## LaddH

LaddH said:


> From the Southwire calculator
> 
> 1 conductors per phase utilizing a #10 Copper conductor will limit the voltage drop to 7.87% or less when supplying 15.0 amps for 300 feet on a 120 volt system.
> For Engineering Information Only:
> 30.0 Amps Rated ampacity of selected conductor
> 1.1417 Ohms Resistance (Ohms per 1000 feet)
> 0.05 Ohms Reactance (Ohms per 1000 feet)
> 12.0 volts maximum allowable voltage drop at 10%
> 9.444. Actual voltage drop loss at 7.87% for the circuit
> 0.9 Power Factor
> 
> Go with # 10 , you can live with the 8% voltage drop since it is a lighting load.(check the lighting specs)You will have 110 volts at the end of the run if you start out with 120 volts. #4 is 3 to 4 times as expensive as # 10 and the conduit will have to be larger adding more cost.
> I do not see how it will end up cheaper in the long run to install # 4 unless you are sure you will need more power. in the future.
> # 4 would probably be nice but you would not being doing it yourself if you weren't concerned about cost.


Another way to skin this cat would be to add an additional # 10 wire in the conduit , run a 240 volt double pole ckt down there , hit a subpanel on the dock and go from there to your loads. This would reduce your load per wire and thereby your voltage drop and allow some cushion if needed in the future. For the cost of one additional #10 wire and a cheap panel and a few breakers.
BTW a # 4 wire will not fit in a 20 amp breaker without some contortions.


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## MikeS2942

2 x Length x Constant x Amperage / Volts x 3%

So the formula works out like this

2x300 feet x 12.9 x 15-amps / 120-v x 3%

116100 / 3.6-volt = 32250 Circular Mils

Table 8 shows *#4 wire*

Will you actually need 15-amps is the true questions.


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## bassmaster2004

Wow anything from #10 to #4 wire. Well, my math shows to use #4 wire. Always, have a 75/25% safety factor.


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## 71 Fish

#4, your kidding. Underwater lights, if flourescent, you might want to confirm minimum voltage for that but unless for a constant motor load where voltage is important #4 is not necessary. What is your actual load? I would consider that plus a little maybe for the calculation. The extra wire / 240 volt comment is true but for 240 volt loads only, which I doubt is the case, but it does bring up a thought. You could transform 7.5 amps at 240v (with 2 hots and a ground by the way) to 15 amps at 110v at the load (as you have probably noticed, voltage drop increases with current draw). Since it is that far, I would run a 1" PVC with #10. If I had the extra cash, #8 at the most.


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## padrefigure

If you are using fluorescent lights, run them at 240V. If they come with residential ballasts, you will need to change to a commercial grade multivolt ballast (operates on any voltage from about 90V to about 300V). If you are running HID lights, get multi-tap ballasts (120/208/240/277) and run at 240V. This will cut your voltage drop in half. If others have not made this clear, stay away from motor loads with this long run. The voltage drop will probably burn the motor up. This means drills, fans, pumps, etc. If you want to run the lights at 240V and still need 120V for a radio, battery charger, etc. you will need to pull a fourth wire (2 hots, neutral, ground). The ground can be smaller, but the hots and neutral should be sized appropriately).


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## EndTuition

As stated in the first post. Fishing lights, 15 amps.Went with #6. 1000 watt spot llight, no problems. It's all good.


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## carryyourbooks

EndTuition said:


> As stated in the first post. Fishing lights, 15 amps.Went with #6. 1000 watt spot llight, no problems. It's all good.


what is your voltage at the fixture with fixture off? and then on?


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## EndTuition

carryyourbooks said:


> what is your voltage at the fixture with fixture off? and then on?


I have no idea. I'll check it when I put the wire in conduit in few weeks.


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