Wire awg for long run

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CaptainCowie

New User
Marcus
I need to run a 20 amp 120 volt single phase circuit that is 200ft long. What awg of copper wire is needed for this? Also, how deep does direct burial cable need to be buried? Thanks!
 

Chipper

New User
Steve
12 AWG is the minimum for 20A circuit to meet NEC but there will be a 13V drop at full load and a 10v drop at 15A load. 10Ga. will give you a 6v drop at 15A and a 8v drop at full load.
 

CaptainCowie

New User
Marcus
At what point is the voltage drop going to become a concern? I know with home theater equipment I wouldn't do the install if it was less then 117 volts under load. What is the "accepted" drop for general household use?

Also, how deep does it need to be buried in the ground? Thanks for the fast reply!
 

JackLeg

New User
Reggie
Just to be safe, I'd run 10 ga. Bigger is better when the run is longer!
The ditch need only be 6-12" deep unless you're going to be plowing over it. m2cw
 

Glennbear

Moderator
Glenn
I always go beyond code for fear of the errant garden shovel etc but the NEC does allow UF to be at 12" if it GFCI protected and 20 amp protected circuit. This exemption only applies to residential work, As far as voltage drop is concerned, the norm is no more than 2% before you might have problems.
 

CaptainCowie

New User
Marcus
I think I will go with 10agw. I don't think they will be plowing over the line but this is going to be installed at a dog kennel and who know what they might be doing out there later. So I think I I will go about 12-18'' deep depending on how tough thats going to be with a ditch witch. Thanks for all the help guys!
 

woodnick

New User
Nick
When you bury it put white sand on top of it about 6" under the surface that way your know to stop digging when you hit the sand.
 

DaveO

New User
DaveO
When you bury it put white sand on top of it about 6" under the surface that way your know to stop digging when you hit the sand.

Nick that's a geat tip :icon_thum Another good idea is to take some accurate measurements from at least two points so you can triangulate the location of the wire run later, when a landscaper or someone else wanting to dig in your yard asks you to locate any private wire runs. Ideally if you can run the wire in a straight line from two known points i.e the point where it comes out of the house to the corner of the kennel, you should be able to locate the wire later with ease.

Dave(hates digging up wires in clients yards, that they thought were over there):)
 

CaptainCowie

New User
Marcus
Thanks for the tips guys! I was going to draw a scale map out lining where the wire is in relationship to the house. I think I will use that white sand idea too!
 

Gofor

Mark
Corporate Member
Realize there is also an ampacity loss due to heat buildup caused by direct burial. If using type UF (underground "romex" type) 12 AWG will be minimum for code, but 10 will be better to guard against melted insulation and voltage drop. Minimum depth per code (2005 NEC table 300.5) is 12" for residential 120v or less if it is a 20 amp breaker. If it has a larger breaker it is 18" minimum.
The burial depth is less if in rigid or intermediate metal conduit.

Go
 

scsmith42

New User
Scott Smith
Marcus, since you will be exceeding the maximum recommended 2% voltage drop at full load, what will you be running off of this circuit?

In some instances, a step-up transformer on the supply end can correct the voltage drop issue.

Scott
 

CaptainCowie

New User
Marcus
I was told that they will only be using lights so I don't think that the drop will be that bad. If they tell me other wise how much do the transformers tend to cost?
 

woodydiver

New User
curt
hello,
if they are only running lights and not close to full load you should be fine. since you only need a litte boost you could use a buck-boost transformer, but they arent cheap, probably run 200-300 dollars. (10 guage wire would probable be cheaper). with only a 15 volt drop light bulbs will last longer any way. my two cents
curt
 
M

McRabbet

Marcus -- I re-read all of the posts and it is not clear what the outdoor line is serving. IMHO, if it is going to an out building, then it is always a sure bet that more demands for electrical power will materialize in the future. In that case, I'd recommend an even heavier feed wire (like 6AWG) to a 50 Amp panel (230V single phase feed). If it is for outdoor lighting (maybe some of the poles would have weatherproofed receptacles for an electric string trimmer), then I'd run 10 AWG.
 

JimmyC

New User
Jimmy
Marcus,

If you're going to run 10awg, you might think about running 10/3 +ground instead of 10/2 + ground. You can then run and extra outlet/breaker for future usage, the extra cost is negligible .

Just my .02

Jimmy:)
 

Steve W

New User
Steve
Just from my experience:
All of the folks recommending the larger wire are on the money if you're going to use the circuit for anything near its capacity.

The autotransformers (variously known as Variacs or Powerstats -- which are trademarked names) do indeed cost that much new from a supplier. You can find used stuff on fleabay or at just about any ham radio flea market. You can find a 20A unit for under 50 bucks if you look around. If going that route, make sure that you get one that's rated for single phase, 120V, 60 Hz. Avoid ones made for three-phase, 277/413V or 50Hz.

If you're only every going to use this for lighting and the occasional use of a shop vac, I wouldn't worry much about voltage drop.

When I wired my shop, I ran 6/3 out there with a 60A breaker at the main panel in the house. The electrician and the building inspector both wanted to see that UF wire 2 feet down. This is really a good idea anyway, since it virtually eliminates any chance of anyone ever accidentally hitting the wiring. Part of my run was only 12" down and we put that in galvanized conduit. I don't have to worry about hitting wires when planting hostas. :jiggy:
 
J

jeff...

why wouldn't you want to bury the wire in that funky gray plastic pipe? That's what I was told to do by a local electrician whenever burying wire.
 

Gotcha6

Dennis
Corporate Member
That funky gray plastic pipe & the wire to pull in it is more costly. Also at issue here if there are any EEs listening, is the equipotential plane issue. This requires bonding the metal surfaces of the confinement area to the grounding conductor in order to negate stray voltage in livestock containments. If you're keeping dogs as big as Great Danes you might want to think about it anyways.
 
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