We live in a rural area and I am running a circuit to to our gate for a couple of post lights and maybe a receptacle. The run is 485 feet from the closest panel. I am installing THHN wire in a 1" diameter PVC conduit. Due to the low amperage draw of the lights (<5 amps) I can calculated I can get by with #6 THHN. I will install a 15 amp breaker on this dedicated circuit. My question is can I get by with a #8 ground or should I run a #6 THHN ground as well?
Electrical – What size equipment grounding conductor is needed for this gate lights circuit
electricalgrounding-and-bonding
Related Solutions
One trench the whole way will be easier to pull cable through. You could make it direct, one straight line, or closer to it than otherwise.
Fences can get blown over, run into, replaced for service, or removed for aesthetic reasons, which will become more of a pain to deal with if you run conduit along the fence. Also its less pleasurable to look at conduit than to not.
Your municipality or county should be able to tell you your local minimum depth for buried cable. It depends on your jurisdiction if you're asking about code as I assume.
I would recommend oversizing the conduit significantly to make pulling easier and allow for easy upgrades in the future. 2" can't be that much more than 1". It will be more durable and it could save a lot of work later on.
You can save costs on grounding by using bare wire, or using metal conduit as your grounding conductor. But I would not bury metal conduit to avoid dealing with corrosion. Even a bare ground conductor inside a plastic conduit is going to fare worse than a sheathed over time.
Paint a white line where you plan to excavate and call your utility locating service out to mark obstacles. The white line or shape will keep them from needing to mark unnecessary things in far off parts of your yard.
Rent a trencher and make the work easy on yourself.
Bury conduit larger than you need, because excavation sucks.
Dig depth is often 2foot minimum for nonmetallic, 6 inch minimum for metallic, but ask your codes department what they will approve.
For wire gaguge, use a calculator like http://wiresizecalculator.net/.
By my estimate you would want 6awg, but maybe the direct patch can cut down distance and let you use smaller.
That conduit body is not large enough to contain a splice. You'll have to either run two grounds, or find a different place to splice.
References:
- National Electrical Code 2017 314.16(C)(2); Allows splices, taps, and devices in conduit bodies, but only if the volume is stamped on it and it's large enough.
- National Electrical Code 2017 314.16(B); Says that the CB would have to be at least 11.25 cu.in. to have a splice. (4 pass through conductors + grounds = 5 fill units. 5 * 2.25 = 11.25).
At least that's how I interpret the code.
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Best Answer
Where the grounding conductors are increased in size (from the minimum) the grounding conductor also needs to be increased in size proportionately per 2014 NEC 250.122. I used the southwire voltage drop calculator. The calculated value needed for a 5 amp draw is #8 copper for 5 amp load at this distance 2.8% voltage drop. The problem with down sizing the conductor in this case would come if the lighting was changed at a later date using more of the available ampacity of the circuit then the conductor would be under sized. 120V @ 12 amps would require a #4 conductor and the #8 would be two small to limit the voltage drop for a short circuit.