Thanks for the replies and advice. Not sure of the initial amp usage Bree but low with a DC charger, LED lights, occasional Christmas stuff, maybe a wifi camera. So I'm somewhere between 6 and 16 gauge...
Answers bring more questions:
What size conduit could ensure a 6 gauge wire pull later, given that I have to navigate that 90 bend?
Would it be acceptable to tie a 6g wire into 12 gauge wire on a short run from the breaker box?
And then what type of conduit is appropriate for a 6/2 wire run at (hopefully) a 18" depth?
Minimum, not taking into account voltage drop, would be #14 THHN Cu conductors, rated at 15A and to be installed on a 15A OCPD (fuses or breaker).
Taking into account the distance and either a 15A or 20A circuit (12A or 16A maximum for loads for any loads running continuously for 3 hours or more), over a distance of 170ft (150ft run + ~10ft into panel + ~10ft into gate enclosure), a #8 line & neutral conductor would provide 2.07% voltage drop @ 12A and 2.76% @ 16A. This would provide the proper conductor sizing for either a 15A or 20A circuit, based upon the 3% allowable voltage drop on branch circuits per NEC 210.19(A).
Given the size of conductors, I would highly suggest using a 20A breaker, as it will likely be difficult to locate a 15A breaker that has a proper lug for a #8 wire. You will have to research the lug size of breakers available specifically for your panel.
Based on a 120V circuit, with a #8 THHN Cu line conductor, a #8 THHN Cu neutral conductor and a #12 THHN Cu grounding conductor, your conduit fill for 3/4" schedule 40 PVC conduit would be 23.25%, which is within the 31% / 40% limits of NEC 300.17.
I would highly recommend, given the size of conductors, to upsize your conduit to 1" schedule 40 PVC conduit for where buried and schedule 80 PVC or rigid, where subject to damage, if applicable.
Per NEC table 300.5, you will have to have a minimum of 18" of cover to the top of the conduit where buried, provided it is not under a concrete / asphalt roadway, concrete pad, encased in concrete, under a sidewalk, etc. With the 18" cover requirement, unless required otherwise by the authority having jurisdiction (AHJ), I would suggest you dig your trench no less than 20".
As you backfill your conduit, I would also recommend installing burial tape at 6" below finished grade in the trench so that the conduit will be less likely to be hit if future excavation occurs.
When routing your conduit, I would recommend the straightest shot between your panel and gate electrical enclosure and try to avoid 90s in the middle of the pull whenever possible.
It is also important to remember that you can have no more than 360 degrees of bend (standard offsets, 45 deg bends, 90 deg bends, etc.) in a conduit between pull points
If there is a spot where you see a strong / standard 90 as unavoidable mid run, I would highly recommend utilizing a ground box to 90 the conduits into so you can have easier access to the pull point.
Once the conduit is in place, as dcg9381 suggested, use a pull string, attached to a plastic bag (grocery bag, animal waste bag, etc.) and use a vacuum to **** the pull string through the entire conduit, then attach your conductors and start pulling.
You can also get a 200~250ft steel fishape (leader highly recommended) to pull in your conductors.
If you use a light weight pull string (survey string, etc.), you will likely want to pull in a larger poly rope to the pull string to ensure your pull line does not break when pulling in or cut through 90s.
When pulling conductors, I always urge people to spend a couple of extra dollars and get a roll of 3M Super33+ electrical tape to make up your wire head, as it is much stronger and has a stronger bond than traditional electrical tapes and is less likely for you to loose a conductor over the pull distance, resulting in you potentially having to pull out all of the conductors and having to start over.
Just my two cents.
