Questions about outside outlet

[Jim Koepke]

There are calculators for such things > https://www.calculator.net/voltage-drop-calculator.html

jtk

[Jim Becker]

The OP's use is not mentioned, but standard GFCI recepticals are rated at 15 amps..

There are also 20 amp rated GFCI outlets available for additional shekels...

[Thomas McCurnin]

Unless the receptacle if for light tools or lighting, both the cable size and the receptacle should match the breaker size, e.g., with a 20a breaker, assume a 20a load, and a 20a receptacle. Anything less, is inviting trouble. By the way, some power tools are particularly susceptible to voltage loss, like my 20a Hilti power shovel. It will overheat and just shut down if used with a 100' undersize extension cord. Electric welders have similar finicky problems.

[Cameron Wood]

Hilti's biggest (I believe) breaker, at 60 lbs, is rated at 15 amps. If you have trouble running it on a 100' #14 extension cord, OK,

but suggesting running #8 wire to a convenience outlet in the yard is ridiculous. I ran that recently for a 240v 40 amp hot tub.


(sorry, feeling grumpy tonight)

[Maurice Mcmurry]

When GFI's were a new requirement and cost $25 a builder in our town would only buy one and use it to protect all of the required outlets in the whole house. At that time a 250 foot roll of Romex was $12. What a thrifty guy! His approach passed inspections. It took me a while to learn how to troubleshoot those houses.

[Charlie Velasquez]

18”
Assuming thwn conductors?

Need to qualify my answer.
I was assuming you would follow the advice of the other members wrt running those conductors from pigtails from the line side of the gfci outlet.
If you run it from the load side of that outlet and your conductors are gfci protected all the way there you can use the 12” depth.

[Steve Demuth]

Hilti's biggest (I believe) breaker, at 60 lbs, is rated at 15 amps. If you have trouble running it on a 100' #14 extension cord, OK,

but suggesting running #8 wire to a convenience outlet in the yard is ridiculous. I ran that recently for a 240v 40 amp hot tub.


(sorry, feeling grumpy tonight)

I agree. I don't know where you'd even find a 15A receptacle that would accomodate #8 wire.

[Bill George]

I agree. I don't know where you'd even find a 15A receptacle that would accomodate #8 wire.

Plus if you did a Voltage Drop calculation you will find even drawing a full 20 amps on #12 AWG wire on 100 ft you will find little or no reason to go larger on the wire. Thats all I use #12 wire and 20 amp rated outlets. Plus unless they have changed the Code its a Minium of 18 inches on all buried wire.

Wire.JPGVoltage2.JPG

[Charlie Velasquez]

….. Plus unless they have changed the Code it’s a Minium of 18 inches on all buried wire.

Rigid = 6”
protected by 2” or more of concrete is less than 18”
gfci protected = 12”
IMG_1345.jpg

[Bill George]

But local Code can require deeper. Yes you are correct and when was that changed? Because if the depth was to avoid damage to the conductors it does not make sense?

[Scott Winners]

My one contribution here, in agreement with most, is to err on the side of caution. When a GFCI trips, there might be enough capacitance, enough current, stored in just the cable to make a mess of delicate things like fingertips.

I personally would use a GFCI doohickey at every junction. Planting posts and burying wire below the local frostline counts as "in a workmanlike manner" in my book. I did read where the OP was located when I started reading this thread, but I don't remember now on page 2.

With no outpatient followup like OP wound care or OP prescriptions, just showing up at your local ER with a minor to moderate electrical burn is going to be $5-10K before insurance coverage. Let this knowledge inform your materials purchases and trench depth.

Electrical infrastructure is one of those "buy once/ cry once" sorts of things, though outdoor electrical does add a level of sophistication. If you do good work now that meets current code it should be safe and fine after it has to be grandfathered in by your own grandchildren, as long as the current draw on our circuits doesn't change.

In the late 1990s I had no problem running 75 feet on buried 12AWG/20 amps/ 110-120 volts with GFCI at every connection. I don't know if that meets current NEC, but the outlets I did run are probably fine. Except for the above ground connections. Out in the weather you got to open your best possible jiffy boxes every couple years to look for oxidation, corrosion, and impending failure. And test them, twice annually. Every spring and every fall hit the 'test' button on your GFCIs to make sure they are still working. You may have an ice cold gin and tonic in one hand while you are pushing the test and reset buttons with the other hand, but everyone with outdoor circuits has some obligation to maintain them.

[Steve Demuth]

Planting posts and burying wire below the local frostline counts as "in a workmanlike manner" in my book. I did read where the OP was located when I started reading this thread, but I don't remember now on page 2.

Frost depth here in NE Iowa easily reaches 48" some years. To be safely below frost, as for a water line, e.g., you need to be at a minimum of 5'. No one to my knowledge buries electrical lines that deep - not the 14.4kv lines from the overhead grid to your transformer, not the service entry from the transformer to a building, and not for outdoor outlets or appliances.

I can't imagine where you are, anybody goes below frost either (and in many areas not far from you, you obviously can't, since the frost goes down dozens of feet).

[Scott Winners]

In my experience the trouble with outdoor circuits is freezing/frozen ground lifting the posts up out of the ground. The cable is going to be fine, but as your posts lift up winter after winter and year after year, perhaps a fraction of an inch each year, it will still add up over time.

For my mail box post I dug a I think a 36" hole, then 4" of gravel in the bottom before the post went in, then gravel judiciously tamped up beside the post within 2 inches or so of grade. Then I put in about two inches of Sakrete, sloped, high at the post and more or less at grade level at the outside perimeter. I can pretty much count on my neighborhood snow plow guy to snap the post at grade level before it gets frost heaved out of the ground.

For convenience outlets, sure. If you just want to hang some Christmas lights on the x-berry bushes at the far end of the back lawn, yes you can cut some corners. But if you want to run an underground cable to say a detached shop with its own 100 amp panel, don't screw around trying to save three dollars on dirt work. For hardwired items it is always cheaper to do it correctly the first time compared to doing it correctly the second time through.

[Bill Howatt]

Had linemen come to disconnect service while doing an upgrade. We are in very sandy soil - like the beach once below a few inches of topsoil. He said a problem they have with buried service lines are rocks, although rare here. The cable moves against the rock with the seasons and damages the insulation. No, the cables are buried nowhere near the frost depth. Because of the well-drained sand we don't have much trouble with frost heaves although people put foundation posts and the like down at least 4'.

[John Lifer]

Insure that you purchase a WATERPROOF GFCI if you put it outside in a box. There is a difference and I didn't in the past. Even a waterproof box will allow enough moisture to trip.