Underground wiring, UF alone or in pvc pipe?

[Glacial_Speed]

Wife is making noises about wanting a lamp post down by the patio.

I'm thinking 15 amp or 20 amp circuit, and it has to go underground for about 110 feet. Only lawn, no other obstructions, driveways or anything like that.

According to the code (300.5) I can just use UF cable 12 inches deep, but is that the best practice for longevity. Would putting it in PVC pipe make it last any longer? I don't want to do this more than once.

Also, is there anything besides a small trencher to put the cable in the ground that a homeowner could use?

Thanks

 

[^&right]

Mine was buried in PVC, roughly the same run as yours. Doesn't cost much and piece of mind.

 

[nh_yota]

Running UF in PVC is an exercise in futility. Longevity-wise the best solution is PVC with THWN individual conductors because you can re-pull conductors in the future if needed without digging it up.

However if it's just going to be a post light then I'd just bury some UF and be done with it.

 

[CNGsaves]

Go MUCH Deeper than just 12" . . . . i'd say 24" minimum so you won't be tearing into it later when sprinkler system might be installed.

Any kind of continuous plastic roll pipe for conduit would be better than burying wire bare in the ground. PVC electrical conduit would be best, depending on what you have handy.

Make yourself a scale drawing on grid paper so you KNOW where that line is buried for future use. Keep copy by electrical panel.

Probably good idea to also bury Red caution tape in trench after some backfill.

GJ Sparky's will give you details like GFCI circuit, wire size, wire type, etc.

 

[nh_yota]

Up here it's not uncommon to run UF through black irrigation pipe for protection because it's easier to pull through than sectional gray PVC. Is it code? Probably not, but it gets the job done.

 

[Murphy4570]

I'd put it in schedule 10 stainless myself. Overkill and expensive? Yeah. Will you damage anything if you hit it with a shovel when digging years later? Nope. I'm not an electrician though. Bounce your question off of a certified sparky or two.

Also, 20 amps is pretty overkill for a few lights, isn't it? How many and what amperage lights are we talking about?

 

[Norcal]

At 12" burial depth a GFCI is required and only in residential. Forget UF and use PVC it is cheap insurance.

 

[cat06]

you can use a vibrating plow to install either the uf or the pvc. it cuts a slit in the ground and drags the wire or pvc along as it moves, no trench or backfilling

 

[383 240z]

I didn't run my UF feed to the shop in PVC. Big mistake. The theory I'm working with is due to freeze/thaw cycles a nick was made in the insulation from moving rocks. I was working last Sunday all was good had solid 240v. Then it rained and I lost one leg of the feed. I'm guessing the nick in the insulation, leaked the voltage to ground. So I only have 110v on half the breakers in the shop

Now I have to dig it all up, I'm running copper in PVC this time!

 

[Glacial_Speed]

At 12" burial depth a GFCI is required and only in residential. Forget UF and use PVC it is cheap insurance.

Yeah, it's residential. The GFCI is going onto an outlet and the lamp will be downstream at the other end. I thought GFCI breakers were like $80 but I see they're actually about half that cost. Hmmmmm. Still, a 20 amp GFCI outlet is only about $15~$20.

Insurance? From rocks? Or something else? Won't the PVC fill with water from condensation and when it rains?

Thanks for the info 383 240z, it convinces me that pipe is the way to go.

Would you use stranded THWN/THHN inside the pvc or the UF? I'm likely going to use 12 gauge and 3 conductor plus ground so I can make it turn on/off from either end. So it's either a $120 roll of UF (250' with lots left over) or a 500' roll (4 pieces 125' each...) of THWN ($45) plus conduit ($30). Looks like THHN is the better choice for cost.

Do I have to follow any wire jacket color code or can I just tape the ends red/black/white/green for identification? (not than anyone is going to ever see this besides me).

Many discussions I've read say to leave a pull in case you ever need to run more wire. What do most people use? Nylon cord or will that rot inside the pipe?

I'm going 20 amp because I'm also putting an outlet at the end (wife wants a little fountain for the bird bath too.....a puddle pump) and I imagine at some point there will be a high amp device put on the end (leaf blower? electric chain saw? Weed Eater? hair dryer? who knows).

CNGsaves, no sprinkler system for me, And not a chance in hell I'm going deeper than 12 inches if I don't have to, it's rocky here, not sand, 24" deep is a major PITA. Even at 12 inches deep I'm sure I'll run into at least a half dozen rocks over 6 inches in diameter.

cat06, that vibratory plow looks like what I want, I'll look for one to rent and see how much, or even IF I can find one....I don't know if there's too much rocky soil around here, they might not even rent them . Thanks for the suggestion. I might just say screw it, forget the hassle of a rental (mainly getting the machine to and from the rental place) and buy a mattock. If I trench it by hand that lets me not worry about rental time how long it will take hitting rocks or roots.

 

[Norcal]

Yeah, it's residential. The GFCI is going onto an outlet and the lamp will be downstream at the other end. I thought GFCI breakers were like $80 but I see they're actually about half that cost. Hmmmmm. Still, a 20 amp GFCI outlet is only about $15~$20.

Insurance? From rocks? Or something else? Won't the PVC fill with water from condensation and when it rains?

Thanks for the info 383 240z, it convinces me that pipe is the way to go.

Would you use stranded THWN/THHN inside the pvc or the UF? I'm likely going to use 12 gauge and 3 conductor plus ground so I can make it turn on/off from either end. So it's either a $120 roll of UF (250' with lots left over) or a 500' roll (4 pieces 125' each...) of THWN ($45) plus conduit ($30). Looks like THHN is the better choice for cost.

Do I have to follow any wire jacket color code or can I just tape the ends red/black/white/green for identification? (not than anyone is going to ever see this besides me).

Many discussions I've read say to leave a pull in case you ever need to run more wire. What do most people use? Nylon cord or will that rot inside the pipe?

I'm going 20 amp because I'm also putting an outlet at the end (wife wants a little fountain for the bird bath too.....a puddle pump) and I imagine at some point there will be a high amp device put on the end (leaf blower? electric chain saw? Weed Eater? hair dryer? who knows).

CNGsaves, no sprinkler system for me, And not a chance in hell I'm going deeper than 12 inches if I don't have to, it's rocky here, not sand, 24" deep is a major PITA. Even at 12 inches deep I'm sure I'll run into at least a half dozen rocks over 6 inches in diameter.

cat06, that vibratory plow looks like what I want, I'll look for one to rent and see how much, or even IF I can find one....I don't know if there's too much rocky soil around here, they might not even rent them . Thanks for the suggestion. I might just say screw it, forget the hassle of a rental (mainly getting the machine to and from the rental place) and buy a mattock. If I trench it by hand that lets me not worry about rental time how long it will take hitting rocks or roots.

You must use the correct color wire, it is not permitted to re-identify a black or whatever color to either green or white, unless it is 4 AWG or larger. With such a shallow depth, it is going to be easier to hit the pipe or cable with a shovel or other tool, if in PVC, it can be repaired & new wire pulled in, with UF cable, it's either dig it up and replace or use a underground splice kit, I don't care for either option.