What's the depth for UF wire to an outside lamp post?

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  #1  
Old 05-12-11, 04:39 PM
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What's the depth for UF wire to an outside lamp post?

I have undertaken a project where I am moving a lamp post about 15 feet closer to the sidewalk into a new bed. Tonight, I decided to dig around the existing lamp post to see the connection, how it was fed, etc.

I assumed, based upon the conduit coming out of the house and into the ground, that the previous owner who did a lot of the electrical work in this house had ran conduit all the way to the lamp post.

Lo and behold as I tore up the sod, there was a UF wire running into the lamp post. It was only about an inch or two below the sod. So I went back to the house and dug around the conduit coming out of the house and again, the wire came out of the conduit a few inches below the ground surface.

Now, maybe I am wrong, but I thought non-conduit wire such as UF (rated for sunlight exposure mind you as this wire is) still needed to be buried a minimum of 24 inches below the grass level.

I think this guy took a shortcut and just ran the line from the house to the post and threw grass over top.

I now have a major problem on my hands. I already applied for a permit. I could eitehr just cover up the wire like before and pretend I know nothing about the problem. That's a non starter with me. I need to fix the problem. But that entails me digging a freaking trench which I hate doing! LOL.
 
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  #2  
Old 05-12-11, 05:13 PM
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If you use a GFCI breaker the depth can be as shallow as 1 foot.
 
  #3  
Old 05-12-11, 06:50 PM
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If put it in Rigid steel pipe you can 6" down but that might be a little overkill. I agree with ray, GFCI it.
 
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Old 05-12-11, 06:56 PM
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You can even rent a trenching machine to dig the trench.
 
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Old 05-13-11, 09:42 AM
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To summarize:

24" plain cable w/o GFCI
18" in plastic/PVC conduit w/o GFCI
12" cable or conduit with GFCI
6" threaded steel conduit with or without GFCI
 
  #6  
Old 05-13-11, 01:36 PM
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Well the new added issue is that fact that there is a large tree also in the front yard. The trench would cut around 7-10 feet from the tree. So using a trencher I could possibly damage or kill the tree. Now I know why the previous owner took a short cut and buried the cable just below the surface. The tree is located at the corner of the house where the power comes out so no matter which direction I try to take the trench, it's going to cut across roots.

I might just keep the old lamp post and give up! LOL.
 
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Old 05-13-11, 05:19 PM
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Slicing through a few roots 7-10' away will not kill a tree. It just might be tough to run a trencher through.
 
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Old 05-13-11, 05:24 PM
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I've found a Sawzall with a 12" brush blade is great for root infested digging.
 
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Old 05-13-11, 05:36 PM
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Have you thought about converting the lamp post to low voltage?
 
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Old 05-14-11, 01:56 AM
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Originally Posted by Justin Smith View Post
You can even rent a trenching machine to dig the trench.
Absolutely! If you're going more than a few feet, it's definitely worth it. I just rented one last week to install a sprinkler system in my yard. Cost me $60 for 4 hours (plus $15 for a trailer because I have an SUV and it didn't fit inside), and I was done with almost 1000' of 18" deep trench in just under 2 hours. It would've taken me a week to dig that by hand (and another week to get over the sore back)
 
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Old 05-14-11, 01:08 PM
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Have you thought about converting the lamp post to low voltage?
He would still need to dig a trench, plus you would have to worry about voltage drop and buy an xfrmr.
 
  #12  
Old 05-14-11, 01:38 PM
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Originally Posted by GBAB1973 View Post
I already applied for a permit.
A permit? You need a permit to relocate a lamppost in your yard? Your local AHJ most really need the money to charge you for getting a permit for this type of work. Do you also have to have it inspected?
 
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Old 05-14-11, 02:47 PM
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Originally Posted by Msradell View Post
A permit? You need a permit to relocate a lamppost in your yard? Your local AHJ most really need the money to charge you for getting a permit for this type of work. Do you also have to have it inspected?
Technically any new or modified installation requires a permit and inspection. At least in MN it does.
 
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Old 05-14-11, 07:28 PM
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Same here. In my town any electrical or plumbing work needs a permit pulled. Anything else can be done by the homeowner without a permit if the material cost is below $200. A HO permit for electrical or plumbing is only $5 here though.
 
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Old 05-14-11, 08:21 PM
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Originally Posted by JerseyMatt View Post
Same here. In my town any electrical or plumbing work needs a permit pulled. Anything else can be done by the homeowner without a permit if the material cost is below $200. A HO permit for electrical or plumbing is only $5 here though.
Here it's $500 without a permit. Since he's just relocating the lamppost the material costs are certainly going to be minimal. That's why I was so surprised he had to pull a permit. Of course in a lot of those NE and upper Midwest states everything having to do with the trades basically is run by the unions song sure that has some influence.
 
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Old 05-14-11, 08:39 PM
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I don't see how the cost of the materials has anything to do with performing electrical work correctly and safely.
 
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Old 05-14-11, 10:22 PM
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It doesn't. Read what I said again.. ANY electrical or plumbing requires a permit regardless of cost of materials. Anything ELSE doesn't need a permit if the materials are under $250 and the HO does the work. I'm sure Msradel will find the same stipulation in their permit requirements for plumbing and electrical.
 
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Old 05-15-11, 07:30 AM
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Originally Posted by JerseyMatt View Post
It doesn't. Read what I said again.. ANY electrical or plumbing requires a permit regardless of cost of materials. Anything ELSE doesn't need a permit if the materials are under $250 and the HO does the work. I'm sure Msradel will find the same stipulation in their permit requirements for plumbing and electrical.
Sorry JM. My reply was at Msradell's post.

Here it's $500 without a permit. Since he's just relocating the lamppost the material costs are certainly going to be minimal. That's why I was so surprised he had to pull a permit.
It's the same here JM. Electrical work requires a permit. There are some exceptions for maintenance, but relocating a lamp post wouldn't be maintenance and would require a permit. To pull a permit here one must be licensed, but there is another exception for home owners. A home owner may pull his own permit and perform the electrical work himself if he can pass a test given by the county.
 
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Old 05-15-11, 11:04 PM
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Originally Posted by CasualJoe View Post
Sorry JM. My reply was at Msradell's post.
Gotcha.

It's the same here JM. Electrical work requires a permit. There are some exceptions for maintenance, but relocating a lamp post wouldn't be maintenance and would require a permit. To pull a permit here one must be licensed, but there is another exception for home owners. A home owner may pull his own permit and perform the electrical work himself if he can pass a test given by the county.
Exactly.. "Maintenance" only goes as far as replacing an outlet or changing a fixture. We don't need to take a test here to pull a HO permit, but the inspector does go over everything much more closely. He was quizzing me as we were walking through my last two inspections, and I haven't been tagged for anything either time, so at this point he's pretty confident that I know what I'm doing.
 
  #20  
Old 05-16-11, 07:07 AM
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Yeah, I need a permit and inspection. Not really that big of a deal, just the hassle of filling out the paperwork, etc.

Given the amount of roots, etc. a neighbor suggested just using rigid metal conduit since I will only have to bury the conduit 6". I know it's more expensive (say $15 for metal conduit for a 10 foot piece opposed to a few bucks for PVC) but if it can save me time from having to dig a 18" trench and having to cut through a ton of roots it might be worth it. Plus there is a long bed along the driveway which means I could possibly just bury the conduit under the bed and not have to dig too deep into the turf.

How tough is it to use metal conduit in terms of cutting the conduit, add 90 degree connectors, etc? I've typically only used PVC before. And do I need to use threaded, rigid metal conduit (RMC) or can I still use EMT and only have to bury it at 6"?
 

Last edited by GBAB1973; 05-16-11 at 08:02 AM.
  #21  
Old 05-16-11, 09:17 AM
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One more question, if you guys don't mind.

The existing lamp post connection is run through a PVC LB on the house. It has a PVC pipe attached the runs about 6 inches into the ground and then the UF wire comes and was was buried as described below.

If I use a metallic conduit arrangement, do I have to replace the LB with a metallic one or can I connect the metal conduit to the existing PVC piping with a PVC/Metal connector? Also, if I wanted to install an outlet outside could I replace the LB with a receptacle - have the line from the house run into the receptacle and then run out of the bottom of the receptacle into the conduit set up?
 
  #22  
Old 05-16-11, 10:52 AM
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With rigid pipe (you may NOT use EMT in the ground) you use a bender to make bends in the pipe. You do not use 90 degree fittings as you will never be able to run your wire through it. Use one size larger bender than EMT. (EX: if you using 1/2 rigid, you would use a 3/4" bender) I suggest running the pipe as straight as you can or with a nice, wide, easy curve.
All rigid pipe is threaded together.

If you can, change the LB to a metal one. If you have to leave the plastic one you will have to run a ground wire in the pipe with the other wires as you will loose your grounding path. You plan to add a receptacle/box will work too.
 
  #23  
Old 05-16-11, 11:05 AM
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Originally Posted by Tolyn Ironhand View Post
With rigid pipe (you may NOT use EMT in the ground) you use a bender to make bends in the pipe. You do not use 90 degree fittings as you will never be able to run your wire through it. Use one size larger bender than EMT. (EX: if you using 1/2 rigid, you would use a 3/4" bender) I suggest running the pipe as straight as you can or with a nice, wide, easy curve.
All rigid pipe is threaded together.

If you can, change the LB to a metal one. If you have to leave the plastic one you will have to run a ground wire in the pipe with the other wires as you will loose your grounding path. You plan to add a receptacle/box will work too.
I thought there were fittings for rigid pipe? I was going to go with 3/4 inch rigid pipe. The local Home Depot guy (yeah, I know Home Depot guys can be clueless) showed me slight 90 degree bend elbow fittings to make the turns and said I could use them. Is that a negative? He also said something about pull elbows that have a plate in them but I thought they were only for EMTs.

Forgive me for these silly questions as I have not really worked with rigid conduit before. I know I would need a pipe cutter to trim the pipe but then wouldn't I need to re-thread the pipe after I cut it?
 
  #24  
Old 05-16-11, 11:22 AM
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Originally Posted by GBAB1973 View Post
I thought there were fittings for rigid pipe?
Yes you can get premade fittings. They do make it more likely a wire will snag in the pipe but you can make it work with such a small job.

He also said something about pull elbows that have a plate in them but I thought they were only for EMTs.
I would use an LB fitting instead.

I know I would need a pipe cutter to trim the pipe but then wouldn't I need to re-thread the pipe after I cut it?
Yes it needs to be threaded after a cut. You can cut it with a hacksaw/sawzall, but you should use the right tool to ream and thread it. Most hardware stores and home centers will ream and thread it for a small fee. It is the same threading as plumbing pipe (NPT standard) so you might need to ask the guy in the plumbing department for help with their threading machine. You also may be able to use slip/compression couplings but I am not sure if those are approved for underground use. Maybe somebody else can chime in on that one.
 
  #25  
Old 05-16-11, 01:32 PM
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Thanks ibp. I'd too be curious about compression fittings but it seems in my quick research they are not really accepted for underground usage. But I was told as long as I have the measurements, Lowe's might do all of the cutting, threading for me. It will be like a jigsaw puzzle when I put the pieces all back together! Haha.

One more question, if you don't mind. Obviously the lamp post light is connected to a switch. I am likely going to run a new line since the current circuit has so much on it (previous owner did some electrical work). So with a new line, I would like to have the lamp post and possibly an outside receptacle. However, if it is switched then the receptacle will be tied to that switch as well if I use the existing set up and just tap into that line. I would like the receptacle to be hot all the time. Can I utilize a 3 way wire configuration to make that happen? FYI, the existing setup has power coming into a JB (because of other connections on the line), a line up to the switch and then out to the outside light.

Additionally, can I attach TWHN single wires to run to the lamp post from that set up?

Thanks again guys, for all you help. Although I have used this website infrequently, I usually get great answers from here for various issues. Thanks!
 
  #26  
Old 05-16-11, 03:53 PM
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You could run a switched hot and a constant hot in the conduit. The neutral would be shared.

Any fitting with an access plate would need to stay accessible. It should not be buried.

ThWN conductors in the proper colors and sizes would be appropriate for use in the conduit.
 
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Old 05-17-11, 01:27 PM
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The receptacle needs a bubble cover, be listed weather-resistant, tamper-resistant, and be gfi protected
 
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