Wiring Lamp Post

Reply

  #1  
Old 03-03-02, 07:20 AM
vivona
Visiting Guest
Posts: n/a
Wiring Lamp Post

I am installing a new 3" diameter, 7-ft tall, outdoor lamp post. I have run PVC conduit out to the location but am puzzled as to how to run the wiring up inside the post to the lamp fixture.

If I had run UF cable, it would be a simple matter of entering the open bottom of the post and running the UF cable up to the fixture. But, with PVC conduit I am running individual 14AWG wires through the conduit. I could set the post directly over a vertical run of the conduit and make sure the conduit runs up inside the post a few feet to protect the end from water, but if a lawn tractor ever hit the post, it would damage the conduit. I am trying to have some give to the wiring so knocking down the post won't have a dramatic effect on the wiring.

I know I could come up above ground by the post base with a junction box and then exit the box with UF cable back underground to the post bottom, but that would leave me with a junction box the lawn care people will most likely run over -- and there goes the conduit! Is there an approved way to splice from individual wires to UF cable underground?

I am thinking of transitioning to flex underground and then running the flex (with the individual wires) up the interior of the post. That would allow some give in the wiring to guard against a post impact. But I am not sure if flex conduit is rated for underground.

Naturally, every wiring manual on my shelf just shows UF cable used for a lamp post.

I would appreciate some ideas - and soon. My wife wants the lamp installed ASAP.

Thanks!
 
  #2  
Old 03-03-02, 10:01 AM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
I was with you right up to where you're trying to allow for the lawn tractor knocking down the post.

I assume that you have use wire approved for wet locations inside that conduit. If not, you'll want to pull new wire anyway.

I think your idea of continuing the conduit up into the post is the best idea. If you knock down the post, then just repair the conduit. But try real hard not to knock it down.
 
  #3  
Old 03-03-02, 01:29 PM
Wgoodrich
Visiting Guest
Posts: n/a
Flex is not allowed in contact with earth. If this post is a metal round post then I would drill a hole through the side of the metal post the size of a half inch knock out . Then I would use a terminal adapter on the end of the conduit and use a lock nut to connect that conduit to the post.

A second option;

Most metal post for post lights have an access hole below grade. Often times you can buy a PVC sweep 90 to glue on the end of your PVC conduit run and slide that sweep 90 into the access hole and let it come up above finished grade. Then let the wires run through the post using the metal round metal post as your conduit.

Hope this helps

Wg
 
  #4  
Old 03-03-02, 03:57 PM
hotarc
Visiting Guest
Posts: n/a
Talking

You should find some new lawn care people who don't knock down lampposts and run over junction boxes with their mowers!
 
  #5  
Old 03-04-02, 05:56 AM
vivona
Visiting Guest
Posts: n/a
Wiring Lamp Post - Comments and Questions

Thank you for your replies.

As to finding a new lawn service, I have had several lawn companies take care of my lawn over the years and the reality is that they all use big riding mowers and work quickly. Occasionally, you find where they have hit a fence post or house corner. So I am being cautious and wanting to design an installation that would not break up the conduit if the post were to be hit. With my luck, they would hit the post while I was on vacation and the broken conduit would expose the wiring underground for a week.

The suggestions to attach a terminal connector, or fit a 90 degree sweep, to the post will not survive a post hit. At this point, I am considering running the conduit to below the post, then going 90 degrees up into the center of the post with enough conduit to get above ground level. That way there could be a bit of play in the post (if hit) before the conduit would be affected.

I could get even more protection from a post impact if I transitioned to liquid-tight flex below the post and flexed the conduit up 90 degrees into the post. The post could probably be completely knocked down withoug breaking the conduit.

But, what I can't find a difinitive answer to is if liquid-tight non-metallic PVC flex is approved for underground burial. Anybody know for sure?

Mr. Vivona
 
  #6  
Old 03-04-02, 08:49 AM
BrAhern
Visiting Guest
Posts: n/a
Try this

They make these plastic boxes that surface mount in your lawn. Basically ive seen them used for this installation in my town when they put decorative lamp posts up all over the city. They are green and can be walked on and yes, mowed over. Automatic sprinkler systems use a similar variant. Go up to Home depot or menards and ask them about it. From there you can run UF. Just a thought.
 
  #7  
Old 03-04-02, 09:00 AM
J
Member
Join Date: Sep 2000
Location: United States
Posts: 18,497
Received 0 Votes on 0 Posts
Since your wire will be GFCI protected, any hit that would expose the wire would almost certainly also trip the GFCI. So I don't think you'd be leaving an exposed danger.
 
  #8  
Old 03-04-02, 09:32 PM
Wgoodrich
Visiting Guest
Posts: n/a
Sounds like the one who asked the question is answering his own questions. However I do not agree with that opinion. The design of a post light post is to have an oblong access hole in the side of that post located underground. This oblong hole has a rounded edge allowing UF cable to be direct buried entering that hole without any further connection or securing. The oblong hole with the rounded edges is designed to protect from cutting that cable. A PVC sweep 90 also lays loose inside this oblong hole. If a post is hit the post can regularly be shoved to a 45 degree angle and both the UF cable and the PVC most commonly will survive the impact and movement of the post due to this rounded edge of that oblong hole.

A question was asked if sealtite is approved for direct burial. Some are some are not. YOu must look at the listing and lableing to ensure that the sealtite is approved for direct burial. Look in the UL white book or go to UL.com and look it up if you have a referance number.

John Nelson mentioned GFI protection. Post lights are not required to be GFI protected unless that post light contains a receptacle. Taking John suggestion of GFI protection may be a good idea. It would provide protection beyond minimum safety standards and also may provide the installer a safer feeling about his or her installation of that post light.

It is not required but often done and in my opinion advisable to set concrete in the hole of this post installed below the oblong access hole.

As for the idea of going below the buried end of the post and entering the post from its end, the reason for the oblong hole in the side is due to the fact that this post weighs downward [settles]. If you install the wire below the post's end then you are not installing as per the manufacturer's instructions therefore not meeting the requirements of 110.3.B requiring you to follow the installation instructions of that post advising you to use the oblong hole in the side of the post.

If you decide to install the wire into the bottom of that post regardless of following the rules then you need to install this wire under the end of the post in a conduit approved for subject to physical damage. Sch 80 PVC or rigid or IMC conduit. DO NOT INSTALL SEALTITE UNDER THAT POST. Sealtite is not approved where subject to physical damage.

Hope this helps

Wg
 
  #9  
Old 03-05-02, 11:56 AM
vivona
Visiting Guest
Posts: n/a
Wiring Lamp Post

Thank you for all the suggestions.

As to the post having an oblong hole...it doesn't. It has a 1/2" circular punched hole without rolled edges. So conduit going into that hole would be subject to shear against a sharp edge if the pole settled.

The sealtite I am considering is Alflex Ultratite Type B non-metallic liquid-tight, which the Alflex web site (and UL) says is suitable for direct burial.

It appears that my goal would be met by cutting the hole larger and in an oblong shape with the long side up/down. I could cut a series of slices along the radius of the hole and fold them out and flat against the outside of the pole to make a semi-rolled edge. Then I could transition from my rigid conduit to the Alflex a foot or so outside the hole and continue with Alflex up inside the pole to above grade. That would allow for pole settling as well as the possibility of a pole hit.

I will set the concrete base below the conduit hole. I am considering setting the concrete base with a piece of 3" ID tubing in the middle so the pole will slide in. That should make pole replacement much easier if it ever is needed. All I would have to do is dig down to the concrete and pull the pole out of the base. I will stick a piece of scrap conduit through the bottom of my pole socket to allow for drainage.

As to GFCI, I have already installed that because the pole comes with a convenience outdoor outlet mounted on the side.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: