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Old 12-26-2016, 11:44 AM
Kamaski Kamaski is offline
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Best way to make an underground wire splice?

Im trying to tap into an underground wire that goes to a lamppost to run more lights off that wire. Is there some kind of an underground junction box for this task.
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  #2  
Old 12-26-2016, 11:50 AM
boytyperanma boytyperanma is offline
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Originally Posted by Kamaski View Post
Im trying to tap into an underground wire that goes to a lamppost to run more lights off that wire. Is there some kind of an underground junction box for this task.
Yes there are specific PVC boxes for this purpose. If it's a UF wire you'll want a UF underground adapters as well.
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Old 12-26-2016, 12:23 PM
TriPolar TriPolar is offline
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Is the wire in conduit now or just buried? You should be able to find boxes that match the conduit if it's there. The same kind of boxes for PVC conduit should also have bushings made to connect free wire or the ends can be filled with foam or silicone.

BTW: Is this household AC? You may want to consider low voltage and LED fixtures to replace what you have.
  #4  
Old 12-26-2016, 12:50 PM
Kamaski Kamaski is offline
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There is no conduit, its just Uf wire buried. I like low voltage but I don't think they have enough power for my application.
  #5  
Old 12-26-2016, 07:11 PM
Snnipe 70E Snnipe 70E is offline
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You are going to need to put in a splice box.
  #6  
Old 12-26-2016, 08:03 PM
Chefguy Chefguy is offline
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Originally Posted by Snnipe 70E View Post
You are going to need to put in a splice box.
Or use a direct burial splice similar to this.
  #7  
Old 12-26-2016, 10:16 PM
engineer_comp_geek engineer_comp_geek is online now
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You shouldn't hide or bury junction boxes. They need to be accessible in case there is ever a problem with the connection.

Can you make the junction at the lamppost?
  #8  
Old 12-26-2016, 11:16 PM
md2000 md2000 is offline
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Most streetlights, for example, have a plate down near the base of the post itself which can be removed to expose the feed wire to light pole connection. An underground splice runs the risk of getting wet and shorting (or corroding). you want the wire to come up to the surface, splice in a protected location, or else have a waterproof housing or ball it in something waterproof like a huge glob of silicone caulking maybe.
  #9  
Old 12-26-2016, 11:24 PM
K2500 K2500 is offline
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Junction boxes are required to be accessible. Not that I think there is any logical reason for it on direct bury cable when direct bury splice kits are available.
If possible I would recommend making your spices above ground. Either in the lamp post or before they head underground from the source. A little extra wire saves a lot of headache down the line.
  #10  
Old 12-27-2016, 07:28 AM
TriPolar TriPolar is offline
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Good points above about not burying a junction box. That's advice to be followed.
  #11  
Old 12-27-2016, 10:47 AM
Mr. Duality Mr. Duality is offline
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There are waterproof wire connectors which are used when installing underground sprinkler systems. Look at a sprinkler supply store or even a hardware store for them and the plastic containers used to house sprinkler system valves. A hardware store would have these items during the warmer months, but maybe not in Winter.
  #12  
Old 12-27-2016, 11:52 AM
watchwolf49 watchwolf49 is offline
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Originally Posted by Mr. Duality View Post
There are waterproof wire connectors which are used when installing underground sprinkler systems. Look at a sprinkler supply store or even a hardware store for them and the plastic containers used to house sprinkler system valves. A hardware store would have these items during the warmer months, but maybe not in Winter.
I've seen these and they seem to work very well ... but they are used strictly inside the irrigation boxes ... every electrical connection must be accessible ...

If this was me, I'd install an appropriate irrigation box near the existing lamp post and pull that existing wire out of the lamp and up into the new box ... run a new wire into the exist lamp ... and then another new wire to any of the new lamp posts ... now we have three wires in our irrigation box ...

The waterproof wire connectors I've seen achieve this waterproofing by encapsulating the connection in epoxy ... so leave plenty of extra wire ... these connections can't be undone but have to be cut off ... and we never want our wire to be too short in case this becomes necessary ...

As I remember, UF wire needs to be buried two feet down ... or otherwise armored by either conduit or under a concrete slab ... and if you are burying more wire, add a single wire along side it ... I'm not sure how, but with this parallel single wire a device can be used to detect it from the surface ... extremely important if and when someone later wishes to find where all the buried wires are ...

Alternately ... look into these new fangled solar cell/battery combinations and maybe skip the whole new wiring hassle altogether ...

Last edited by watchwolf49; 12-27-2016 at 11:53 AM.
  #13  
Old 12-27-2016, 03:58 PM
usedtobe usedtobe is offline
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I had seen weird boxes atop two tubes coming out of the ground.

This place has two - they are the (1980's) junction boxes for the wires going to the pool and spa lights (neither of which work).

Ideally, you'd find the wire, dig it all up, and replace it with grounded wire in conduit.

Conduit is now plastic and can be cut with a hacksaw - no tubing cutter required.

Unless your new lights are in a straight line from house to existing fixture (in which case, the junction box can be at the lamp), I'd put all the splices in a single box near the house - much easier to find, and, more importantly - easier to avoid when cutting vegetation.
  #14  
Old 12-27-2016, 09:01 PM
Kamaski Kamaski is offline
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How long would a splice made with electrical tape last versus epoxy?
  #15  
Old 12-27-2016, 11:45 PM
watchwolf49 watchwolf49 is offline
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Originally Posted by Kamaski View Post
How long would a splice made with electrical tape last versus epoxy?
Underground? ... electrical tape wouldn't last very long at all ... otherwise, hard to say ... electrical tape junctions would only be safe as long as the stickum on the tape didn't dry out ... years perhaps ... the problem here is electrocution hazard once the tape fell off ...

Use wire nuts or some other connector ... never just use electrical tape ...
  #16  
Old 12-28-2016, 05:25 AM
Mangetout Mangetout is offline
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I feel stupid asking this, but you're not talking about a public streetlight, are you?
  #17  
Old 12-28-2016, 07:02 AM
ZonexandScout ZonexandScout is offline
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Originally Posted by watchwolf49 View Post
As I remember, UF wire needs to be buried two feet down ... or otherwise armored by either conduit or under a concrete slab ... and if you are burying more wire, add a single wire along side it ... I'm not sure how, but with this parallel single wire a device can be used to detect it from the surface ... extremely important if and when someone later wishes to find where all the buried wires are ....
In a residential installation, burial depth (cover) is either 6" (general yard area) or 18" (driveways and parking areas) per NFPA 70 (NEC).

All splices below grade are considered to be in wet locations and require suitable splicing methods. Electrical tape would not suffice.

You do not need to bury another wire alongside the UF cable. A cable locator set can easily use either of the current-carrying conductors or the ground conductor to locate the cable later.

I agree that the best approach would be to use a junction box at the existing post and extend the new cable from there.
  #18  
Old 12-28-2016, 07:08 AM
ZonexandScout ZonexandScout is offline
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Originally Posted by ZonexandScout View Post
In a residential installation, burial depth (cover) is either 6" (general yard area) or 18" (driveways and parking areas) per NFPA 70 (NEC).

All splices below grade are considered to be in wet locations and require suitable splicing methods. Electrical tape would not suffice.

You do not need to bury another wire alongside the UF cable. A cable locator set can easily use either of the current-carrying conductors or the ground conductor to locate the cable later.

I agree that the best approach would be to use a junction box at the existing post and extend the new cable from there.
I'm sorry. I mistyped. It should be 24" (not 6") for the yard, as the original poster noted.
  #19  
Old 12-28-2016, 07:57 AM
Mr. Duality Mr. Duality is offline
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Originally Posted by watchwolf49 View Post
The waterproof wire connectors I've seen achieve this waterproofing by encapsulating the connection in epoxy ...
The one I've used encapsulate the connection in grease and may be reusable.
  #20  
Old 12-28-2016, 09:23 AM
DrCube DrCube is offline
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What you need is a handhole. Similar to a manhole, but only big enough for your hands. It's basically an underground junction box.
  #21  
Old 12-28-2016, 01:02 PM
Kamaski Kamaski is offline
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The lamppost base is set in concrete with the wire so making the junction at the lamppost is not possible. And where the wire goes into the ground is under a concrete slab so running a new wire isn't really possible either. There might be enough play in the wire to get it in an above ground box, I'll have to see. How long do those direct burial splice kits with the heat shrink tube last? 5 yrs? 10yrs? 100yrs? Are they just as good as the wire itself or a signifificant weak point.
  #22  
Old 12-28-2016, 01:04 PM
davida03801 davida03801 is offline
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CadWelds work good, but that is a commercial solution.
  #23  
Old 12-28-2016, 03:12 PM
watchwolf49 watchwolf49 is offline
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Originally Posted by Kamaski View Post
The lamppost base is set in concrete with the wire so making the junction at the lamppost is not possible. And where the wire goes into the ground is under a concrete slab so running a new wire isn't really possible either. There might be enough play in the wire to get it in an above ground box, I'll have to see. How long do those direct burial splice kits with the heat shrink tube last? 5 yrs? 10yrs? 100yrs? Are they just as good as the wire itself or a signifificant weak point.
You might want to consider having these new lamps on a new circuit ... and this is well into the "qualified electrician" types of projects ... your new wire will start at the service entrance and be on a separate breaker ... if you can find enough play in the existing wire, great ... if not, hire an electrician ...

The EPCO product I looked at for the heat shrink method claims "No penetration after 236 hrs (min) of continuous immersion" ... as a rule of thumb, all connections are significantly weaker than the wire itself ... although this may err on the side of caution, and there's nothing wrong with extra caution in matters electrical ...
  #24  
Old 12-28-2016, 03:55 PM
t-bonham@scc.net t-bonham@scc.net is offline
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You might want to consider having these new lamps on a new circuit ... and this is well into the "qualified electrician" types of projects ... your new wire will start at the service entrance and be on a separate breaker.
That might be a good solution. But you could just connect this new UF cable to the same breaker in the panel (assuming you aren't overloading it). That would save the cost of an additional breaker (and, often more important, finding an empty breaker space).
  #25  
Old 12-28-2016, 06:59 PM
Snnipe 70E Snnipe 70E is offline
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Originally Posted by Kamaski View Post
The lamppost base is set in concrete with the wire so making the junction at the lamppost is not possible. And where the wire goes into the ground is under a concrete slab so running a new wire isn't really possible either. There might be enough play in the wire to get it in an above ground box, I'll have to see. How long do those direct burial splice kits with the heat shrink tube last? 5 yrs? 10yrs? 100yrs? Are they just as good as the wire itself or a signifificant weak point.
Is the wire set in the concrete? Or does it pass through conduit that is set in the concrete?
  #26  
Old 12-30-2016, 10:09 AM
Kamaski Kamaski is offline
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Yeah the wire is in the cement.
  #27  
Old 12-30-2016, 10:34 AM
watchwolf49 watchwolf49 is offline
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Yeah the wire is in the cement.
My guess it this installation didn't consider any expansion ... and there may be good reasons for that ... I don't know ... it would probably be a waste of time to check at your local county seat to see if an electrical permit was pulled for this ... either way your safest option is a new circuit (or tap into an existing circuit) ... and presumably a qualified electrician will do the job so that it can be expanded at some later date ...

Perhaps the lesson here for everybody is to not be afraid of added extra wires where expansion is possible ... I once ran 10-guage romex to a gas heater to run the little fan ... simply so someone in the future could replace the gas heater with an electric one ... and not have to fool with running the correct wire to it ... pretty smart if you asked the electrical inspector ...

Last edited by watchwolf49; 12-30-2016 at 10:34 AM.
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