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Direct burial wire splice

Joe Sullivan | Posted in Energy, Heating & Insulation on January 16, 2007 05:20am

Friends:

My parents live in a old lodge in a virgin forest, and have been systematically upgrading or emergency replacing things like power service and the septic system, as well as working to restore the house. My father says that there has never been an excavation done over the last two years that did not dig up some buried cable, whether power or phone.

A few weeks ago, while I was visiting, someone turned on a porch light and there was a tremendous power surge followed by a tripped breaker. Turned out that a feeder to an outdoor lamp about 70 feet from the house had been dug up, and had shorted in the snow. I disconnected the cable at the house, capped everything off, and went my way.

Problem is, they NEED that light. Second problem is, the cable had been buried for many years, and to bury a new one in a forest would involve digging through lots of roots, as well as stone here and there. Therefore, I’d like to splice it. Ideal has a line of wire nuts that are rated for direct buriel I have some. The question is, would a box or other strain relief be required, and if so, what kind?

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  1. User avater
    McDesign | Jan 16, 2007 05:42am | #1

    I've done it in "Scotch" kits, where you crimp it in a sleeve, snap a large clear plastic sleeve around each conductor, and fill it with a pourable epoxy.  Not sure if they are available for small (UF)wire.

    Forrest

  2. misfit | Jan 16, 2007 06:06am | #2

    Ideal has an Underground UF Splice Kit #46-100

    I have one right in front of me, dug it out for the part #

    1. cap | Jan 16, 2007 06:52am | #5

      Yup, this is THE ONE for line voltage (120V).  Other methods (direct-bury filled wirenuts) are for low-voltage wiring, e.g., 24 volt lor lower irrigation valve circuits.  DO NOT use filled wirenuts unless: they are intended and UL-listed for power circuits, typically a 300V or 600V listing, and, you make the splice in the appropriate junction box.  There are j-boxes made for direct burial.

      Now, it'll be interesting to see if the old direct-buried cable is UF (underground feeder, rated for direct burial) or just NM (romex to you, buddy).  I've seen way too many instances where regular romex was direct buried.  When I get called to repair buried romex, the client wasn't too happy to hear that I won't repair it, and will have to re-un it.  That's why, when I trench, I always:

      --call underground locate service to find and mark public utilities;

      --give the client the opportunity to mark where their buried wires and pipes are (which they usually don't have any idea of), or tell me where water, power, telephone, and other services are present on the property;

      --take the time (built into the bid) to locate their wires and metallic piping, where the presence of a service would indicate a line running; and,

      --include a clause in my contract that any lines I may cut while trenching that I didn't find because I was not advised of the presence of a service, will be repaired at the client's expense.

      About that third point, I can almost always locate underground wires if it's apparent that there's a wire or metallic pipe somewhere.  The fourth point is important because sometimes the client doesn't tell me that there's power running to a hidden outlet at the far end of the lot...and, plastic pipes sometimes show up in unexpected places.  If the plastic piping has no tracer wire, oh well...

      Cliff

    2. User avater
      BillHartmann | Jan 16, 2007 07:02pm | #10

      Is that a typo?I could not findthing with a 46-100, but did find 46-400http://www.idealindustries.com/IDEAL-EZ/products.nsf/ItemMasterLookup/p46-400?OpenDocumentAnd there are others in the 46-4xx series.IIRC I recently saw a new product annoucement for a repair kit. was
      basicall a similar, but double ended with a couple of inches of between
      the ends to so that you had slack left in the cable. Don't have any idea of what or where I saw that..
      .
      A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

      1. misfit | Jan 17, 2007 05:06am | #22

        Yeah, my mistake. 46-400 is what it should have said.

        Thanks for the correction

  3. DanH | Jan 16, 2007 06:14am | #3

    There are several different wire splice mechanisms that are available for direct burial. I (NOT speaking from experience) would tend to favor something that includes at least a modicum of strain relief, vs just using grease-loaded wire nuts or the like, since freezing and thawing can produce stresses that could pull the connection apart.

    I've seen, eg, kits that include set-screw wire couplers, a plastic insulating body to hold the couplers apart, and a heat-shrink tube to surround the whole thing.

    Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot
  4. junkhound | Jan 16, 2007 06:30am | #4

    I've used the scotch kits in military applications, but not for home use as pretty pricey, and very sensitive to proper installation.

    Probably not per the latest code, but I've wrapped and soldered wire underground and poured hot tar around the whole mess, and has lasted over 35 years. Roofing cement would likely work also. 

    You could always put a GFCI at the source of the UG circuit and it would trip if the splice leaked.

    1. User avater
      Luka | Jan 16, 2007 10:53am | #6

      I wonder if you could solder/twist, then use those copper crimp sleeves, and then lay them in a bed of bondo and cover them with more. Kinda like the scotch things and epoxy, only cheaper...

      Get over it....... The angry going eat you up. ~Brownbagg '06

      1. DanH | Jan 16, 2007 01:58pm | #7

        I've seen the splice kits I described for something like $15 a throw. Can't see that it's worth it to muck around with chewing gum and bailing wire.
        Half of the harm that is done in this world is due to people who want to feel important. They don't mean to do harm but the harm does not interest them. --T.S. Eliot

        1. Joe Sullivan | Jan 16, 2007 05:13pm | #8

          Interesting.  Thanks to all for the input.

          My Ideal direct burial wire nuts are PN 30-060.  They are rated for direct burial use with wires from 18awg to 8awg, and up to 600v AC.  I was given them by a guy from Ideal itself with whom I had dinner at a recent meeting.  I had asked him about the epoxy kits, and he said that testing had shown that under the right (or wrong) temperature conditions, epoxy will crack and admit moisture.  He was then kind enough to send me some for the purpose I described above.

          However, I forgot to ask him about junction boxes or strain relief, and fear that calling him to ask would look like I wanted more freebies. 

          Sounds like I need to get a direct burial box and make the splice inside it using these nuts.  Does that make sense?

          Who makes the boxes?

          1. User avater
            BillHartmann | Jan 16, 2007 07:16pm | #11

            Here is the page for those.
            http://www.idealindustries.com/IDEAL-EZ/prodcat.nsf/Tables/Weatherproof-Underground?OpenDocumentThe top links or for a sales sheet and for free samples. But they don't answer your question.Note that there are two different lines; waterproof (above ground) and underground.Here are some of the applications;# sump and well pump installations
            # ejection pumps And those are 120/240 applications..
            .
            A-holes. Hey every group has to have one. And I have been elected to be the one. I should make that my tagline.

          2. Joe Sullivan | Jan 16, 2007 07:34pm | #12

            Bill:

            Right you are.  There is no question but that they are approved for line voltage.  The instructions that come with the wire nuts mention other uses as well:

            Deck/patio lighting

            Decorative lighting

            Outdoor power outlets

            Valve control boxes

            Really, there may not be a requirement for strain relief, but I do worry about frost heaving in that upper midwestern climate.

      2. junkhound | Jan 16, 2007 05:50pm | #9

        Bondo will leak as it is not flexible, and the connections corrode.

        Silicone would work, but defeats the 'cheap' aspect.

        Tar was the preferred method in the 'olden days', and some of those installations can still be found , all are free of corrosion.

        1. Grott | Jan 17, 2007 03:04am | #17

          Is silicone conductive?

          1. junkhound | Jan 17, 2007 03:17am | #18

             

            No. It is an excellent insulator.  I often use it for high voltage (25 to 40 kV) system work.

            There are some specialty silicones that are silver filled that are semiconducting, that cost $100s per tube BTW, but you dont want those for a splice.

            edit PS:  If you want to go the silicone route, do what Sam said and clean and rough the insulation at the splice. Rough it up with sandpaper wrapped around the insulation, not by sliding it axially along the wire. (note; that is part of the instructions in the specialty 3M splice kits)

            Edited 1/16/2007 7:20 pm ET by junkhound

  5. renosteinke | Jan 17, 2007 12:36am | #13

    What you are trying to do is put a bandage on something that was done incorrectly in the first place.

    Yes, there are 'direct burial' splicing devices. Yes, there is 'direct burial' cable. However, simply purchasing these items guarantees a proper installation no more than buying a car makes you a safe driver.

    Look at this short as either the result of a defect in the original method, or as a warning sign that things are wearing out ... or, maybe both.

    Unprotected cable needs to be run DEEP, often 24" down ... not the three or four inches often seen. It needs to be laid in clean dirt or sand ... not sandwiched between rocks.

    When I do such an install, I almost always use pipe .... and oversized pipe at that. PVC pipe is cheap, lets you dig less deep, and lets you later pull new wires. Use cable alone, and you're sure to need to dig again in the future.

    When I am near the light post, I like to come up into an "N-9" fiberglass handhole. This 'handhole' is about the size of a 5 gallon pail, is open on the bottom, and has a lid on top. I also bring the wires from the post into this box, and splice them there. The silicone grease filled wire nuts are fine here. I like using the handhole because it is a lot easier to work with other wires (if you're continuing to other lights), and allows replacement of the post without damaging the main wire run.

    However you power the light, I suggest that the wires be run both deeper than one shovel blade, and well under any sprinkler pipes, etc. This makes it harder for something to get hit by accident.

    I also advise AGAINST using weathertight "Bell" boxes in the ground. They are neither dirt nor watertight, and will quickly corrode away in most soils. Any splices ought to be in a proper handhole.

    1. Joe Sullivan | Jan 17, 2007 01:26am | #14

      Thanks for your advice.  I'll look into the handhole thing.

      Just FWIW, though, the short was NOT caused by improper installation.  It was caused by a careless backhoe operator who pulled the wires to the surface and broke them.  He was going quite deep -- working on septic lateral lines.  We knew they were in the air -- or my father did -- but he had not had time to fool with it before the early December snowstorm put a drift over the wires and pushed them down.  Then, when the switch went on, it was the two broken ends shorting through snow and wet dirt.

      I would prefer not to have to lay 75 feet of cable through difficult ground just to repair that break.  If you look at my original post, this is a pole lamp about 70 feet from a lodge i the middle of a virgin forest.  No sprinklers or anything else.  Just thousands of ancient tree roots, and a lot of rocks.  The trees top 150 feet, so you can imagine the roots.

      1. renosteinke | Jan 17, 2007 02:29am | #15

        Thank you, Joe. It sounds like an "oops" happened to a perfectly fine install in your case. I try to make my answers somewhat 'generic,' as I guarantee that you're not the only person to have this come up. Indeed, it came up at my home when I was a kid! I've had to fix several such problems ... and the run was almost always done improperly in the first place. Indeed, only once was it a case like yours, where the backhoe hooked the cable. If you look at sundry 'handyman' type magazines (or forums), there is no shortage of advice that is ... ahem ... somewhat contrary to the electric code. Usually the justification given is "but it works." Sure it does ... for now .... with no concern for tomorrow. It is some of these other "experts" that I was addressing - as well as you original question. Thanks for your understanding.

      2. User avater
        SamT | Jan 17, 2007 02:52am | #16

        First let me preface this by saying that it will NOT meet code. Its' performance, however, will exceed any method prescribed by code.

        Second, it was an accepted method for splicing wires at up to 60' deep in salt water in the mid '70s.

        If you know how to do a Western Union splice, start with that, else use a wirenut and achieve one full twist in the insulated part of the wires outside the nut.

        Use acetone or PVC cleaner, not the purple primer, and clean the wires for about a foot on each side of the splice.

        Lay the nut against the cable to make a smaller bundle. Starting right on the wirenut, or WU splice, wrap with rubber electrical tape, stretching it about 50% and using a 50% overlap, towards one side till you have one complete wrap on clean insulation, then turn back and wrap to the other wire the same way, then turn back again and wrap to the place you started from.

        With the rubber tape, fill in low spots untill you have a tapered bundle. Using the same 50:50 stretch and overlap,  and the same center to end to end to center method, wrap with vinyl electrical  tape. Use 3m brand (333?), not some cheapo. Remember to extend each layer of tape one full wrap onto bare insulation.

        Armor this bundle with electrical friction tape. This armoring tape does NOT stretch, but you should still get at least 50% overlap. Smooth it all down, not worrying about wrinkles, and paint it with a layer of Liquid Tape.

        Let the liquid tape dry/cure thouroughly before proceeding.

        If you're repairing romex or other armored cable, clean 6"of the armor and repeat the all the above, except this time run the tape out onto the armor. Get at least 1" of clean armor covered with each layer of tape, this is the weak spot. If you're not repairing armored cable, you can just repeat the first steps, from rubber to Liquid Tape.

        After the second layer of Liquid Tape has set, throw a couple of wraps of vinyl tape with NO stretch over the end of the last layer of friction tape and paint some LT on the end of the last wrap of the vinyl.

        If you have good tight twists on the splice; If you preclean everything the tapes sticky side touches; If you really get 50% stretch and overlap on every wrap; if every layer of tape extends one full wrap past the previous layer: This repair will outlast the rest of the circuit.

        Unless it meets another backhoe.SamT

        So much of the success of a company is not determined by degrees but temperature. gb93433 83537.46

        1. Joe Sullivan | Jan 17, 2007 03:22am | #19

          Very interesting procedure.  Thanks.

           

          J

          1. arrowshooter | Jan 17, 2007 04:33am | #20

            You can make waterproof splices using standard PVC pipe and fittings to completely surround the welltaped splice then fill both ends of the PVC with silicone. Use the smallest pipe that will fit over the wire then step up to a larger size if needed to cover the splice area then step back down to the smaller pipe. Use about six or eight inches of pipe on each side of the splice area and really force the silicone into each end. Then thoroughly tape off each end of the PVC , wrap the whole assembly with several layers of six mill black polyethlene lay it in the ground, mark the location and bury it.

            (I like to bore a wire size hole in a PVC end cap and fill it with silicone for each end of the small pipe.)

            I would not invite an inspector to look at this because they don't like anything that is not factory made but it works. 

             

          2. User avater
            SamT | Jan 17, 2007 05:06am | #21

            Milspec extreme environment technique.SamT

            So much of the success of a company is not determined by degrees but temperature. gb93433 83537.46

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