Looking to find an underground junction box

Need to bury a junction box and don't know if the ones at Home Depot
etc are watertight or could be made watertight. Essentially, need to
take a 12/3 line off the outside of my house, into conduit and into
the J box, then split into 3 seperate 12/3 lines in conduit (down the
driveway, along the driveway and to a flagpole).
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Just be sure it is listed as a wet location box (usually grey). Nothing underground us really "waterproof", that's why everything has to be listed "wet location". Use wet location splices! You are really better off if you can "homerun" all of your current carrying conductors or splice them above ground. Ask electricians who do old work and they will tell you virtually every underground raceway system collects a certain amount of water.
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Thanks for the info. Unfortunately, I have no choice but to bury this thing otherwise, I'd have to dig 3 extra trenches out into the yard about 200 feet. Good to know about wet location splices though. Thanks!
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In reality there is no such animal. There are some designs that will keep water from entering if you were to bury the box with no penetrations for conduit, or cable entry. As soon as the box has penetrations cut into it all bets are off. If the installer takes great pains, is very careful with the installation, and uses connectors designed for the purpose, water entry can be kept to a minimum, but if there is any moisture available underground (high water table, or consistent rain, water collecting on the ground above the box, etc.) there will be water in the conduits, and boxes.
If you use an approved underground box, appropriate connectors, and good workmanship, to keep the water entry to a minimum, chances are you wont experience too much difficulty. If water conditions exist as mentioned above, have your electrician use epoxy filled splice pouches (made by 3M and others) to seal the wire nuts in the box (leaving the wires stripped out of the cable a bit longer in case they need to be cut loose, and reconnected later), and don't worry about the water.
Louis-- ********************************************* Remove the two fish in address to respond
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Louis Bybee
Have you considered some kind of access hatch? (perhaps one of the ones sprinkler systems use) The last thing you want is that splice failing underground, and having to dig again. I myself would look for ways to keep the splices above ground.
-- Steve
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Steve Smith
"Gfretwell" wrote
Would it be "legal" to make the splices in the wet location box like normal and then fill the box with two-part epoxy?
Reply to
Anthony Fremont
Two things generally determine 'legality'. 1. the item is listed (usually UL), which means 'approved' for the location in question, and 2. the AHJ, that is the "authority having jurisdiction".
Number 2 is especially important. Usually, if you call the local "authority" (read "Electrical Inspector") and ask him what to do, maybe even ask if this or that will work, you will get his pre-approval for what you want to do. Doing this may even allow him to bend the rules a little for an unusual installation. If you blindly stumble on, you can wind up ripping things out and starting over, thus justifying the cost of using a real electrician in the first place.
In forty plus years in this business, number 2 has never failed me, tho NOT using number 2 has cost me a couple of times. (slow learner)
oh yeah....I would ask if your two part epoxy is UL listed as an insulating medium for the voltage at which the splice will operate?
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User 1.nospam
It's not rocket science but probably more involved that you thought - Telecoms systems use underground junction boxes all the time, and the phone still works...
The standard method we use is to sink a small concrete pit (appropriately sized), with a lid, with the conduits entering and leaving through holes punched in the pit walls. The pit has holes in the bottom to allow stormwater buildup to drain away. Once the cables are pulled, you seal the conduits with expanding foam to prevent the conduits becoming part of your drainage system.
The jointing is done with 3M epoxy splices (as mentioned in other posts) or by using a more expensive "openable joint" (OJ) if you need to change things later (Google search).
Once the jointing is done, the whole pit is filled with sand or weak-mix cement to keep (most of) the water out.
Have fun! Cameron:-)
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Cameron Dorrough
The other responders have given you good input. I would try to find a way to locate an outdoor-listed box above ground, and run the conduits up into the bottom of it. You can buy them with various threaded hub arrangements, and you might be able to hide it in the landscaping somewhere.
Ben Miller
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Ben Miller
Actually, even when the cable is buried, the junctions and cable splices are usually above ground around here (Virginia).
When a underground telephone subscriber "drop" is damaged (by construction, lightning, trees, or whatever) "they" do make an undergrond splice. The splice is protected by a mess (I use the word deliberately) of silicone based jelly.
The silocone jelly approach is also used to keep water out of splices for high voltage power (19.8 kV) splices. For low voltage power they keep the water out with a layer or two of special tape.
Most places would consider what you described to be an underground "vault." It's equivalent to pulling the splices in a basement.
Where is that done?
Reply to
John Gilmer
Not over here. It's extremely common to find telephone, fibre and cable services below street level - all terminated in concrete pits using Openable Joints.
Things that require regular access, like multiple consumer connections, are run to above-ground pillars, but if we are talking about cable splicing and jointing - yep, that's what the pull-pits are for. (and BTW, the pits are usually full of water :-( )
Industrial sites.. Petrochemical plants.. Factories.. Airports.. all kinds of places. The need to go to this extreme would depend on the service you are running, the need for regular access and the voltage involved.
*All* HV underground cable-jointing I've seen (and I've seen a few) have used the weak-mix method and several LV ones also - particularly where you have a low water table problem or a flammable liquids site. I have also used sand-filling with optic fibre cabling to protect the cable against potential pit failure in high traffic areas.
The idea is to "bury" the cable in a water-excluding mix to keep the splices as dry as possible. (The sand used is the really fine stuff - and it's amazing how well it works - but for larger pits, weak mix is better)
HTH, Cameron:-)
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Cameron Dorrough
Thanks everyone for the great feedback. After much thinking and such, we actually ended up not needing a J box. We're running out of the house from the existing outside box to 1 lamp, then on to the other and then to the final lamp. To get over to the other side of the yard and the flag pole, we're going to run an entirely new circuit out the side of the house and up to a switch in the foyer.....
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