I’m replacing an outdoor lamp post with a new one. I noticed the Romex (cable?) coming into the lamp has a bad break on it down to one of the wires. I’ve always been able told not to tape this kind of thing up, but replace that part of the cable. I’ve worked with Romex inside the house, but not outside. Is there such a thing as outdoor Romex? Or is it called something else for wiring that has a white, black and ground wires but can be used outside that it can be buried in the ground? The existing wire inside the lamp post has no conduit on it.
They make Romex specifically for underground applications. IIRC, it’ll say UG on it. It’s heavier than the normal stuff and harder to work with. I wouldn’t attempt to splice a new section, but just replace the entire run if that’s feasible. But I don’t know how to make splices underground.
Home Depot/Lowes will have it, it’s usually gray instead of yellow or white and it’ll say it’s rated for underground/burial.
Type UF-B (Underground Feeder-Branch). Looks similar to Romex, good bit more expensive, used just the same except it is much trickier to strip. You may want to practice cutting away the solid-cast cable body (without nicking the individual conductor insulation) with your razor knife, before trying your actual installation.
Thanks for the reply.
This is for a lamp post that can support three 100 Watt bulbs which is 110v or 120v and is connected to a 15 Amp which is shared with lights and stuff on the same circuit. Does that mean I should use a 14/2 plus ground UG Romex? Or because it’s outside use something more heavy like 12/2? And I can’t tell what the existing Romex is, because it’s coming out of the ground and any printing on it is either rubbed off or too hard to read.
Thanks for the suggestion. When I have seen experienced electricians work, they make it look too easy and work very fast. I only need something like 4-5 feet of Romex for this, but I will purchase more feet so I can practice with it.
Not the right answer per code but if you’re simply wanting to cover the break, my local NAPA Auto Parts carries large diameter, glue lined heat shrink tubing. They use it on custom battery and welding cables. A 4" long piece would bond to the existing Romex and seal the break.
Nefario: Is this stuff a closed tube or is it a self-adhesive sheet you wrap around your cable? Said another way, can it be installed without disconnecting the cable at either end?
I’m asking not for the OP, but for a different but similar problem I’ve got where I’d like to heat shrink over a damaged section that’s impossible to disconnect at either end.
They do make splice kits for underground cable. I’ve never used one but have seen them in the store. Two or three splice sleeves with screw logs and a bunch of heat shrink tubing. The outer piece of heat shrink is adhesive filled so the whole thing is water proof.
Here’s one example.
Underground is the same as underwater, I’d be suspicious of a product designed for use on cars. I’ve seen underground cables sliced through and spliced together again. These ‘normal’ connections are encapsulated with epoxy, gallons of the stuff. Like a big softball sized chunk of cured epoxy glue around each wire nut. This should last a very long time submerged.
I’d replace the cable myself, and I’d make sure to bury it deep, couple feet or more. A 15 amp breaker will carry 14 gauge wire safely, I do believe, but that’s a good question to ask about.
The stuff I found at NAPA was closed tubing that I used to repair a used welding handpiece that was broken.
BUT - there used to be self-healing silicone? tape that could be wrapped around an intact wire and forms a solid rubbery mass. I didn’t want to suggest this and get into a debate about whether this would be weatherproof. No connection to me…
Or try McMaster - Carr.
Thanks. My application is low voltage signaling, so no danger.
Just wanted to post an update and say thanks again! I bought the UF-B and you weren’t kidding, that is very hard to strip compared to indoor Romex. I’m glad I got extra feet to make sure I had enough to practice with. I finished the project and got the new lamp post installed.
Tip to anyone else working on outdoor lighting, start the project as early in the day as you can so you don’t end up trying to finish it while it’s getting dark. 
Yes, but those are pretty expensive. Usually more than the 6 feet of UF that the OP needs.