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AU_Prospector 11-13-2011 02:32 PM

Outdoor light at mailbox problem
I live in "one of those" subdivisions where everyone has a pole light mounted to their brick or stone mailbox at the end of the drive on the street. The light is supposed to be on all the time in darkness, hence my problem.

Last year mine stopped working in the middle of the winter. This happened during a major cold snap where there was a lot of rain, then major cold and snow on top of it all. I live in Georgia, this is a very rare weather event.

Anyway the circuit tripped.

Also on this circuit is the front entry way to my home, some light switches and a few outlets. In the crawl space of my home there is a grey power cable which drops down out of the front foyer of the house and connects in a box to another grey power cable that then goes through the foundation and down the lawn to the mailbox.

I simply disconnected the circuit in the crawl space so at least I have power to the front of my home, however the mailbox light of course doesnt work. I am now trying to fix this. There is a box at the mailbox and I seem to have continuity between this box and the crawlspace of my home. I also have continuity between the mailbox box and the wires where they connect to the fixture. I have replaced the fixture, that wasnt it.

Before I go and dig up 80 feet of buried wire, are there any suggestions? If an animal chewed through the buried wire, would I still have continuity? Cause I seem to have just that. :mad:

AU_Prospector 11-13-2011 02:43 PM

I think I have some digging to do. I simply disconnected everything at the mail box and put wire nuts on all the wires. breaker still trips even though there is nothing attached.
I assume this means there is a break in the wire underground between the crawlspace and the mailbox, agreed?

So what do I rewire this with and what can I use for conduit? PVC okay? ABS?

joecaption 11-13-2011 02:59 PM

Not likly an animal has eaten the wires, more likly someone has hit the wire while digging, wrong wire used (it should be gray wire feeding the box and say UF on the insulation) corroded connections, someone spliced the wires instead of one continuous wire and did not use below grade connectors, loose connections. To name a few that come to mind.
Yes it's possible to get an ohm reading showing continunuty, say from black to black and white to white, but if another color is also touching another color
it will not show up with an ohm test in most cases. But if you did the same test and touched the black and the white wire at the same time on the opposite ends it may show the same result as black to black and white to white.
Wire needs to be buried at least 18" below ground. In most cases just using UF wire is fine. As an added precaution you can use gray underground rated PVC but it's not required and a real pain to do this way.
If you go with UF with not PVC you need to use Gray Pvc where ever it's above ground and water tite connection boxes called LB's.

AU_Prospector 11-13-2011 03:16 PM

With the power disconnected I did the following test. Wire nut black to white in the crawlspace. Touch black and white at the same time at the mailbox and got continuity.

The box in my crawl is basically a splice between the wire coming from my living space and the wire going to the mailbox. This is grey wire, it is labeled UF/B, the wire coming from the living space is also grey but it is different and not labeled UF. Most all the other wires in my home are yellow.

At the initial time of my problems, there was no one digging. Is it possible the problem would be delayed after the digging event by months? Come to think of it, I have lived in the home 4 years and have not used a shovel anywhere close to this area.

So you agree, I need to excavate the power cable right? This is not something I take lightly. Kind of like one of those chores I dont really want to do.

kok328 11-13-2011 03:54 PM

check for shorts in the wire leaving the crawlspace and again where it surfaces at the mailbox. If your lucky, you'll find a nick in the wire that is causing the short.
Otherwise, check for continiuty between (earth & hot) and (earth & neutral). If you find continuity there, you will need your shovel.
I wouldn't waste time trying to locate the short and just bury a new wire if nothing pans out for you.

joecaption 11-13-2011 04:03 PM

Disconnect the wires on both ends of the circut.
Then check for continuity from point to point, white to white, black to black.
Then check black to white. White to black. If there's still continuity there's a short.

AU_Prospector 11-13-2011 06:18 PM

Hey really? 18" deep? The frost line around here is only about 5" maybe less.
18" means I have to go rent a trencher I guess. What is the purpose of 18"? I cant get that deep with a spade. Heavy clay, rock hard stuff where I live.

nealtw 11-13-2011 09:16 PM

You want 18" for safety and code not frost protection.

BridgeMan 11-13-2011 11:25 PM

It does sound like you have a short circuit somewhere underground, as if someone did a "mickey mouse" splice in midstream to save a few nickels. Now you get to pay for it. Have you checked to see if, by chance, your mailbox feed is enclosed in conduit? If so, you lucked out (no digging required)--just pull your new wire through, attached to one end of the existing line. Blow some conduit lube in from both ends with compressed air to make the pull easier, as 80 ft. could prove stubborn.

I built a brick, lighted mailbox at a former house in NM, simply because the going thing for bored teenagers was to drive through neighborhoods and smash mailboxes with baseball bats. Worked like a charm, and even survived a direct hit from a BMW who's driver smacked it during an ice storm (driving way too fast for conditions--I was standing there when it happened). His precious BMW had to be towed, but my mailbox (and light) came through unscathed.

bobsmith12 08-22-2012 06:21 AM

Hey it has been such a long time since you have posted about your mailbox issues. Your problem has been solved or not?

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