Outdoor post light blows fuse when turning on

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Old 10-11-09, 06:09 PM
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Outdoor post light blows fuse when turning on

Hi -
My Outdoor Post Lantern worked beautifully ever time I fliped the switch located in the garage. Now when I flip the switch it blows the fuse - every time.

I replaced the bulb and the switch. Even tried connecting the wires directly, without the switch, which of course blows the fuse. I have tested and confirmed that current is flowing to the switch in the garage. Am not able to figure out why the fuse is blowing.

My guess is that their is something wrong in the wire from the switch to the lantern. The wire to the outdoor post lantern is all underground inside a pcp pipe from the garage all the way to the lantern at the start of the driveway. There has been no construction so no chance of it getting cut or damaged.

It did rain heavily for a few days when the fuse started blowing. But since then its been dry yet the fuse blows.

Any suggestions on what maybe wrong? How to identify and fix it? I am not that technically savvy so please provide suggestions in layman's terms. Thank you!!
 
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Old 10-11-09, 09:00 PM
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Disconnect at the light and test. if it still blows the fuse you need to replace it with wire specifically THWN. If it is cable you need to replace it with THWN wire. #14 for a 15 amp fuse. #12 for a 20a fuse.

My guess is someone wired it with Romex and that won't float.
 
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Old 10-12-09, 07:43 AM
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I disconnected it at the light and tested as suggested. Still blows the fuse. Since it worked perfectly for over two weeks - I am not sure if it has to do with the type of cable/wire installed since the existing cable is THWN per specifications suggested. Could there be any other cause that I can check for before I start replacing the cable? Thx
 
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Old 10-12-09, 08:18 AM
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Maybe the pros will have a idea but short of using a Megger (hipot insulation tester) to check the wires I don't have an idea.
 
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Old 10-12-09, 02:53 PM
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Lots of questions. I'm trying to understand how you put this in so you can avoid pulling the wire out, which shouldn't be that bad if it's conduit.

How does the wire enter the post light? Does it come up directly into the post or along the side and in through an LB. Once inside the post is the wire just loose THWN or in a cable to connect to the fixture? Is there a junction box on the fixture?

Where is the feed coming from? Is it all conduit or are you using some romex to a separate junction box. Check the j-box for loose connection.

First thing, disconnect the wire as low in the post as possible and check it out.

How did you install the conduit and wire? Did you install the conduit and then pull the wire? How hard did you pull? You can damage the wire if you pull too hard.

Or did you put the wire in a section, then glue on another section and feed the wire into the next section and so on. In that case, the glue may have damaged the insulation.

Are there any splices in the conduit?

It's not uncommon to find conduit with water in it. That's why the wires have to be weather resistant.

Hope this helps.
 
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Old 10-12-09, 07:50 PM
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All insightful questions. It came preinstalled when I bought the 4 year old house. Here is what I know:

The wire comes up directly into the post. Once inside the post the wire is just loose THWN. I have checked the connection in the junction box on the fixture where the THWN wire connects to the wires into that connect to the socket which holds the bulb. The feed is coming from inside the garage through a pcp pipe which is underground. It is all conduit and no romex. It seems to be one entire THWN wire from the garage to the post. The wires are weather resistant. The fuse blows even when I have the ends of the THWN wire in the post not connected to the wires of the bulb socket.

There maybe splices in the conduit but its all underground. So unable to tell. Did not pull the wires since the light worked without blowing the fuse for a couple of weeks.
 
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Old 10-13-09, 10:19 AM
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If the wiring was going to get damaged it would probably be where it enters the post. The garage is not going to move, but most post lights will move some in the wind. It is possible that the wire coming into the post chafed the insulation at that spot.

If you do find this to be the case make sure you put a bushing on the post to prevent this from reoccurring.

Unfortunately, I think you're going to end up pulling the wire to inspect it. Make sure you have strong cable attached to the wires so that you can pull the wires, new or old, back in place. It is doubtful that you can pull one wire so plan on pulling the bundle. Use plenty of wire lube when reinstalling.

As an alternative, as long as it is all in conduit and you can find the damage, you could bring the conduit above ground, put in a junction box, maybe add an outlet?, and then return underground to the post light. You can't do this underground as splices have to be accessible.

Hope this helps.
 
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Old 10-26-09, 07:34 PM
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Great suggestion. I did not find the damage where it enters the post. So will pull the wire. Have never done it. Would most appreciate guidance on how to do that. You mention attaching a cable to the wire. Which cable as I'll have to go buy one. And do I just tape it to the existing wire before pulling? There is only one heavy duty wire (it has really thick ground, and then red and black wires inside the insulation). Thanks in advance and will post on how this project goes.
 
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Old 10-26-09, 08:50 PM
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I'm confused by your description of the wire. I thought you said that the wire underground was in a pipe, all the way from the garage, that would be conduit? If so, it should not be one cable, it should be several individual loose wires.

You also say thick ground, red, and black wires? You don't see any white? Are you in the US?

You can use conduit for mechanical shielding but you're not supposed to run UF cable the full length in conduit. The length is somewhat up to interpretation however. I think you'll find pulling UF-B cable (looks like romex) if that's what it is through the conduit to be very difficult, if not impossible.

You can not, by code, have splices in the conduit. You'd need a junction box.

If it's is THWN in the conduit, individual wires, you'll have to pull them all at once as they are most likely intertwined. You can attach the new wires to the old and pull them that way. Use plenty of wire lube, you can get it at the big box store or an electrical supply house. Don't just tape it, do a mechanical connection too. Have a helper feed the wires so they don't get damaged.

If this is UF-B and it is only in conduit in a few locations, you'll be digging it up. You can repair UF-B but you'd need to find the damage first.

Post back to clarify things, OK?
 
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