Low Voltage Question
 

For the brain trust. Installed yard lights down stream from my transformer. Low voltage LED fixtures. Worked well, then my connection go wet and no go. Have pulled the wiring from the ground and was testing. Lights flicker. On touching the wire, it was hot, very hot to the touch. I thought there is little current running through so I am surprised at the heat. Transformer is rated for many more fixtures than I have on the line. Now have four plus the two in question

Will re-splice all connections and heat shrink them again. Thoughts on why the wire was hot?

Will a ground of some sort cause current to keep flowing and produce heat?

It's a misconception that low voltage will not produce heat when wires are crossed. That is what is happening there. You have to go back over everything and find the short.

Can be tedious but with your simple system not bad. Just be thorough and you'll find the issue.

Potential issues: transformer, cable, LED fixtures, LED bulbs, connections.

I don't heat shrink my connections - I use wire nuts filled with dielectric grease.

Thank you Baz. So, I have a cross connect positive/negative. I can fix that. I have tried wire nuts with the dielectric grease, but those did not work for an extended period. Its in an area around a fountain that has proven beyond troublesome.

Will just get out there and reconnect things.

Baz, one more question. It appears as though the two wires on the fixture have differing wire color. Assuming I keep like to like to be sure. Will it matter when I connect them to the main power wire coming from the transformer? Not sure how that wire is connected, which side to which pole.

No, it won't matter which side is connected. Wire is wire. The wires just can't touch each other, obviously. Otherwise, no such thing as positive and negative to keep track of. Hope that helps, Rocketman!

yep, I'm on it. And for that advice, a little remake of Peter Green's Station Man, Pete Townsend playing

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Thanks, brother. My fav. song off Kiln House. And PT is great! :)

Heh. I was making tantalum carbide in school with a vacuum furnace that ran at 6V. There was however about 2000 amps though going through those graphite heating elements. It was at least 1800C - the peephole in the door projected a nearly white light across the room.

The safety lesson was, besides the heat and the (related) importance of keeping the cooling water on, you can touch the conductors but for god's sake don't drop a wrench on them. You'll get blowed up.

Electricity is strange...

Before the heat shrink use some dielectric grease. I suggest a brand callled super lube.

Was the entire cable hot or just the where the joint is? If it is the wire getting hot, is it rated for direct burial?

my first thought. heat in a circuit = short.

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Couldn't see my mistake when I first pulled is apart. I now have the fee cable (2 wires) and the two low voltage fixtures with 2 wires a piece When the sun quits hitting the site (105 right now) I will carefully connect two of the fixture wires to one of the feed, heat shrink and electric tape wrap, then do the other 2 fixture wires to the feed. Repeat.

May even send a pic or two so the brain trust can tell me what I am doing wrong.

I wonder if the liquid electrical tape stuff would do a good job of sealing the connections from moisture. I used it on coax cable for TV many years ago (I kept planting stuff and forgetting about the cable. :rolleyes:) and it seemed to work.

Couldn't see my mistake when I first pulled is apart. I now have the fee cable (2 wires) and the two low voltage fixtures with 2 wires a piece When the sun quits hitting the site (105 right now) I will carefully connect two of the fixture wires to one of the feed, heat shrink and electric tape wrap, then do the other 2 fixture wires to the feed. Repeat. All rated for direct burial.

Wire was hottest near the connections, but warm for a bit of a distance

May even send a pic or two so the brain trust can tell me what I am doing wrong.

Any resistance in the line or joints will likely create heat, if you can, twist the wire tight and solder it, then wrap it to protect from moisture. how many Amps are each LED light and how many lights?

heat comes from current and resistance

P = I^2 * R

If there is a short or really a ground, it will heat up the wire. If you have a wire smaller than the rating of the transformer, it could heat up to the point of fire.

Photos are always helpful.

Also, there is a way to troubleshoot where certain components can be eliminated as the problem.

Start with transformer - measure output in volts. 12v? Good.

Hook up cable and connect to known good light fixture. Comes on OK? Good.

Now you know the transformer and cable are OK.

One by one re-connect each fixture.


Other than that - the problem might be associate with a deterioration of your components and/or connections due to weather and natural elements.

Like I said earlier - it's very basic and should be straight forward to toubleshoot...

At a youthful hangout party...a bunch of kids sat on a dented hood...which somehow connected down to the (12V+) battery terminal.
A five foot fountain of sparks with a small hole burning through the hood followed.

I think it only takes 1/10th amp to stop the human heart.

(and yet Tesla could repeatedly shoot lightning from his fingertips)

I am not a sparky, just a simple country metallurgist, but the lore is that an early lesson for those in that line of work is to keep one hand in your pocket so that if shocked - it's less likely to go across one's chest.

Having worked with HV things like explosive firesets and X-ray generators, my early lesson was to let someone else do it. My nephew's doing those "burned/etched in wood" art things with HV from a neon sign power source. Allegedly safe-ish but it's a complete "NOPE" from me. Looks cool but there was some San Francisco detective's less-than-most-famous quote was "A man's gotta know his limits".

so the saga continues. Tried to upload a photo but for some reason, that function is not working.

Thought I had it figured, pulled my connections apart, reconnected using butt connectors, good and tight, turned on the circuit. No joy. The wire that was hot is the original feed wire. So that meant an archeological dig to find it. Seems that the wire in question was covered by a vinyl sleeve, but not really well sealed. I have found the second feed that goes to a light that is working. When the photo upload thingy works I will post the current conditions.

Baz, thanks again for your help

http://forums.pelicanparts.com/uploa...1654358845.jpg
Ah, safari let me upload.

Two separate wires at lower right feed the light that works. Assuming there is a buried connection that I have not found. The black vinyl sprinkler piece connected to what appears to be sprinkler line is the feed that failed. In digging I pulled it out. So my next step is to find that wire, verify no breaks, reconnect and hope for the best.

What does the brain trust think of crimped butt connectors inside of heat shrink wrap for this buried condition. I am a good 18" down. Typically in AZ we do not get water penetrating that far. And frankly this dirt is like chipping concrete.

Have my soldering iron (cheap battery powered Weldon) and can a solder.

The extra wire in center left is the offending wire that proved the problem.

sorry wires in lower left (my other right)

Sorry Rocketman.....I can't figure out what's happening from your photo and comments.

Are you saying the cable that is getting hot is buried? If so, I would just lay a new one if possible and abandon the old one.

Before you do that, lay a cable along the ground and connect everything just to test it out. If it works OK proceed to bury.

Of course, make sure you buy the correct size and type of cable.

12 gauge is the thick stuff for longer runs and more lights. Most LED system don't need anything that heavy but other than cost it doesn't hurt to use it.

You can also use 14 gauge and then down to 16 gauge and that's it.

I actually use a lot of just 16 gauge here and it works just fine.

I use wire nuts filled all the way up with dielectric grease and have never had a problem and it's a lot swampier here than where you are. Just make sure the wire nut isn't too small, you twist the wires together good, and the wire nut is completely filled up with the grease.

Your crimping system could also work but that's just not how I do mine, FWIW....

The one that got hot came from the sprinkler piping. You can see the blue ring on the connector. Looks like he ran the wire inside, turned it 180degrees. Not sure why. The two wires to the left of the black pipe is the circuit I know to be working. The whole thing is fed by a long direct bury wire from the transformer.

There must be a "Y" somewhere under ground that splits the main feed. Originally had two lights, so a splice is needed.

Your suggestion is wire nut filled with dialectic grease and then just bury?

http://forums.pelicanparts.com/uploa...1654362060.jpg
OK, total brain cramp. Went back to the transformer. Original install is two cables each connected to the feed at the transformer source. He then split the casing and ran the two wires to the fixtures. That way no connections in the ground.

The wire you see coming in from the left, is the wire that was the problem. In my earnestness, I pulled the wire and you can see it separated. Not sure how I could have put enough force on it to rip the wire. I'm not that strong.

So now the issue is this. The remaining wires feed a fixture I know works. Why the continuous wire from the transformer failed in the sheathe is a mystery.

Thinking two options. One dig the main feed back enough to strip the sheathe and do a splice.

Or go to the fixture that works and splice the feed there

The sprinkler is just that, a line we capped when we put in the fountain.

how I hate electrical issues.

Thinking of calling an electrician to test continuity of the cables to verify the one I think is working is in fact not compromised then make plans for the failed connections

OK let's see if this helps.

From what you wrote - there are 2 cables coming from the transformer. A cable is two wires molded into a single cable.

One cable works - the other doesn't.

These were to feed two light fixtures.

You know what? If your light fixtures are LEDs - you probably only need one of the cables.

Disconnect both cables at the transformer. Attach a light you know works at the cable end you said doesn't get hot. Then attach each cable - one at a time - until you see the light come on. Then go ahead and just use that cable and leave the other one unattached - and abandoned.

You should be able (like I said) to run both your light fixtures off the one good cable.

LOL!
safe-ish, like car surfing and lawn darts.
https://www.nbcnews.com/pop-culture/viral/wisconsin-couple-electrocuted-attempting-viral-wood-burning-art-techni-rcna26109

I'll bet that was something to see!
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Apologies for continuing this thread, but I have a question.

Decided to take the advice and connect all fixtures to the one feed I know to be working. Did so, and got the fixtures to flash once then go out. If I connect the one that has always been working, it works just fine. Connect the other two, flash and then out.

So then connecting the one I know works and only one of the other two at the same time. One works fine, the other does the flash and out.

Looking at the wire in the suspect fixture, the copper is no longer bright. It has turned dull and dark. In the second fixture, one wire is bright, the other turning dull. And the one that works, all wire is bright copper.

So here is the question, is this an issue of bad wire or has my ground problem somehow affected the wire to make it discolor. When connecting the problem fixture alone, I get the same issue of flash and out.

I don't know enough about the effects of a grounded circuit on wire.

Any help is appreciated. Hope I have explained that well enough

Sounds to me you need to cut back enough cable to get to some clean bare wire and you should be set.

Use a pair of side cutters or even a wire stripper to cut the wire off - just enough so there's no more bare wire showing. Then split the wire casing so you can strip back the casing enough to get bare wires for your connection.

Make sure you now have clean bare wires, like the fixture has that is working.

See how this works and let us know...

Thanks Baz, but it does not matter how much I cut off, wire shows discoloration. I stripped about a foot off the end.

I am wondering whether this is affecting the conductivity and creating my issue. Logic says the bright wire works, the dull wire doesn't. I have not taken the fixture apart to see the wire condition at the bulb.

Very strange I must say.

I have seen many a discolored wire that still functioned.

Not sure what kind of fixture you have there.

If the LED bulb is replaceable, that would be your next step in troubleshooting.

Many consumer level fixtures do not have replaceable bulbs, so might be easiest solution at this point just to get a new fixture if that's what you have.

Can you show or tell us what you have there?

http://forums.pelicanparts.com/uploa...1654461128.jpg
http://forums.pelicanparts.com/uploa...1654461128.jpg
very simple fixture. Like the minimal design. But you can see if you look closely at the discolored wire. The one that works has been in place with the wires buried as long as this one. Go figure

Hard to know for sure but looks like you can swap out those LED bulbs. I don't think it's the wires.

Try putting in a new or known working bulb and see what happens....

I will go back to the place I bought them and walk through the issues. See where that goes

took the offending fixtures to the store where I bought them. We tested both, one worked the other with the discolored wire did not. His assumption is the wire got hot enough to melt onto the wire affecting its ability to conduct. Not sure I agree.

So a new fixture and we will see. When it cools down, I will go back out again.

While there asked about under ground connections. He sold me a pretty cool brass connector with allen screw terminals and a heat shrink cover. Says the high end landscapers use them. Will send photo when I am able.