Landscape low voltage wiring heating up

dwojoMay 30, 2013

I've got a section of my low voltage landscape wiring that was repaired years ago and is now spliced and connected via outdoor wire caps. The wires are big - the standard kind of outdoor low voltage - I'd guess 12-14 gauge. Periodically the wires seem to heat up very hot - too hot to touch and intermittently that portion of the lighting doesn't work. Can't figure it out - I've trimmed the wires and reconnected them and they work fine....for a while and the same thing happens.

When they are working there are no problems - all the lights work just fine. What could be the issue here? Thanks in advance.

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What is the total load for the wire that's heating up?

How many watts is your low-voltage transformer?

Since you mentioned it was repaired years ago I'm going to assume you're using halogen MR-type bulbs?

    Bookmark   May 31, 2013 at 3:16AM
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I have one transformer - standard 200 watt transformer. Three wires coming out of it but just one transformer - total lights on there is 12 - not sure of the individual wattage of each bulb - most are 20 watts I think. No halogen lights.


    Bookmark   May 31, 2013 at 11:30AM
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It's time to do an accurate and complete inventory of the total wattage of the bulbs. Low voltage transformers don't like to be overloaded (more than 100% of the rated load, and some even a little less) or underloaded (less than 50% of the rated load). Also, how long is the run of wiring?

This post was edited by kudzu9 on Fri, May 31, 13 at 13:17

    Bookmark   May 31, 2013 at 1:09PM
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Thanks. So to make sure I understand correctly - if I have a 200 watt transformer I need to keep my total wattage of lights in series at 100-180 watts? If I replace old high wattage bulbs with lower wattage halogen bulbs that alone may fix the problem? Or else need to decrease the # of lights or buy a bigger transformer? thx

    Bookmark   May 31, 2013 at 1:48PM
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Depending on the manufacturer, some say you can go to 100% of rated load and some say keep it 5-10% under. I don't know if you are overloading your transformer, but it is possible if your bulbs are 20 watts. If you are loading on too many watts, you can simply replace some of them with lower wattage bulbs as long as they have the same base. I am also presuming that you don't have any low voltage light fixtures where you are using a bulb with a higher wattage than the fixture specifies (for example, a 20-watt bulb in an 8-watt max fixture).

Also, is this a single line with all the lights connected sequentially, one after the other? Or loop circuits? Or...?

And are any of the lights closer than a wire run of 5-10 feet from the transformer? Sometimes having the first light(s) closer to the transformer than this can cause problems.

    Bookmark   May 31, 2013 at 2:34PM
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Never load to 100%, no matter what the manufacturer claims.

It is generally 'puffery' to claim reliable long term operation at 100% for much of anything.

Aplice need to be carefully made to avoid a 'hot spot' in these wires.

the overlap of the two conductors should be 4-5 times their diameter, and then solidly soldered for the whole length.

You want enough solder to nearly fill in the valley between the two wires on both sides.

Do not forget to slide some heat shrink tubing on the wire before soldering, then move it to cover the splice and at least an inch in each direction and shrink it in place.

The tubing with a heat activated gel on the inside is better for wet locations.

This post was edited by brickeyee on Fri, May 31, 13 at 17:33

    Bookmark   May 31, 2013 at 5:15PM
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I don't see how the problem could be the rating of the transformer.

Keep in mind that a splice with a resistance of just one ohm is going to get quite hot. You need to do a better job splicing the wires... or better yet replace the section with the splices.

    Bookmark   June 1, 2013 at 10:30AM
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Ok so I have a 300 VA Justin/Vista low voltage transformer. One line coming off of it (it's wrapped so it appears that way at least) with 10 in ground lights - 20 watt bulbs in each and then 2 lamp post 12volt, indandescent bulbs rated at 50 watts each. I imagine that's the problem.
I'm a neophyte here so please explain it simply. Can I replace those 50 watt bulbs with something more efficient and keep about the same brightness?? Thanks for all

    Bookmark   June 5, 2013 at 11:25AM
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