Thursday, October 24, 2019

More barn wiring

Rat's nest is both figuratively and literally true.

I have been looking at the wiring in the barn closest to Sprite's house and it is starting to make sense.

The first generation of lighting was incandescent bulbs on 12 gauge wire.

The second generation of lighting was Metal Halide on even heavier wire.

The third generation was big, LED corn-cobs screwed into half of the incandescent fixtures.
A wire in the peak of the building that has been capped off. There is a reasonable chance this wire is hot and it is my second choice for powering-up the run of wire I will be using.
There are at least four runs of wire scrapped-in-place up in the trusses.

Room for two more breakers but I don't want to screw around with that
My plan is to re-purpose one of the 12 gauge wires and to tie it back into breaker box via a receptacle that the wire will reach. This is not considered best practice because lighting should be on a dedicated circuit so an overload will not cause the lighting to dump.

The scrapped run of wire already goes to a flood-light on the exterior of the building. I will replace that flood light with a motion activated light with two, 9 Watt BR-30 bulbs in 6500K. Then I will daisy-chain a second motion activated fixture just around the corner to light that side of the building.

I will be living in sin because the outdoor cable I have is 14 gauge and it will be fed by a 20 Amp breaker in the box. 14 gauge copper is rated for 15 Amps/1500 Watts.
Second motion activated light will be on the shady side of the barn
My excuse is that the run will only be six feet* and the load will be 18 Watts. It seems incredibly unlikely that anybody will find a way to put more load on the end of that six foot length of wire, 12 feet up in the air.

*There are exceptions in the National Electrical Code that recognizes a class of wiring sometimes called "chassis wiring". That means that the electrician must run heavy wire to the electrical dryer but internal to the dryer the manufacturer can use lighter gauge wiring. The rational is that runs less than 12' do not cause appreciable voltage sag AND because copper wire rejects heat out the ends as well as by convection to air. Short segments can avoid overheating failures if they have more generous wire gauge

High temperatures caused by a loose connection. I want to call your attention to the fact that the cable temperature decreases as you move away from the heat source, indicating that heat is being conducted along the cable, away from the heat source.


  1. What is pictured? Is that the feed into the panel or a dryer plug? I'd check for aluminum wire. Just the sort of thing that could be had cheap for use in a barn. And of course, you know about anti-oxident.

    1. The infrared image was pulled off the internet.

      The first image is from beside the door and includes two metal receptacles, an outlet and three runs of wire, all abandoned.

  2. The IR image was making me panic for you.

  3. Read the tap rules, you may have an exception for that short, 14ga run to the outside light. Or, just put a 15A breaker on that circuit. Or, put a 15A fuse in the circuit upstream of the 14ga cable.

    For the lights fed through the outlet, remove the outlet and make it a junction box.

  4. That's a double-ditto on that aluminum wiring. I've had to re-lay a buried main line to a barn over just precisely that issue, vintage 70's stuff.


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