Code for low voltage lighting wiring.

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Old 12-22-17, 11:46 PM
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Code for low voltage lighting wiring.

I need to install some 12VDC infrared flood lights on or around the outside of the house to illuminate the exterior for security cameras. These lights can pull 2-3A each and need to be wired safely. I'm struggling to find code that dictates the safe installation of low voltage lighting.

The best way for me to install these is to have a 12V power supply in the basement (probably just a computer power supply) and pull 2-conductor cables up from there. Some runs will involve pulling the wire exposed outdoors and other runs up through walls. This is all very similar to pulling coax.

Without any further guidance I would just plan to select reasonable cable for my load and put small fuses on each run to protect the cable from overload.

But what does code say???
 
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Old 12-23-17, 07:16 AM
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The rules for low voltage wiring is much less restrictive then for line voltage wiring. You could almost run whatever cable you want as long as it is rated for the location it will be installed. Speaker wire with an overall jacket would be my first choice. Something similar to this: https://www.amazon.com/Mediabridge-1...=speaker+cable
 
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Old 12-23-17, 09:51 AM
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CL2 speaker cable was going to be my first choice as it's rated for in-wall and is readily available and fairly cheap. However I'd probably want to source some suitable for outdoor install (UV resistant jacket).

Can anyone link me to a source that describes low voltage wiring codes? There must be some requirement to limit current to the wires. 12V from an ample power supply can absolutely start a fire if there is a short.
 
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Old 12-23-17, 11:00 AM
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There really isn't too much in the code that will apply directly to what you are doing. Using common sense will be very helpful. Since you are using a power supply that is not listed by your IR providers.... the protection is placed on you. Yes... you should definitely protect the wiring if you are using a high current power supply.

If you have a 3A load use a 5A fuse at the power supply.

You could also use #14 UF cable outside for power.
Low voltage lighting wire is usable outside only.

Weather resistant CL-2 cable is pretty inexpensive. For what you are doing #16 would be a good size. CL-2 outdoor wiring.
 
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Old 12-23-17, 03:16 PM
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I have some spots where I may want to place 2-3 24W lights pointed in different directions, so now we're looking at around 6A total on the line. 16awg with a 10A fuse seems like it should be ok. 16awg at 10A is less heat per foot than 12awg at 20A, or 14awg at 15A.

I was thinking maybe 16awg with 10A fuse or 18awg with 5A depending on the load (or just buy all 16awg if pricing dictates it.

Of the not "too much code that will apply", what can I refer to? There must be something in the NEC about low voltage wiring.
 
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Old 12-23-17, 03:19 PM
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Weather resistant CL-2 cable is pretty inexpensive. For what you are doing #16 would be a good size. CL-2 outdoor wiring.
I would not choose CCA wire for any application.
 
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Old 12-23-17, 04:36 PM
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CCA is copper clad aluminum. No... you certainly wouldn't choose that.

At a lower voltage there is more voltage drop at a higher current. The lower the size.... the larger the wire... the less drop. If you keep the run short... #16 should be ok. Otherwise look in to using a larger gauge wire.,
 
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Old 12-23-17, 08:05 PM
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Here is an article discussing a new section of the NEC concerning low-voltage lighting systems. Code Rules for Low-Voltage Lighting | Electrical Construction & Maintenance (EC&M) Magazine

Also, you can do a Google using the search term low voltage + nec for more reading.

While the term "low voltage is somewhat ambiguous in its definition, some say under 30 volts, some say under 50 volts, the NEC most assuredly DOES address it in several different articles.
 
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Old 12-24-17, 12:23 AM
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CCA is copper clad aluminum. No... you certainly wouldn't choose that.
The link in your previous post was for CCA wire, that's what prompted my comment.
 
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Old 12-24-17, 10:39 AM
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Interesting. I hadn't seen that in the fine print.
 
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Old 12-25-17, 02:06 PM
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Funny thing is that I was thinking all about safety when considering the wire. I finally did some simple calculations and realized running 12V out to a 24W light (or 2 or 3 as I was thinking) is completely unfeasible. You start dropping volts real quick while your wire doesn't mind, your light fixture will. Seems you really need to pull 120vac closer to your light, then run off an adapter. So, a central computer power supply in the basement really doesn't work too well.
 
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Old 12-25-17, 02:22 PM
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Yes.....at low voltages.... the drop increases rapidly.
With that type of installation.... I usually use a single cable to each emitter.
 
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