# What is smallest gauge wire for 110 AC light?

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• posted on October 17, 2003, 2:54 pm
I have an outdoor light that has a very narrow feed hole for the wiring. I'm interested in adding another pair of AC wires to feed a 40 watt bulb (which would be unswitched...unlike the existing pair) but since the hole is small I want to use very small gauge wire. It's only about 12 inches from the bulb socket to the J-box. I did some quick calculations and a 40 watt bulb draws less than .3 amps, seems like I could use all the way down to 22 gauge wire and not have a over heat problem. Anybody care to comment? I would appreciate it. Mark
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• posted on October 17, 2003, 3:27 pm
try using small luminescent bulb, a 40 watt equivalent would draw .1 amp.
i

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• posted on October 17, 2003, 5:42 pm
On 17 Oct 2003 15:27:13 GMT, Ignoramus29325

Where did you come up with that? W=IE, 120V*0.1AW
A 40W bulb draws 333ma while running at temperature, but possibly 10 times that during startup.
Try running a 40W light with a 1A fast acting fuse. It'll blow.
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• posted on October 17, 2003, 6:06 pm
I said "equivalent".
A 40watt "equivalent" luminescent bulb only uses 11 watts, but it puts out as much light as 40 watt incandescent.
I use such a bulb in my chicken coop.
i
wrote:

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• posted on October 18, 2003, 5:25 pm
TCS wrote:

Probably correct, but the turnon surge won't last long enough to heat the link in a 1 amp fast acting fuse to its melting temperature.

NOT!
Tell us if you've actually tried this, or if you know what the turnon surge current vs. time curve of a 40W light bulb looks like and what the (I^2)*t rating of a fast acting fuse means.
A 1A fuse might blow if the bulb happens to burn out with a "tungsten arc" effect, which doesn't happen every time a bulb dies, but it won't burn out at turnon. If it happens, you'll get a blinding burst of light from the bulb at burnout.
I've got four table lamps in my home with 150W bulbs in them which I protected with 2A Buss Type 3AG fastblow fuses. I put the fuses in because I got pissed at having to replace the solid state "touch dimmers" in those lamps when the occasional tungsten arc burnout of the bulbs fried the dimmers. My beta test was slapping a direct short across a powered bulb. The fuse blew, but the dimmer survived, because the dimmer's triacs and printed circuit tracks had a higher (I^2)*t rating than the fuse. Since I put those fuses in the lamps about three years ago I've had maybe six bulbs burn out in them, but I've only had to replace a fuse along with a bulb once, and it was a lot cheaper than buying a new touch dimmer.
http://members.misty.com/don/bulb1.html#sur
Jeff
--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone to
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• posted on October 18, 2003, 5:25 pm
TCS wrote:

Probably correct, but the turnon surge won't last long enough to heat the link in a 1 amp fast acting fuse to its melting temperature.

NOT!
Tell us if you've actually tried this, or if you know what the turnon surge current vs. time curve of a 40W light bulb looks like and what the (I^2)*t rating of a fast acting fuse means.
A 1A fuse might blow if the bulb happens to burn out with a "tungsten arc" effect, which doesn't happen every time a bulb dies, but it won't burn out at turnon. If it happens, you'll get a blinding burst of light from the bulb at burnout.
I've got four table lamps in my home with 150W bulbs in them which I protected with 2A Buss Type 3AG fastblow fuses. I put the fuses in because I got pissed at having to replace the solid state "touch dimmers" in those lamps when the occasional tungsten arc burnout of the bulbs fried the dimmers. My beta test was slapping a direct short across a powered bulb. The fuse blew, but the dimmer survived, because the dimmer's triacs and printed circuit tracks had a higher (I^2)*t rating than the fuse. Since I put those fuses in the lamps about three years ago I've had maybe six bulbs burn out in them, but I've only had to replace a fuse along with a bulb once, and it was a lot cheaper than buying a new touch dimmer.
http://members.misty.com/don/bulb1.html#sur
Jeff
--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone to
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• posted on October 17, 2003, 3:35 pm
I'm not an electrician but I always thought that whatever the amps the breaker at the box is rated for then all the wiring in that circuit has to be at or above(lower#) the guage rated for that amperage. In your case you would have to hook up a sub-breaker rated for 22 guage wire. Otherwise if you had a short your wire would burn up before it blew the breaker.

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• posted on October 22, 2003, 2:48 pm

That's true for the house wiring, but the wiring from the plug to the lamp doesn't have to meet the same standards, at least in the US. There's no good technical reason for this, it's entirely because of lobbying by the manufacturers.
Look at the really skinny wires in plug-in christmas lights, for example.
Outside the US, some countries have fused plugs for low-current lamps/ appliances that allow this.
Tim.
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• posted on October 22, 2003, 6:40 pm
Whereas On 22 Oct 2003 07:48:41 -0700, snipped-for-privacy@trailing-edge.com (Tim Shoppa) scribbled: , I thus relpy:

They have fuses in the plugs of series strings now.

Not many though. Outside of the UK (where nearly everything has a fused plug, due to the nature of the 32A ring circuits used there),and the aformentioned US series lights, I cannot think of any country where the plugs used on lower current appliances are fused.

--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

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• posted on October 17, 2003, 5:08 pm
Mark, listen to Joe. He is correct about wire size vs circuit breaker. You can't wire anything up in the house smaller than the correct size for the particular CB. There wouldn't be any protection for the 22 gauge wire. It's NOT ABOUT THE AMPERAGE DRAW OF THE LITTLE LIGHT YOU PLAN TO INSTALL. It's about a potential short circuit heating up the wire, which WOULD melt long before the CB blew.
dave
Mark wrote:

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• posted on October 17, 2003, 6:26 pm

I am not recommending this, but wouldn't it meet code to put an outlet in the box and plug the light in with a #22 wire? Or, would that require that everything be out in the open and readily unplugged: which presumably is not true in this case. Lamps routinely use #16 and #18 wire, but plug into 20a circuits.
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• posted on October 17, 2003, 7:41 pm
good question. I can't recall seeing any device that plugs into a 110V outlet be wired with less than 18 gauge. Can't say it would be wrong; I just can't confirm that it would be "legit".
dave

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• posted on October 17, 2003, 7:45 pm
besides, the OP cannot just put wires through any "hole" in the walls. It needs to be protected with metal conduit.
i
wrote:

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• posted on October 17, 2003, 9:29 pm
Bay Area Dave wrote:

I believe that is the smallest wire that will meet UL requirements. Christmas tree lights use smaller wire but, IIRC, are required to have a fuse built into the plug.
--
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Steve

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• posted on October 18, 2003, 4:12 am

You are right, but that's an extension cord (effectively) not the house wiring (circuit). Fuses or breakers protect the house wiring not things that plug into the house wiring. Nonetheless, isn't the simple solution to make the hole bigger?
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• posted on October 18, 2003, 10:19 pm
You mean I can't use a radio with 18 gage lamp cord on a 20 amp circuit?
--

Christopher A. Young
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• posted on October 19, 2003, 2:51 pm
Whereas On Sat, 18 Oct 2003 18:19:01 -0400, "Stormin Mormon"
, I thus relpy:

You cannit use 18 guage as part of a fixed circuit, unless the device has been approved for it.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

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• posted on October 18, 2003, 9:02 pm
Whereas On 17 Oct 2003 07:54:47 -0700, snipped-for-privacy@yahoo.com (Mark) scribbled: , I thus relpy:

The size of appropriate for the breaker protecting the circuit. No smaller. If thise is wore in the light fixture itself, the fibre coated #16 or #18 wire may do.
--
Gary J. Tait . Email is at yahoo.com ; ID:classicsat

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• posted on October 19, 2003, 1:10 pm
I assume there is no way to enlarge the feed hole. Louis
On 17 Oct 2003 07:54:47 -0700, snipped-for-privacy@yahoo.com (Mark) wrote: