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
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.
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.
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".
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.
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?
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.
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.
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.
I never considered the circuit itself. Doh! I guess I'm going to try to get 18AWG wire through the small tube that feeds the lamp. 18G is what the existing lamp is wired with from the factory. And, check me here, but 18G should support 16 amps. 20G will only support 11 amps.
Required wire gauge is related to the breaker or fuse of circuit. 120 vac and 20 amp requires 12 gauge wire and 15 amp requires 14 gauge (or heavier in either case, such as for longer runs). Your small hole must be sufficient to pass an entire romex cable or whatever, containing the correct gauge conductors.
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.
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