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Old 05-17-2011, 04:15 PM   #1
dvd
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12V DC with 120V AC lamp wiring

I'm not a complete idiot when it comes to electricity but I seem to have a mental block on understanding electron flow dating back to my undergraduate P-Chem days when I never did get the hang of balancing chemical equations. Since that time I've rewired houses, an old MGA, etc. and managed to stay alive, but I have a question for someone who understands this area better than me.

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I have a couple of old (early 1800s) solid brass kerosene wall lamps which were converted probably about 10 years ago to 120V AC wiring (typical copper stranded wire), have a candelabra bulb base in them and a 5A 120V switch. If I wanted to install these as 12V interior cabin lights, would they work with the small amount of stranded (about 6") internal wiring hooked up to my DC circuit? Would the existing switch work with 12V? I have found 15W 12V candelabra-base bulbs which I could use if this would work.

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If these lamps had been left unconverted, they would have been worth BIG BUCKS, but since their bastardization, their value is minimal. Nevertheless, I don't want to attempt tearing them apart to rewire them since they are 1) solid brass and 2) very old.

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Thanks,

DVD
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Old 05-17-2011, 05:58 PM   #2
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RE: 12V DC with 120V AC lamp wiring

If you can provide the watts of the existing light at 120 volts and the gauge of the wire you can get an accurate answer.
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Old 05-17-2011, 05:59 PM   #3
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RE: 12V DC with 120V AC lamp wiring

You'll be fine.* Keep*the lamp*to 50 watts or less to keep the*current below 5 amps.
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Old 05-17-2011, 06:05 PM   #4
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RE: 12V DC with 120V AC lamp wiring

It had been wired into a household circuit using a 60W bulb and it was wired with 14G stranded copper wire. If I use it on the boat, I would likely only use a 12V, 15W bulb (although a 30W bulb is available).

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Old 05-18-2011, 12:25 AM   #5
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RE: 12V DC with 120V AC lamp wiring

If the wire is as you say , 14 ga, then it will handle the current of a 12VDC bulb of up to ~180 watts - far more than you indicate you want to use.
So a 30 or even a 50 watt bulb will be a piece of cake.

14ga wire generally is rated, in cable, at 15amps. 15A x 12V = 180 watts. There may be some other considerations if you were to use it at that level. In your lamp 14ga will be fine. Just give it a good inspection for condition and protection from sharp edges.

Even the switch should be fine but limited to 50watts or about 4amps at 12VDC in this application, a light bulb.
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Old 05-18-2011, 06:20 AM   #6
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RE: 12V DC with 120V AC lamp wiring

They will work if the wire is in good condition.
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Old 05-18-2011, 07:19 AM   #7
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RE: 12V DC with 120V AC lamp wiring

Quote:
dvd wrote:
It had been wired into a household circuit using a 60W bulb and it was wired with 14G stranded copper wire. If I use it on the boat, I would likely only use a 12V, 15W bulb (although a 30W bulb is available).

DVD
*That'll work.
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