Fuse and wire size for LED dome light

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Fuse and wire size for LED dome light

Postby Tukanu » Tue Mar 03, 2020 9:38 am

I beginning my wiring and have a few questions.
I am running 16ga wire to a couple of LED reading lights, and a dome light.
The leads on the reading light are extremely skinny. I don't know the gauge but they ARE skinny!
I am guessing I need a pretty small fuse?? My panel uses the two-prong type of fuses.
The dome light has 9 LED's.....fuse size??

I know the fuse size protects the wire, not the light, so is there a fuse guide for these low wattage lights?
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Re: Fuse and wire size for LED dome light

Postby Pmullen503 » Tue Mar 03, 2020 11:20 am

I'd run a 10 or 15 amp fuse. If it's good silicone wire you'd be good to 20A continuous in open air. If it's cheap copper coated aluminum in a plastic sheath, buried in foam insulation, I'd go down to 10A.

The problem is heat generation. You could theoretically run undersized wire, overfused to allow high current enough to melt the insulation on the wire. An often overlooked problem is the connections. A poor connection (splice or terminal) has the same effect of running too small a wire. SO DON'T BURY YOUR CONNECTIONS! Make sure place your splices and connections where you can inspect and repair if necessary.

Lastly, there is a lot of cheap Chinese wire out there that is not pure copper or is copper coated aluminum and it tends to fail at connection points. I've had to rewire my trailer twice in five years due to the wiring corroding to powder. This was supposedly marine rated wiring from a reputable trailer parts supplier.
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Re: Fuse and wire size for LED dome light

Postby Tukanu » Tue Mar 03, 2020 12:00 pm

Thanks for the response. The 16ga wire was sold to me as pure copper...true USA gauge. But the leads on the (China) LED lights are very skinny.
As a basic electrical question: The 10 amp will protect the 16ga wire...but shouldn't I be using a fuse that protects the skinny leads?
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Re: Fuse and wire size for LED dome light

Postby Sparksalot » Tue Mar 03, 2020 12:10 pm

I have 5 amp fuses on most of my lights. The wire could do more, but the wattage doesn't require a big fuse.
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Re: Fuse and wire size for LED dome light

Postby Pmullen503 » Tue Mar 03, 2020 12:23 pm

I would say no.

It's rare, but not unheard of, that you have a dead short in a new electronic device. That theoretically could create enough heat for a fire but not trip the fuse on the line. That's very unlikely, conditions would have to be perfect for that to happen. Usually you would burn a PCB trace or a component would fail before significant heat could be produced.

Test everything on the bench before you install it and you should be fine and don't worry. Worry about your high amperage connections and devices. Make sure those are correct and well made.
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Re: Fuse and wire size for LED dome light

Postby Tukanu » Tue Mar 03, 2020 3:46 pm

Thanks...bench test, good advice.
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Re: Fuse and wire size for LED dome light

Postby tony.latham » Thu Mar 12, 2020 9:22 pm

As a basic electrical question: The 10 amp will protect the 16ga wire...but shouldn't I be using a fuse that protects the skinny leads?


I think you do. Wiggle that down to a five-amp fuse or so for the skinny wired circuits.

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