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Issues and safety precautions to take with a 50-70 feet 12v bus line? Answered

Hi
 i am thinking of building a emergency LED setup with some 1w or 3w LEDs which will be connected to a 12v bus line powered from a deep cycle battery. I will be using a fuse between the battery and the bus line. I am thinking of placing a cluster of LEDs every few feet(7-10 feet). Each LED will be powerd using a mr16 LED driver using power from the bus line and the driver should consume somewhere around 350ma of current. Each LED will be mounted on a heatsink. Max LEDs in a LED cluster will be 3 no.s . Total current used when all the LEDs are on should be around 6 amps max.

So, the question is, what kind of safety issues should i look out for and what type of wire i should use for bus line and the lines to leds. Also, should i be using relays for LEDs or will switches be fine? And what precautions should i take  ?

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bipl12

4 years ago

Thank you for your reply everyone. I am thinking about using 12 gauge wires for use in the main bus line. The voltage drop would be around 1.5v at the end of the line when using this wire, from what i have come to understand from various online voltage drop calculators. I think that should be acceptable as the MR16 drivers can operate at around 8v or so, but i am unsure if the wire would be able to handle the current load when all the lights are on. I am hoping it would be able to handle 6 amp current that might pass through the wire when all the LEDs are on, but i am unsure. I would appreciate any feedback relating to this matter

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seandoguebipl12

Answer 4 years ago

12ga seems a bit overkill for 6A, although granted, its lower resistance will reduce line losses. However, 18ga should be more than suitable for a total load of 6A.

R(12ga ) ~ 1.5mOhm/ft

total resistance over 60 ft ~ 0.1 ohm

loss at 6A ~0.6V

V at line end ~ 11.4VDC

18ga > ~6.4mOhm/ft

total resistance over 60 ft ~0.38 ohm

loss at 6A ~2.3V

V at line end ~9.7VDC

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seandogue

4 years ago

@12VDC, no special considerations are required, aside from gauging the wiring to handle the max load (good engineering)

I'd recommend applying a fuse or circuit breaker for the output line (inside whatever enclosure is housing the power supply) just to protect the supply-side in case of a short circuit in the line at some point in the future.

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Burf

4 years ago

Assuming you are either in the U.S or Canada, check the NEC (National Electric Code) section on low voltage systems, less than 30 volts. Generaly, but not totally, on systems under 18 volts, anything beyond the transformer is not regulated by code because they are considered safe and no regulations are necessary.

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steveastrouk

4 years ago

There aren't any safety issues related to this really. The voltage is very low, and the current high enough and lengths are so long, you need to use a cable rated for voltage drop, rather than current, which means you'll be using a cable that can easily handle 6A.