I was already planning of converting to LEDs, I did my trailer last year and they are so much brighter.
Wire Size
- Thread starter rlongfield
- Start date
Wire nuts no matter where they are shouldn‘t be on a boat anywhere no matter what!
Also the awg for AC and DC are greatly different. There are less losses through an AC line than a DC line so the wire gauge can be much smaller yet carry a higher voltage and current.
NEVER unfuse any device. And ALWAYS fuse near the battery, not near the device. Even if there is a fuse at the device, you need one that is properly rated at the battery too.
Bigger isn’t always better when it comes to DC wires. There gets to a point where the bigger wire will actually have just as much loss as a smaller wire. The electrons flow on the outer layer of the wire, and the more wire you have the more electrons can flow, thus a higher current capacity. But if you don’t get an adequate volume of electrons through the wire, you will actually lose capacity. For example take a 6v lantern battery and 10’ of 0 awg cable for both the positive and negative and have a 6v light at the end… then do the same with 10’ of 14g wire. The light on the 14g wire will be brighter, there will be less loss at the given current level. So gauge your wires according to the needs of the equipment you are powering for best results. You will prolly not see that big of a difference between a 10g and 16g when powering a stereo, or lightbulb on your boat, but the 10g will cost more, and the 16g will be more than adequate for the job.
One more thing to consider and remember. The bus feed into a fuse panel from BOTH the positive and negative need to be able to carry the current of ALL devices at the same time. You will see in many cases a 10g wire for the ground/negative and a 4g wire for the positive. In reality both wires are going to carry the same loads, therefore they should both be 4g. People get used to automotive type wiring where they see a small ground wire leaving a device, but you have to consider the entire body of the car is the negative lead (bus) and the small wire is for that singular device only. When you get back to the battery, you will notice a large cable that is the same size as the positive cable… this is the return side from the vehicle to the source. So do the same with the bus lines in the boat.
Also the awg for AC and DC are greatly different. There are less losses through an AC line than a DC line so the wire gauge can be much smaller yet carry a higher voltage and current.
NEVER unfuse any device. And ALWAYS fuse near the battery, not near the device. Even if there is a fuse at the device, you need one that is properly rated at the battery too.
Bigger isn’t always better when it comes to DC wires. There gets to a point where the bigger wire will actually have just as much loss as a smaller wire. The electrons flow on the outer layer of the wire, and the more wire you have the more electrons can flow, thus a higher current capacity. But if you don’t get an adequate volume of electrons through the wire, you will actually lose capacity. For example take a 6v lantern battery and 10’ of 0 awg cable for both the positive and negative and have a 6v light at the end… then do the same with 10’ of 14g wire. The light on the 14g wire will be brighter, there will be less loss at the given current level. So gauge your wires according to the needs of the equipment you are powering for best results. You will prolly not see that big of a difference between a 10g and 16g when powering a stereo, or lightbulb on your boat, but the 10g will cost more, and the 16g will be more than adequate for the job.
One more thing to consider and remember. The bus feed into a fuse panel from BOTH the positive and negative need to be able to carry the current of ALL devices at the same time. You will see in many cases a 10g wire for the ground/negative and a 4g wire for the positive. In reality both wires are going to carry the same loads, therefore they should both be 4g. People get used to automotive type wiring where they see a small ground wire leaving a device, but you have to consider the entire body of the car is the negative lead (bus) and the small wire is for that singular device only. When you get back to the battery, you will notice a large cable that is the same size as the positive cable… this is the return side from the vehicle to the source. So do the same with the bus lines in the boat.
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@mikeracca, "Bigger isn’t always better when it comes to DC wires. There gets to a point where the bigger wire will actually have just as much loss as a smaller wire."
Not true,
increase in cost....yes,
inability to fit in connections.....yes,
inability to carry light current loads......false.
Not true,
increase in cost....yes,
inability to fit in connections.....yes,
inability to carry light current loads......false.
Keep reading and you will see the setup of an experiment I did in school. Read the part with the 6v lantern battery and the 6v light. If you don’t believe me try it yourself! It’s even more pronounced with a “D” sized battery and a 2V lightbulb. The higher the voltages the less visible this is as a higher voltage has more electron volume than a lower voltage, but the same still happens. Why does the small wire get hot? Too many electrons trying to vie for the same space creates resistance, which creates heat. This is why we need larger wires with larger loads, more surface area to handle a larger electron flow, thus less resistance and less heat.
AC, particularly at high frequencies, travels along the outer surface of the wire. That’s caused by the oscillating current inducing an EMF within the wire itself. DC current flows in one direction only, so there’s not that kind of EMF, allowing the current to flow through the entire conductor. So with DC what matters is total cross sectional area of the cable, not surface area.
Do you have any sources you can point to on how that works? I’d like to learn more about it if it’s the case, but I can’t find anything like that, and it’s totally counterintuitive.
I had done some research myself before posting and everything points to bigger has less drop, less drop has less resistance, less resistance provides unrestricted amperage to the device at a given load, low load larger cable results in less voltage drop. In your experiment was the negative the same size and the positive conductor?
How was the very light load connected to the larger than needed cable?
It sounds as if the connection methodology was causing a relatively high voltage drop for your given voltage source resulting in your observation.
In my real world case I changed out florescent fixtures on the boat to LED strip lighting, reducing the load per fixture from approximately 1.5 amps to 0.15 amps, the existing wire feeding the fixtures is 14ga (grossly oversized for the load) there is no noticeable difference when lighting a single strip (approximately 8 LED squares) when testing at home with a 12 volt battery connected with 20ga wire and the light output on the boat when connected with 14 ga wire, and I can't image any difference if connected them with 1/0 cable, if the connection could somehow be made.
How was the very light load connected to the larger than needed cable?
It sounds as if the connection methodology was causing a relatively high voltage drop for your given voltage source resulting in your observation.
In my real world case I changed out florescent fixtures on the boat to LED strip lighting, reducing the load per fixture from approximately 1.5 amps to 0.15 amps, the existing wire feeding the fixtures is 14ga (grossly oversized for the load) there is no noticeable difference when lighting a single strip (approximately 8 LED squares) when testing at home with a 12 volt battery connected with 20ga wire and the light output on the boat when connected with 14 ga wire, and I can't image any difference if connected them with 1/0 cable, if the connection could somehow be made.
It was an experiment that was done back in high school electricity class (back when they actually taught useful things like that) it was an extreme circumstance experiment but it showed us that too much of a good thing is sometimes not so good. So we had a piece of wood that was 10 or 15 feet long. A brass horseshoe SPDT switch that was connected on one side to 0awg wire (welding cable) and the other side to 16awg wire (lamp cord). On the other end was a pair of light bulbs that were the same. My teacher had a light meter we used for the readings. We flipped the switch to the 0g side and measured the intensity of the light, then flipped to the 16g side and did the same. The light was visibly brighter on the 16g side, and the meter showed the same. There was no hidden resistor or anything like that, we even moved the bulbs around to make sure it wasn’t the bulb, same results. Our teacher compared it to the flow of water through a hose. The 16g was a garden hose and designed for the flow we had available, and thus got the most out of it, then the 0g wire was like a 4” fire hose with the same water flow. Yes it will work, and yes the water will get to the other end, just losing something along the way.
With a difference between 14 and 20g wire this effect will be pretty much non existent at 12 v. Maybe at .5v you would see something. The experiment I referenced was one of extremes, but we were being taught that there is a right size and wrong size for a job. We didn’t go the other way by putting massive voltage and current through the welding cable, and then the lamp cord to see the other end of the extreme. We would have fried the lamp cord obviously, and we did experiments with fuses to prove the opposite of the other experiment instead.
Are you familiar with Ohm's Law:
I = E/R
It was proposed in 1827 and is still used today.
Bigger wires with bigger resistance and :
Yes I’m well aware of ohms law, and it DOESN’T apply here. I can’t remember the formula for this phenomenon but it relates to the surface area of the conductor. Hell it was 30 years ago when we did this experiment. But you guys seem to be too close minded about this actually being something that could be a reality.
as for calling me a flat earther… you can kiss off.
No, you DON'T know the first thing about Ohm's Law or you wouldn't be embarrassing yourself by making these ridiculous statements. Remember, we're talking about DC and not AC current.
See, you don't know the first thing about DC current either, do you ? It's already been pointed out that induced EMF causing higher skin current only occurs in hi frequency AC and not DC currents.
Because there's just too much proof against it as we've tried to tell you, just like:
Flat earth
Cold fusion
Perpetual motion
And the sun will go nova tomorrow.
Proof, proof, proof .......................... not suppositions or foggy high school experiments of 30 years ago.
You the funny thing here is, you are trying to make me look the fool. Not the first time I have made this claim, not the first time someone has stated the same thing as you have and not the first time what I said was true and proven after someone else did the same experiment. the last time it was with a group of model railroaders. One of these guys decided to prove me wrong. He decided to use actual rail, and some speaker wire he had. He had about 100’ of speaker wire and a 12v battery. You would never guess what he found…
So you can just keep on thinking you are so smart with out doing the same experiment, or you can do the experiment yourself and say wow, Mike was right, this is crazy. Like I said before, this was an experiment of extremes, and going between 14 and 20g wire will not have the slightest difference, and Ohms Law would be correct. In the welding cable or steel rails at a higher voltage, you wouldn’t have this happen either, but an extremely large conductor passing a small voltage isn’t efficient and there are losses. Enjoy your ignorance.
@mikeracca
Mike, I've been following your rebuild thread and think you're doing a great job. Keep up the good work.
Otherwise, I simply don't get this one though. OK, I give, I'll never guess what he found. I am a model railroader, too. Could you please explain? (I've read this one from start to finish, maybe I missed it.)
Like this one?
A larger garden hose example means nothing gets lost long the way, the volume remains the same, the pressure is less. That's all. Compare a garden hose to a culvert big enough to walk upright through. Trickle a garden hose into one end of the culvert. The amount that comes out the other end is exactly the same, just with less pressure.
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He found out that a too large conductor with a small voltage/current will have similar losses to smaller conductors over a distance. My teacher compared it to a garden hose and a fire hose. If you hook a fire hose to the spigot at your house, it will still flow water, but it won’t be useful (large conductor small voltage comparison), just as if you hooked your garden hose to the fire hydrant, you are likely to burst your hose (small wire too much current comparison).
Did the same in my house. Everything is 12ga even though lights don't need it.
My very limited knowledge of DC circuits and playing around with this handy calculator I see very little difference between 10 and 14 awg. Where I see the biggest difference is when increasing the load on the wire. The higher the load the greater the loss in voltage. the difference between 10 and 15A is surprising, it's nearly 1V over a 20 foot run.