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Old 16-03-2015, 15:57   #46
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Re: Hopefully a simple 12v question

Quote:
Originally Posted by Cthoops View Post
We're not trying to rewire the entire boat before we splash.

We're about to start our third season on the boat, and up until the middle of last season the only thing we used the electric for was 1 or 2 LED cabin lights for approx 10-15 minutes at night, and of course the electric start on the outboard.
We then purchased a Nature's Head which has a small computer fan (less than 2 amps over 24 hours) for which we used a temporary splice off of one of the LED lights. Now we'd like to remove the splice from the light.

We read the relevant Casey chapters, bought 16 gauge marine grade wire to use instead of the cheap wire that came with the fan, and were caught off guard when we removed the panel and didn't see positive and negative wires like we thought we would.

I'd like to think that with the help of our books, plus the Internet, we can figure out what should be a reasonably simple task within the next week - let alone six - without calling in a professional.

Come on folks

Read this OK.
Or go to the Natures Head site and check out the fan that comes with it.---Well crap---the site does not say. Maybe the papers OP got with it.......or an email...........
Sheesh.

Quote:
Originally Posted by GILow View Post
One last gripe. The OP talked about the fan drawing 2 amps over 24 hours.

Unlikely, more likely the fan draws a total of 2 amp hours over 24 hours. Point is, 2 amps is an instantaneous rating, the 24 hours is irrelevant in that context. The fan would have drawn 48 amp hours over 24 hours if the rate of draw was 2 amps.

If it is a conventional pc fan the former case is more likely. I have a 1.6 amp, 12 volt server cooling fan in my spares box and is more like a lawn mower than a fan.

I'll stop griping now.

Matt


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Perfect.
good to hear.
Let us know how your grass is doing. Do you use it in a box for your dog to poop in while aboard?

Quote:
Originally Posted by um saudade View Post
A small point on the ampacity of wire:The maximum current a given wire can take never determines the size of the over current device.The circuit must be derated as per all the consideration thereof, including the length of the run, whether in free air or bundled or conduit (its all different), the temperature rating of any hardware in the system(for example a 75 degree rated connector would drop the entire circuit to the 75 degree rating) and on and on. The pie in the sky ratings of the really fancy insulated wire means that you can usually start with a smaller wire for the given circuit but the amperage of a circuit for #16 wire should not exceed the derated value and that’s about 10 amps.
Now you can’t run ten amps at 12 volts anyway because the voltage drop in #16 would kill the practicality of the circuit.
I will stake my life on the NEC.I don’t care if it’s on a boat, it does not change the laws of physics and the rules, rules that are well understood by people who know how to wire something.
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Old 16-03-2015, 16:00   #47
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Re: Hopefully a simple 12v question

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Originally Posted by Therapy View Post
...........
If you are worried then get some dielectric grease, remove wire nut, coat wires, re-install nut. ..........


NO WIRE NUTS ON A BOAT!
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Old 16-03-2015, 16:35   #48
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Re: Hopefully a simple 12v question

I'm surely gonna die! Just repaired the ground wire to my autopilot with a wire nut. Nice anchor marine tinned wire though.

Only wire nut on the whole boat. Except in the spares box.

Let's call it a field expedient repair. :-)
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Old 16-03-2015, 18:05   #49
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Re: Hopefully a simple 12v question

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NO WIRE NUTS ON A BOAT!
No ****.
But they are there and have been there for how many years?

Till next haul out............
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Old 16-03-2015, 18:09   #50
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Re: Hopefully a simple 12v question

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Originally Posted by four winds View Post
I'm surely gonna die! Just repaired the ground wire to my autopilot with a wire nut. Nice anchor marine tinned wire though.

Only wire nut on the whole boat. Except in the spares box.

Let's call it a field expedient repair. :-)
OMFG
Not a tinned wire nut?

Yer gonna DIE.


In like 15 minutes. Cuz that fan draws 2 amps and that means your Otto draws 50. BZZZAAPPPPOSPARKADOODLE for sure.

RIP.
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Old 25-03-2015, 12:19   #51
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Re: Hopefully a simple 12v question

Most boats will have a grounding point, near the fuse panel. It is just going to be a strip mounted, with a row of bolt terminals, likely having one larger wire going to the negative on the battery, and smaller wires going to the variouls lights, radio, depth sounder etc.

If it is a computer style fan you just want to hook the red to positive, (the fuse panel) and the black to ground/negative strip.

Would be worth while to confirm the fan is 12 volt, I think most of them are.

If your fuse panel has a fuse socket that is not used you can hook to that, then install a very small fuse, (that depends on wire size and then the device current, though remember it is important to never run too small fuse and/or wire for current draw, another source of potential fire).

It is very important to not run a larger fuse size than the current the wire can handle. If the wire will handle less current than the fuse, that may lead to a fire later. VERY important to fuse for wire size, you can search wire size charts for a better understanding of that.

If your panel does not have an unused fuse socket, then an inline fuse, of decent marine quality is neccesary, and again a fuse size to match device and wire.

Fan likely has red, and black, red to fuse panel, black to ground/negative strip. If you can't readily see the ground/negative strip, try tracing the wires from the battery.

Example: If device draws max 100 milliamps (.1 amps) then a fuse larger than that, but not 10 times that. Motors that draw running current often need double or more than double current to them, during startup and stall loads. But that only becomes an issues with larger motors, not tiny fans.

Keep in mind if the fan runs 24 hours, you miltiply the running current by the time, and that equals the 24 hour draw. 100 milliamps (.1 amps) for 24 hours is 2400 milliamps (2.4 amps) 10 days, is 24 amps, etc. If the boat is to be left without charge, it is important to not put loads on the battery that will kill (discharge) it before it gets a chance to charge back up.

Sorry for being long winded hope this helps!

Terry Turnbull
Nanaimo BC
Electrical Technician
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Old 25-03-2015, 12:25   #52
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Re: Hopefully a simple 12v question

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I will stake my life on the NEC.I don’t care if it’s on a boat, it does not change the laws of physics and the rules, rules that are well understood by people who know how to wire something.
applying documented codes of practice ( or legal codes etc) in an environment that they were not designed for , is bad engineering. If you (or one) don't understand the first principles, do not involve yourself in the process.
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Old 25-03-2015, 12:40   #53
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Re: Hopefully a simple 12v question

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I think many would be amazed at how many "dangerous" wiring is done by owners whose boat actually Don't catch on fire.
We could make the same connection between carrying life jackets and sinkings. So should we leave our life jackets on the dock?
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Old 25-03-2015, 18:31   #54
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Re: Hopefully a simple 12v question

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We could make the same connection between carrying life jackets and sinkings. So should we leave our life jackets on the dock?
Yes. It is my belief that if one is willing to accept the consequences of their actions then one is allowed to make their own decisions.

Unless the laws of wearing a jacket also apply to penises.
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Old 25-03-2015, 19:03   #55
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Re: Hopefully a simple 12v question

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Originally Posted by Therapy View Post
OMFG
Not a tinned wire nut?

Yer gonna DIE.


In like 15 minutes. Cuz that fan draws 2 amps and that means your Otto draws 50. BZZZAAPPPPOSPARKADOODLE for sure.

RIP.
Did you not notice the red wire nut on a ground circuit? It's just all kinds of wrong. lol

Oh the humanity! What have I wrought.

Clearly, as I motored past Tate's Hell Forest on the ICW I should have called in a Certified Marine Electrician to be dropped in by helo to end this madness.
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