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Old 15-03-2015, 21:28   #16
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Re: Hopefully a simple 12v question

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Originally Posted by Cthoops View Post

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.

Edit:

Nah, scrub what I said, I don't know what I am talking about. You are good to go, wire it however feels right to you. 16 guage wire on a 15 amp fuse should burn just lovely. Bring the marshmallows, but watch the smoke from the insulation, it makes a strange taste.

Matt
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Old 15-03-2015, 21:35   #17
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Re: Hopefully a simple 12v question

When you find out where to splice the wires add an inline fuse, which I really hate, as close to the splice point as possible. 16 gauge from the lighter socket to the fan is plenty. Size the fuse appropriately.
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Old 15-03-2015, 21:37   #18
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Re: Hopefully a simple 12v question

For such a low amperage draw item you should be fine with 16 gauge wire but you must make sure that your fuse matches the wire. The fuse panel shown is only the positive side there must be a negative busbar located somewhere else. I only see two photos not sure if I should see more. On closer inspection of your fuse panel I see you have a circuit labeled instrument if your instruments are low amperage it might be better to have the fan on that circuit. Nevermind I just realized that your instruments would be on all the time
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Old 15-03-2015, 22:24   #19
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Re: Hopefully a simple 12v question

Come on guys. So far we have suggestions to add what sounds like a vampire tap to a circuit with an inline fuse, or add a non critical component to a critical circuit.

This is not sound/responsible advice. These are electrics. They should be done right, not mashed together the quickest way possible.

My Aussie sense of humour might not translate well to all countries, but my point remains, these are recipies for trouble.

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Old 15-03-2015, 23:06   #20
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Re: Hopefully a simple 12v question

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Originally Posted by GILow View Post
Edit:

Nah, scrub what I said, I don't know what I am talking about. You are good to go, wire it however feels right to you. 16 guage wire on a 15 amp fuse should burn just lovely. Bring the marshmallows, but watch the smoke from the insulation, it makes a strange taste.

Matt
What kind of cheap wire do you buy? The wire I buy has an ampacity of 25 amps for 16 gauge (105 degree insulation). 15 amp fuse would be fine to protect the wire, but folks have been recommending a correct size fuse for protect the fan from burning up. He's drawing 2 amps, table shows 50' round trip for 5 amp 10% drop.
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Old 16-03-2015, 00:27   #21
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Re: Hopefully a simple 12v question

He's drawing 2 a / 24h. So he's taking ah Probably like 100ma fan. Computer fans are tiny

Who the hell runs 25a through 16awg... I would 't run that through 12.

16awg wire with 1a inline fuse spliced off the cig plug switch would be fine. nether is critical.
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Old 16-03-2015, 00:36   #22
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Re: Hopefully a simple 12v question

GILow, I understand what you are saying. The OP is going to do it anyway. Might as well help him make it as safe as possible even though not best practice.
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Old 16-03-2015, 02:21   #23
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Re: Hopefully a simple 12v question

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GILow, I understand what you are saying. The OP is going to do it anyway. Might as well help him make it as safe as possible even though not best practice.

You are right mate. These sorts of posts really worry me though. You know how many subtleties get even the experienced sparky. Cobbling a computer fan onto a working boat electrical panel just begs a problem. I'll cool it now.

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Old 16-03-2015, 02:25   #24
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Re: Hopefully a simple 12v question

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What kind of cheap wire do you buy? The wire I buy has an ampacity of 25 amps for 16 gauge (105 degree insulation). 15 amp fuse would be fine to protect the wire, but folks have been recommending a correct size fuse for protect the fan from burning up. He's drawing 2 amps, table shows 50' round trip for 5 amp 10% drop.

Yeah, yeah. I buy the best wire I can afford. There is probably better and worse than what I buy.

But the standards rate 16ag wire at 5 amps, and how sure are we this was properly constructed wire? The point being your fuse should be unequivocally the weakest link. There is absolutely no evidence that this is the case here.

Let's try to encourage the OP to give the system a chance hey?

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Old 16-03-2015, 02:28   #25
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Re: Hopefully a simple 12v question

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He's drawing 2 a / 24h. So he's taking ah Probably like 100ma fan. Computer fans are tiny

Who the hell runs 25a through 16awg... I would 't run that through 12.

16awg wire with 1a inline fuse spliced off the cig plug switch would be fine. nether is critical.
You wouldn't because of the voltage drop. The wire is rated to be safe with 25 amps through it. The post I was responding to was saying a 15 amp fuse was not adequate to protect 16 gauge wire from burning up.

If you had wire with 60 degree rated insulation and bundled it and/or put it in an engine space, then 16 gauge is rated around or under 15 amps, and then you can possibly have problems with fire.

Check out Ampacity of wire versus what is considered reasonable voltage drop. Ampacity concerns what the wire is capable of, voltage drop worries are for the device being run.
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Old 16-03-2015, 02:30   #26
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Re: Hopefully a simple 12v question

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.

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Old 16-03-2015, 02:34   #27
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Re: Hopefully a simple 12v question

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Originally Posted by GILow View Post
Yeah, yeah. I buy the best wire I can afford. There is probably better and worse than what I buy.

But the standards rate 16ag wire at 5 amps, and how sure are we this was properly constructed wire? The point being your fuse should be unequivocally the weakest link. There is absolutely no evidence that this is the case here.

Let's try to encourage the OP to give the system a chance hey?

Matt


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What standard are you referring to?
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Old 16-03-2015, 02:56   #28
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Re: Hopefully a simple 12v question

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What standard are you referring to?
Good point, not a standard at all. Just various web sites like Engineers toolbox. Recommended current is 5 - 7 amps for multistrand, which I hope is the wire being used. Single strand ain't gonna travel too well I should think.

Anyway, I said I'd stop griping now so I have to be nice. No more Mr Grumpy Sailor from me. I'm cured.

The OP should wire their boat however they see fit I reckon. And good luck to 'em.

Matt


Edit: But OMG, I am missing the point again. The point is the FAN is likely rated to a couple of hundred milliamps.


I'd forget my head if it wasn't... er... hang on....
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Old 16-03-2015, 03:11   #29
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Re: Hopefully a simple 12v question

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Originally Posted by GILow View Post
Good point, not a standard at all. Just various web sites like Engineers toolbox. Recommended current is 5 - 7 amps for multistrand, which I hope is the wire being used. Single strand ain't gonna travel too well I should think.

Anyway, I said I'd stop griping now so I have to be nice. No more Mr Grumpy Sailor from me. I'm cured.

The OP should wire their boat however they see fit I reckon. And good luck to 'em.

Matt


Edit: But OMG, I am missing the point again. The point is the FAN is likely rated to a couple of hundred milliamps.


I'd forget my head if it wasn't... er... hang on....
Try this -
Marine Wire Size and Ampacity | West Marine

Or this -
https://www.bluesea.com/support/refe...e_Sizing_Chart

and this -
http://assets.bluesea.com/files/reso...ence/20010.pdf
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Old 16-03-2015, 03:22   #30
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Re: Hopefully a simple 12v question

Excellent. OCD, alive and well and sailing.

You can relax now.

Matt
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