Hopefully a simple 12v question

[Cthoops]

Originally Posted by GILow

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

I didn't intend for my post to sound quite so snarky. It was late, and I was frustrated that yet another "simple" boat project is morphing into something that is starting to take hours without being much closer from where I began.

Anyway, I've been reading every post closely. Our long-term plan is to go cruising full-time (on a different boat, of course), so we really want to learn this and to do it properly (although given our electrical use, I think re-wiring the entire boat is a project for another day). For some reason I'm finding myself strangely "drawn" to the challenge of figuring out basic electrical work. Perhaps because it seems so mysterious on the face of it.

According to the Nature's Head manual, the computer fan draws less than 2 amp hours over 24 hours, so .083 ah. We purchased Ancor Marine 16-2 gauge flat duplex safety wire, with the gauge based on the tables in the Casey book.

It doesn't have to run off the cigarette lighter if that's part of the safety concern (aside from my obvious newbie-ness). We could also run it from the "cabin lights" circuit which has 4 LED lights with switches. Running it from "instruments" would mean the depth sounder is always on, so I'd prefer not to use that.

So based on the responses so far, the positive is running from the panel and the negative should be attached to a busbar. I also need to make sure I have an appropriately sized fuse for the load. I have a blurry picture of the battery from last year. I never knew what those phone jack looking things were, but based on the posts I'm thinking these are the busbars:



I don't want to clog the thread with continued super-basic questions, so I think I may hold off on more posts until the Calder book arrives on Wednesday and I can study it for a bit. Thanks everyone for the help so far.

And by the way, not that it matters, but the OP is a she. Thanks again.

[Wotname]

FWIW a busbar is simply a bit of metal which allows you to connect a heap of wires together at one point

There are many shapes and sizes, try googling busbar images for some ideas!

[GILow]

OK, so now I feel like a big grump. Sorry for being a big grump.

I understand your frustration with the job, but its a boat. Things get complicated.

I rewired our boat from scratch. Then a friend who certifies aircraft for safety came along for a day sail and tore strips off me in a hundred little places. I would rate myself about a 7 out of 10 for electrical competence (so, incidentally did the aircraft engineer) and I can still make mistakes. So my point about a pro is that if a pro can help me, then I reckon a pro can really help someone who is still figuring out the first steps. No, I don't advocate handing the boat over to have it rewired, but I do advocate finding someone who knows their stuff to come and give you some pointers, and check what you have done. That way you learn, and you know what to do when (not if) it goes all pear shaped.

My point about the wire was that regardless of the wire you use, the device in question is way too small for the likely rating of the fuse on the circuit. I've been greatly educated in the ratings of 16 gauge wire now, and have a new happy respect for it, but that does not change my initial concern that the fuse must match the device. DeepFrz gave one solution, and also flagged his dissatisfaction with that solution. Personally, I would do it clean, from scratch. But that's me.

Then my aircraft certifier can come and tell me how I did it wrong.

You are male, female, still deciding...? Did I say "he" somewhere? I don't mind either way. Girls are just as capable of burning the boat down as boys. They generally look better while doing it in my opinion, but that could be a male gender bias thing.

Matt

[GILow]

As per Wotname's post, that photo is not a busbar. That looks like the top of a battery with some kind of current/net use monitoring device, or perhaps temperature sensors for the charging system.


It is usual to locate the busbar some short distance from the battery, attached via a single heavy cable, in some cases with a master fuse in line.


I don't know why but every boat I have bought seems to have had half the latter additions of electrical equipment wired straight to the battery terminals, and it makes for a big, hazardous mess.


If the matter is urgent, I second DeepFrz's solution of a vampire tap onto the positive feed from the cigarette lighter plug with a small inline fuse. You don't want to go near the battery system until you know what each of those wires do.


Or, to keep it really simple, grab a plug that plugs into the cigarette lighter socket and use that to drive the fan. At least you can yank it out in an emergency. I have half a dozen of those lighter plugs with long cables ready to go on our boat, very useful for emergencies. I believe it is even possible to buy them with an insert for a blade fuse of smaller capacity where required, but I don't have one of those.


Matt

[Wotname]

Originally Posted by GILow

......

I don't know why but every boat I have bought seems to have had half the latter additions of electrical equipment wired straight to the battery terminals, and it makes for a big, hazardous mess.....
Matt

'Cause even the least literate most drunk brain dead sailor can work out that the two wires has gotta go to the battery so let's take them there right away. The ones with double digit IQs can even work out the red wire goes to the positive terminal so the other one must go to whatever terminal is leftover. As for the hazardous mess, well she'll be right clobber, crikey its a dry argument, crack anotherie matie, wadda ya reckon.

So I appauld the OP for wanting to learn and wanting to get it right. This electricity can be a bit of a mystery at first but sooner or later the penny drops and soon she will be posting good advice to other new chums

[four winds]

Actually if the OP pops open those little red an black boxes on the batterry she will discover they are small bus bars, or terminal extenders, for lack of a better term. Have some in my spares box just like that. I bet there is an unused terminal there as well.

Simple wiring on this boat, no? I'd bet the larger red a black wire there feed the fuse panel, or maybe the bilge pump.

Anyway 16 guage is fine for the current draw of the fan in question. And changing the fuse in the cig lighter circuit fuse holder to 5 amp would be appropriate as well, no inline fuse holder needed.... assuming the lighter socket is being discarded. Did I read that? Not sure now.

So, wire the positive to the panel output and the negative to the black terminal block on the battery. Seems like the simple and safe solution.

[Time2Go]

First thing I'd do would be to test the cigarette lighter plug
Perhaps there is some confusion because it is not wired to function
and there is no circuit to trace. Also isn't at least one bilge pump supposed to be wired directly to the battery? Aren't different color wires used to aid in tracing circuits? In my land based world of TV studios Green is always ground
Not so on boats?

[DeepFrz]

The new(er) standard(?) for boat wiring is that Yellow is the -12 volt (gnd) wire color. However, until fairly recently Black was the color to use. But because AC Black is hot...well I'm sure you get the picture. Solid Green as seen in the OP's picture could be mistaken for AC grnd.

try googling busbar images for some ideas

Yes, and stay away from the ones with bright lights.

Note to OP, bookmark the URL for Blue Sea Systems. They have everything boat electrical with pictures and many wiring diagrams.
https://www.bluesea.com/

[svfinlandia]

It is truely a simple problem. Forget about the 12 volt outlet and PLEASE get rid of the wire nuts (there and anywhere else you may find them on the boat) and replace them with a proper splice on the 12 volt outlet. While you are at it, it would be a good idea to wire re-wire the 12 volt outlet with the proper size and color wire with a 15 amp fuse in the circuit.

The positive from the fan should go to the positive buss on your electrical panel and the negative to the negative buss with the proper size fuse in the circuit.

It would be nice to know the exact amperage draw of the fan. Less then 2 amps in 24 hours sounds a bit low to me unless the fan is running intermittently and not continuously. Most small DC fans draw less than an amp though, so I suspect that you are fine with the 16 gauage marine wire as long as it is not a long run, and be sure to install no larger than a one amp fuse.

Al, S/V Finlandia

[rwidman]

Originally Posted by Stu Jackson

One of the basics that I continue to note is that pictures of wiring without an electrical diagram are useless in trying to help OPs.................

Not always. In this case, the picture shows wire nuts used for electrical connections. That is a serious problem. Wire nuts should never be used on a boat except possibly for a temporary repair.

I shudder every time I see a post like this where someone with absolutely no clue is attempting to do electrical work on a boat. I suggest putting a plug on the fan and plugging it into the cigarette lighter socket. The positive wire from the fan goes to the center contact on the lighter plug, the negative wire goes to the shell or outer connector. If the fan runs backwards, reverse the wires.

And have a competent marine electrician go through the boat and eliminate any wire nuts and other mickey mouse work done by previous owners. You'll sleep better at night.


PS: If you want to learn how electricity works and how to safely wire your boat, I suggest enrolling in a local community college or trade school. It's not something you an learn by doing or by casually reading a book.

[tlavino]

What you're seeing in the picture is the positive side of the circuit - many times older installations or those done by less knowledgeable folks don't follow the ABYC recommendations in terms of wiring color, using anything whatever they had. If you go back to the cigarette lighter you will see the other half of the circuit go to a DC negative buss bar to which the negative side of all the other circuits are tied to. Concur with the recommendations regarding a fuse for the fan, getting rid of the wire nuts and creating your own as-built wiring diagram. You will then eliminate any "black boxes" and truly understand your boat's electrical system.


Take a look on Ancor's web site (Products | Ancor), a reputable source for marine wiring and associated tools and information. They have a copy of the ABYC table regarding wiring size vs. load and length. Always use tinned stranded copper wire with crimped spade lugs (use a professional crimping tool @ $150 not the hardware store special) covered by adhesive lined heat shrink tubing (don't forget the heat gun, not a hair dryer) and you will eliminate many issues plaguing less well done installations done by professionals and amateurs alike. Calder is a good (if a bit to detailed IMO) resource...

[boeing1]

agree, wire nuts have no place on a boat.....

[um saudade]

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.

[Therapy]

I skipped page two.
Hope I didn't miss anything serious.
Someone asked about the fan current draw so I know they skipped some stuff.

Here is my opinion. It varies and will be boring and repeats of others ideas too.

OP has used boat for three seasons. Great.
OP has not used much of the electric system. Nothing about anchor lights all night - just LEDs for beddy-bye right?

Just use a "Lighter plug" with inline fuse. Have fun.

If you are worried then get some dielectric grease, remove wire nut, coat wires, re-install nut. Make list of things to do starting with Check Wiring!
I think many would be amazed at how many "dangerous" wiring is done by owners whose boat actually Don't catch on fire.

Then of course, it is not nearly as tragic unless it happens to you.

[Wotname]

Originally Posted by Therapy

.....
I think many would be amazed at how many "dangerous" wiring is done by owners whose boat actually Don't catch on fire.

Then of course, it is not nearly as tragic unless it happens to you.

Good point and I willing to bet for for every electrical fire from poor wiring practices, there will be thousands of circuits that simply don't work at all