Newbie Yacht Re-Wire HELLLPPPPPPPPPP

[737guru]

I have my 24' Yacht. It has old out of date wiring which is deffinitly in need of up grade. I am going to rewire but have found myself bewildered by the sheer choice of hardware and advice out there and at the moment if I did attempt this I'd really be stabbing around in the dark.

The components I have now are:-

2 Batts, Linked by a 1/2/both heavy switch.
Nav Instruments
Auto Helm
Nav Lights
Cig lighter socket
Radio
Fwd and aft internal lights

I would like the new system to be entirely 12v. It should be possible to charge (both batts at once) by the engine alternator or by shore power which is 240 v 50 hz.

I have an idea of the various components out there which will do all this. But what I don't have is the experience of having done this before! So what I am asking for is your opinion of what components to use in what combination to achive a reliable and expandable system whilst optimising the use of components to keep the budget realistic. My ideal response would come with a scematic so I can start to build my own from it.

Some other info you may want is:-

Engine is a Yanmar single cyl diesel 9HP (starter motor load?)
lighting is four halogen 10w 12v bulbs
Batts are 12ft away from engine and proposed switch panel location.

Specific q's I have are

Is there a "box" out there that has a 12v alternator and 240v shore power input with two isolated batt bank out puts?

What are the best switch panels to use and is there one which incorporates a battery monitor in it?

Thanks very much in advance.

737guru.

[PAR]

This is a relatively simple system for an experienced electrician, but it would appear you're in a little over your head.

You have a few choices, muddle through it the best you can, hire an electrician or gain some education. I'd start with the book "The 12 Volt Bible for Boats" by Brotherton/Sherman. This is available at the book store on this site.

[marshmat]

I like the third option suggested by our friend PAR.

Muddling through is likely to result in something over budget that looks like a rat's nest and blows fuses (or, worse, energizes metal fittings on board without blowing fuses).

Hiring an electrician is easy, but expensive and no fun.

Sitting down for a week or so with some good books strikes me as the place to start. Being trained as an engineer, I could probably rhyme off a bunch of 900-page textbooks that none of us ever actually bothered to read. But there's plenty of more accessible, less mathematical stuff out there, that is actually interesting to read and is actually useful. I've heard good things about Nigel Calder's "Boatowner's Mechanical and Electrical Manual" but have not found a copy for myself yet.

Shorepower is a potentially dangerous game that will require a fair bit of additional reading above and beyond what you need to build a good 12V system. (While a bad 12V system might give people mild shocks and galvanically erode your propeller, a bad shorepower system might dissolve your running gear, set the dock on fire, or kill people who swim too close to the hull. So an extra level of caution is called for here. It's not hard to do it right, but there are a lot of ways to do it wrong.)

[Landlubber]

Nigel Calders "The Boatowners Electrical and Machanical Manual" should be read by every boat owner, like our freind PAR, Nigel is one of those fellas that you can rely on to tell it how it is. Many boat builders (like myself), have ideas and ways of doing what we do, but few get it right always, some of us may disagree with the process, or the application, but it is not "wrong", it is still a recognised method of doing things correctly. Nigel has that ability, so go buy the book, ne needs the money too poor fella, he is building a new boat.

[mydauphin]

Nigels books are great, He must owes me a free lunch by now. I have bought all his books... Anyway on wiring - have a "professional" do it for you, but read Nigel book and make sure he does it right and that you understand it perfectly. It will save you a lot of grief and money later.

[FAST FRED]

It is very poor engineering practice to have low voltage DC in the same area as AC power.Especially on the same panel.

Not illegal, just a good way to kill someone.

FF

[thudpucker]

While we are on this subject....I dont mean to Hijack this guy's thread, but years ago sombody told me not to put two different voltages down a Conduit.
Is there anything to that?
I dont mean AC and DC, Just DC.

[alan white]

It's not legal in buildings to share conduits or boxes between low and high voltages.
As I read it, the commenter asking for help didn't mention anything beyond 12 volts.
Such a system is dead simple. Each individual circuit has a single wire from panel to devices. The ground for all the devices can be shared. It can be a larger guage wire. It is connected to the ground terminal of each device using as short a wire as is needed to join the larger ground wire.
Sizing of wire should anticipate all circuits being used simultaneously, meaning the larger ground wire should have an amperage rating that is at least as high as all of the individual hot lead wires combined.
Wire size can be confusing. That's because wires are rated in a somewhat arbitrary fashion that anticipates an average run in feet, but in fact a wire run a very short distance can be much smaller than one run a long distance and yet both wires would be subject to about the same voltage drop.
Wire, like water or gas needs to be larger-sized for long runs.
I usually would install 12 ga tinned marine wire for all of the circuits discussed. I know I could use smaller sizes for a GPS or radio that's inches from the panel, but I prefer to stick with one size everywhere as long as the longest run and highest amperage device will be adaquately served by that wire size. wire is relatively cheap for what it does.
If you haven't wired before, you can at least begin by running the wires and labelling them. I like to solder all connections rather than crimping them. Connections to a common ground require baring a short (1/4") portion of the larger wire and soldering the smaller wire to it, and then properly wrapping the connection with rubber (not vinyl) electrician's tape.
At the panel, allow extra wire. Use as many different colors as possible. Ground can be black. The battery (battery main switch) side of the fuse panel is one single (red) connection between battery switch and fuses and the circuit side of the fuse panel is where each individual circuit feed is connected. The main (common) ground wire connects directly to the battery switch.

[thudpucker]

Thanks I wasn't meaning to make a point, just ask a related question.
In a boat the guy might have 12Vdc in a conduit along with his speaker wires which might be nearly any voltage.

I took a NASA Soldering course some years ago. He mentiond a couple of good reasons for Crimping wire terminal ends instead of soldering.

[alan white]

What reasons?

[PAR]

Corrosion and movement fatigue are common in soldered connections. Done properly, preferably with the adhesive lined heat shrink, crimped connections survive longer. Many will suggests that strain relief is sufficient for soldered connections, but this doesn't address the corrosion issue and even if the strain relief is very close to the connection, vibration will eventually get at the soldered joint, as anyone with a diesel or full plane powerboat can attest. All the major manufactures have switched to crimps, from their previous custom of soldering and it's also the recommendation of the ABYS and Lloyds.

[CDK]

Originally Posted by thudpucker

Thanks I wasn't meaning to make a point, just ask a related question.
In a boat the guy might have 12Vdc in a conduit along with his speaker wires which might be nearly any voltage.

I took a NASA Soldering course some years ago. He mentiond a couple of good reasons for Crimping wire terminal ends instead of soldering.

Boat wiring should not be compared with home installations. There are all sorts of signals, voltages and currents, ranging from antenna signals in the millivolt range to the large 200 Khz spikes for the depth sounder. Absolutely no need to keep these away from each other as long as the proper cables or wires are used. AC should best be transported by a 2 or 3 lead cable, DC by separate wires of sufficient size.
My radar antenna is connected to the display unit with a single 22 wire cable that carries power, control voltages, video signals etc. Some are shielded, some are twisted, the power leads are straight black and red. No problem as long as you know how to do it.

Looking at the original post, my advice is to find someone who is capable to do the installation without asking help from a forum. I could do it with my eyes closed, but a friend of mine who is a retired veterinarian has already asked me a thousand questions and still does not have his wiring 100%.

As to soldering versus crimp:
Crimp connections are cheap and fairly reliable, that is why the industry uses them. If you use terminals from AMP or Molex and the proper, expensive tools they can even be quite good. Crimp a terminal to a wire, grip the terminal in a vise and pull the wire. If you did it right, the wire should break behind the terminal; if the wire is pulled out the quality is not sufficient.

Serious manufacturers first use acid free solder to tin the leads, then crimp the terminal on the wire. You can also reverse the order.
That way your connection is mechanically sound and protected against capillary action, which is the main enemy of marine wiring.

[alan white]

Thanks for the info. I've done both soldering and crimping successfully, but my experience has been on sailboats that don't have much vibration. the corrosion issue is another thing, and I suspect internal cabin wiring is not the same as masthead terminals, etc..

[thudpucker]

Soldering (NASA)
They found most 'field' repairs were done with the wrong kind of solder, and the heat was often excessive.

Any terminal solderd at a factory is probably dipped in the right solder at the right temp. Good stuff always.

Vibration is the worst problem with solderd wires. If the wire is cooked or the Solder the wrong mix, the wire will eventually lose strands to vibration.

On crimping. A factory (Several factory's) had to put out Service bullitens on incorrect crimps. It seems the wire was fed into the crimper too far. The insulation was crimped onto the terminal.

Not all wire lends itself to soldering. Some have too much Stainless in the mix and must be crimped.
Some teriminalends are similar, and wont solder very well.

Having repeated all that from the experts, I still solder some stuff.

[alan white]

Yes, I imagine that technique is as important to success as anything else. A very well made solder connection would be superior to a poorly made crimp, while both methods if well executed will last.
I think stiffening the point where the wire meets the terminal (either by tape or a plastic sleeve or shrink insulator) goes a long way toward preventing strands breaking by fatigue in areas that are open. Engine compartments in particular often have wires breaking at the point of connection to the terminal.