12V Supplies to various locations?

[Richard10002]

Hi,

I want to fit 12V supplies to various places on the boat, e.g.

Saloon to feed Triax UFO aerial power supply
Cockpit to supply Lowrance 3600i Plotter

Can I just find an existing 12v supply near to where I want the new one, and take a feed of this, or do I have to feed completely new wires back to the electrical panel?

Many Thanks

Richard

 

[ShipsWoofy]

No

You could end up attaching to the light circuit, so to use the aerial or gps you have to have the lights switched on. That is manic to say the least.

The other consideration is current and safety, my radar circuit is on a 12A trip, i would not want my GPS (which uses milliamperes) on the same circuit.

There are two things here, maybe you should ask someone who knows this stuff to come and have a look or digest the 12v bible. This is not to be patronising, but without seeing how your boat is wired first hand, seeing what circuits are available and in what condition I would not like to give a definite answer. If I suggested adding to your instrument circuit presuming it had been done properly, but in fact on your boat it had a 15A fuse and bell wire I would not be doing you any favours.

It seems most fires on small boats are caused by electrical faults, hence my trepidation.

 

[Guest]

Why not sort out a general run ... and then you have it for alter additions as well.

Using the ring-main principle. take HD cable and run it round boat with junction box's at intervals. The red ends both terminate back at positive supply via fuse on each. Black ends at -ve etc. The junction box's provide the power take off to sockets / additional items as you fit.

You fitted the cable - you know it's capability and you know it can be added to.

 

[lancsjohn]

Note one fuse supplies a ringmain cable both reds join together at the fuse. This fuse should be sized to prevent total overload on the ringmain cable, each piece of equipment should have its own fuse rated to protect itself. Fires are offend caused by overloading cables try not to bunch them together so they keep cooler a short circuit on 12volt can cause a lot of heat.

 

[William_H]

You can do a makeshift job or a super sophisticated system to be proud of. I must confess I go for the former. Wiring should be simple easily understood and safe.
Fusing for fire safety is the big question. So what is the load you need to draw from the new outlets? Miniscule for the amp to medium for the plotter, I think. What is the load and fuse rating of the supply you intend to tap into. It will need at least a 5 amp fuse. If it has a 15 amp fuse then you must fit wire right through to the amp that will carry 15 amps easily withpout smoking or burning. (The worst fault scenario.) It has to carry the current to blow the fuse. Alternatiely if you fit a smaller fuse in your extension wire (it can be an in line fuse behind the panel work) then you can use much lighter wire as dictated by the new fuse value.
I would prefer to see heavy wire throughout with less fuses (sharing is OK) (provided total load is less than the fuse value) Fuses seldom fail from fault conditions they are supposed to protect you from but often fail themselves from corrosion poor contacts etc. Heavy wire tends to survive corrosionn etc far better than light wire. good luck olewill