Sizing main 12v DC feed

[gradyrod]

Besides adding new Battery 1-2-Both switch and a second batt, I want to run a new wire from the Battery common on the new 1-2-Both switch up to the electrical panel. Can someone tell me what size wire should be used. Can I use 10 ga. for this run (15 ft each way, 30 ft total), or do I need larger? I wonder what Grady sized this feed wire at? My accessories include VHF, fishfinder, horn, bilge pump and deck flood light (5 amp draw).

Also, can anyone recommend where to buy replacement toggle switches to put in the panel? The existing ones are pretty corroded.

Thanks.

Rod
1985 Fisherman 204

 

[Grog]

I'd use #8 (for + and common) and maybe a new breaker.

 

[Curmudgeon]

10 ga is fine. Grady used 12 ga on my older T-22 ...

 

[gradyfish22]

10 ga is fine, if you were going over 20 ft I'd say maybe 8 guage due to the distance, but at 15 ft 10 is more then enough for what the panel itself can handle. I just ran a new fuse block and used 10 on mine. Buy marine grade 10-2 wire, easier to run just once with both wires in protective coating. West marine price is outrageous, $3.20 i think a ft, I got it at a local yard, $2.10 / ft for the same stuff. Using a 10-2 is better then just 10 guage wire since the wire has another protective coating, this is the only wire you should run below decks on boats. I'd suggest getting a 6ft fiberglass wire puller, they are about $25-35 bucks and will make running wires both on the boat and in the house super easy. Ran my Auto pilot wire's, LED rope light wire's, spreader light wire's and a new fuse block power line in no time, without it I'd still be running the first wire.

 

[Walkers Edge]

Just like Gradyfish said a wire puller is worth its weight in gold (and time saved) a cheap alternative is just the semi-flexible all purpors wire that you can find in the hardware section at any HD or Lowes type store. Rolls of 150' are about $8 and I just throw it away after each use and havent managed to use a roll up yet. It can be cut to make short pulls in akward spaces too.

 

[seasick]

From an engineering perspective, this is how you size the wires:

Calculate your maximum sustained current draw or just take 80% of the main breaker if there is one. If not, you really need to add up the loads. Electronics ( as opposed to starters and small duration high current devices) like to see a voltage drop of 3% or less. If you have lights on the same feeds, add up them also. They are usually high draw. use the peak draw for you radio. Measure the total run (both directions) and go to any of the wiring sizing tables available on the internet. Use you figures to size the wire. For example, 30 feet at 20 amps draw would require a 6 AWG wire. Use marine grade wire only.. repeat...marine grade only...

 

[Grog]

30' run, do it right once and be done with it. #8 wire $15 for 25' spool, #10 is $8 for 25', two spools of each $30 vs. $16. It's your money, cut it close for a saving of $14?

Grady may have used #12 but it's also untinned. Don't copy what they did.

 

[jdsmith]

Rod,

Please email me at jerrydsmithjr@aol.com