wmk0002
Well-known member
I would like to install a negative bus bar below the bow deck of my boat under my not yet installed nav light and future fishfinder, light bar, and 12V outlet. I'd prefer to do this in hopes that only fishing positive wires up there in the future would be easier since I won't add these electronics all at once. My question is, if using a bus bar, how do I size the gauge of the wire running from the bar to the battery at the stern? Typical wire sizing is based on current draw plus round trip wiring....in this case, the positive wire would be sized based on the round trip length and current but the negative would need to be much larger to handle simultaneous electronics running at peak current draw correct?
Using a sizing guide, I sized wires for the electronics assuming 5A draw for nav lights (3% V drop) & 5A for fishfinder, 5A for 12V outlet, and 10A for small lightbar (these 3 at 10% voltage drop). I then summed the cross sectional area of each wire and got 7.04 mm. The cross section of 8 AWG is listed as 8.37 mm. Is this an appropriate sizing method? Before even looking at any numbers I was leaning toward 10 AWG because that is a common size of power feed wire to pre-made switch panels. If I use 10% voltage drop for all electronics and sum the current, the guide agrees with 10 AWG.
Another thing I was wondering related to this: could the negative trolling motor battery be increased by one size and act as a ground wire for the bus bar for all electronics plus the TM without any kind of issues like interference? It would simplify it for me as I plan to run the TM wiring up the middle strake all the way to the tip of the bow under the deck while running wiring for everything else either up one strake over or along the side in conduit. This would allow me to size the TM wiring accordingly (guide says 30' at 50A needs 8AWG, assuming 10% V drop)
Using a sizing guide, I sized wires for the electronics assuming 5A draw for nav lights (3% V drop) & 5A for fishfinder, 5A for 12V outlet, and 10A for small lightbar (these 3 at 10% voltage drop). I then summed the cross sectional area of each wire and got 7.04 mm. The cross section of 8 AWG is listed as 8.37 mm. Is this an appropriate sizing method? Before even looking at any numbers I was leaning toward 10 AWG because that is a common size of power feed wire to pre-made switch panels. If I use 10% voltage drop for all electronics and sum the current, the guide agrees with 10 AWG.
Another thing I was wondering related to this: could the negative trolling motor battery be increased by one size and act as a ground wire for the bus bar for all electronics plus the TM without any kind of issues like interference? It would simplify it for me as I plan to run the TM wiring up the middle strake all the way to the tip of the bow under the deck while running wiring for everything else either up one strake over or along the side in conduit. This would allow me to size the TM wiring accordingly (guide says 30' at 50A needs 8AWG, assuming 10% V drop)
