Circuit Breaker size for dedicated electronics run

[mhardt]

After reading many posts regarding running clean power to electronics, I’ve decided to run 8 gauge from my battery to a Blue Sea fuse block at the console and then 10 gauge from there to the bow to power graphs up there.

What I’ve read is many of you add a circuit breaker (at the battery) between the battery and the fuse block. However, others with this same setup just run a perko style on/off switch that doesn’t appear to have a breaker.

id like to add the breaker for protection as many have suggested, however, nobody has stated what size. I’m going to be running 3 HDS Live 12”s, Active Target, Sonic Hub and NMEA2k off this run.

This is the breaker I was leaning toward as it serves as a switch as well. But what size?
https://www.bluesea.com/products/713...face_Mount_30A

Also what gauge wire to run from the breaker to the positive on the battery.

Thanks in advance.

[Bill Reynolds]

30 amp

[justinp61]

^^This^^

[aj306]

The size of the breaker is determined by the wire size and length of the wire. Charts are available online to tell you what you need. I used a 40 amp breaker at the battery that serves as a cutoff with 8 gauge wire that was run to the fuse panel in the starboard rod box

[Crestliner16]

I put a bluegrass breaker on both of my trolling motors and my electronics and my circuit box is a blueseas.

[SLYDoggie]

The size of the breaker is determined by the wire size and length of the wire. Charts are available online to tell you what you need. I used a 40 amp breaker at the battery that serves as a cutoff with 8 gauge wire that was run to the fuse panel in the starboard rod box

Wouldn't you also need to take into consideration the combined Amp draw for all the equipment connected to that line?

[justinp61]

Wouldn't you also need to take into consideration the combined Amp draw for all the equipment connected to that line?

There you go bringing reasoning into an electrical discussion!

[1BADAIR]

The breaker protects the wire not the components. The wire size is determined by component draw. 30amp would probably be good then the fuse for each component at the front .

[bgibson]

This is what I used

https://www.bluesea.com/products/713...face_Mount_30A

[mhardt]

I recently decided on 6 gauge from the battery to fuse panel instead of 8 gauge. Still running 3 12’s and Active Target down the road, does that change the breaker size from 30a to something larger? Should I be fine with 8 gauge or would you all recommend 6 gauge?

[Bill Reynolds]

I recently decided on 6 gauge from the battery to fuse panel instead of 8 gauge. Still running 3 12’s and Active Target down the road, does that change the breaker size from 30a to something larger? Should I be fine with 8 gauge or would you all recommend 6 gauge?

Concerning wire size: the primary consideration for wire size in this situation is voltage drop. The chart below gives the appropriate wire size for a 3 percent voltage drop at the amp draw and conductor lengths specified.
In your case the current would be acquired by adding up all the amperage from the devices on the circuit. If you don’t have this number handy, you can find it on the Amped Outdoors website. It lists the specified amperage for all brands of electronic devices.



Concerning breaker size at the battery: The purpose of this breaker is to protect the wire from the battery to it’s termination point. It is sized such that in the event of a fault, like a direct short, the breaker will open before the insulation can heat to the point of causing a fire. As a practical matter this is a maximum breaker size allowed and in this case is many times the ampacity load on the system so 30 amps is fine for either of the wire sizes you mentioned.
My boat has a 6 gauge wire from the battery to the console breaker panel that handles all the electrical load on the boat and it has a 30 amp breaker at the battery.

[mhardt]

Thanks Bill, I appreciate it. I think I understand this chart for a continuous run such as three graphs pulling a total of 10 amps for a run of 50ft which in this case would be 8 gauge. But what if the first run is 6 gauge going from battery to the blue sea fuse box at the console where the first graph would be and then two separate 10 gauge runs for the two 12’s at the bow. How does this chart work for that? I’m really confused since I’m using two separate wire sizes. I’m certain the 6 gauge will work based on what others have done with the same type setup but the fuse panel in the middle of the run separating two different gauge wires confuses me with this type of chart. Does that make sense. One more question, what gauge wire should be used from the 30amp circuit breaker to the battery? Do I use the same size as the run to the fuse box at the console? Thanks for all your help I’m truly greatful.

[Bill Reynolds]

Size the wire for each run based on it’s amp draw and length.
This chart shows the max current for a Humminbird 12 as 2.7 (call it 3 ) amps. So the 10 gauge is huge overkill for a single unit.
That’s ok if you have the tools to make quality connections. I am confident in my tools and connectors up through 10 gauge but less so with 8 and 6 gauge. The quality of your circuit is no better than your weakest connection.
In this case I would be inclined to run 10 gauge to another fuse panel close enough to the device that you can attach the factory wiring from each unit, keeps it simple.




Concerning wire size from the battery to the circuit breaker, use the same size as the cable run.
I read somewhere that code requirements dictate that the circuit breaker for the cable run should be within 7 inches of the power source. That seems impractical in some cases but there are inline breakers, like the Blue Seas, that can be attached near the battery terminal.
BTW: Blue Seas has a circuit design App that sizes wire and recommends proper circuit devices. Very handy.

[mhardt]

Thanks Bill for the time and effort you put into your detailed responses.