Adding amp. Use buss bar?

muskyfins

muskyfins

Chief Petty Officer
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Jun 7, 2012
Messages
578
Planning on adding a stereo amp with a 40 amp built in fuse. I suck at electrical ,but peak output power is 94 watts x 4 channels, so 376 watts/12.5= 30 amp draw. Sound right?

Ok, then per the following chart, and about a 20 foot run from the battery switch to distribution block, I need to use 6 gauge wire. How do we all feel about using the distribution block/fuse panel with a 30 amp circuit max? (below) Is it too small on wire size? Seems like I'm right at the max, but I don't expect to push the amp very hard. Or do I go with a buss bar first and either the fuse panel or in-line fuse the amp? PS-I also plan on putting my power anchor on the same fuse panel, but can't see the stereo and the power anchor being used at the same time. As always any thoughts are appreciated.

http://www.iboats.com/Screw-Termina...0148692--session_id.988318770--view_id.163740


American Wire Gauge (AWG)
Length
(feet)		Current (amps)
5101520253040506070
1516121010886644
201412108866444
25141088664422
30121086644222
4012866442211/0
501086442211/01/0
60106642211/02/02/0
7010642221/02/02/03/0
808642211/02/03/03/0
90844211/02/03/03/04/0
 
bruceb58

bruceb58

Supreme Mariner
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Mar 5, 2006
Messages
30,537
The wire gauge you pick depends on the amount of voltage drop you want. Your chart is kinda useless without it taking into account the length of the circuit which is 40' in your case. If you are willing to have a 10% drop, 10 gauge is ok. For 5% 6 gauge is what you want.

I would put a circuit breaker near your battery and run the leads from there directly to your amp. Don't put your anchor on the same circuit.
 
gm280

gm280

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Jun 26, 2011
Messages
14,604
muskyfin, however you decide to go, make sure you start from the battery with a suitable fuse or circuit breaker. Reason? Because IF you some how get a short between the battery and the fuse block assembly, there needs to be some type fuse or circuit breaker to protect the boat and the folks in it... Once to get your fuse block buss bar set up, then it protects things down the line form there. But also, make sure you also use the appropriate wire size for the fuse amperage. Using too small wire size in a 30 amp circuit will heat up and glow red hot if it shorts and maybe not even blow the fuse or pop the breaker. So everything has to be appropriately size to work together properly... If you run some small amperage circuit from the 30 amp block, install a inline fuse for that circuit and wire capability. JMHO!
 
muskyfins

muskyfins

Chief Petty Officer
Joined
Jun 7, 2012
Messages
578
The first column on the chart is circuit length and the chart is set up for 3% drop or less, so 6 gauge should work fine.

Yes, circuit breaker. Forgot to mention it.

But why run straight to the amp? The panel in the link from my first post is intended as a distribution block. The wiring would be following the same scheme as this:

View attachment Typical Wiring.pdf

Where else would I get power for the anchor? I was hoping to avoid adding a bunch of wire all over the place.

Also, why run from the battery rather than the switch? (two battery set up). When the switch is off, I don't want power anywhere other than the automatic bilge pump.

Again, much thanks. Virtual beer for everyone!!!:very_drunk:
 
muskyfins

muskyfins

Chief Petty Officer
Joined
Jun 7, 2012
Messages
578
kinda like this. battery switch not shown.
amp wiring.jpg
 
Last edited:
bruceb58

bruceb58

Supreme Mariner
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Messages
30,537
Yes, when I say from the battery I mean from the switch.

It would be fine to use a distribution block if the sum of the currents didn't exceed 30 Amps.

Fortunately, your amp will rarely be drawing more than 10A.
 
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