Circuit protection question

[bear_69cuda]

Hi Gang,

Attached is a basic diagram of my wiring system mainly focusing on the power distribution. Does anyone have an opinion or advice if I should install circuit protection (fuse or breaker) in the red box area's? Would I be okay only with (fuse or breaker) with A boxes directly form batteries? Or only B boxes (fuse or breaker) protection from + buss feed to other fuse boxes (stereo, aux, lights, etc), or should I protect both A & B?

I know this may be a dead end question... But any suggestions on what amperage fuse or breaker would be also greatly appreciated.

Regards,

 

[Silvertip]

Re: Circuit protection question

Diagram is too small and fuzzy. Can't read the fine print. You have no ground jumper between the two batteries on the switch so the switch does you no good if you have a dead start battery. The battery cables between the switch and the positive terminals of the two batteries should not have a breaker. The reason being the engine draws too much current during startup. Your cars and trucks don't have them and there is no reason for a boat to have a breaker on the battery cable either. The boat harness to the fuse panel should be protected and that usually is a 20 amp fuse with a 10 gauge wire to the fuse/breaker panel. The engine harness is protected with a fuse at the engine. Gauges and any ignition switched accessories are powered via that system.

 

[bigskiohio]

Re: Circuit protection question

i clicked on image it is full screen, words are a little fuzzy but readable.

 

[bear_69cuda]

Re: Circuit protection question

When the switch is in combine it jumpers both batteries.

This is the switch I'm using. http://bluesea.com/products/5511e

Thanks for the info Silvertip!

So circuit protection from my + house battery buss to fuse box is a good idea correct? I plan to dissect my harness and only put starting requirements on cranking bat 1, and all other boat electrical functions on house bat 2.

 

[bear_69cuda]

Re: Circuit protection question

Maybe this pic has better resolution?

Sorry if not... I only have MS paint.

 

[Silvertip]

Re: Circuit protection question

Sorry -- too much stuff I can't read. I think you have some grounding issues (as in too many of them). I'll need to bow out of this one.

 

[bear_69cuda]

Re: Circuit protection question

I truly apologise for the lame diagram. Besides drawing by hand and scanning, this was the only was for me to transpose to Internet. Funny I was hoping you were the one that could help me Silvertip. :redface:

So having 2 ground points is not possible? If both are grounded to engine, and Neg battery posts, using either one should work correct? I just figured having multiple ground points would shorten wire runs. I'm very green with electrical systems....

My other two Bus's are switched + Pos distribution

 

[Mark_VTfisherman]

Re: Circuit protection question

All electrical and battery grounds should be connected, preferably at the battery.

 

[bear_69cuda]

Re: Circuit protection question

Both my ground buss are connected via 2 AWG directly to the neg battery posts. Running ground wire from accessory, nav lights, bilge, stereo, etc... to this buss should be fine I would think? Not physically the negative battery stud but close...

 

[Mark42]

Re: Circuit protection question

Yes, you can have all the grounds connected to both the neg terminals. Do it the way you planned, by jumping the two neg posts, then run a ground line to each ground buss.

I don't think that the wire between the battery and batter selector switch need fuses. The wire feeding the + buss bar should probably be fused.

Hey! That diagram ain't so bad! I could read it!

 

[bear_69cuda]

Re: Circuit protection question

Thanks Mark,

Please excuse my ignorance....

But if both neg posts are connected to engine, would not the engine be the jumper between the two batteries?

 

[Silvertip]

Re: Circuit protection question

Yes it would. But - when distributing power and ground a "star" scheme is always the most trouble free and you run the least risk of ground loops and electrical noise on sensitive electronics like locators and radios. Star grounds consist of one single ground point and one single distribution point. This isn't always done in boats because there are two distinct power delivery systems (three if you have an AC system as well). The engine harness feeds power to the control box, tilt & trim, engine, and gauges. The boat harness feeds the fuse/breaker panel and the accessory items. In both of those systems the negative terminal of the battery is the ultimate ground but since the large battery cable is connected to the engine block it is ground as well. But since you don't want extra wires running into the engine central ground is considered the battery. Also, the engine harness is not capable of supporting high current draw items -- hence the dual distribution system. Lastly, if you lose engine block ground, everything you power using that point as ground is dead. Will your system work -- certainly! How reliably is the question. There are many ways to do things, but there are more reliable ways to do it. Think about your house wiring. Where do ALL of the power, neutral, and ground wires originate and terminate at? The fuse/breaker panel right? Even automobile wiring is becoming so sophisticated that ground issues need to be addressed carefully.

 

[bear_69cuda]

Re: Circuit protection question

Thank you Silvertip,

I plan on thinking through my plan thoroughly this weekend, and incorporating all the wisdom, and advice from all on iboats... I do want to have a "reliable system" That's my intention and main goal! My main concern is the safety of all aboard my boat, so I want to do this correctly...

I find it interesting you know what the "DIN" is! I don't hear folks use that word much....