Random Electrical Questions

[TortolaTim]

I'm in the process of re-doing my electrical system based on some excellent templates and advice from here, and MaineSail's various posts. Couple of things that came up today...

1. I'm wiring the alternator direct to my new battery bank and was looking for a spot to mount an alternator service disconnect switch in the eng compartment, and it looks like there is NO room anywhere for it. Has anyone installed one, and if so, where?

2. I'm trying to do a little cleanup behind my DC panel before I tackle replacing the whole thing next year. I mounted a Neg Bus bar on the hull behind the panel to re-route the ground wires there. Is there a neg ground wire for the DC panel itself, or just each individual component circuit that runs to the panel for switching? It is quite the rat's nest back there and I want to make sure I get everything. In my factory wiring diagram, there are 2 #10 red wires that run from the "C" post on the switch to a neg bus bar. What are these wires for?
Thanks!

[KWKloeber]

(A)
Is there a neg ground wire for the DC panel itself, or just each individual component circuit that runs to the panel for switching?

(B)
In my factory wiring diagram, there are 2 #10 red wires that run from the "C" post on the switch to a neg bus bar. What are these wires for? 

(B) - If you follow that circuit on the schematic, its not just a neg buss.  In fact it's NOT a buss bar (CTY used incorrect terminology) -- it's a terminal strip that has jumpers bonding the common terminals.

That term strip holds both the panel pos feed (the two red 10 awg wires) and the neg returns.    So the two red #10s carry across the term strip and feed the two sets of 12v circuits on the panel.

(A) - Not sure what you are saying "each individual component circuit that runs to the panel for switching"
Regardless, a neg cable runs to the neg (combination pos/neg) buss bar. 
Not shown on the schematic.  (No boat mfgr. at all is world-renowned for documenting their electrical (and other) systems!)

-ken

[Stu Jackson]

1. I'm wiring the alternator direct to my new battery bank and was looking for a spot to mount an alternator service disconnect switch in the eng compartment, and it looks like there is NO room anywhere for it. Has anyone installed one, and if so, where?

2. I'm trying to do a little cleanup behind my DC panel before I tackle replacing the whole thing next year. I mounted a Neg Bus bar on the hull behind the panel to re-route the ground wires there. Is there a neg ground wire for the DC panel itself, or just each individual component circuit that runs to the panel for switching? It is quite the rat's nest back there and I want to make sure I get everything. In my factory wiring diagram, there are 2 #10 red wires that run from the "C" post on the switch to a neg bus bar. What are these wires for?
Thanks!

Tim,

I'm sure you've also read through the Electrical Systems 101.

1.  It doesn't have to be in the engine compartment, which is kinda full already.  That service switch could be anywhere.

2.  The C post of the 1-2-B switch is +.  Regardless of the colors of the wires, they should NOT run to anything negative.  Ken explained that those terminal strips are not truly bus bars,  by definition.  Look more carefully.  When I first got our boat, I traced each wire on those terminal strips.

[TortolaTim]

Stu, yes quite extensively over the past year.

1. I figured it wouldn't fit in the engine compartment, was just wondering where others have installed it.
2. After a several hours of tracing and studying the rat's nest today, I got the back of the panel cleaned up considerably. I traced all the wires, and added a neg bus bar to better organize the wiring. The PO had reds, yellows, blacks all mixed together, and not necessarily correctly, so I re-wired the incorrect stuff today and tested out the components successfully. I just wanted to make sure I wasn't missing something before I re-introduced power as the schematics didn't look anything like what I had on the boat

Thanks again for all the info

[Ron Hill]

Tim : When I installed a new hi output alternator I ran the wiring direct to the batteries. 
I placed a shunt in the compartment wall just inside the side door by the galley inside a Tupperware box (so I could protect the terminals with a snap on lid).  Then ran the wiring into the battery compartment with a fuse on the positive terminal. That could be disconnected if need be.

I also ran a negative #4 ground with the positive wiring which was connected to the alternator case.  It ran under the flooring into that area of the shunt.

Later when I added a battery monitor and I connected a #8 wire from the batteries (-) to that negative busbar you moved to the hull. I never had any negative grounding problems!!   

A few thoughts

[mark_53]

I'm in the process of re-doing my electrical system based on some excellent templates and advice from here, and MaineSail's various posts. Couple of things that came up today...

1. I'm wiring the alternator direct to my new battery bank and was looking for a spot to mount an alternator service disconnect switch in the eng compartment, and it looks like there is NO room anywhere for it. Has anyone installed one, and if so, where?

Frankly, I never saw the need for the disconnect switch.

[Stu Jackson]

1. I figured it wouldn't fit in the engine compartment, was just wondering where others have installed it. >>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>>>>>>>>

I use the fuse, which is located in my battery box.  A switch would be far easier, but I've never gotten around to installing the one I have in hand after 15+ years.

The fuse has to be there anyway, and the number of times I have to take it out compared to how easy it is to just back off a couple of bolts just wasn't worth the work to add the switch.  It's simply a convenience item for something that doesn't get used that much.

The more important thing to realize, learn and know is that your alternator is always connected directly to your bank.  Some would say it's hot, but not really...only if you try to take it off!!!   

Your boat, your choice. 

[TortolaTim]

Thanks for all the input. I was thinking of just using the fuse as well. Realistically, I'll be the only one ever working on the boat, so I will know that I have to remove it to service the engine. Maybe I''l make a placard for the engine compartment as a reminder

[mainesail]

A service disconnect switch is for a service technician who may not know how the boat is wired. This is why it is best located, and well marked, in the engine bay.. If you're the only one who works on the boat, then you can manually disconnect the alt B+.