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Old 30-03-2013, 13:04   #1
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Lighting circuit question??

I am adding two new parallel interior lighting circuits. One for each side of the boat. I am wondering. What is the approved three wire connection for each branch?
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Old 30-03-2013, 13:23   #2
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Re: Lighting circuit question??

Welcome to CruisersForum.

Three wires? Is this an AC circuit?
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Old 30-03-2013, 13:31   #3
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Sorry. These are 12v dc circuits. I am referring to the connection between the 2+ wires of the feed and 1 + wire of the light. Three wires. Or the same for the - side.
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Old 30-03-2013, 13:39   #4
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Re: Lighting circuit question??

So what you are creating is two new DC circuits from your DC panel? It's pretty simple, use two spare breakers at your DC panel, one for each lighting circuit. Gauge the wire so that you do not have more than about a 3 percent voltage drop through the circuit when all the lights on that circuit are turned on.

If your lights have switches on each light you might have more flexibility by putting all the lights on one circuit and then having each individual light on or off as you choose. You would also save having to use an extra breaker at your DC panel.

Do you need the tables on how to gauge the wire?

http://www.bestboatwire.com/catalog/...size_3pct1.JPG
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Old 30-03-2013, 13:43   #5
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Sorry. These are 12v dc circuits. I am referring to the connection between the 2+ wires of the feed and 1 + wire of the light. Three wires. Or the same for the - side.
A bit confusing here. Are the switches integral to the light fixture?

The hot +12vdc should be coming from the breaker panel and the - should be hitting a bus bar the ties to the negative on the battery. In parallel all the negatives should be common and the same with the positives.

What gauge wires are you using? I would suggest a good water tight type of connector. They are worth the extra money to avoid future issues.
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Old 30-03-2013, 13:53   #6
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Re: Lighting circuit question??

Your lighting circuit negative should go back to the bus bar at your DC panel and not back to the battery. Your DC panel already has a large negative wire running back to your battery. It would work to do this but all you would be doing is cluttering up your DC system making it unnecessarily complex and difficult to trace and troubleshoot.
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Old 30-03-2013, 14:10   #7
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Thanks for the help so far. I feel comfortable with wire size and all connections except for the one I'm attempting to describe. The circuits are 10 awg runs with branches for each individual light with an internal switch. My question is with the branch connection. I know their are three way connectors but they don't look appropriate. Nor does using a butt connector and putting two 10 gauge wires in one side and one out the other. Do I need to use terminal blocks for each branch/ light? Or is there another approved method. I hope that makes more sense.
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Old 30-03-2013, 14:23   #8
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Re: Lighting circuit question??

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Originally Posted by ffjme View Post
My question is with the branch connection. I know their are three way connectors but they don't look appropriate. Nor does using a butt connector and putting two 10 gauge wires in one side and one out the other. Do I need to use terminal blocks for each branch/ light? Or is there another approved method. I hope that makes more sense.
I question the necessity of 10 GA wire for the lighting circuits.

But anyway... you can splice 3 wires in a number of ways:
- some mfrs actually makes a 3-way splice Yeah they look silly
- the butt splices with 2 wires in one side and 1 in the other
- crimp on eyelets and use a terminal strip

Electrically, all good connections work equally well so it's down to what connection will fit in your space. The butt splices will be fine.
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Old 30-03-2013, 14:36   #9
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Re: Lighting circuit question??

How many total amps will your lights be drawing on each circuit? You cannot determine the proper size wire gauge without knowing this.

Avoid using butt connectors because there can be a voltage drop across them and they also have the potential of pulling apart. Terminal blocks with ring connectors are fine to use. Avoid spade terminals because they can pull out.

I don't understand why this is being made so complex? Do you have a spare breaker on your DC panel? You don't need butt connectors or terminal blocks if you do. Keeping your electrical system simple means there are fewer links in the chain that have the potential of breaking.

If you answer my questions then I can better help you..such as if your lights each have individual switches and if you have a spare breaker on your DC panel. If for whatever reason you don't want to answer my questions then there is no way I can help you.
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Old 30-03-2013, 16:21   #10
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Hmm. If the light have screw down terminals inside I use them. Daisy chain them together and they will still be parallel electrically and you will only have to terminate on wire at the breaker. With the gauge your using if no terminals I would do the same and use household wire nuts with the wire tips coated in no ox grease.
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Old 30-03-2013, 17:45   #11
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Re: Lighting circuit question??

Never use wire nuts on a boat. Always crimp the ends of your wires.

I hope you are not considering Romex.
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