Proper way to tap into 12VDC wire? - Page 2 - SailNet Community
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post #11 of 49 Old 04-27-2012 Thread Starter
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Re: Proper way to tap into 12VDC wire?

Thanks, guys!

I guess I'll suck it up and wire the new ones to a terminal strip; then add the others to the strip as I replace them with LED. Should be slightly less current draw with a single unbroken conductor to each light, right?

Ken

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post #12 of 49 Old 04-27-2012
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Re: Proper way to tap into 12VDC wire?

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Originally Posted by CarbonSink62 View Post
Thanks, guys!

I guess I'll suck it up and wire the new ones to a terminal strip; then add the others to the strip as I replace them with LED. Should be slightly less current draw with a single unbroken conductor to each light, right?

Ken
Your long run to the terminal strip is shared, if that's the same gauge wire as the individual wires going to your LED's then it's going to account most of your losses. Also LED's don't draw much power so I doubt it's a big factor. It's all V=IR with V being the voltage lost and R determined by cable gauge and length.

To answer your question specifically (and with unnecessary detail) it depends. A better connection to the battery will always deliver more watts to your load but whether this matters depends on the load. LEDs lights limit current in 3 main ways: a resistor (simplest), a regulator (constant current/brightness) and a switching regulator (most efficient).

In the first example the LED presents as a resistive load so lower voltage actually means lower current but also lower brightness. In the second example the current is the same no matter what so it doesn't matter (to a point) how much voltage gets to the load. And in the 3rd example, the circuit will draw a more-or-less constant power so then yes, lower voltage means higher current. You might be able to tell by looking at the light as you can sometimes see a resistor, or a chip or a circuit board which would roughly correspond to the 3 scenarios I described.

But again, bottom line, with LEDs there is so little current involved that it's unlikely to matter.
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post #13 of 49 Old 04-27-2012
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Re: Proper way to tap into 12VDC wire?

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I never liked crimp connections, but in a freshwater environment you can get away with them. In a saltwater environment they're nothing but grief.
Gets the popcorn, sits back to wait for the fireworks to begin.
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post #14 of 49 Old 04-27-2012
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Re: Proper way to tap into 12VDC wire?

Please not that the ABYC code calls for no thinner than 16 gauge wire, no matter how small the load is. Best thing is to go to the marine chandlers, get a long piece of 2 16 gauge core, red and yellow, sheathed "boat cable". (boat cable also has the appropriate temp rating for the insulation). Then whenever you need to do some wiring you'll have the right stuff and won't be tempted to use something else.

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post #15 of 49 Old 04-27-2012
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Re: Proper way to tap into 12VDC wire?

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...and won't be tempted to use something else.
Like 20 gauge speaker wire.

I have come across it on boats - sometimes large boats!

Brian
Living aboard in Victoria Harbour
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post #16 of 49 Old 04-27-2012 Thread Starter
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Re: Proper way to tap into 12VDC wire?

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Originally Posted by MarkSF View Post
Please note that the ABYC code calls for no thinner than 16 gauge wire, no matter how small the load is. Best thing is to go to the marine chandlers, get a long piece of 2 16 gauge core, red and yellow, sheathed "boat cable"...
Now it gets ugly:
Galley
Chart table
Cabin (x2)
Pilot berth
Head
V berth

To do it correctly would mean 7 lengths of sheathed 16g 2 conductor wire. If I want to add reading lights to the settees (I do) that's 2 more. I'm not against doing the work (I actually love this stuff!) but I wonder if the cable runs will hold all of that wire.

It might be better to have 2 light circuits, Cabin & Head/Vberth; the Head/V berth circuit could run forward on 14g to it's own terminal strip and step down to 3-4 runs of 16g from there.

You can see why 'some people' just use wire nuts and wrap it all in duct tape!

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post #17 of 49 Old 04-27-2012
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Re: Proper way to tap into 12VDC wire?

Yes my boat has a terminal block in each lazarette, port and starboard, for each light circuit port and starboard.

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post #18 of 49 Old 04-28-2012
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Re: Proper way to tap into 12VDC wire?

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Originally Posted by MarkSF View Post
Yes my boat has a terminal block in each lazarette, port and starboard, for each light circuit port and starboard.
Most boat builders, and marine electrical installers, will run a port/starboard lighting run and perhaps a third over head run. Each light is then pulled off the main feed in a parallel manner often using a two position bus bar.. Running an individual wire from the panel to the light is nice but not necessary if the lighting circuit is sized appropriately for the allowable voltage drop..

Some even ran one main feed up one side to the v-berth then across the v-berth and back down the other side of the boat. Ericson for example did this on many of their boats. By the time you get to the end with incandescent bulbs the voltage drop gets pretty high if the wire is not sized right....

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post #19 of 49 Old 04-28-2012
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Re: Proper way to tap into 12VDC wire?

Carbon-
"but the connectors will not shrink and seal properly because one end will have 2 wires coming out." And that can be corrected by using butyl or silicone "self vulcanizing" or "self fusing" tape on the connection. Especially on the 2-wire side, where you start the tape on one of the wires, then come around the pair and back over the crimp fitting. Done neatly and allowed to set up overnight, it will fuse down on itself and make a very nice watertight cover.

Given a little time (for multiple coats to set up and dry) you can use Liquid Lectric (i.e. vinyl dip) instead, it also forms a nice seal. Either way you'd want to secure the connection itself to a bulkhead or something to prevent movement from affecting it, the same way you'd secure a terminal strip down to something solid and not leave it dangling.
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post #20 of 49 Old 04-07-2013
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Re: Proper way to tap into 12VDC wire?

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Originally Posted by travlineasy View Post
If you have relatively good access to the area, strip about 1-inch of the insulation from the main wire. Strip about 1.5 inches of insulation from the other wire.
Next, carefully wrap the second wire around the bared area of the first, then solder the joint. After it cools, apply a couple coats of clear, silicone cement to the connection, making sure to overlap onto the insulation by at least 1/4-inch at each end. The connection will never corrode and the connection is as secure as it can possibly be.
I like this method, especially using the Knotted Tap Joint method as shown in Botherton's 12 Volt Bible for Boats. However, as he points out, once you solder, you defeat the advantage of using stranded wire (flexibility). He suggests supporting the T joint in a "harness clamp" to minimize flexing (and potential breakage).
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