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Old 05-05-2015, 22:56   #1
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DC cabin lights wiring

I'm thinking about rewiring the overhead dome lights and reading lights in my boat, I have already rewired other larger electronics and pumps. The reason for the lights is that I have most of the overhead paneling down checking for leaks and running wires. The girlfriend and I would like to just take the rest of the paneling down to remake them, most are rotted badly from leaks, and really cover with new fabric. Since this would require cutting the wires on the existing lights to remove the panels, we got a nice look at the state of wiring of them all. I'm not sure if it's standard practice but the lights are wired in series. They have soldered connections which some have broken loose, so that's an issue right there.

Now when I rewire these, how do I wire them? Each light has its own wire and I send all those to bus bars and one larger wire from bus bars to electrical panel breaker? Or do I do series again and jump from light to light? I'd like to do series if I can to save on wire and unnecessary weight of it all.

Other than that, I am very familiar with crimping and connectors, shrink, etc. Also, I have the correct tools for the job. Lights will have LEDs or be LED fixtures. So I was going to use 18/2 awg marine wire, and probably 12 awg from the bus bars to respective panel connections.

- Ronnie...on the geaux
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Old 05-05-2015, 23:03   #2
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Re: DC cabin lights wiring

Parallel to the breaker with proper gauge wire. Try to have two circuits....like port lights and starboard lights in case either side fails.

Edit: I think 18 awg is typically to thin and fragile. 16 awg is the minimum I would us regardless of length of run.

Matt
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Old 06-05-2015, 00:24   #3
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Re: DC cabin lights wiring

Are you sure they are series wired? They should be connected in parallel. You run the pos. to one fixture pos. connection and from there to the next fixture pos. connection. Same with the neg. Use marine rated duplex cabling.
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Old 06-05-2015, 05:21   #4
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Re: DC cabin lights wiring

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Originally Posted by DeepFrz View Post
Are you sure they are series wired? They should be connected in parallel. You run the pos. to one fixture pos. connection and from there to the next fixture pos. connection. Same with the neg. Use marine rated duplex cabling.
I THINK that is how the OP's boat is wired but he has mistakenly called it series wired.
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Old 06-05-2015, 05:24   #5
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Re: DC cabin lights wiring

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Originally Posted by funjohnson View Post
Parallel to the breaker with proper gauge wire. Try to have two circuits....like port lights and starboard lights in case either side fails.

Edit: I think 18 awg is typically to thin and fragile. 16 awg is the minimum I would us regardless of length of run.

Matt
OK, 16 it is.. Good thing I already have rolls of that. It is separated on two sides.
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Are you sure they are series wired? They should be connected in parallel. You run the pos. to one fixture pos. connection and from there to the next fixture pos. connection. Same with the neg. Use marine rated duplex cabling.
Yes, I am incorrect. They are in parallel, not sure why I said series. (maybe because it's a series of lights?) so yes, +/- go into one light and another +/- comes out to the next light. But there are some that are "jumped" into the wire with a shoddy solder and some old tape to cover it..

Here's a picture of one light.. And the leak in the jib car track I'm trying to stop without taking it up Click image for larger version

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So that's acceptable to do parallel like that, instead of each light getting its own wire?

- Ronnie...on the geaux
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Old 06-05-2015, 05:25   #6
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Re: DC cabin lights wiring

You probably know this. but just in case .... LED lights are polarity sensitive, ie there is a plus and a minus side to hookup.
Ditto what funjohnson says. Bad thing to undersize circuits.
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Old 06-05-2015, 05:47   #7
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Re: DC cabin lights wiring

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So that's acceptable to do parallel like that, instead of each light getting its own wire?

- Ronnie...on the geaux
Yes, it's acceptable but bear in mind the wire size has to accomondate the total current of all lights connected to the feed so it needs to big.

Using a seperate circuit to each light allows for a smaller size to each light. In this circumstance your 18 awg would be fine for each LED light. Of course the wire to the bus has to bigger.
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Old 06-05-2015, 05:50   #8
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Re: DC cabin lights wiring

FWIW, most 12 volt LEDs are quite voltage tolerant so providing you aren't putting heaps of LEDs on the circuit, your 16 awg wire should suffice (just IMO).
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Old 06-05-2015, 09:12   #9
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Re: DC cabin lights wiring

Quote:
Originally Posted by dpddj View Post
You probably know this. but just in case .... LED lights are polarity sensitive, ie there is a plus and a minus side to hookup.
Ditto what funjohnson says. Bad thing to undersize circuits.
An interesting thing concerning LED lighting that I haven't implemented yet, I plan to use LED lights almost everywhere when I get to that project, on the mast spreader lights where you might want the choice of red or white, I can implement this without stringing any new wires, just a fancy switch reversing polarity on the wires. Wire the LEDs back to back, red LED one wire positive and white the other.
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Old 06-05-2015, 09:16   #10
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Re: DC cabin lights wiring

Soldering wires together is supposed to be the best connection type EXCEPT in vehicle applications where the connection is subjected to vibration. Then the hard connection will metal fatigue and fail, like those broken connections you pointed out. Connections in marine use should be with a gel-filled crimp-connect splice to prevent corrosion in the splice.

If you can't get those, regular crimp splices, silicon caulk and heat shrink (or tape) to contain it all will work. The idea is to seal the splice.

LED lighting is low current, maybe 20% for same lumens, so 16 ga wire is probably more than adequate.
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Old 06-05-2015, 09:23   #11
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Re: DC cabin lights wiring

Another possibility:

Twist on wire connectors (otherwise known as wire nuts in the US) work well and can be sealed with caulk. However, according to Wikipedia: "They are widely used in North America, but are not approved for use on low-voltage wiring in countries in the European Union and in many other countries"

So, using the ones with metal wire inside will work, and work well, they may not be your answer. Just FYI...
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Old 06-05-2015, 09:45   #12
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Re: DC cabin lights wiring

Quote:
Originally Posted by trifan View Post
Another possibility:

Twist on wire connectors (otherwise known as wire nuts in the US) work well and can be sealed with caulk. However, according to Wikipedia: "They are widely used in North America, but are not approved for use on low-voltage wiring in countries in the European Union and in many other countries"

So, using the ones with metal wire inside will work, and work well, they may not be your answer. Just FYI...
NOT.

Just plain wrong advice.
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Old 06-05-2015, 10:08   #13
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Re: DC cabin lights wiring

Not only are LEDs voltage tolerant but they draw very very little current... Usually .2a compared to a 10-20w bulb that draws 1-2A. Accordingly 5-10 LED done lights draw the same Amps as just one bulb done light. If you were concerned about headliner weight, you could go way down in wire size... to 20ga. Even smaller, but any smaller gets hard to work with the small wires in even the smallest crimps (red color).

A usual practice working with smaller gauge wire is to strip them back twice a far back and fold the the stripped end over on itself. This gets enough bulk in the crimp to hold well after the crimp. Get/ use a good electrical crimp tool... don't just squash it with pliers.

I think/ hope what you're calling 'in series' was really what is a ok wiring technique called 'daisy chain'. Each dome light wire pair does not have to home-run direct to the circuit breaker panel or even an intermediate buss strip. Parallel power wires can go from light to light to light. This greatly reduces weight/ wire use and back to the issue of double stripping... if you are daisy chaining to the next light, you can strip all you wires just a little longer than normal and twist the two blacks together, insert, crimp, test by pulling. Sane for reds.
By the way... no electrical connections (including crimps) should ever be done in inaccessible/ covered areas.

While hams with good soldering skills will use solder for certain connections to the radio equipment and many who know how to solder well prefer soldering coax cable connectors on... but, in general, solder should never be used in boat wiring... use crimps... only crimps. This is because the solder stiffens part of the wire and over time with vibration from engine/ rough seas that cause everything on a boat to move/ flex the area where the solder made the wire stiff has a high probably of breaking from the rest of flexible wiring flexing.

By the way, because your LEDs draw so much less current/ and their own pigtails wires are so small gauge... you should really reduce the value of the breaker controlling- protecting your dome circuit.

While I was in San Diego, returning to my boat I smelled smoke from a older Chriscraft power boat just a few slips from me. I knocked, banged, called for help/ 'dial 911' and opened the door and went in (I don't recommend this) to turn off the battery switch. On my way I saw flames coming out from behind a 12 V fluorescent ceiling light. With now both 12v and dock cord disconnected we took a dock water hose a lightly sprayed the light fixture/ ceiling area... but I could still hear active fire crackling from up under the wood headliner. We quickly got a big screwdriver and bucket and as I pried off the fixture I could see that the small gauge pigtail wires of the fixture had gotten smashed under the edge of the metal edge of the fixture during the original installation. Over time the edge apparently cut through the insulation and shorted the wiring. Later talking to the owner I asked if he had changed his breaker. He said no. A 15a breaker allowed that very small pigtail wire to glow red hot and start a fire WITHOUT TRIPPING the now overly high breaker just like a toaster can glow red without tripping a big house breaker.

If changing out your breaker is a big task and need to delay it... at least wire in an in-line fuse with an appropriate size fuse 1-3a should do. The fuse will be your protection... the breaker can still be your switch.


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Old 06-05-2015, 10:12   #14
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Re: DC cabin lights wiring

Quote:
Originally Posted by trifan View Post
Another possibility:

Twist on wire connectors (otherwise known as wire nuts in the US) work well and can be sealed with caulk. However, according to Wikipedia: "They are widely used in North America, but are not approved for use on low-voltage wiring in countries in the European Union and in many other countries"

So, using the ones with metal wire inside will work, and work well, they may not be your answer. Just FYI...

Good god no!!! Please never ever do this on a boat.... or anywhere that isn't using solid core wire.
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Old 06-05-2015, 10:34   #15
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Re: DC cabin lights wiring

Hmmm... such passionate replies. Ok, here's the real deal: wirenuts (the ones with the spiral of wire inside the nut) do work with stranded wire AND they work in mobile environments but there are some caveats which weren't stated in my post.
1) the wires need to be twisted together first
2) the wirenut, after twisted on, needs to be made immobile re: the fixture so that its mass doesn't move (vibrate) and cause wire breakage due to metal fatigue.
3) not to be used with aluminum wire (but who uses that on a boat)
4) after attachment the wirenut should be sealed with a non-acidic sealant (not most bathtub silicon caulks)

Having said all that, wirenuts are still not a first choice and should be relegated to "jury-rig" or repair-only status. But they DO work.
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