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Old 06-05-2015, 10:34   #16
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Re: DC cabin lights wiring

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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...
wire nuts will loosen with vibration-glue or no glue.

get the book sailboat electrics made simple by Don casey. amazon or even (god forbid) west marine. other chandleries will have it. it's easy to understand for and novice. I used it as a text book when I taught DC electric at a community collage.
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Old 06-05-2015, 10:45   #17
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Re: DC cabin lights wiring

I've been doing a lot of rewiring on my boat as well. I would think that 16 AWG marine wire would be fine for lighting...especially LEDs. The other thing is that you should "fuse" for the wire ampacity. That makes it kind of difficult if you have, say, 16 ga wire going from light to light but the light manufacturer provided the light with 20 ga wire to the actual fixture. In that case your breaker or fuse should be rated for the 20 ga wire not the 16 ga that you are using. I've actually rewired the fixtures in a couple of cases but I'm sure that I have some that are still not correct. Good, heat shrink crimp connectors with heat shrink tubing over them.

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Old 06-05-2015, 10:56   #18
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Re: DC cabin lights wiring

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Originally Posted by SailRedemption View Post

Here's a picture of one light.. And the leak in the jib car track I'm trying to stop without taking it up Attachment 101475
This photo is a perfect example of why I suggested 16awg. See how it is being used to hold-up the lamp and head liner? Do this a few times with 20awg and you'll pull the wire apart.
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Old 06-05-2015, 11:15   #19
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Re: DC cabin lights wiring

I recently added a few cabin lights, so here's how I went about it :

I placed one of these on each side of the boat, powered up by one breaker each, labelled port and starboard :

https://www.bluesea.com/products/cat.../TerminalBlock

They are close to the first light.

You can use these to turn the terminal block into a bus :

https://www.bluesea.com/products/cat..._Block_Jumpers

The wiring to this block should be able to take more current than the breaker. This is a general principle of boat wiring. I used Ancor 14 gauge, 2 core boat cable, with the white sheath. Easier to route, and tougher, than 2 separate conductors.

16 gauge is the minimum that should be used on a boat, according to ABYC standards. 16 gauge is still OK for a 20 amp breaker.

The individual lights then connect to these blocks. The cables should still be 16 gauge, as in a fault condition the breaker has to trip before one of the light cables melts.

An alternative to the block would be one of these :

Blue Sea Systems ST Blade 6 Circuit Fuse Blocks

You can then have a fuse for each light, so that one faulty light won't take them all out. In my experience, interior lighting is the least reliable thing in the boat. It's the only thing that's ever made my breakers trip.

The correct terminations for wires, and for joining two wires, are heat shrink crimps. You need a quality ratcheting crimper, and a heat gun. I had to do a couple of solder joints inside lights, no practical alternative, but keep it to an absolute minimum. But I added strain relief so the solder joints can't be stressed.

I'd second the recommendation for Don Casey's book. The complete sailboat maintenance manual includes the important wiring chapters.

When I got the boat, I added a couple of electrical items and ended up going back and doing it again, when I had learned more. So do your research and do it right first time.
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Old 06-05-2015, 11:21   #20
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Re: DC cabin lights wiring

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Originally Posted by trifan View Post
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.
If your emergency repair kit includes wire nuts, why can't it include butt crimps instead so you can do the job right?
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Old 06-05-2015, 11:26   #21
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Re: DC cabin lights wiring

W3GAC's story points out "fuse the wire size, not the load" - i.e. If you're running 18g wire, don't use a 15a fuse.

I use minimum of 14g for power on the boat. Why? Some other fool that buys the boat after me may load that crap up. Or I may need to. (Just as the p.o. powered the TV from the light circuit)

LED's _are_ voltage tolerant if you get the right ones. Ones with a regulator in them. The super-cheap ones will blow if you end up turning on a light during a equalize of your batteries. (usually 15+ v) This is because the cheapies just have a string of LED's wired in series until the voltage drop across that chain of diodes is enough to use one current limiting resistor. But as the voltage across that resistor changes, the current can change quite a bit, and thus now the diode has too much current thru it and the smoke comes out.


I'd use crimp connectors, I'd daisy-chain them. I'd fuse 16 at 10A.
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Old 06-05-2015, 11:36   #22
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Re: DC cabin lights wiring

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Originally Posted by jeepbluetj View Post
W3GAC's story points out "fuse the wire size, not the load" - i.e. If you're running 18g wire, don't use a 15a fuse.

I'd use crimp connectors, I'd daisy-chain them. I'd fuse 16 at 10A.
Why would you do that? 16 gauge wire is rated for 25 amps, or 21 amps in a machinery space.

I wouldn't fuse anything unless I had to. ABYC standards call for re-settable breakers.

I find it simplest to just have a long length of 14 gauge, 2 core boat cable as it exceeds the rating of ALL my breakers. (they are all 20 amp). Therefore I can do any repairs properly.
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Old 06-05-2015, 11:45   #23
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Re: DC cabin lights wiring

Just to emphasize:

- If you have any wire nuts (twist-on style) on the boat - take them off. You should always carry a selection of crimps for various uses and crimp tools to make "emergency" (and non-emergency) repairs. A butt splice crimp will need less wire than a wire nut to make an emergency splice and is just as fast to make.

- In general, you should use a minimum of 16ga wire for electric power circuits of all flavors. Might be OK to use 18ga for short runs in an enclosed space for things like backlighting or something. 18ga and below can be used for electronic data wiring. Which ever size is used - the proper size connectors/crimps should be used.

- If you can afford it, nothing wrong in using gel filled crimps or heat shrink but IMO is overkill for most areas on a boat that are not wet (more than just moist sea air wet) - provided you use tinned wire and tinned crimps.

- I'd recommend 16ga for your light circuits as well depending on the total amp draw and length per standards - fused or on circuit breaker of proper size for the wire.

- Doing two light circuits - port & starboard - is good advice if you can do it. I don't like to have all lights on just one breaker or fuse if possible.

- Avoid solder on all boat wiring - except sometimes for electronics and coax terminals as needed.
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Old 06-05-2015, 11:51   #24
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Re: DC cabin lights wiring

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Why would you do that? 16 gauge wire is rated for 25 amps, or 21 amps in a machinery space.

I wouldn't fuse anything unless I had to. ABYC standards call for re-settable breakers.
I'm a bit conservative and I'm almost irrational terrified about fire. Add to that the pigtails on the fixtures are typically smaller.

By "fuse" of _course_ I mean fuse or breakers. Depends on the age of the boat and what's on the panel. Most folks aren't gonna remove their "cabin light" fuse and replace the whole panel for just this change. "Fuse" also works as a verb where "breaker" doesn't work as well.
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Old 06-05-2015, 12:04   #25
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Re: DC cabin lights wiring

Just thought of one tip. If upgrading to LEDs, keep an incandescent at the chart table. LEDs can cause interference on the VHF, so you might need to turn of all the LED lights when making a radio call.
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Old 06-05-2015, 13:01   #26
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Re: DC cabin lights wiring

I want to reiterate what funjohnson said:"Try to have two circuits....like port lights and starboard lights in case either side fails." I think that this is important, and not only if one side fails. If you want to add anything, like another light fixture, or change anything or blow a fuse/breaker you'll still have lights on at least one side of the cabin in which to work.
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Old 06-05-2015, 13:11   #27
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Re: DC cabin lights wiring

LEDs can create rfi (noise) but if you buy good ones they won't. I have a friend who installed a cheap LED cabin light and then found he could not play his stereo while the light was on...a loud whistle in the stereo. I'd check Marinebeam...not cheap but lots of lumens and no rfi.

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Old 06-05-2015, 13:41   #28
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Re: DC cabin lights wiring

A few things to let everyone know:

I have the correct heat shrink crimps, along with the correct ratcheting crimper for said crimps. I always dip the end of the stripped wire ends in dielectric grease to lightly coat the wire before the crimp to help stave off corrosion. I will not use wire nuts because that's not correct item to use for this application. I will use the 16ga wire because I have a couple rolls of it already on the boat. It will be split to port and stbd, and common bus bars will be used on each side and a 14ga wire from those to the panel. Some lights will have their own wire run due to their location and some will be chained together in parallel. I'll be using either marine beam replacement dome light bulbs, or Scad Sensibulb replacements for the domes and reading lamps, so no RFI. The fluorescent will get the LED treatment as well.

Regarding breakers and such, the old frail breaker panel may get replaced with a blue sea ac/DC panel, if I can fit the one I need. It will most likely be using a 15a for the lights.

I plan on doing this once, correctly, and once only. If I need something else later I'll run a separate wire for it. I appreciate all the help and tips/reminders on this subject, always nice.


- Ronnie...on the geaux
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Old 06-05-2015, 14:31   #29
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Re: DC cabin lights wiring

I've had cheap, expensive, and really expensive LEDs and sensibulbs have been the worst. If I tap them just right, they finally come on, but half the time I give-up and use a different fixture. Buy the Marinebeam instead.
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Old 06-05-2015, 14:46   #30
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Re: DC cabin lights wiring

Series wiring is a no no as if one light is out they all go out. I always use marine rated tinned cables in my boat. Plain auto type copper wire will rot away in a salt water marine environment as we have in Auckland NZ. If the cables are too lightweight there will be a voltage drop in a long run. Heat shrink crimps or heat shrink tubing over standard tinned crimp joins are a good idea. You can use a hot air nozzel on a gas soldering iron to shrink. A flame from a gas stove lighter works but can leave soot marks. Absolutely use LEDs inside. I have been advised that the printed circuits in each lamp can fail in exterior LED replacement lamps subject to salt air. No such problem yet with my LED Nav lights. Maybe they are well sealed as designed as LED.
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