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Rewire - All home runs or some terminal blocks?

Discussion in 'Ask All Sailors' started by UpperPintle, Jul 9, 2018. Add this thread to a FAQ

  1. UpperPintle

    UpperPintle

    Joined Dec 5, 2017
    3 posts, 0 likes
    Unspecified Unspecified
    US Where it is
    I'm rewiring my boat (36', all wiring already removed) and want to know if it's better to run all home runs to each device from the DC panel or to use terminal blocks for groups of devices. For example, devices up forward in v berth (fan (1), berth light (1), storage compartment lights (2), is it better to run those to their own breaker on the main DC panel or run them to a terminal block in the v berth area, then a single home run from that terminal block to the DC panel breaker (correctly sized for voltage drop/distance/load). All lights are LED and the fan is 1 amp. Boat is 12v system. For larger consumers (fresh water pump, sump pump, washdown pump, etc...) I'll use home runs for those. This question is more focused on lighting, 12v outlets, and fans. I seem to have a lot of them (lights in the larger compartments, under cabin sole to illuminate bilge, cabin lights, low light lights ("night lights", etc...). Each fixture's leads will be connected to feed wire (whether home run or not) with a terminal block to eliminate splices.

    Attached is an example.
    Thanks
     

    Attached Files:



  2. NotCook

    NotCook

    Joined Dec 29, 2008
    539 posts, 99 likes
    Treworgy 65' Custom Steel Pilothouse Staysail Ketch
    US St. Croix, Virgin Islands
    I can tell you that on our vessel, we have one breaker for the forward cabin ("fo'castle"), one for the main saloon Port, another for the Stbd side, one for the galley, one for the aft/master cabin, one for the head, one for the engine room, etc. Each of those are a 15A breaker. The individual lights/outlets are not each home runs. Hope that helps.
     


  3. rgranger

    rgranger

    Joined Jan 19, 2010
    4,885 posts, 866 likes
    Hunter 26
    US Smith Mountain Lake
    With the quality of today’s LED puck lights. I wonder about the need to wire lights at all? I’d consider replacing all lights with stand alone pucks. And then I’d feel free to have a lot more and in convenient places.
     


  4. topcat0399

    topcat0399

    Joined Aug 22, 2011
    991 posts, 68 likes
    MacGregor Venture V224
    US Cheeseland
    I just finished rewiring - and I wish I had just installed a fuse block with ground buss in the Vberth and the Laz and ran a single set of heavier wires to those remotes blocks from the panel. I home ran everything.
     


  5. RoyS

    RoyS

    Joined Jun 3, 2012
    332 posts, 73 likes
    Hunter 33
    US Bay Pointe, Quincy
    I like your plan to use terminal blocks as described. I would run separate home runs to critical circuits, no matter how small the load, such as your running lights to prevent a short circuit in, say, a cabin light from disabling this vital circuit. Bilge pumps are another example. Terminal strips, as you point out, eliminate splices. They also make future additions easy and aid in troubleshooting without causing any appreciable voltage drop.
     


  6. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,656 posts, 489 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    No problem with home runs or local distribution centers. Just make sure the distribution blocks have appropriate over current protection for the step down in wiring eg: 10GA feed to 14GA branches, or are well protected by the panel breaker. Heavy gauge runs for lighting, to smaller shorter runs close by, also means more connection points to have issues with and means trouble shooting will be all over the boat vs. just behind the panel or at a device. When ever you do localized distribution please don't hide it or bury it or it will make trouble shooting even more difficult.

    For example on my own boat she has a single breaker for "Nav Station" which is a large gauge feed to a small fuse panel behind the nav station. We run the stereo, wifi amplifier, cell phone amplifier, 12V Outlets, a fan, etc. off this breaker. Our navigation instruments, GPS, N2K network, Garmin marine network bus etc. are also one breaker with the exception of the radome which is on its own circuit. We then have one breaker for all instruments (wind, depth, speed, temp) and the AP.
    Many builders, for unknown reasons, used three or four breakers for cabin lighting. This makes little sense especially when you look at the cost of a panel based on per breaker slots. Cabin Lighting can be one breaker, easy and simple. Cabin lighting can also be Cabin Lights & Fans. Our compass light comes on with the nav light circuit.

    Always buy a panel with more breakers than you plan to use, you will use them.
     


  7. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,656 posts, 489 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    A terminal strip is a form of splice only with four connections vs. two. Properly installed butt splices actually survive longer than a terminal strip with exposed connections in the marine environment.

    Sadly butt splices get a bad rap when not installed "properly" with the proper tooling but, done correctly, in many cases I prefer a butt splice to a terminal strip for reliability and durability in the marine environment.

    For example a quality heat sealed but splice is made from a continuous tube of tinned copper with no brazed seam to fail. This is a far more robust crimp terminal to a ring terminal with a brazed seam or far better than cheap ring or spade terminals that lack any brazing of the seam.. A brazed seam can split, especially when cheap or inadequate tooling is used or poor crimping practices are employed..

    A butt splice will have two total connections left side and right side. A terminal strip will have four connection points and exposed metal surfaces to corrode. Wire to crimp terminal, crimp terminal to terminal strip X two.


    Absolutely and the distribution aspect, as well as the trouble shooting aspect, of a terminal strip can't be over looked, it is a huge benefit in certain installations.. Butt splices obviously make little sense for non-home run distribution but, don't discount using them where you need to. Also don't discount placing a terminal strip in at least a water resistant enclosure and coating it with a terminal protection product when done.

    I have seen far too many owners convinced by local "dock experts" that splices are a no, no. They then use terminal strips in areas where a terminal strip has no place residing. A year or two down the road there is trouble and they can't figure out why? One really needs to use the proper tool for the job at hand and in many cases, on a boat, that will be a heat shrink sealed waterproof butt splice.
     


  8. UpperPintle

    UpperPintle

    Joined Dec 5, 2017
    3 posts, 0 likes
    Unspecified Unspecified
    US Where it is
    Thanks for the advice. Attached is a preliminary drawing of the DC devices that do not have a dedicated breaker (radios, pumps) or are not directly connected to battery (bilge pumps, device memory). This shows only from the DC panel inward. The wiring to the DC panel from sources is a separate diagram. Also, I did not show the negative wire runs because that would make the diagram too cluttered.
    These are mostly lights/usb outlets/fans. I have some work to do to eliminate any that are unnecessary. I don't have most of the fixtures, so I don't know how far they spread light. Once I nail down which fixtures I will use, I will know if I really need 5 lights under the cabin sole to illuminate that area (about 4' wide, 1' deep, 15' long) or if I really need one fixture at each end of each settee, etc....

    Once I remove excess fixtures that are not really needed from the first draft schematic, I will get a better idea of how many devices I will have. What I don't understand is how to feed devices when the total number of devices exceeds the total number or breakers, unless I use terminal blocks, then feed those terminal blocks to the breaker, stack the wires (ring terminals) on the DC panel (but limited to for per stack) or parallel the wire to devices. Then only certainty at this point is that I will have more devices than breakers in DC panel (Blue Sea 8382 DC panel).

    Take this example of starboard cabin lights. Let's say I have four lights on the starboard side and one fan. Each light has two 18 ga pigtails adn the fan a + and - terminal. When wiring in parallel, I can attach the ring terminals to the fan and continue on with the wire run.

    When I get to the lights, how to I connect the light's pigtails to the inbound and outbound wires so they are secure and to mitigate corrosion? I am awazre of the 3-way butt splices, but those have exposed metal in the center. I also want to keep all connections where I can get to them easily for maintenance and trouble-shooting.

    Regarding battery-powered lights, I'm going to use as few as possible because I've had too many devices ruined by leaking batteries. I'll stick with wired devices as much as possible. There might be some spots where it's too difficult to run a wire.
     

    Attached Files:



  9. RoyS

    RoyS

    Joined Jun 3, 2012
    332 posts, 73 likes
    Hunter 33
    US Bay Pointe, Quincy
    The problem with many applications of butt splices is that there are three or more wires terminating together, eg a string of existing cabin lights. Butt splices, in that application, are not as reliable as a terminal strip. I have seen people bolting and taping ring terminals to accomplish this but IMHO that is the worst solution. In a past life I worked with subway trains. There were hundreds of conductors that typically ran between large junction boxes and landed on numbered terminal strips. All of these wires were stranded and crimped with ring terminals. Virtually no failures at the terminal strips despite the thousands of terminations on a fleet of trains that were expected to last 35 years or more. Butt splices were not permitted anywhere.
     


  10. Justin_NSA

    Justin_NSA

    Joined Jul 7, 2004
    4,579 posts, 685 likes
    Hunter 30T
    US Cheney, KS
    I like the idea of correctly fused distribution. It makes me ill to see all of the stacked terminals behind the main panel.
     


  11. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,656 posts, 489 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    That would not be considered a "proper" installation of standard heat sealed butt splices. In a case like cabin lights quality terminal strips are a fine choice provided the location is dry.
     


  12. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,656 posts, 489 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    Behind a panel there should be no more than four terminals stacked on any post or stud or screw terminal, if you are wiring to the safety standards.
     


  13. Maine Sail

    Maine Sail Moderator

    Joined Feb 6, 1998
    10,656 posts, 489 likes
    Canadian Sailcraft 36T
    US Casco Bay, ME
    In an application like that there would be no reason for a butt splice and 35 years would be easy to do in a dry environment. Problem is we're not working on subway cars we are dealing with boats that reside in extremely humid environments with lots of salt air.. For lighting circuits, away from any deck leaks, a good quality nickel plated barrier strip terminal block will do fine for many years, if coated with a terminal grease, but in a bilge or engine space they simply don't hold up like a water proof butt splice would. The application & location is critical in determining what type of splice or junction to use..

    This was just this past May. Owner installed this terminal strip in 2015 and chose it over butt splices due to local "dock expert" talk... I was called to the boat because his alternator had "failed"... The only thing that failed was the owners land grade terminal strip, due to corrosion. If this had been done with heat sealed butt splices, which in this location is really the only suitable fix, if you don't want to add a lot more wire, the terminations would have been 100% water tight and would easily outlast an el-cheapo Eurostrip by about 25+ years. On this particular boat there was no way to get a terminal strip to a "drier" location without completely re-wiring the engine side a cost the owner simply did not want to pay for. Since I began using water tight adhesive lined butt splices, in the mid 90's, I have never had a single failure nor a single failure due to corrosion. Many items today actually require the use of butt splices from bilge pumps & switches to pig-tail navigation lighting....

    This boat needed a lot more than just this terminal strip being fixed......
    [​IMG]
     


    Mark Maulden likes this.
  14. JimInPB

    JimInPB

    Joined Aug 22, 2017
    866 posts, 240 likes
    Hunter 212 & 170
    us West Palm Beach
    When wiring larger boats, I do like to have at least 2 different breakers powering different areas of the cabin lights. That way, if a lighting breaker trips at midnight, I will probably still have some of the lights on & I may have a good change of finding my way to the breaker panel without doing a face plant into a hard object. I agree that 3 or 4 lighting breakers tends to be excessive & counterproductive.
     


    jviss likes this.
  15. jviss

    jviss

    Joined Feb 5, 2004
    2,603 posts, 258 likes
    Tartan 3800
    US Westport, MA
    [​IMG]
     


  16. jviss

    jviss

    Joined Feb 5, 2004
    2,603 posts, 258 likes
    Tartan 3800
    US Westport, MA
    I absolutely agree! I wish mine were split across a couple of breakers or fuses. Fortunately I have 'courtesy lights' on a separate breaker, red foot-lights that are turned on at bed time. If the cabin lights are out at least you can find your way around.
     


  17. UpperPintle

    UpperPintle

    Joined Dec 5, 2017
    3 posts, 0 likes
    Unspecified Unspecified
    US Where it is
    Thank y'all for the information. It looks like the best approach is to use butt splices in damp area (bilge, chain lockers) to get the pigtails up above the cabin sole, then use good quality terminal blocks that are treated to resist corrosion (Dielectric gel, BoeShield/CorrosionX) and put in a box for additional protection as well as safety because these terminal strips will be in areas that are easily accessible and it seems prudent to cover them up to prevent contact between pos and neg terminals/buses. This will consolidate the runs to each local terminal strip, with a home run (sized correctly with appropriate breaker) to the DC panel.
    Now I need to sort out my list of lights (all LED).
    Thanks again for the help.
     



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