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Re-wiring - NMEA 2000?

bbboat

Member II
Anyone out there have any experience with the new NMEA 2000 wiring systems? Now that I've redone the deck on Pie-Rats, I want to eliminate the rat's nest (pun intended) of wiring behind the old DC panel, and eventually upgrade the electronics (Signet vintage 1985). I'm also putting in new lighting, and now's the time (before a new headliner goes in).

NMEA 2000 in theory sounds great. A 3-cable backbone is all that runs through the boat, and you supposedly just "tap in" at the closest point to the backbone to add gear. NMEA 2000-compliant equipment "talks" to all the other devices, so you can theoretically plug-in a Raymarine display unit, for instance, and it will immediately recognize and be able to use the data from, say, an AirMar weather station/GPS. The backbone cable can also supposedly provide DC power to lights, etc. The descriptions remind me of Firewire or USB 2.0 for computers.

I'm wondering if this new system is DIY-friendly, or if I should consider this, or just stick with rewiring the traditional way?
 

rwthomas1

Sustaining Partner
Do you mean rewiring the whole AC/DC system or just the electronics/instruments/etc? I just did a bit of both.... I installed new IS20 autopilot (ap24), wind, speed/depth/temp setup from Simrad. The system is very simple to install. It all just plugs together in a "simnet" There is no need to connect in any particular order and new gear can be added anywhere there is a junction. Like a small computer network I suppose.... The depth/temp transducer plugs into the speed transducer that plugs into the wind indicator with a T fitting at the mast, then back to the compass, etc. etc. in a daisy chain. There is one master "buss" with 7 connections but that is just to make it easy. There is a NMEA adaptor inline to allow the Furuno radar/chartplotter to talk with the Simnet, I hope... The Tech will be making the final connections and calibrating it all on Friday. So far I really like the Simrad stuff but it seems like all the manufacturers are making network style systems now that will integrate with almost anything. Buy what you like.


Regarding the dc system I also did a bit of work on that. On my dc panel all the grounds returned to the back of the panel which didn't make sense, made working on the panel very difficult. I installed a negative bussbar behind the panel and ran all the negatives to that with a small wire to handle the panel negative requirements. I also consolidated all the negative battery cables to a power post/central point. Previously there were 5 separate negative cables to the engine block and well as other wires connected at the batteries, etc. Now it makes much more sense. I also stripped out what had to be 200ft of wire that goes nowhere. 24 years of PO's adding and removing equipment but not removing wires. The electrical system is much less complex once you pull all the unconnected/old wires out. Also did a new Blue Sea battery switch. I did find some "black wire" disease so I know what my project will be next winter.

I read about the "3 wire boat" a while back. The idea is there is a negative, a positive and a control wire that run the length of the boat (dc system). Anywhere in the length a light, accessory, ANYTHING can be tied into the system with a slave switch that accepts those three wires and attaches to/controls the accessory. The switch is a circuit breaker and is digitally controlled by the control wire. The main panel still has the master switches we are all familiar with but each master switch is programmed to the slave switches at each accessory. As you can see this would make wiring a boat extremely simple. The slave switches also have a manual override to allow control should the main panel fail. IIRC, Victron Energy was selling a system like this? Would make a great and easy upgrade compared to a full rewiring job. Was this type of system what you were refering to as well?

I highly recommend just cleaning up the existing system and reworking wires, time well spent.

RT
 

Gary Peterson

Marine Guy
MTU and other European manufacturers use a German data system called CAN. It uses three wires to communicate between all devices on the system. ( CAN high, CAN low, and a bond). While being simple in theory it is very complicated to set up and program. All devices have different Node numbers and heaven help you if one is progammed wrong!
I believe NMEA 2000 is a simple version of this.
 

bbboat

Member II
Ideally, I'm talking the whole AC/DC system.

The A/C system is effectively non-existent right now (the breaker box was an old 4-breaker house box and the outlets aren't even GFCI - all ripped out) so I'm starting from scratch there (already have a Newmar AC Panel I plan on using).

The DC system appears to be original, with things added in the 80s during a repower, and other things quickly added by the P/O in not the best fashion (example: the wind speed indicator was wired with TWO red wires - a tag was added to one labeling it as "DC Pos" and the other "DC Neg." Guess all he had to work with was red wire???).

The DC panel on this boat is directly under the companionway steps above the engine, with barely 6" of depth before hitting the cockpit bulkhead, so it's truly a rat's nest (the panel barely closes). Everything works, but still...

Right now everything is open and relatively accessible (no headliner, lockers and cubbies all gear-free).

Rob, by "just cleaning up the existing system and reworking wires" are you recommending taking what I have and re-doing it properly using traditional wiring techniques? Do you feel the 3-wire system is just too new (or too much $$) to consider? Cost is an issue here.

I don't think I have the same issue of multiple ground wires going back to the engine block, but it's still a scary thought working on all of it.
Thanks!
 

rwthomas1

Sustaining Partner
If you have it all open/apart then a full rewire might not be a bad idea. The 3-wire setup seems like a great idea but what do the specialized switches, panel, parts, etc. for it cost? Can you get spares easily? In my case, what I did recently will do for now. It all works, is safer, etc. than it was. I will likely try to replace the "black wire" next winter. I doubt I will replace the ac or dc panels as they fit the space nicely and have enough breakers for my needs now and in the future. Reworking the panels will also be cheaper. I plan to put mine on a hinge though.

Hope this helps....
RT
 

chaco

Member III
Secondary Ground Buss

The E35II has been ReWired with new AC/DC Breaker Panel. One of the things I install is a Secondary Ground Buss Fore and Aft, run back to the Main Ground Buss in the Battery Locker. This allows you to Ground to the Secondary Buss without making the LONG runs back to the Main Buss :nerd:
My total load on each Secondary Buss was 20 Amps. A #10 Wire will handle this load with a run of 20ft back to the Main, instead of (6) #12 without the Secondary Buss :) The NMEA (3) Wire System sounds like a bunch of C....P from an Electrical Genius. Just stick with the common wiring practice and you will have a reliable system that YOU can work on ;)

Happy ReWire :egrin: :egrin:
 
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