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Old 23 July 2017, 20:38   #1
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Wiring - best practice + commoning of negative

I'm rewiring a 16ft boat. Nothing fancy. Bilge + GPS + VHF + Fishfinder + fag lighter

What's considered best practice?
One large waterproof fuse feeding a little 8 way blade fuse 'board'?

If so then what do people generally use for commoning of the negative? My Google-Fu isn't working on this. Bus bars, Common block, common connector & many other search terms have got me nowhere.

If I add an isolator, do people isolate the engine too generally, or just all auxilliaries?
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Old 23 July 2017, 21:45   #2
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https://www.bluesea.com/systems simple circuit diagrams may be helpful.

Buy proper tinned cable and terminals.

A negative bus bar worked for me and the isolator disconnected everything except auto bilge pump.
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Old 24 July 2017, 05:25   #3
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Originally Posted by Iron Dials View Post
https://www.bluesea.com/systems simple circuit diagrams may be helpful.

Buy proper tinned cable and terminals.

A negative bus bar worked for me and the isolator disconnected everything except auto bilge pump.


Sounds about right
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Old 24 July 2017, 10:25   #4
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I've got some silver plated ptfe cable. Horrible to work with, but great stuff for harsh installs.

Where do buy negative bus bars? I just can't seem to find any. 12 way or more, spade or screw receptacles. maybe I work with too many yanks - all my searches only return devices in USA
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Old 24 July 2017, 12:03   #5
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My XS rib has a -ve post where they all converge. The + is distributed in the loom.

If I was doing it I would use busbars.
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Old 24 July 2017, 12:06   #6
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Electrical - Aquafax
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Old 24 July 2017, 20:19   #7
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Blue sea worked for me.
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Old 24 July 2017, 22:19   #8
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I used kojaycat.co.uk,
You could use 2 x 6 terminal bars, may also add convenience of having two local -ve bars in different locations on the boat.

As with most things a good supplier can be very helpful on a 5 min phone call.
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Old 25 July 2017, 01:48   #9
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Sounds about right
Invest in good quality crimp tool. Screwfix do a professional ratchet one and a kit of crimp connectors but you will probably need to buy extra female spade connectors. It a seem expensive compared to the other non-rachet versions available at a much lower cost, but these will give you hassle.
I strongly second the use of Tinned copper wire, not the domestic stuff. Reliability is the name of the game in marine electrics. Enjoy your project.
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Old 25 July 2017, 08:08   #10
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I've got some silver plated ptfe cable. Horrible to work with, but great stuff for harsh installs.

Where do buy negative bus bars? I just can't seem to find any. 12 way or more, spade or screw receptacles. maybe I work with too many yanks - all my searches only return devices in USA
Any yacht Chandler which sell Blue sea parts. Force4, Marinescene
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Old 25 July 2017, 09:05   #11
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Quote:
Originally Posted by simonl View Post
I've got some silver plated ptfe cable. Horrible to work with, but great stuff for harsh installs.

Where do buy negative bus bars? I just can't seem to find any. 12 way or more, spade or screw receptacles. maybe I work with too many yanks - all my searches only return devices in USA
Use the "screw" type with ring terminals.

As a guideline, ABYC/NMMA standards (section E-11) allows up to 4 ring terminals to be stacked. They must be stacked with the highest ampere draw on the bottom and lowest on top. "Fork" connectors are not allowable.
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Old 25 July 2017, 12:54   #12
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Some Blue sea fuseboxes have a negative busbar built in.
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Old 26 July 2017, 16:52   #13
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Some Blue sea fuseboxes have a negative busbar built in.
I used a bluesea circuit breaker panel with negative bar. Then supplied power to switch panel with darling switches shown. I didn't want a separate negative bar but it would have been cheaper. BEP Busbar • 6 Input | Force 4 Chandlery Busbars very readily available.

Force 4 5 Gang Waterproof Switch Panel with USB Socket | Force 4 Chandlery Cheap power distribution.

Personally I'd avoid fuses. There is only so many of so many different ratings you can store on board, if your at sea and develop a fault, you could end up dead. . Circuit breakers are my preference, as they reset especially the MAIN circuit supply. The only down side is some breakers only push to reset and can't be operated like a switch. Fine if you have one of those switch panel things.

I'd also echo what other said. Use tinned wire, and heatshrink crimps with a decent crimp tool. Then shrink with heat gun.

The simplest type of diagram I've attached. But if it's open boat with auto bilge pumps they will have to be supplied from the battery direct (via fuse or breaker)
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Old 27 July 2017, 02:01   #14
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I agree with all the comments made by gtflash, except for the breakers. Being electro-mechanical devices the are sensitive to vibration, where fuses are not sensitive provided the fuse holder is mounted correctly. Fuses/Breakers are there to protect the wiring from causing fires, not the equipment and their fuse values should reflect the wire sizes used to connect the equipment. Should the equipment fail internally and draw excessive current, then normally the internal wiring/circuit board tracks will burn out without causing a fire. Having said that fuses need to be chosen to reflect the thinnest wire in the circuit for a device or group of devices. ONe can normally get away with 1A, 5A and 15A fuses.These are far more reliable than breakers (MCBs) in a marine rib environment.

Most electrical faults are caused by wire breakage and wire chafing causing shorts, which can draw large currents leading to wiring loom fires. I used Spiral-wrap to bind my wiring loom and then used P clips to secure the loom at frequent intervals. Loose wires, even in a conduit, will eventually break/chafe.

I also used additional negative bussbars in the console and Transom to simplify the wiring. I used much heavier wire to common the bussbars back to the main negative busbar.

Normally a fuse will not blow, but a breaker can trip if you hit a big enough wave
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Old 28 July 2017, 05:56   #15
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Quote:
Originally Posted by simonl View Post
I've got some silver plated ptfe cable. Horrible to work with, but great stuff for harsh installs.

Where do buy negative bus bars? I just can't seem to find any. 12 way or more, spade or screw receptacles. maybe I work with too many yanks - all my searches only return devices in USA

12V Battery Accessories terminal clamps covers cable isolator switches

marine and auto electrical supplies and wiring - kit car parts and electrics - iem services uk

Ordered from both. Very good service
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Old 28 July 2017, 14:23   #16
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I agree with all the comments made by gtflash, except for the breakers. Being electro-mechanical devices the are sensitive to vibration, where fuses are not sensitive provided the fuse holder is mounted correctly...... These are far more reliable than breakers (MCBs) in a marine rib environment....Normally a fuse will not blow, but a breaker can trip if you hit a big enough wave
This is an interesting comment and one that I'd briefly thought about whilst planning for the re-wiring of my RIB. Your post made me look into it a little bit.

The UK MoD use circuit breakers in their Pacific 24 RIB and the RNLI use them in their all weather boat. I couldn't find details on the Atlantic 75 / 85.

As a result whilst there is potentially a price penalty I'd say circuit breakers are possible on a RIB.
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Old 28 July 2017, 15:05   #17
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Interesting discussion re circuit breakers.
FWIW I went through the debate and decided against them and instead chosing blade type fuses in switch panel (Blue Sea).
My reasoning was that while there is a huge advantage in being able to reset by merely pushing there would inevitably be a mechanical fatigue level (not the perfect technical term) over time as the circuit breakers endured the physically demanding, sometimes extremely so, envelope a rib can operate in.
So a brand new rib, or MOD paying to replace parts I would probably go for circuit breakers. A rib I will use for years, mainly in isolation and without back up , then popping off the cover and slipping a new fuse in seems more reliable in the long term.

Anyone here have good or bad experience with circuit breakers?
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Old 30 July 2017, 11:41   #18
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Bobg. Interesting take on it. Mine are all thermal cct breakers. I think they are less suspetsble to vibration but only time will tell. I wonder if Fuses are suseptsble to mechanical damage. Never considered it when re wiring. I used to have a track car on coil overs, headlight bulbs lasted weeks cause of the hardness of the ride. I wonder if fuses are similar in design?

In industry we have moved on to electronic solid state circuit breakers now. Obviously not practical on a rib but very cool none the less.

Most new cars still use fuses?
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Old 30 July 2017, 16:26   #19
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Have replaced many circuit breaker which are generally about 15 years old, usually the push button type which would not hold in. Probable causes are internal springs which have been weakened by age and/or corrosion. The rocker switch type seem to be more robust. I have replaced these when the lense becomes damaged due to UV light and the device disintegrates. Blade fuses are much more reliable and have been used in vehicles for many many years. If an electrical circuit is correctly fused, then it is only likely to blow if there is an actual fault. Then replacing the fuse will only cause the new one to blow as well!!
The moral is that if you only plan to keep the rib for 5 years, use whatever you want. For much longer, use blades.
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Old 01 August 2017, 18:16   #20
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Bobg. Interesting take on it. Mine are all thermal cct breakers. I think they are less suspetsble to vibration but only time will tell. I wonder if Fuses are suseptsble to mechanical damage.
Thanks to all for all the replies - some great sites. The bad news is I've spent a fortune on bits, only a fraction of which I'll use. Lovely to have good stocks though.

Re fuses. I've routinely changed fuses in situations where high availability is paramount, but I'm with Bobg - car fuses are a very robust solution & I'd say less prone to failure than a breaker.
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