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Old 10-09-2015, 12:12   #1
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Building new Electrical system

I'm in the process of rebuilding the electrical system on my Morgan OI 41. The original electrical system has been so hacked on that there were little fuse blocks everywhere on board. the primary electrical system is almost non existant, It's just a 1-2-both switch with the leads for the starting battery missing! Instead of trying to sort it all out I've decided to just do a Rip and replace. Start again so to speak! I've attached my current design for the Primary wiring. Does anyone see any glaring errors?

The main battery switch is one of the new generation of dual bank isolated switches. I like the marinco one because you can still have bank 1 turned on while bank 2 ( engine) is turned off. Second position turns on both circuits ( still isolated from each other) and 3rd combines them. I've added a battery combiner solenoid for alternator charging purposes.

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Old 10-09-2015, 12:21   #2
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Re: Building new Electrical system

The biggest job on the boat I'm guessing.

Start with a decent schematic. This way you can rebuild one circuit at a time.

You might like to start with your wiring space claim. Setting up your trenches and bulkhead penetrations first will make the rebuild much faster. You can also seal the penetrations with penetrating epoxy befor running any cables. Leave plenty of room.

I dont bother labelling wires. It's much too slow. But choose your colors logically. The ABYC suggestion isna good start.

After thenwiring space claim I'd install all my terminal blocks. They're great for troubleshooting too.

Do all your sizing on the schematic.

Get a decent crimper and use the marine heat shrink and goop filled connectors. The job will go quickly once you're all setup.

Keep the schematics updated as you go along. I use D3 javascript Sankey diagrams. They auto size as you add to the schematic. I can also grep the json files used by d3 to find individual and groupings. Great for troubleshooting.

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Old 10-09-2015, 12:30   #3
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Re: Building new Electrical system

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Originally Posted by leftbrainstuff View Post
The biggest job on the boat I'm guessing.

Start with a decent schematic. This way you can rebuild one circuit at a time.

You might like to start with your wiring space claim. Setting up your trenches and bulkhead penetrations first will make the rebuild much faster. You can also seal the penetrations with penetrating epoxy befor running any cables. Leave plenty of room.

I dont bother labelling wires. It's much too slow. But choose your colors logically. The ABYC suggestion isna good start.

After thenwiring space claim I'd install all my terminal blocks. They're great for troubleshooting too.

Do all your sizing on the schematic.

Get a decent crimper and use the marine heat shrink and goop filled connectors. The job will go quickly once you're all setup.

Keep the schematics updated as you go along. I use D3 javascript Sankey diagrams. They auto size as you add to the schematic. I can also grep the json files used by d3 to find individual and groupings. Great for troubleshooting.
Leftbrainstuff, thanks. I have the tools to do the crimps and heat shrink ( I've done this before, just 15 years ago!). I'm going to reuse the existing chases where I can. good idea to label the schematic with the wire sizes. I have a bit of measuring to do so that I can verify my sizing calcs. I'm using the 3% rule for all my wiring as I'll be installing LED everywhere so most of the usage load ( aside from the fridge) will be pretty low)
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Old 10-09-2015, 12:36   #4
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Re: Building new Electrical system

Send the alternator output to your house bank, not the switch.
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Old 10-09-2015, 15:52   #5
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Re: Building new Electrical system

what size engine is this? 250a starting fuse is tiny. for an inboard more in the 500a range. 250 maybe for a 100hp outboard.


also as above depending on the size of alt I would run it direct to the house battery if over 80a or so. the tiny ones doesn't make much difference.


weird the drawing changed.. the alt should have it's own fuse on the house bank. not share the 250a house one which is likely too big for the alt cable (unless it's 2/0) fuse the alt for the alt size ~150%. the MRBF's are really handy here.


also the 50a solar fuse should be on the battery side. hard to tell from pic but kinda looks like it's on the controller side of wire. (depends how far apart they are)
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Old 10-09-2015, 16:12   #6
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Re: Building new Electrical system

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what size engine is this? 250a starting fuse is tiny. for an inboard more in the 500a range. 250 maybe for a 100hp outboard.
memmbbee not

Engine Starting Loads - Amp Draw Data (by Maine Sail)

Engine Starting Video / Real World Amp Load Data - SailboatOwners.com

And these, from Electrical Systems 101

OEM 1-2-B Switch Wiring History http://c34.org/bbs/index.php/topic,4....html#msg30101

Basic Battery Wiring Diagrams This is a very good basic primer for boat system wiring: http://c34.org/bbs/index.php/topic,6604.0.html

This is another very good basic primer for boat system wiring: The 1-2-B Switch by Maine Sail (brings together a lot of what this subject is all about)
http://forums.catalina.sailboatowner...d.php?t=137615
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Old 10-09-2015, 16:25   #7
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Re: Building new Electrical system

the 50 amp fuse for the solar controller is on the battery side. The engine is a Perkins 4.154 changing out the fuse size here is easy can easily put in a 300 or 350amp fuse. good idea to add another fuse for the alternator. I'm planning on using 1/0 for everything. all the runs are going to be very short.
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Old 10-09-2015, 16:32   #8
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Re: Building new Electrical system

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I'm planning on using 1/0 for everything. all the runs are going to be very short.

Can't really comment on wiring size without loads, but that sound like way overkill. I have some longer runs and my AO is #2 for a 100A alternator, external regulator and 90 ah house bank.
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Old 10-09-2015, 16:37   #9
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Re: Building new Electrical system

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Originally Posted by smac999 View Post
.... the alt should have it's own fuse on the house bank. not share the 250a house one which is likely too big for the alt cable (unless it's 2/0) fuse the alt for the alt size ~150%. the MRBF's are really handy here.....
No need to fuse the alternator end of the circuit, providing the wiring is sized to exceed the alternator rated capacity.
Alternators by their design are current limited sources so providing the wiring is correctly sized, there is no requirement to provide circuit protection at the source end.

EDIT. re-reading smac999 post, I may have misunderstood him. I concur there may be a requirement to fuse the alt wiring at the battery end depending on wire sizing
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Old 10-09-2015, 16:53   #10
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Re: Building new Electrical system

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No need to fuse the alternator end of the circuit, providing the wiring is sized to exceed the alternator rated capacity.
Alternators by their design are current limited sources so providing the wiring is correctly sized, there is no requirement to provide circuit protection at the source end.

EDIT. re-reading smac999 post, I may have misunderstood him. I concur there may be a requirement to fuse the alt wiring at the battery end depending on wire sizing
yah I'm commenting on a pic that isn't actually posted here. so it's probably confusing. if you click on the picuture and scroll to next picture he has made a new one with wire going to 250a house bank fuse. but he hasn't updated picture in thread yet.
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Old 10-09-2015, 17:24   #11
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Re: Building new Electrical system

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Originally Posted by leftbrainstuff View Post

I dont bother labelling wires. It's much too slow. But choose your colors logically. The ABYC suggestion isna good start. app

I always label wires
If not by what they actually are. ( positive leed to cabin light)
Certainly by number. That is every wire has the same number at both ends
Common practice in all audio video studios
Saves lots of grief
You can buy these pre made and they take just seconds to apply
Cableorganizer.com
Bradyid.com

Cheers
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Old 10-09-2015, 19:22   #12
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Re: Building new Electrical system

Updated with the alternator feeding the house bank directly. can probably add a smaller fuse for the alt wiring, say 120amp (80 amp alternator)

primary wiring is all 1/0 mostly because i got a deal on 2 50' rolls and I need some of that for my windlass install.

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Old 10-09-2015, 19:40   #13
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Re: Building new Electrical system

The only things I would change is a bus on the neg. side instead of a post, or maybe as well as the post and as a personal preference a ground lead from the alternator to the engine ground post. I don't like using the engine as a power lead.
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Old 10-09-2015, 19:53   #14
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Re: Building new Electrical system

I'm a strong believer in whatever I could do wrong - I eventually will. So I don't like 1-2 battery switches since it's possible to leave it set wrong and drain the start battery. I'm not exactly sure if that's possible with the Marinco switch you're planning.

Consider running the alternator cable to the house battery as you have but use something like the Balmar Duo Charge to keep the start battery always fully charged. If you must have an emergency switch to combine the two banks, mount the switch away from other switches so it doesn't get turned accidentally - maybe inside the engine compartment. It will hopefully never be used because the start battery will always be fully charged.

The Duo Charge also allows different batteries for house and start. Use a good deep cycle for the house bank but for the start battery an AGM start battery that will really kick the starter. I love the Optima Red Top batteries for this purpose. Because it will be always be fully charged, it will be reliable for many years.
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Old 10-09-2015, 20:49   #15
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Re: Building new Electrical system

I like the bus bar idea, makes the connections neater. I'll revive to include that.

Not a huge fan of using AGM mixed with deep cycle batteries as they have a different charging profile.

Next question: tie the windlass into the house bank or starter battery? I hear people talk about connecting to the start bank as the engine will typically be running when the windlass is in use. On the other hand there is more reserve power in the house bank.
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