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maccauley123 02-28-2008 11:28 AM

Wiring Diagram Review
1 Attachment(s)
After all of the great information I have gotten from members of this forum I have to put this for review. Sailnet members are too good a resource to not take advantage of. :)

I am rewiring my boat, fixing the rats nest and hodge podge of wiring from the PO. The boat will be out of the water this summer while I complete this and a bunch of other projects so I am in no rush.

Based on information from here, Don Casey and Nigel Calder attached is my planned wiring diagram. It is a pretty simple system, no major components. I don't plan on ever installing a major power draw like fridge or a windlass. All of the major components like panel, batteries and engine are within a few feet of each other.

I know the format is not "standard" for a wiring diagram but I hope it has all the info needed. I want to do this right so want to make sure my understanding of everything is correct and plan will work and be safe.

Thanks and let the comments begin.

hellosailor 02-28-2008 01:29 PM

A fast look:
You have two 100-amp fuses in series at the engine grond cable. Fuses in series is pointless. What you need is one fuse on each battery positive, preferably on the battery itself or immediately adjacent to it.

You also don't show the engine starter. Some folks would take that directly to the battery (bypassing the fuse) others would run it on a fubsible link or fuse of its own. Or through the main fuse, if the ratings alllowed for that.

Personally, I don't see any reason to route the two switch panels the way you have with "cabin" feeding the second group. I'd just power two sets of switches and leave each one to be turned on/off individually. Or, perhaps put
"depth" "chartplotter" and GPS (not provided for?) on one switch called "instruments" since they usually are used together. And to add the compass light (? not shown?) to the running lights, since again both usually are either on/off. But, whatever logic works for you--it is your panel.

maccauley123 02-28-2008 01:33 PM

I uploaded a new image because I realized the original was a little off. It made it look like I was putting the fuses on the return ground when there is actually one on each of the hot leads to the switch. It should show correctly now.

chucklesR 02-28-2008 05:58 PM

A couple of thoughts,
Bilge pump (if equipped with a float switch) hard wired to one battery (house) with a suitable fuse, no switch, no distribution wired to float switch.
As is wired with switch for 'manual' operation
- that is safer, otherwise you have to be onboard or remember to turn it on.

You show no charger, inverter, etc.. so I assume none. I would add at least a charger - saves diesel and time.
You show no 'auxiliary' or spare breakers. Figure on two at least - you will want a GPS and or chartplotter or 12V outlet - you will want a 12v with at least a 10amp capacity, adding now is simpler than wishing later. Put a 12v outlet at a minimum in the cockpit (think searchlight and / or GPS).
For 30 bucks or so, add at least a DIGITAL voltmeter in there (don't go cheap with analog, you will regret it) - switchable by battery so you can get a 'gross' estimate on the state of charge by voltage. Add in a few more bucks and shunt and you can add a amp meter and work out rates of discharge for various loads - always very useful.

Making life real simple - rather than wire in a cabin fan - get one with a 12v plug, add outlets in the galley, salon and cabin - move the fan where you want it. Do the same with a light because flashlight batteries are always dead when you need them most.

If that's a Visio file, send me the .vsd please, email address PM'd.

btrayfors 02-28-2008 06:14 PM

The cable for connecting the two battery banks together, and for feeding the engine (AWG 4) is much too small. Even for short runs, it would be better to use much heavier cable.

The "radio" position on the bus (not the VHF position) that for a SSB???

If so, it should be wired directly to the battery...with appropriate fuses on both the positive and negative sides.


maccauley123 02-28-2008 06:29 PM

Bill, Thanks for the info. The radio position on the bus is a car stereo music radio so very low draw. No SSB.

maccauley123 02-28-2008 06:42 PM

Chuckles, thanks for the thoughts, couple of answers.

Bilge pump - Bilge Pump has an internal float switch so is just a two wire. I have a small device that allows me to connect up to 3 lines directly to my house battery.
Charger - I have no charger now but will be getting at least a small solar charger I can plug into a 12v outlet to keep batteries topped up. Would connect to outlet in cockpit when leave the boat. Maybe bigger later.
Spare breakers - I rearranged the panel a little so I now have 2 spots on the panel open. The outlets on the Main fuse bus is for 2 12v outlets. Was going to put one in cockpit and 1 in cabin. A couple more is a good idea.
Voltmeter - I have an analog voltmeter I forgot to put on the diagram. Was going to install with a switch so I can check either battery. Digital is a good idea.
Cabin fan - I have a hard wired one now but like the idea of a 12v one. I like the idea of more 12v outlets.

My diagram says chartplotter but it is really just a removeable bulkhead mounted GPS. This is now on a shared switch with the Depth.

sailingdog 02-28-2008 07:39 PM

For some reason, a 30-amp panel sounds awfully small for what you've got listed. A good stereo system can easily use 10-12 amps if you've got it turned up and four speakers attached.

I'd also agree with Btrayfors that the 4 AWG is way too small... For a 3% drop in voltage, for 100 amps and a total distance round trip of 15', wire that is 2 AWG is recommended, and I'm a big fan of going up at least one wire size as a safety factor... If the distance is more than 20' round trip 1 AWG or 0 AWG wire is recommended. :)

You also might want to re-think the running light breaker setup. You'll probably want at least three switches for the running lights, especially if you have both deck-level running lights and a tri-color.

One switch would turn on the deck-level lights (stern & bicolor), one switch would turn on the steaming light (required when you're motoring), and one switch would turn on the tricolor.

An alternative setup would be one switch for the deck-level bicolor, one for the tricolor and one for the stern light, and you could use your anchor light for both the stern and steaming light when under power. :)

A digital voltmeter is a much better idea...since they're accurate enough to give you a rough idea of battery charge state. 12.6 VDC is roughly a fully charged battery, 11.6 VDC about dead... 12.1 VDC about 50% discharged and time to charge again.

peikenberry 02-28-2008 07:56 PM

Circuit breakers Or fuses (overcurrent protection) are required to be withing seven inches of the power source. So the breakers between the batteries and the Battery Switch need to be close to the batteries. Same goes for the breakers off the main positive bus. (a bus is considered a power source.) I agree with the comment about cable size from the batteries to battery and to the negative and postive bus. This should be O or OO, or maybe 1 but definitely not 4.

Bilge pumps are normally wired directly to the batteries with a bypass switch so you can turn it on and off manually. That gets a little more complex but when your boat is unattended you still want that pump to come on if the bilge is filling up. Most boats sink at the dock.

Starter circuits generally do not have a fuse or circuit breaker. The current draw of a starter is so large it would probably pop any circuit breaker you put in the system. Plus that the only time there is current in the line is when starting so there is really no need.

On the following page are links to sample wiring diagrams for various types of boats. You might want to take a look at them. New Boatbuilders Home Page - Electrical Systems

Also on the Alden Trull Web page there are schematics for ten different boats. This may give you some ideas as well. Alden Trull Yacht Electrical Design

sailingdog 02-28-2008 09:02 PM

Be aware that the Alden Trull site doesn't open in some browsers properly. :)

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