Cruisers Forum

Join CruisersForum Today

Thread Tools Rate Thread Display Modes
Old 17-03-2013, 16:39   #1
Registered User

Join Date: Mar 2013
Posts: 2
j29 re-wire

about to set off on my spring project of re-wiring my J-29. it's a relatively simple 12 volt DC setup, with an outboard engine, so no alternator. attached is my plan. looking for any feedback to make sure i don't have to christen my fire-extinguishers. i've read don casey's book cover-to-cover, and have delved into the relevant chapters of calder's. have also browsed the web trying to dig deep into my college physics memory of circuits and ohm's law. my specific questions are with regard to choice of wire gauge. i can figure out the individual circuit gauges using the 3% tables, but i want to verify the size of the battery wires... do i just add up the amp-draws of the entire curcuit? my plan is to go with 4 awg to and from batteries to busbars, 6 awg for nav lights and bilge pump, 10 awg for cabin lights and mast light, and 16 awg for instruments (which draw a miniscule current). does that sound reasonable???
Attached Files
File Type: pdf j29.wiring.pdf (63.7 KB, 61 views)

amtdys is offline   Reply With Quote
Old 17-03-2013, 17:24   #2
Registered User
TheOffice's Avatar

Join Date: Jun 2012
Location: Annapolis
Boat: Hylas 44
Posts: 406
6 sounds way too heavy for nav and bilge pump. Even regular lights don't draw much, LEDs draw almost nothing

TheOffice is offline   Reply With Quote
Old 17-03-2013, 17:26   #3
Registered User
Target9000's Avatar

Join Date: May 2009
Location: New Orleans LA
Boat: 74 Westsail 32
Posts: 1,377
Re: j29 re-wire

I agree, up the size of the battery connections and lower to 10awg for the bilge and nav lights.

And yes, circuits are sized for their max current draw accounting for the length of the run.
Let your heart tell you where to go, but let your brain tell you how to get there.

Sundowner Sails Again
Target9000 is offline   Reply With Quote
Old 18-03-2013, 04:46   #4
Moderator Emeritus
GordMay's Avatar

Cruisers Forum Supporter

Join Date: Mar 2003
Location: Thunder Bay, Ontario - 48-29N x 89-20W
Boat: (Cruiser Living On Dirt)
Posts: 29,364
Images: 240
Re: j29 re-wire

Greetings and welcome aboard the CF, amtdys.
Gord May
"If you didn't have the time or money to do it right in the first place, when will you get the time/$ to fix it?"

GordMay is offline   Reply With Quote
Old 19-03-2013, 01:15   #5
Registered User

Join Date: Mar 2013
Posts: 2
Re: j29 re-wire

thanks for the advice! hope to get started this weekend.
amtdys is offline   Reply With Quote
Old 27-03-2013, 11:41   #6
Registered User

Join Date: Mar 2013
Location: East of the river CT
Boat: Oday Mariner 19 , Four Winns Marquis 16 OB, Kingfisher III
Posts: 212
Send a message via Skype™ to Colin A
Re: j29 re-wire

Check the actual draw listed on the devices you choose. It's easy to say generically what they require but it's best to check the equipment spec. If you are reusing installed equipment you may want to pick up a multi-meter with a current clamp and check what the equipment is currently drawing. I picked up a meter with a DC clamp (make sure it's rated for DC many at the Home Depot and Lowes are not) for about $60.00 this fall and find it invaluable around boats and campers. Mind you this price won't get you great accuracy like some of the Flukes I have at work but for this type of thing they are wonderful. There are ABYC wire charts online and blueseas also has a wire calculator on their site. Circuit Wizard - Blue Sea Systems
Work for
Bass Products
Colin A is offline   Reply With Quote
Old 27-03-2013, 17:46   #7
Registered User

Join Date: Dec 2008
Location: Oriental, NC
Boat: Mainship Pilot 34
Posts: 1,429
Re: j29 re-wire

Two observations:

Your branch wire sizes look way too big. Even your 4 gauge main feeder looks big. I would expect 8 to 10 gauge for the main and 14 gauge for most branches. And I doubt seriously if your bilge pump pulls 15 amps. Most pull 6-8 amps.

Your fuse sizes look like they are sized to protect the load. The fuse should be sized to protect the wire. Increasing the size will limit spurious trips.

djmarchand is offline   Reply With Quote
Old 27-03-2013, 17:59   #8
Registered User
rcmpegasus's Avatar

Join Date: Sep 2008
Location: San Diego & Port Townsend
Boat: Formosa 51 Ketch
Posts: 142
Images: 1
Send a message via Skype™ to rcmpegasus
I am currently rewiring my boat, using much smaller wire in general than you describe. I have led lights and am using 16 for them. I'd check those numbers.
Bob Mathews
S/V Pegasus
rcmpegasus is offline   Reply With Quote
Old 28-03-2013, 06:10   #9
Registered User

Join Date: May 2011
Location: Toronto
Boat: Sandpiper 565
Posts: 2,597
Re: j29 re-wire

Yeah, seconding the comments to reassess some of those load currents before investing in wire.

other comments:
- you only require one 30 A fuse in the battery run. Omit the fuse to the right of the battery switch
- I would upsize the wires between the battery and the bussbars, and select a battery fuse type that you could later upsize... to permit future expansion.
- why not install a small DC breaker panel instead of fuses and switches?
- add a circuit for your VHF radio. How 'bout a stereo
- I like to add a cigarette-lighter-type 12v socket or two on a 10A breaker for stuff like a 12v cooler, fans, spotlight, trouble-light, computer charger, small (75w) plug-in type AC inverter, 12v to USB for phone charging, etc etc.

If you could update your drawing with rough estimates of the wire runs, it would be easier to double-check your wire gauge choices.

Lake-Effect is offline   Reply With Quote

Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

Our Communities

Our communities encompass many different hobbies and interests, but each one is built on friendly, intelligent membership.

» More about our Communities

Automotive Communities

Our Automotive communities encompass many different makes and models. From U.S. domestics to European Saloons.

» More about our Automotive Communities

Marine Communities

Our Marine websites focus on Cruising and Sailing Vessels, including forums and the largest cruising Wiki project on the web today.

» More about our Marine Communities

Copyright 2002-2015 Social Knowledge, LLC All Rights Reserved.

All times are GMT -7. The time now is 23:23.

Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.
Social Knowledge Networks
Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2016, vBulletin Solutions, Inc.

ShowCase vBulletin Plugins by Drive Thru Online, Inc.