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Old 29-07-2007, 18:45   #1
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Joining two greatly different wire sizes

I need to connect a #4 wire to a DC 30 amp breaker for my autopilot drive unit. The current drop will be less than 3% using that wire size for the twenty-something feet the duplex wire will travel from panel to the unit. Any problems with joining the #4 with a two foot section of #12 or #14 at each end to actually mate to the breaker or the terminals? I can crimp, solder or use a terminal strip with appropriate lugs for the actual attachment.
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Old 29-07-2007, 19:10   #2
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There's no need to do that. You can find lugs for #4 wire which will fit a standard-size 30A breaker, or a terminal. Also, you could use a separate breaker for the autopilot, like one of the bulkhead-mounted or panel-mounted models by Blue Sea Systems.

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Old 29-07-2007, 21:53   #3
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And don't solder them. The acid flux is corrosive giving the salt atmoshere a head start.
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Old 29-07-2007, 22:05   #4
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Quote:
Originally Posted by delmarrey
And don't solder them. The acid flux is corrosive giving the salt atmoshere a head start.

I agree about the availability of connectors, but who uses acid flux? I never have, rosin core only for me. Never had any problems with it in over 20 years.

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Old 29-07-2007, 22:39   #5
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Never mind!

My memory is not as good as it use to be. I had this thread on mind.

"Ohm's Law & Boats"

Quote:
Appendices:

1. Soldered Joints:
ABYC does not permit soldered-only joints (Section E-9.17.12.8). Where crimped joints are also soldered, adequate support must be provided, so as to minimize flexing. The solder causes a ‘hard spot’ in the wire, which is subject to breaking.
While soldering will greatly reduce moisture penetration and joint resistance; it’s is often very difficult to accomplish in the tight quarters encountered. I seldom solder terminations, except for Bilge Pump wiring (where water/moisture is a huge problem), and Battery Lugs (where hydrogen gassing causes corrosion).
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Old 30-07-2007, 02:36   #6
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As Bill suggested, use the proper terminal, such as Ancor #230253 (or #210253) Ring Terminal for #4 AWG wire c/w #10 Stud Hole.
ancorproducts.com/Products/Connectors/pdf/38.pdf
http://www.ancorproducts.com/Product...ors/pdf/38.pdf
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Old 30-07-2007, 03:07   #7
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Just trim the wire down to size and use a lug IF you cannot find the right lug. Go to an electrical supply house.

Ohms law applies to the entire wire, the very little that you trim will not affect it. Please support the wire as close to the terminal as possible.

A splice is Not advised.
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Old 30-07-2007, 08:14   #8
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Roy, if that #4 cable connects back to the battery with similar cable, it is possible a 30A breaker is a bad idea. Even a single good Group27 deep cycle battery can supply over 3300A into a dead short, and the common marine breakers are rated to fail around 3500A, making it possible for the breaker to literally "weld" and fail to open under that kind of load.

Whenever cables that heavy are used, and there is a possibility of that much power going through them, you are safer using a FUSE rather than a breaker, or using the special breakers rated 5000A. (Which were something like $75-100 each as I recall.) I'd rather use a fuse in that circuit, installed as close the to power distribution panel as possible. (And of course similar fusing on the battery bank itself.)

The large "glass cartridge" fuses used by car stereo shops seem to be perfectly suitable and WAY less expensive than all the fancy marine fuses. Easier to find, too.
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Old 30-07-2007, 08:57   #9
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With the above mentions properly crimped lugs, heat shrink and a Blue Sea Maxi Fuse block you'll get a nice looking setup. You can almost always find the fuses for about $2 at any auto store.
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Old 30-07-2007, 09:16   #10
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Roy’s #4 cable is going From his Distribution Panel To an Autopilot drive, not from the battery to panel. The standard 30A breaker (/w 3,500 AIC) will protect the branch circuit.
He has (wisely) oversized the cable in order to reduce voltage drop.
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Old 30-07-2007, 09:25   #11
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Gord, that's all fine and good--as long as the distribution panel isn't ALSO carrying something like #4AWG back to the battery. I can't tell from what's been posted, would rather err on the safe side.
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Old 30-07-2007, 09:36   #12
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hellosailor: One circuit at time ...

Further to my previous:

AIC = Amperes Interrupting Capacity

Interrupting Capacity (IC) is the maximum fault current that can be interrupted by a circuit breaker without failure of the circuit breaker.

It should be noted* that not all fuses, notably the aforementioned “Maxi”, have higher interrupting capacities than breakers.

* See the Interrupt Rating Comparison for Blue Sea Systems' Fuse and Circuit Breakers (below):
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Old 30-07-2007, 11:11   #13
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Yeah, Maxi Fuse looks nice, but I would always go with Gord's or Hellosailors advise!
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Old 30-07-2007, 11:22   #14
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Quote:
Originally Posted by Roy M
I need to connect a #4 wire to a DC 30 amp breaker for my autopilot drive unit. The current drop will be less than 3% using that wire size for the twenty-something feet the duplex wire will travel from panel to the unit. Any problems with joining the #4 with a two foot section of #12 or #14 at each end to actually mate to the breaker or the terminals? I can crimp, solder or use a terminal strip with appropriate lugs for the actual attachment.
Yo Roy,

do not solder.

If you CANNOT provide the correct terminal for #4 wire to your breaker, use a terminal strip located close by the breaker, with a short length of #10 wire.

best, andy.
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Old 30-07-2007, 13:08   #15
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Quote:
Originally Posted by Terra Nova
Yo Roy,

do not solder.

If you CANNOT provide the correct terminal for #4 wire to your breaker, use a terminal strip located close by the breaker, with a short length of #10 wire.

best, andy.
IF you don't know how to use a piece of heatshrink for support, yea, don't solder. If on the other hand you DO know how to use heatshrink as a wire support, then by all means solder. The 'rule' of not soldering must be a hold out and meant for the average person who really shouldn't try to use a soldering iron. I've been soldering wires at terminals, many involve systems that are subject to much greater stresses than any boat will ever see. Think SPACE and DEFENSE. One such prototype was a guidance system mounted in the nose cone of SAM missles.

I've begun to believe that when it comes to electronics and the AYBC or whoever wants to set up rules for boats and electronics, they must be stuck in the analog age.
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