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Old 03-25-2017, 12:24 PM   #1
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Bonding cable size

I'm planning to replace some old solid () bonding wire on my boat with tinned, stranded green marine cable. My plan is to use 10 AWG green wire from Genuine Dealz.

Does this sound about the right size? Another section of bonding cable is a braided non-insulated strap like this. It looks like it's in very good shape. Is this proper and sufficient?

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Old 03-25-2017, 12:43 PM   #2
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Boat builder's usually use #8 insulated green wire and maybe ABYC specifies this as well. Maybe more for corrosion allowance as I can't imagine much current flowing through the bonding wire even if there is a DC fault to the bilge.

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Old 03-25-2017, 12:57 PM   #3
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When we redid the engine room, I was told a minimum of 8 awg and 6 awg for lightning/bonding. This came from 2 ABYC electrical techs.
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Old 03-25-2017, 01:01 PM   #4
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Quote:
Originally Posted by FlyWright View Post
I'm planning to replace some old solid () bonding wire on my boat with tinned, stranded green marine cable. My plan is to use 10 AWG green wire from Genuine Dealz.

Does this sound about the right size? Another section of bonding cable is a braided non-insulated strap like this. It looks like it's in very good shape. Is this proper and sufficient?

Hey, Al. I'm just finishing replacing all the bonding on Stella. The ABYC-certified electrician I'm using told me nothing smaller than #8 and bigger is fine. (I used 6 as the "trunk of the tree" and 8 for the "branches."

What is the braided strap made of? If copper, and you have clean connections that can be bolted on, it may be fine--again connections matter. My boat has a common copper strip running the length of the ER that all the nearby through hulls bond to. ABYC requires threaded connections into that strip or nuts and machine screws compressing the connection the the strip. Self-tapping screws are not approved for good reason--metal and fiberglass expand/contract at different rates and many of the self-tapped screws that penetrated both on my boat were loose.

I would not bond to a common bus--braided or solid--that is made of steel. Steel has a small fraction of the conductivity of copper and the whole point of the bonding system is to offer minimal resistance between the metals you want to protect and the sacrificial anodes.

FWIW, I also used heavy duty lugs with heat shrink for the connections. The large 3/4-inch studs on the struts were a problem since I couldn't find lugs for #8 wire and 3/4" holes. So, I made some copper plates, drilled them to fit both the studs and the 1/4" machine screws connecting the bonding wire. Everything will get a spray of Boshield once tightened.



Steve D'Antonio can give you more authoritative guidance, but this is the approach I'm taking. Good luck!
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Old 03-25-2017, 01:13 PM   #5
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I believe #8 or larger is what is recommended and my guess is that it's the lower resistance rather than current carrying capacity that is the concern here.
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Old 03-25-2017, 02:28 PM   #6
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Thanks, guys! 8AWG it is!!

Angus, I'm not sure what the braided strap is made of. I'll have to take a closer look and measure it all. I'm thinking I may just rip out all of the old and replace it all with new #8.

I'll also pay attention to the stud sizes so I get the right lugs. I guess it's time to invest in a "proper" crimper. The hydraulic one I had been using from Harbor Fright gets terrible reviews from CMS for improper lug sizing.

Thanks for the ideas and advice, fellas!

Cheers!
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Old 03-25-2017, 02:35 PM   #7
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If I remember correctly it is 8AWG minimum and 6AWG minimum if the bonding is used for lightning protection too.
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Old 03-25-2017, 02:44 PM   #8
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Thanks, guys! 8AWG it is!!

Angus, I'm not sure what the braided strap is made of. I'll have to take a closer look and measure it all. I'm thinking I may just rip out all of the old and replace it all with new #8.

I'll also pay attention to the stud sizes so I get the right lugs. I guess it's time to invest in a "proper" crimper. The hydraulic one I had been using from Harbor Fright gets terrible reviews from CMS for improper lug sizing.

Thanks for the ideas and advice, fellas!

Cheers!
Al, again FWIW, I use FTZ heavy duty lugs and an FTZ crimper. Bought it all from Bay Marine Supply (out on your coast, I believe) because they had the best selection and price I could find. I bought one of their more expensive crimpers because I was working with 4/0. They make good crimpers for smaller wire as well. No affiliation other than the checks I wrote.

Search results for: 'ftz crimper'
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Old 03-25-2017, 02:46 PM   #9
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Al: When we bought all our wire, lugs and heat shrink we looked at the same company you did plus their sister company, Bestboatwire. Genuinedeal offers free shipping and the wire was a little more vs Bestboatwire where you pay the shipping but the parts are cheaper.

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Old 03-25-2017, 02:46 PM   #10
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Thanks, guys! 8AWG it is!!

Angus, I'm not sure what the braided strap is made of. I'll have to take a closer look and measure it all. I'm thinking I may just rip out all of the old and replace it all with new #8.

I'll also pay attention to the stud sizes so I get the right lugs. I guess it's time to invest in a "proper" crimper. The hydraulic one I had been using from Harbor Fright gets terrible reviews from CMS for improper lug sizing.

Thanks for the ideas and advice, fellas!

Cheers!
You can order the wire and lugs (terminals) from genuinedealz and for a modest fee. they will install the terminals for you. That would be easier and far less expensive than buying a quality crimper.
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Old 03-25-2017, 02:57 PM   #11
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Thanks, guys! Larry, I'll take a look at the sister site.

I think you're right...if I have all the lengths and lug sizes correct on the order. Those real crimpers are not cheap!

It just dawned on me that I might be able to borrow a quality crimper for a few days from my aircraft mechanic friends. That would allow me some flexibility in ordering parts and making the connections as I go along.

I will order the lugs and shrink tubing needed when I order the cable.

Is the proper test of continuity just a simple zero ohm measurement with the DVM?
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Old 03-25-2017, 06:06 PM   #12
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You will usually not get a zero reading with a sensitive meter because you will be measuring the resistance of the leads and the connections. Touch the leads together and see what you get. It will probably be a fraction of an ohm. "Continuity" will be a little more than that reading depending on the length and size of the wires.
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Old 03-25-2017, 06:31 PM   #13
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Also, consider the choice for bolts that could sustain a lightning current. Realize that stainless steel has about 1/42 the conductivity of pure copper. I replaced the 1/2" bolts in my transom zinc with silicon bronze. SB is still a few times worse than pure copper, but not 42x worse.
Braid is a tough sell for me on a boat. Rarely for bonding that solid strap copper (fixed surfaces) or AWG6/8 in THHN green (to engines) is not long lasting.
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Old 03-25-2017, 06:36 PM   #14
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Anyone ever see the lightning damage to a boat?

Anyone think 8 ga wire and 1/2 inch stainless or bronze bolts are going to matter?

Sure the EM pulse can be handled by little stuff...but a hit or spike?....kiss your electrical and electronics goodbye.
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Old 03-25-2017, 06:44 PM   #15
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Guess I would not worry about lightning on a power boat. If hit it will destroy all the wiring between it and the bonding. Sailboat---- different matter but there the only bonding that is important is between the mast and the keel for lightning. A bolt of lightning can produce thousands of amperes creating huge voltage drops across even the larger wire sizes.

Wire size... I think the larger diameter wires were selected mainly for mechanical strength than for their resistance.
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Old 03-25-2017, 06:46 PM   #16
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Plenty of sailboats have sunk because lightning blew a hole thru the hull jumping from the mast bottom to the water.
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Old 03-25-2017, 06:48 PM   #17
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Anyone ever see the lightning damage to a boat?

Anyone think 8 ga wire and 1/2 inch stainless or bronze bolts are going to matter?

Sure the EM pulse can be handled by little stuff...but a hit or spike?....kiss your electrical and electronics goodbye.


RIGHT ON!!!
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Old 03-25-2017, 06:54 PM   #18
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A bolt of lightning can produce thousands of amperes creating huge voltage drops across even the larger wire sizes.
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Plenty of sailboats have sunk because lightning blew a hole thru the hull jumping from the mast bottom to the water.
Not surprised. Had the misfortune in my sailboat which destroyed my electronics
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Old 03-25-2017, 08:09 PM   #19
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Plenty of sailboats have sunk because lightning blew a hole thru the hull jumping from the mast bottom to the water.
True; I've also read where salt water strikes are less damaging than fresh water strikes. Maybe due to less explosive boiling of the water at the high current density area.
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Old 03-26-2017, 12:59 AM   #20
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When I redid my Grand Banks, I used bus bars and interconnected them so that the weren't too many connections piled up. My experience was that you needed to make the connections as you went along to make it neat. Meter each connection as you go. I ended up using about 4 Blue Sea bars including a shaft brush and terminated in a transom zinc. The worst connection was at the transom zinc - stainless sucks as a conductor and I really like the idea of bronze bolts there.
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