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ctj1950 07-10-2012 09:54 AM

Grounding, bonding,AC, DC
Grounding, bonding, AC neutral and green wire ground, and DC minus.

On my 1976 gulfstar I just replaced all my thru hulls and seacocks. *When I was taking them apart I noticed that the chain plates were tied to the seacocks and the seacocks were tied to the backing plate for my cutlass bearing. *All these were daisy-chained from bow to stern.

*I don't understand bringing the energy from a lightning strike down to a thruhulls? I would think you would want to run the lightning protection directly to the backing plate.

*The DC minus was tied to the engine block and the AC green wire ground and neutral went back to shore power. I believe these are correct.

All the bonding wires were either *broken or disconnected or corroded. These I'm pulling out and replacing with new. *I'm also going to replace the backing plate with a 3/8 bronze plate. *And I'm redoing my DC primary wiring.

I pretty well understand how most of this should be except for the chain plates/seacocks. *The chain plate wire is for lightning protection? *The seacocks wire is bonding for stray currents. *Should these two be tied together? * Can I run all these wires to a terminal block, and then a single wire to the backing plate? *Or should the lightning and bonding be run separate to the plate?

Also what size wire should I be using?
I understand that the AC and DC should never be tied together.

TropicCat 07-10-2012 10:25 AM

Re: Grounding, bonding,AC, DC
Wow, opinions vary on this subject. Let me begin by saying that I have been struck by lightning while underway and although electric/electronics were toasted crispy, hull integrity was fine.

Chainplates should be grounded although in point of fact an aluminum mast is the preferred down conductor, being a much better conductor than stainless steel stays. This is the path lightning will try and take and this is where boat lightning protection should be.

Recent information from the lightning capital of the USA. University of Florida

"......If the mast base is on top of the cabin, a downconductor is needed to connect the mast base to the ground strips. Use at least #4 gauge copper with preferably bimetallic copper/stainless connections to prevent galvanic corrosion.

Alternatively, make a strong mechanical connection and additionally braze or solder, to improve the electrical contact and lessen the chance of contact corrosion, then paint with an insulating coating. A keel-stepped mast similarly needs to be connected to the keelbolts with at least #4 gauge copper...."

ctj1950 07-10-2012 01:13 PM

Re: Grounding, bonding,AC, DC
The mast is stepped on the keel. I'm pretty sure it is grounded. I check when I get back to the boat. should I daisy chain everything back to the backing plate?

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