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fmueller 03-18-2012 08:43 PM

Grounding
 
Hi there,

I'm new to this forum and have been enjoying reading but this is my first post. I've got a new boat (new to me). She's a 1970 Dufour Arpege, in decent shape but with some deferred maintenance that I'd like to get around to this spring.

I started today on the electrical system and I'm hoping the forum can help answer some questions about grounding/bonding as I found at least a couple major grounds which were mostly or completed nonfunctional.

Two questions:

-I see a bonding system that connects (or is supposed to connect) the backstay to the keel. Should that also be connected to the neg side of the battery somewhere? if so, where?

-There is what looks like about a 4/0 ground wire running from the motor aft (starting at the same terminal where the battery is grounded to the motor). I followed it back into the aft lazarette and found the end of that wire just laying loose and unconnected in the vicinity of the fuel tank. Is the fuel tank supposed to be grounded? To the motor?

Both of these grounds are in bad shape so I'm going to be rerunning these wires, but before I do I want to know where they are supposed to go. There is minimal electronics on board, but even so I'd like the grounding/bonding system to be right.

Thanks in advance for your help.

~Fortunat

hellosailor 03-18-2012 10:41 PM

Re: Grounding
 
There are DC grounds, lightning grounds, and bonding wires, and which ones to set up, how and why, can be long discussions and choices. (Check around online.) I'd expect the cable from your backstay to the keel is a lightning ground, which you'd want to keep separate from any others.

The fuel tank, and fuel filler hose (there's normally a ground wire from the filler cap), would be grounded to dissipate any static charge, so it can't spark and flash the fuel. I'm not sure what's 'code' on that but would expect both to go to the engine block and the DC power ground.

"Both of these grounds are in bad shape" Stick to fully tinned wire, it is worth the extra price. You can often get fully tinned "type 3 machine wire" which is very similar to battery cable, at a better price.

kwaltersmi 03-19-2012 08:40 AM

Re: Grounding
 
When I saw "grounding" I was getting ready to post about halyard heeling, kedging off, and other such techniques. Now that I know this thread is about electricity, I'm out! :)

fmueller 03-19-2012 09:40 AM

Re: Grounding
 
Kwalter: As I revisited this thread I had the same thought...I should have picked a different name since this is ambiguous...sorry.

hellosailer: Thanks for the confirmation that what you call the 'lightining ground' should be isolated from the DC system ground which includes the engine. And also the confirmation that a steel fuel tank should be grounded.

Since I don't have either shore power or any fancy electronics (not even a hard wired VHF), I think our grounding/bonding plan is about as simple as it gets.

I plan to replace that 'lighting ground' as needed but keep it separate. Then I'll figure out how to re-attach the grounding strap to the fuel tank. I think that should do it.

If anyone sees anything grossly wrong with the above, please let me know.

Thanks for the help

~Fortunat


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