grounding wire from gas tank

[nobrainsd]

I just got a custom aluminum tank. It has a grounding tab. I have read some other posts on this site, checked what CG regs I could find and I asked the manufacturer. The salesman said that the tab was primarily for use with a fuel level sending unit return, but that grounding the tank wouldn't hurt. The various posts I've checked call for grounding the tank, but vary as to whether I should run the ground wire to the negative battery terminal or to a grounding plate mounted in contact with the water. Seems to me that would be the most reliable ground in that it would not be disconnected by battery isolation or outboard removal. Since the tank is "permanently" mounted (not portable) the CG does require grounding, but doesn't specify the method. I'm intending to run a ground wire to an anode I have installed on my ss trim tab plate. Any comments or suggestions to set me right or at ease about this application?

 

[tommays]

Re: grounding wire from gas tank

One objective of the tank bonding is that the filler neck on deck is bonded to the tank so that there is no potential to build a static charge and make a spark during filling


Are you filling dirrectly into the tank on a rib

 

[nobrainsd]

Re: grounding wire from gas tank

I do not have a filler neck. I am filling my tank directly in my non rib futura. The boat has an aluminum floor. Yes, I'm careful about spilling any gas. Hasn't been a problem.

The question is to whether to hook up to a grounding plate or the negative battery terminal. When the boat is on the trailer and there is no earth ground (water contact), would the battery perform the role of dissipating possible static charge? I suppose that might be the advantage of connecting to the negative terminal as opposed to a bonding plate on the transom. I certainly don't know! But I intend to find out.

The aluminum tank is made to fit where my plastic tank went under my console/bench and leave room for my 60lb AGM battery. Just trying to keep as much weight as possible forward in the boat.

 

[kandil]

Re: grounding wire from gas tank

I think you should hoke it up to the battrey to avoid any static charge and make a spark during filling up just like the car!!and I believe that should fit the requirement of the CG.I did a search here and I found this it gives you an idea about basic boat weiring I hope that help. http://forums.iboats.com/showthread.php?t=186986

 

[nobrainsd]

Re: grounding wire from gas tank

Thank you for the informative reply. The negative battery terminal it will be. I'll be sure to post a pic when the install is done.

 

[sschefer]

Re: grounding wire from gas tank

Contrary to popular belief, electricity flows from negative to postive and the negative terminal on your battery is not a ground. Wiring up the negative terminal to the grounding tab will work to cause the sending unit to operate because it completes the circuit not because the unit is grounded. (In Europe its quite common to ground the positive side).

Here's why it's a good idea to connect it to the negative terminal on the battery. You would do this to create an inductor that will absorb the energy of a static discharge and thereby create a path of lower resistance. This is called a floating ground and is the most common type of grounding found in marine vessels.

By the way, the boat traveling through water creates a more significant static build up than you will every find at a gas pump. St Elmo's Fire is one of the most graphic examples I've seen. It is also why we have annodes for hulls and motors.

Humor - If you have an aluminum boat, hook a ground wire up to the hull and the negative terminal of you battery and watch your hull turn to dust.