Grounding Fuel Fill and Fuel Tank

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Onplane
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Grounding Fuel Fill and Fuel Tank

Postby Onplane » Thu May 04, 2017 6:14 am

I'm sure there is already a post for this subject, but I couldn't seem to find exactly what I was looking for... So I apologize in advance if this is repetition...

I have a plastic Moeller Fuel tank, and I bought the Moeller fuel tank installation kit.
Instruction.jpg


The instructions, as you can see in the picture, looks like it shows a grounding wire coming from the underside of the fill neck, to ground. The place where it attaches on the neck looks almost like it's a set screw or something you'd just slip an electrical connector onto. However, the neck itself is completely smooth (no set screw, no threaded hole, nothing). In other words, no obvious electrical attaching point.

Additionally, there are some bold warnings not to trap the ground wire between the neck fill and the fill hose.

So my question is... where do I attach the ground wire on the fill neck, and how?

The fill neck is currently attached with 3 wood screws into the top deck, but I suppose I could replace one of these with a bolt and ground to that, but I'm not sure that's what is required.

The fuel vent line apparently needs to be grounded too. However, I don't see any attachment point for that either. If I use a spot on the metal tie strap does that even provide any benefit?

Finally, with my very limited experience with electrical... my plan is to route all grounding wires to a bus bar that that then goes to the negative terminal of the battery. Is that understanding correct? The product literature on grounding is quite confusing seeing as how I don't have a "mast, lightning ground bar, or engine block" to ground to...

Thanks

Soloboat
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Re: Grounding Fuel Fill and Fuel Tank

Postby Soloboat » Thu May 04, 2017 8:07 am

Using a through bolt to the underside to attach a ground wire is the way to go I did just that however just make sure that there is continuity from fill to your ground verify by using an ohm meter. Connecting to a neg. bus is ok too
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Onplane
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Re: Grounding Fuel Fill and Fuel Tank

Postby Onplane » Thu May 04, 2017 1:30 pm

Found a pic of what I was trying to explain...

fill.jpg


Sounds like a plan. Now, the vent line has a metal thru hull connector that's supposed to be grounded as well, any suggestions on how to do this?

BillW
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Re: Grounding Fuel Fill and Fuel Tank

Postby BillW » Thu May 04, 2017 10:10 pm

Onplane,

On that drawing shown above, the ground wire should connect the filler neck to the fuel sender plate ground connection,
and then to ground.

You say you don't have an engine block, but whether your motor is inboard or outboard, it has a block. If it has electric starting, the
negative battery cable goes to the block, and that is grounded to the water thru the drive shaft, lower unit, etc.

I think that Glen-l offers electrical system drawings now; probably has a lot of good info.

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Bill Edmundson
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Re: Grounding Fuel Fill and Fuel Tank

Postby Bill Edmundson » Fri May 05, 2017 7:53 am

All metal parts of the fill and tank system should be grounded to each other and then to the boat ground. This so all parts are at the same static potential and can't spark. The vent has a serrated washer under the nut. Put the ground under it, then tighten back down. Go to the filler bolt then to the tank, then to the boat ground.

I'm surprised that they don't show double clamps on the vent line.

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hoodman
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Re: Grounding Fuel Fill and Fuel Tank

Postby hoodman » Sun Jun 17, 2018 7:16 pm

Bill Edmundson wrote:The vent has a serrated washer under the nut. Put the ground under it, then tighten back down.


Do you mean just sandwich a ring or spade terminal in between the washer and the nut? Seems like it could come loose that way?

IMG_20180617_213523.jpg

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Milhouse
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Re: Grounding Fuel Fill and Fuel Tank

Postby Milhouse » Mon Jun 18, 2018 7:06 pm

The fill neck is currently attached with 3 wood screws into the top deck, but I suppose I could replace one of these with a bolt and ground to that, but I'm not sure that's what is required.
Yep a bolt is what is needed like your pic shows.

The fuel vent line apparently needs to be grounded too. However, I don't see any attachment point for that either. If I use a spot on the metal tie strap does that even provide any benefit?
From my research, below, this is not required or needed.

Finally, with my very limited experience with electrical... my plan is to route all grounding wires to a bus bar that that then goes to the negative terminal of the battery. Is that understanding correct? The product literature on grounding is quite confusing seeing as how I don't have a "mast, lightning ground bar, or engine block" to ground to...
Yes that is correct.


The Coast Guard regs are in section 183.572, page 98 and 99

Quote of the day from your favorite Government Literature:

CAUTION: BONDING WIRES PUT UNDER THE END OF A HOSE COULD CAUSE A
FUEL LEAK. The bonding wire should be a “bolted connection” on the tank’s ground tab.
At the deck plate the bonding wire may be securely connected to a ground fitting provided
on the deck plate, or securely connected to a deck fill plate bolt.

Matt - Per the section 183.505 the vent is part of the "fuel system" but section 1.83.575 specifically says "Fuel FILL system and Fuel Tank". I read that as the vent does not need to be grounded, note that it is not shown in the diagram for grounding either.

Why: My educated guess is that the fuel fill and the pump filler nozzle may be at different electrical potentials in an ungrounded situation (only actually equalizes charge in ifthe boat is in the water (see below for why) and will create a Spark (aka Electro static Discharge (ESD)). Since you are not filling from the vent there is no need to ground it because the Nozzle and the fitting won't touch.

183.505 Definitions.
As used in this subpart:
Fuel system means the entire assembly of the fuel fill, vent, tank, and distribution
components, including pumps, valves, strainers, carburetors and filters.

183.572 Grounding.
Each metallic component of the fuel fill system and fuel tank which is in contact with fuel
must be statically grounded so that the resistance between the ground and each metallic
component of the fuel fill system and fuel tank is less than 100 ohms.

Per ABYC Section 24.15

24.15 FUEL SYSTEM GROUNDING
Each metal or metallic plated component of the fuel fill
system and fuel tank, which is in contact with the fuel,
must be grounded so that its resistance to the boat's ground
is less than one olnn. Wire ends shall not be clamped
between the fill pipes and hose.

Vent Clamping from AYBC section 24.11.8

24.11.8 Hose used in the fuel tank vent system or the
fuel distribution and return line system shall be secured to
a mating spud, pipe or titting which is formed or machined
to provide sen-at ions (at least 0.15" [.38mm] depth) or a
bead. At least one corrosion resistant metallic clamp shall
be used with a band width as indicated in Table III

Other good reading at: http://newboatbuilders.com/pages/fuel.html

This does not apply directly but helps explain the ESD situation for separation of charges in non conductors nicely:

Recent events have caused the boating industry to examine the policy regarding the bonding of plastic body fuel fills with metallic caps and retaining chains. Existing USCG & ABYC policy states that the bonding of these components is voluntary. A study by IMANNA Laboratories has shown that connecting the metallic retaining chain and cap of a plastic body fuel fill assembly to a boats bonding system may result in electrostatic discharge from a land-based fuel pump nozzle to the metallic components of the assembly when the boat is not in the water. This condition does not exist when the boat is in the water due to the equalizations of the ground potentials between the fuel pump nozzle and the boats bonding system.

It is recommended by ABYC and the USCG that new and existing installations of this type of fuel fill assembly DO NOT INCLUDE any attachment to the boats bonding system. Existing connections should be removed from the point of connection to the boats bonding system to the fuel fill assembly. Removal of the metallic components of the assembly is not necessary; however, the U.S. Coast Guard and ABYC still require that METALLIC body fuel fills be bonded.
Attachments
ground 1.jpg
From USGC
ground2.jpg
From USGC
gas 3.jpg
From http://newboatbuilders.com/pages/fuel.html
Last edited by Milhouse on Mon Jun 18, 2018 7:40 pm, edited 2 times in total.
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hoodman
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Re: Grounding Fuel Fill and Fuel Tank

Postby hoodman » Mon Jun 18, 2018 7:28 pm

Jim, that's a good catch. And that explains why the vent doesn't have any kind of convenient way to attach to a ground. The fill can be easily grounded with a through bolt. It's funny that it's not discussed at all on any of the instructions but there is a wire attached to the deck fill in the installation diagram but not on the vent.


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