Diesel Fuel tank grounding?

[Elysium_Van_Isl]

Maine, et al.

I was down in the bowels of my recently acquired Catalina the other day trying to clean up some of the old wiring. I came across a couple of wire connections to the fuel tank and I'm wondering if you guys can help me puzzle this out:

(The attached photo shows the two black wires that I found, one is connected to the centre of the top access port, the other connects to the rim. I traced them out and one wire goes to a negative bus bar (which was apparently unconnected to the DC system anymore) and the other was just hanging loose under the same bus bar, below a bunch of gear. It seemed to have had no previous local connection. The wire looked cut (on purpose or accident) but there was no corresponding terminal end on the bus bar, nor any other errant comparable wire. Very strange.

1. Anyone know what they could be for? Are you supposed to ground your tank?
2. The PO told me that the tank (installed in 2006) was set up for having a fuel gauge, but had never been 'connected' up. Could this have been related to the wires?
3. It looks like the rim of that access port has a male connector tab on one of the screws, so I assume the factory meant for the tank to have a connection.

Thanks all!
Mike

 

[captcoho]

Fuel tank sending unit

 

[Stu Jackson]

In addition, the fuel tank should have a grounding lug on it, separate from the ground for the fuel sender (electrical).

The manual for your boat (available online from www.catalina30.org or .com) should have this in the fuel section.

 

[Elysium_Van_Isl]

Thanks guys!
I did see another black wire running from somewhere near the tank with "BONDING" written on a tag....but this too seemed strange to me. I thought bonding was a separate system related to lightning, etc protection...and I am 110% sure this boat is not wired for that!

Coho - Thanks for getting me on the right path here. That diagram seems to go to a page where the image is broken. Is the circle on the diagram the actual fuel display gauge?
If so, I bet when the boat was repowered in '06, the mechanic just left that second wire unattended since the PO didn't want a fuel gauge installed. I have found some really appalling wiring so far from that mechanic. Check this one out - main DC return to earth. He didn't have a cable long enough, so thought it was fine to let this thing sit under the flooring!!!

 

[Sailvayu]

You also need a ground wire running from the fuel fill to the tank. This is to prevent static spark when fueling. Ok I know with diesel it is unlikely to cause an exposition or fire but that is the law USCG CFR

Capt. Wayne Canning, AMS
www.projectboatzen.com

 

[Charles Erwin]

So far the answers are confusing - to me anyway

ABYC says:

"E-9.14.4 Grounded Liquid Level Gauge Transmitters (senders) - Grounded liquid level gauge transmitters mounted on fuel tanks or tank plates shall have the transmitter negative return conductor connected directly to the DC main negative bus, the engine negative terminal, or for outboard boats the battery negative terminal or its bus. No other device shall be connected to this conductor. This conductor shall also serve as the static ground and/or the bonding conductor for the tank and fill."

If there is a sender then doesn't this rule mean there cannot be a separate bonding/grounding wire and also that the wire (noted as fill to tank) cannot be connected directly to the tank?

What about a tank that does not have any "grounded liquid transmitter" (sender) do we bond/ground the tank and also provide a fill to tank bonding wire?


Charles

 

[Stu Jackson]

If there is a sender then doesn't this rule mean there cannot be a separate bonding/grounding wire and also that the wire (noted as fill to tank) cannot be connected directly to the tank?

What about a tank that does not have any "grounded liquid transmitter" (sender) do we bond/ground the tank and also provide a fill to tank bonding wire?

Charles,

The way I "interpret" this is

1. The sender needs a ground - this is because of two things, I suspect: that the tank itself should have a separate ground, and that the tank should not be (easily) used as the ground for the sender. The sender's electrical and it makes sense to have its own ground wire to complete the circuit. And Not have "Joe Mechelectric" use the metal tank to ground the sender.

2. The tank and fill ground should be separate from anything else.

3. Tanks without senders should follow #2.

Also, let';s not confuse bonding & grounding (again...comes up all too often). They are separate issues and any bonding (metal thru hulls, masts, etc.) must have their own separate connection to ground and NOT be connected to any electrical circuit grounds. http://www.westmarine.com/webapp/wc...01&page=Marine-Grounding-Systems#.UUJmcFdXr-I

Notice, I said this is MY interpretation.

I do agree that it does create confusion about keeping the tank and fill ground separate from the electrical sender ground.

I'll poke me head inside my tank compartment the next time I'm down at my boat. I'm pretty sure they are separate, but who knows...

Anybody?

Thanks, Charles, for pointing that out.

 

[Charles Erwin]

I do not think rules (that is those that contain the word "shall") should leave any room for interpretation. The word "shall" needs to be regarded as a commandment not an option. If there is room for interpretation then the text is no longer a rule -- only a suggestion.

E 9.14.4 is one of the rules that is mandatory because it uses the word "shall." There is just no room in this rule that allows tank attachment with two wires, three wires nor any other number excepting one - and only one - wire.

The purpose/effect of the rule is completely obvious. Following the rule eliminates all possibility that metal tank material (the sides, top, and bottom) could conduct electrical current and assures that any current path is confined to wiring only. Hence the rule absolutely enforces a "single attachment point" requirement.

The rule as to (conductive) tanks is exactly the same as the rule concerning ship bonding/grounding leads attachments to the motor block -- at one point only.

The whole idea is - or seems to be - that neither the motor block nor the tank skin could itself become a part of any conductive circuit.

Charles

 

[Don S/V ILLusion]

Charles
Please keep in mind the entirety of the standards are recommendations based on opinion. Informed opinions vary.

 

[Stu Jackson]

The purpose/effect of the rule is completely obvious. Following the rule eliminates all possibility that metal tank material (the sides, top, and bottom) could conduct electrical current and assures that any current path is confined to wiring only. Hence the rule absolutely enforces a "single attachment point" requirement.

The whole idea is - or seems to be - that neither the motor block nor the tank skin could itself become a part of any conductive circuit.

Charles

I simply do not think it's that obvious.

A single attachment point for a ground for a tank compared to an electrical device seems counter intuitive to me.

The engine is the ground point.

It's "how you get there" that seems to be the issue.

I would provide a ground wire from the sender to the negative bus.

I would provide a separate ground wire from the tank and fill to the engine, which is the same electrical "point: as the negative bus, but on a separate wire. Subtle but important distinction.

Think of it as two separate single points of failure.

 

[thinwater]

Charles
Please keep in mind the entirety of the standards are recommendations based on opinion. Informed opinions vary.

This sort of standard is developed by a consensus of experts (much different than an opinion), most often after someone got dead.

I belong to several standards orgs. and have done several fuel static investigations. Each time, someone decided "shall" meant it was optional.

 

[anchorclanker]

If I remember ill go find my aviation mechanic books, it should have a good explanation. At any rate I'm not understanding the single ground wire thing and apparently thats not how the boat was built in the first place and makes no sense to me as I have never seen anything like that. In fact I seem to recall tanks with several bonding/ground straps that still used a separate ground for the sender.

 

[anchorclanker]

I belong to several standards orgs. and have done several fuel static investigations. Each time, someone decided "shall" meant it was optional.

Thats just men trying to turn the 10 commandments into the 10 optional suggestions, lol

 

[Maine Sail]

Below are the current standards as to tanks


H-33.15.1

Each metal or metallic plated component of the fuel fill system that is in contact with the fuel and the fuel tank shall be grounded so that its resistance to the boat's ground is less than one ohm.

NOTES:

1. The deck fill is considered to be in contact with the fuel.


E-11.15.2.1

Equipment located in machinery spaces or in contact with a fuel line, or that may be in contact with bilge water or seawater shall be designed so that the current carrying parts of the device are insulated from all exposed electrically conductive parts.

EXCEPTIONS:

1. Liquid level gauge transmitters. For installation of fuel tank transmitters on conductive surfaces.
11.15.2.3

Grounded Liquid Level Gauge Transmitters (senders) - Grounded liquid level gauge transmitters mounted on fuel tanks or tank plates shall have the transmitter negative return conductor connected directly to the DC main negative bus, the engine negative terminal, or for outboard boats the battery negative terminal or its bus. No other device shall be connected to this conductor.


EXCEPTION: Isolated sending units that are isolated from the static grounding and bonding system.

NOTES:

1. This conductor may also serve as the static ground and/or the bonding conductor for the tank and fill.

2. If a fuel tank is included in the lightning protection system see ABYC TE-4, Lightning Protection for recommendations regarding the conductor between the fuel tank and the DC main negative bus.

 

[anchorclanker]

I see nothing in that restricting multiple grounds/bonds.

This seems to be a good discussion of the subject;
http://www.thehulltruth.com/boating-forum/106068-bonding-grounding-aluminum-fuel-tanks.html

In reality, our boats have much more in common with aircraft than any other kind of transportation. But boats arent regulated the same as aircraft. On an airplane, generally the only people who can work on the planes navigation and communication radios and equipment are avionics guys. On a boat any one of us can hook up anything we want, including satnavs, radar, you name it.

 

[Elysium_Van_Isl]

Great info all!
And thank you to those able to quote the ABYC documentation. It is REALLY appreciated.
So here is my plan:
1. I will add in a gauge. This will be wired (pink) from the centre ring of the Sender cap, (red) from the ignition and (black) from the 'tab' connector in my picture to the Main negative bus bar.
2. I will add a grounding wire from the deck filler cap straight to an engine lug.
3. I will add a tank ground wire from one of its mounting bolts to the Main negative bus bar.

Hopefully that does it!
Mike

 

[Elysium_Van_Isl]

OK, so when you guys say "from Sender to Ignition" do you mean an actual connection on the back of the Engine Instrument Panel (ie the ignition switch, etc)? Or somewhere else!

 

[captcoho]

So far the answers are confusing - to me anyway

ABYC says:

"E-9.14.4 Grounded Liquid Level Gauge Transmitters (senders) - Grounded liquid level gauge transmitters mounted on fuel tanks or tank plates shall have the transmitter negative return conductor connected directly to the DC main negative bus, the engine negative terminal, or for outboard boats the battery negative terminal or its bus. No other device shall be connected to this conductor. This conductor shall also serve as the static ground and/or the bonding conductor for the tank and fill."

If there is a sender then doesn't this rule mean there cannot be a separate bonding/grounding wire and also that the wire (noted as fill to tank) cannot be connected directly to the tank?

What about a tank that does not have any "grounded liquid transmitter" (sender) do we bond/ground the tank and also provide a fill to tank bonding wire?


Charles

Bond to the filler tube ??

 

[Chris Patterson]

OK, so when you guys say "from Sender to Ignition" do you mean an actual connection on the back of the Engine Instrument Panel (ie the ignition switch, etc)? Or somewhere else!

The sender "hot" wire should only go to one place, the gauge. The gauge is powered separately from the switch.



Bond to the filler tube ?? (Quote)
Mine is, and it's plastic.

 

[Me and Boo]

The fuel fill hose, deck fitting to tank, should be "wired". A wire is integral to the hose construction so it is connected top and bottom making a contiguous electrical path.