Where to ground my GPS

[ripnlips]

Going to be installing a new GPS in my North River Seahawk this week. My buddy has heard that the ground should be at the battery, not the hull. Would appreciate your thoughts and experiences.

[SouthCoastStu]

Your Buddy's got it right. Don't ground anything to your hull :twocents:

[marys netter]

Your Buddy's got it right. Don't ground anything to your hull :twocents:
Seahawks have a ground bonding terminal block under the front dash bulkhead almost directly above the hatch door.
By the way "don't ground anything to the hull" is not quite correct. your fuel tank must be ground bonded to the hull else there could be bombing consequenses!!:idea:

[SouthCoastStu]

I guess I could have said "don't ground any electrical devices to the hull", but I assumed most people out there with an average IQ would understand that since the original question was about a GPS and not a gas fill spout :berry:

[chucks electric]

hello, the proper way to ground an aluminum boat is to add a ground buss. all of your batteries, engine, grounds at the helm, all go to one location. you add an additional battery cable from the buss to the hull this takes any voltage potential that the hull or drive may have and brings it to 0 volts.
essentially you ground an aluminum boat the same way you would ground a fiberglass.

[lurking_out_loud]

This is about grounding not bonding which are two TOTALLY different things. Seems some people get a little confused between the two.

All grounding of an aluminum boat should be at a SINGLE location. On your SeaHawk, that would the negative terminal bus connected to your battery. There are 2 locations where these sit. One is under your dash, the other is under your battery shelf in the transom. Both connect directly to the negative terminal of your battery. Do NOT make an additional connection from ground (battery negative) to your hull. NR didn't put one in, neither should you. I can give your a bunch more info if you need, but in this forum it is going to be a waste of effort. PM me if you need to.


-LOL (yep, I'm an electrician too.)

[Jan]

Take a bucket of saltwater and a chunk of aluminum like your boat is made of.

Connect a 12 volt battery with the negative side to the aluminum and put it in the bucket with the positive side in the water on the other side of the bucket.

You will see graphic evidence as to why you never want to connect to the hull with a ground wire this as the aluminum will start to fizz.

[ripnlips]

Thanks to all. I get it.You guys are great to share your thoughts and ideas. Good luck in your fishing ventures and now is a good time of year to remind all to be safe.

[Marines511]

lurking out load has it right
you leave the USA and that ground is caslled a return (better name for it)
and bonding is called grounding (i like bonding better)
but the sea hawk does have a grounding terminal block for grounds under the dash use it

[chucks electric]

hello, lurking out loud grounding and bonding are the same thing. it is designed to complete the negative circuit of your 12v system, trust me there is NO confusion on my part. there is more to this than simply adding a ground wire from the gps to the battery. read the post carefully.
jan if you knew anything about corrosion on aluminum boats you would know that in order to control stray voltage from the hull to the drive or vice versa there must be a secure low resistance connection between the engine the hull and the ground connection to bring the voltage potential to 0 volts you don't want the electrical connection through the water because that is how corrosion happens. not to mention what type of anode and how much surface area is needed whether the polarity from the water to the hull should be + or -. further more the coast guard and abyc have rules on how many connections can be on an electrical post. i volunteer my knowledge here, to help not belittle or act like an ass----, when it comes to boats ignorance is not bliss. i don't pretend to know everything but i do know that i have forgotten more about electricity than either of you will ever know. get your facts strait before you lambaste someone. its not professional to respond to negative posts but in this case i will make an exception. now have a nice day!

[lurking_out_loud]

"grounding and bonding are the same thing. it is designed to complete the negative circuit of your 12v system,"

Nope. Not even close. Bonding is used to tie dissimilar metals together to equalize any voltage differentials between them. Bonding systems on land or on the water are NEVER intended to carry current! That's just basic electrical theory!

Here's a summary of what you should know. Typically everything electrical on your boat should connect to the negative terminal on your battery(s). The batteries are in turn connected to your outboard or engine which will be the SINGLE connection to earth ground. The connection between your engine and hull (bolts and mounting plate) will act as your electrical bonding connection between your aluminum hull and electrical system.

From a West Marine article on boat grounding:

DC Ground
Every light or appliance should be wired with its
own DC return wire. Never use the mast,
engine, or other metal object as part of the return
circuit. The DC load returns of all branch circuits
should be tied to the negative bus of the DC
distribution panel. In turn, the negative bus of
the DC distribution panel should be connected to
the engine negative terminal or its bus. The
battery negative is also connected to the engine
negative terminal or its bus. The key factor here
is that the yacht's electrical system is connected
to seawater ground at one point only, via the
engine negative terminal or its bus.

Bonding and Electrolytic Corrosion Due to Hot Marinas
Do not bond any thru-hulls or other immersed metal that can be electrically isolated. Specifically, keep your metal keel/ballast, your metal rudder shaft, your engine/prop, and all thru-hulls electrically isolated, from each other, and from the engine. It's worth understanding the reason. In an increasing number of marinas, there are substantial DC electric currents running through the water. If your bits of immersed metal are bonded, the electric current will take the lower resistance path offered by your boat in
preference to the water near your boat, and the current will flow into one of your bits of metal, through your bonding wires, and then out another bit of metal. The anodic bit of metal or thru-hull that has the misfortune to be on the "out current" side of the current running through your bonding system will also become "out metal" and will disappear, sometimes rapidly.
Your zinc is only intended to protect against the modest galvanic potentials and therefore currents that are caused by the dissimilar metals that are immersed and electrically connected together on your own boat. Your zinc is incapable of supplying enough galvanic potential to protect against substantial DC currents that may be flowing in the water. These
DC currents in the water will cause electrolytic corrosion to your bonded thru-hulls or metal parts.

Wait, here's more:

Grounds and Grounding One of the least understood aspects of a boats electrical system, and the most troublesome, is the proper method of grounding. That we often get questions of whether AC or DC electrical equipment should be grounded to the boat's bonding system is illustrative of this point. AC and DC grounding systems are two separate systems, for distinctly different reasons. If you don't understand these systems, you run the distinct risk of creating a disaster. Actually, there are four separate ground systems: DC ground, AC ground, AC grounding (or bond), and the vessel's bonding system. You can add to this lightning and HF radio grounds as well. Do you know the principles of each? Are you sufficiently confused to discourage you from doing your own wiring? I hope so. For unless you understand each thoroughly, you're headed for trouble.
The AC ground and grounding systems are "free floating," meaning that they do not ground on the vessel, but only to shore. The ground, or neutral, is a current carrying conductor, and is the source of many troubles because people do not regard it as such. The grounding, bond or green wire is the "safety" intended to channel current safely to ground in the event of a short circuit. Both of these circuits are capable of conducting current and can be the source of electrolysis when there are system faults with the dock or marina wiring. This is very easy to test for.
There is only one point where the DC side is grounded, and that is at the battery. It, too, is a "free floating" system in which nothing is ever grounded to any metallic part of the vessel, most especially not the bonding system. Just like a car sitting on rubber tires, completely insulated from earth potential, the battery itself provides the negative potential.
The bonding system, also green wire, has nothing to do with electrical systems. Underwater metals are simply wired together to equalize differences in potential of different kinds of metal. Nothing should ever be grounded to the bonding system. Unfortunately, some people don't understand this and use it to ground electrical equipment, occasionally with disastrous results.

Bonding Systems Bonding simply means wiring all the boats underwater metals together. This is done because of the galvanism caused by the different metals. By wiring them together, the differing potentials are equalized. Bonding does not solve problems of galvanism or electrolysis, but it does spread the the flow of current around over more metal, so that 1/4 volt or so won't cause any damage. Whereas if that 1/4 volt were going to one small seacock, it would probably eat it up in a hurry. In other words, bonding lessens the effect of small amounts of current. On the other hand, it also spreads it around to all underwater metals so that higher currents end up damaging everything.
Bonding systems use wire and ordinary crimped ring terminals. After a while these get wet and corroded. Electricity doesn't flow very well through corroded metal, so your bonding system after a while stops working. To maintain it, simply cut off the old terminals and install new ones. Do you have wires attached to sea cocks with hose clamps? Forget it. This is putting stainless and copper together, which are galvanically incompatible and it won't work.

http://www.yachtsurvey.com/ElectricalSystems.htm


If anyone has any questions, please let me know. Be careful about accepting answers on the internet as factual. You never know if the responder knows what they are doing or are pulling answers out of thin air.

I'm done.

-LOL

[chucks electric]

hello, the a/c grounding system the ground system and the bonding system are all tied together, that way people don't electrocute themselves. galvanic isolation is controlled with the proper anode, galvanic isolators or isolation transformers which is a whole different subject. the comment that they are all the same is meant that they are all part of the grounded conductor. all of these circuits carry current not voltage if they do have voltage then you have corrosion. further more there isn't a boat built today that doesn't have a bonding system that ties all underwater metals together. the mounting connection between the engine and hull is grossly inadequate especially in wooden boats. be carefully about which articles you quote. you started on this course of animosity and i fed it, because its a topic that is important enough that the facts need to be kept strait. heres a question how many boats have you seen that the lower unit is dissolving away but the hull is fine? can you say bad connection. ask these guys if they are catching fish. my appologies to those who i might have offened.

[lurking_out_loud]

Sorry Chuck E, my original comment about confusion was not directed toward any one person but as a comment about people in general. After reading your response above, I could revise it if that would make you happier.

You and I have had this discussion before. Usually I just give up since it would take me far more time to try to re-educate people that are convinced somehow that a direct connection between battery negative and their aluminum hull is acceptable. I stand 100% behind my comments that only a SINGLE connection to ground is proper and that bonding and grounding are two wholly different systems. It really doesn't matter if it's an AC or DC system we are discussing, bonding is not the same as grounding. You should never use your bonding system as a system ground.

As for the dissolving outdrives, typically those boats I see are seldom used, filthy, and in poor physical condition. I would hazard a guess that all of the required maintenance on their sacrificial anodes (zincs) is in every case ignored. Since the outdrive is typically composed of less noble materials than the hull, without zincs it understandably will be the first to go.

Take care.

-LOL

[chucks electric]

hey sorry about being so obstinate, we are each entitled to our opinions and you stuck to your guns and i admire that.
i would never use the bonding system or grounding system as a ground, these are simply parallel systems that are and should be interconnected to the ground system.
as far as the grounding the hull, there is alway going to be a current path between the hull and the engine and it gets worse as a boat ages. my school of thought is add a connection between the hull and ground and eliminate water as the conductor.
have a good one
chuck.

[Chrome Bumper]

So what happens when I connect my bonding system to the 12V ground, will my boat fizz like an alkaseltzer? If I isolate them will I get fried like bacon? What's best for all the electronics I would like someone to buy for me?

Seems like tying it all together and bonding the whole shebang to a sacrificical anode would be the way to fly, maybe with an active system if the zinc or zincs don't last long enough, especially with a metal hull.

[siletzsal]

GOOD GRIEF:meme::dancingman:

[lurking_out_loud]

So what happens when I connect my bonding system to the 12V ground, will my boat fizz like an alkaseltzer? If I isolate them will I get fried like bacon? What's best for all the electronics I would like someone to buy for me?

Seems like tying it all together and bonding the whole shebang to a sacrificical anode would be the way to fly, maybe with an active system if the zinc or zincs don't last long enough, especially with a metal hull.

Here is a good summary of what you need to do for an aluminum boat having a DC electrical system. I took this from the West Marine web site and think it is one of the best (simplest) explanations of grounding and corrosion I've found. Here's the link http://www.westmarine.com/webapp/wcs/stores/servlet/westadvisor/10001/-1/10001/MarineGroundingSystems.htm



Marine Grounding Systems This article was originally published in the October 15, 1996 issue of Practical Sailor. The author, Stan Honey, is a renowned sailor, navigator and electrical engineer.

Marine Grounding Systems

ground n. 12. Electricity A. A large conducting body, such as the earth or an electric circuit connected to the earth, used as an arbitrary zero of potential.In a normal house on land, the problem of grounding is simple. It consists of the green grounding wire in the AC wiring system and serves the purpose of preventing shocks or electrocution. The ground connection is usually made by clamping to a metal water pipe or by driving a long copper stake into the ground.

On a boat, things are considerably more complicated. In addition to the AC ground, we need a DC ground or return line, a lightning ground, and a RF ground plane for the radio systems. Our first thought might be to simply make the ground connection to a metal thru-hull, propeller shaft or other underwater metal. This underwater metal will be grounded by connection to the seawater will serve as our water pipe. Unfortunately, a connection between any of these systems and underwater metal can, and probably will, give rise to serious electrolytic corrosion problems. This article will discuss the particular requirements of each system, resolve the contradictions between the systems and present a consistent and correct solution for a complete, integrated, marine grounding system.


http://www.westmarine.com/images/mg_image002.gif
Figure 1.

The boats electrical system should be connected to seawater at one point only, via the engine negative terminal or its bus.

DC Ground
Every light or appliance should be wired with its own DC return wire. Never use the mast, engine, or other metal object as part of the return circuit. The DC load returns of all branch circuits should be tied to the negative bus of the DC distribution panel. In turn, the negative bus of the DC distribution panel should be connected to the engine negative terminal or its bus. The battery negative is also connected to the engine negative terminal or its bus. The key factor here is that the yacht's electrical system is connected to seawater ground at one point only, via the engine negative terminal or its bus. See figure one.

AC Ground
See Practical Sailor August 15, 1995 for a detailed treatment of the green wire. The best solution is a heavy and expensive isolation transformer. The acceptable solution (for the rest of us) is to install a light and inexpensive Galvanic Isolator in the green wire, between the shorepower cord socket on your boat, and the connection to the boat's AC panel. Then, connect the grounding conductor (green) of the AC panel directly to the engine negative terminal or its bus. Note that this meets the ABYC recommendation. In choosing Galvanic Isolators, make sure that you select one that has a continuous current rating that is at least 135% the current rating on the circuit breaker on your dock box. Certain Galvanic Isolators (e.g. Quicksilver) include large capacitors in parallel with the isolation diodes, which in certain situations theoretically provide better galvanic protection. Unfortunately, these units cost substantially more than conventional Galvanic Isolators. If you feel like spending real money on galvanic isolation, you might as well do it right and buy an isolation transformer.

It is also a good idea to use a Ground Fault Circuit Interrupter (GFCI) in your AC wiring. GFCI's will occasionally "nuisance trip" due to the humidity surrounding the wiring on boats, but the additional safety that they offer (particularly to nearby swimmers) in disconnecting power in the presence of ground currents is worth the nuisance. If your GFCI starts to nuisance trip, it is probably a very good idea to track down and clean up your damp wiring in any event.
http://www.westmarine.com/images/mg_image006.gif Figure 2. Ground fault circuit interrupters (GFCI) should be installed in each AC circuit. A GFCI will disconnect power in the presence of ground currents, helping prevent an electrocution.

Lightning Grounds
Connect a 4 AWG battery cable from the base of your aluminum mast to the nearest keel bolt from external ballast. If you have internal ballast, you should install a lightning ground plate. One square foot is recommended for use in salt water; fresh water requires much more. Do not rely on a thru-hull or a sintered bronze radio ground (e.g. Dynaplate) for use as a lightning ground.

For additional comfort, also run a 6 AWG wire from your keel bolt or ground plate to the upper shroud chainplates, and to your headstay chainplate. Don't bother with the backstay if it is interrupted with antenna insulators. Have each of the cables that are used for lightning ground wires lead as directly as possible to the same keel bolt, with any necessary bends being smooth and gradual.

Given that you have grounded your mast solidly to the ocean, your mast will be at exactly the same electric potential as the ocean. There is no chance that you can dissipate the charge between the ocean and the atmosphere, so don't bother with a static dissipater at the masthead. Wire "bottle brush" static dissipaters may be useful to dissipate seagulls, however, but that is beyond the scope of this article.

RF Ground
Your VHF doesn't need to use the ocean as a counterpoise, so here we are dealing only with the ground needed for your HF/SSB radio.
Mount your automatic tuner as close to the backstay as possible, preferably just under the after deck. Run copper ground tape from the tuner to the stern pulpit/lifelines, to the engine, and to a keel bolt. It is good practice to include the HF/SSB radio itself in this network of ground tapes. If the builder of your yacht had the foresight to bond into the hull a length of copper tape or an area of copper mesh, be sure to run a copper ground tape to this as well, and say a blessing for builders such as these. Sintered bronze ground plates (e.g. Dynaplates) can be used as radio grounds in situations where the ballast or engine is unavailable or awkward to connect. If the ballast, engine, and lifelines are available, however, they generally make a high performance ground.

Bonding and Electrolytic Corrosion Due to Hot Marinas
Do not bond any thru-hulls or other immersed metal that can be electrically isolated. Specifically, keep your metal keel/ballast, your metal rudder shaft, your engine/prop, and all thru-hulls electrically isolated, from each other, and from the engine.

It's worth understanding the reason. In an increasing number of marinas, there are substantial DC electric currents running through the water. If your bits of immersed metal are bonded, the electric current will take the lower resistance path offered by your boat in preference to the water near your boat, and the current will flow into one of your bits of metal, through your bonding wires, and then out another bit of metal. The anodic bit of metal or thru-hull that has the misfortune to be on the "out current" side of the current running through your bonding system will also become "out metal" and will disappear, sometimes rapidly.

Your zinc is only intended to protect against the modest galvanic potentials and therefore currents that are caused by the dissimilar metals that are immersed and electrically connected together on your own boat. Your zinc is incapable of supplying enough galvanic potential to protect against substantial DC currents that may be flowing in the water. These DC currents in the water will cause electrolytic corrosion to your bonded thru-hulls or metal parts.

Zincs and Protection from Galvanic Corrosion
Use zincs to protect against the galvanic currents that are set up by dissimilar metals on your boat that are immersed and that are in electric contact with one another. The best example is your bronze propeller on a stainless shaft. The best protection is to put a zinc right on the shaft next to the propeller, or a zinc on the propeller nut. An isolated bronze thru-hull doesn't need protection because it is not in electrical contact with another immersed dissimilar metal. If electrically isolated, high quality marine bronze, is electrochemically stable in seawater; nothing good can come from connecting wires to it.
http://www.westmarine.com/images/mg_image008.gif Figure 3.

Conductors running from the external keel or ground plate to the mast, stays and to the metal fuel tank will protect against a lighting strike, and there will be no DC connections to the engine or to the electrical system.

Stainless steel is a special case. Generally, it is a bad idea to use stainless steel underwater, because it can pit. When it pits the "nobility" of the metal changes locally, and you end up with tiny galvanic couples that are made up of different parts of the same piece of metal and the pits grow deeper. One school of thought suggests that if you must use stainless steel underwater (e.g. you need its strength), then you should connect a nearby, immersed zinc to it; this protects the stainless steel from itself, reducing the rate of pitting. The electrochemistry of this assertion is compelling enough to recommend that you protect a stainless steel rudder shaft with a zinc. This may be done by mounting a zinc on the hull near the rudder shaft, and electrically connect it (inside the hull) to the stainless rudder shaft. For the reasons described above, ensure that your metal rudder shaft is not electrically connected to anything else. Your stainless steel propeller shaft will be protected from itself, by the same shaft zinc that protects the propeller from the stainless steel shaft. In both cases the pits, if they appear, will appear where the stainless steel is not exposed to the water. Trouble areas are in the cutlass bearing, inside the rudder bearing, and just inside the top of the rudder.

Keep your metal keel/ballast electrically isolated from all other bits of metal. If you have the misfortune to have an external iron or steel keel, however, mount a zinc directly on it to reduce the rate of corrosion. Leave lead keels/ballast isolated.


http://www.westmarine.com/images/wa/mg_image011b.jpg
Figure 4.

To avoid making another DC ground to the engine via the HF/SSB radio copper ground strip, fasten the copper tape securely to an insulating piece of phenolic or to a terminal strip, cut a 1/10" gap across the tape, and solder several 10.15 uF ceramic capacitors across the gap.

Inconsistencies in the Ground Rules
So now, you are annoyed with the inconsistencies. We said to leave all bits of immersed metal electrically isolated when we described electrolytic corrosion and hot marinas, but then we said to connect wires and copper tape to your keel and engine for lightning and RF grounds. So what to do?

RF ground.
The RF ground needs to be a ground for RF signals only. It does not need to conduct DC, and as described in "Bonding and Electrolytic Corrosion..." above, you do not want to connect another DC ground to your engine and to your keel etc.

The solution is to find a dry secure place along each of the copper RF ground tapes that are running to your engine and keel. Fasten the tape securely to an insulating piece of phenolic or to a terminal strip, cut a 1/10-inch gap across the tape, and solder several 0.15uF ceramic capacitors across the gap. These capacitors will be transparent to the RF, which will be happily grounded by the ground tape system, but they will block any DC currents from running through the RF ground system, and will avoid any resulting susceptibility to hot marina electrolytic corrosion. It is worth selecting the capacitors carefully, because they may carry a significant amount of RF current. An acceptable choice of capacitors and vendor are listed at the end of this article.

Lightning Ground
The lightning ground needs to be a direct DC connection to the keel or to a ground plate to handle currents due to lightning strikes. So how do we keep the keel or ground plate electrically isolated as required in "Bonding and Electrolytic Corrosion..." above?

The solution is to connect the keel or ground plate directly to the mast, but make sure the mast is not electrically connected to the boats DC ground system. If your steaming light, masthead light, tricolor, Windex light etc. are wired carefully and correctly, they each will have their own DC return wire; there should be no ground connection between their wiring and the mast itself. Make sure that this is the case. This should also be true of your masthead instruments. The unintended DC connection between mast and DC ground is typically made by the masthead VHF whip, which connects the shield of the coax to the bracket connected to the mast. That shield also connects to the VHF radio which is DC grounded by its power connection. The easiest solution is to insert what is called a "inner-outer DC block" into the coax. This RF device puts a capacitorin series with the center conductor, and another capacitor in series with the shield. This device is transparent to the VHF RF signals in the center conductor and shield, but blocks any DC current in either the center conductor or shield. This device can be made by a good radio technician, or purchased from radio supply houses, pre-fitted with any kind of coax connection on both ends. The commercial units look like a coax "barrel" connector. A vendor is listed at the end of the article.

Once the DC connection from the mast to the VHF is broken, check for any other connections with an ohmmeter, and straighten out any other wiring errors or unintended connections. If your metal fuel tank is also bonded to the lightning ground system (per ABYC) then make sure that it does not have DC connections either to the engine via the fuel line or to the electrical system via the fuel level sensor. A piece of approved rubber fuel hose in the fuel lines to the engine solves that connection, and a well designed fuel level sensor will not make electrical contact with the tank.

When you're done, there will be heavy conductors running from the external keel or lightning ground plate to the mast, stays, and to the metal fuel tank, but there will be no DC connections to the engine or to the yacht's electrical system. See Figure 3.

Summary
By using capacitors to block DC connections in a few key areas, it is possible to have perfect ground systems for AC, DC, RF, lightning, and corrosion, and have a boat that is immune to stray DC currents that are traveling through the water in "hot marinas."

In the old days, the technique of bonding everything together worked okay. In its defense, the "bond everything together" approach makes your boat less sensitive to electrolytic corrosion that can result from faulty wiring on your own boat. The problem is, the "bond everything" approach leaves your boat totally defenseless to wiring errors in nearby boats and nearby industry, that cause stray DC currents to run through the water.

Today the technique of bonding everything together would still work fine if your boat spent all of its time on the high seas, in remote anchorages, or in marinas that were wired perfectly and in which all of the nearby yachts were wired perfectly. Having underwater metal bonded together in crowded marina's today, however, is asking for expensive trouble. As outlined above, it is avoidable trouble. It is possible, with careful wiring and a few capacitors, to have the best of all worlds, good RF and lightning grounds, ABYC approved DC and AC grounds, and security against electrolytic corrosion caused by hot marinas.

Again, hope this information helps clear the air that a single point of ground is the ONLY acceptable method for DC electrical systems.

-LOL