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I have a 23 Regulator center console. Which I am mounting a RM E120. There is mention of earth grounding the display unit. What is a proper earth ground on a samll boat such as this. I was thinking the Aluminum T-top however this is not bonded to the water to my knowlege. I do not have grounding plates, should I? Can I ground to the motor through the transome bolts? Any help is appreciated..
__________________ Capt. Don
26 Regulator - BEAR
BEAR Sportfishin LLC
Always the BEAR, never the Salmon!
By earth ground I obviously mean water as it is referenced earth in all the installation manuals. I have about the same amount of electronics as most bigger boats. GArmin GPS, Furuno FF, 2VHF's, recently a full blown E120. I was looking to set this stuff up with the perfect scenerio. The question is would bondling all, metals together be benefical? Also would this help to protect against lightning?
__________________ Capt. Don
26 Regulator - BEAR
BEAR Sportfishin LLC
Always the BEAR, never the Salmon!
Bonding & grounding is a very complicated issue - even more on boats. Typically thru hull fitting are bonded to prevent galvanic corrosion. Superstructure & antennas are bonded for lightning protection. On larger vessels a ground plane is esablished for electronics (SSB, etc). It is my understanding that each of these sub-systems are not bonded together. If you do a search on Google you will find tons of info, some of which contradicts others.
IMO separate electronics bonding is unnecessary for small f/g boats
I asked this question to Don Casey when I was rewiring my 21 Mako. Basically, he said that on smaller boats, the negative side of the battery can be considered the ground. Where as all the electronics negative wires are all connected to a common negative terminal bus which is in turn connected to the negative side of the battery. You can take the additional step and ground the negative bus to a thru hull or a grounding lug on a motor which is connect to the earth via the water. However, protection from lighting is another matter all together. I will see if I can find his response and post it here.
I installed a thru-hull Wonderbar Grounding Plate which is equivalent to somewhere in the area of 100sq-ft of copper, so they claim. I ran a 12-gague wire from the plate to the ground sides of my electrical fuse panels, decreased the SWR's on my VHF along with better reception and it seemed to increase faster aquisition of sats on the GPS.
As has been said grounding is a very complicated topic - there are several types of grounds they are DC ground, AC ground, Battery ground, RF ground, Lightening ground, galvanic ground and bonding. Each has a purpose and are not necessarily the same. Here is a basic schematic of a DC system -
For the most part DC ground in the smaller boat is the battery negative - For lightening protection you need a ground plate to the water and tie the metal superstructer to the ground plate with minimum #4 AWG wire - For corrosion protection tied all thru hull metal together with copper strapping - The more metal you tie together the better the ground plane will be for VHF communications -
Ground plates are usually separately mounted with bronze bolts and tied to the circuit with heavy #4 AWG wire - For best results I would install a ground plate - Installing any thing thru the hull belo the water line can be a chore on itself - Once a hole is drilled you need to make sure that the coring material is sealed - I would recommend over sizing the holes like 1/2" for 3/8" bolt then filling the holes in with epoxy let dry then redrill the 3/8" hole in the epoxy - Touch up with gelcote and mount the grounding plate - Now the coring is sealed and no water can get in and rot the coring material - You will also want to seal the bolts with 3M 4200.
Lots of good advice above. I do not use a bonding/ground strip on smaller boats--even with lots of electronics. The only ground I run is for the HAM/Marine SSB combo. For lightning protection--you are better unplugging all of the electronics--including grounds, neg and pos battery, antennas, etc and putting them in a metal box (for example a surplus Amno Box, which acts as a Faraday cage. No matter what you do for lightning ground, you still have a very real possibility of a near by water strike and conducting high voltage/amperage power into the ground/neg systems.
There is little way to protect a 26 foot CC from lightning--and even the best (a mast, with a dissipator, and direct connection for at least a sq foot ground plate right under this mast) will give marginal protection from a direct strike.
There is a lot of disagreement if a sintered bronze plate (sych as wonder ground or Dyna plate) really give the effective advertised area. I have done experiments with HF radio (VHF really does not fall into the category of being helped with a direct sea water ground)--and found that definately there is slightly better propigation with both a sq foot of copper and one of the equivilant Dyna plates--but the difference was not measurable. SWR is only a relationship of the wave from the radio and the antenna. Ground does not enter into this.
Yes if you are going to protect from lightening strike the system is totally separated from all other circuits and electronics - This can be a chore if you have tall antennas and want to protect the boat -
Also in the case of RF ground for HF (SSB) the RF bonding needs to be separated from passing DC it is a RF ground hence to use the bonding system you need to separtate the DC from the RF - The solution is to find a dry secure place along the copper RF bonding 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 closer to the tuner the better. These capacitors will be transparent to the RF ground, 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.
As I said before depending on the needs grounding may become very complex situation depending on which ground we are talking about and for what reason -
gonfish'n - I'm glad you clarified. The diagram that you previously posted shows everything connected together with no isolation which is certainly incorrect.
You seem to have a good handle on this. I have 3 thru-hull fittings. 2 are bonded, 1 is not. Some things I read show that a lone bronze thru-hull (not connected to another type of metal) does not have to be bonded. Other sources recommend bonding all thru-hulls. Do you think the 3rd thru-hull should be bonded to the others (which are connected to the hull mounted zinc) ?
Bob is pretty much right on the money. Most people don't realize that a NEARBY strike can fry your electronics -- it doesn't have to hit YOUR boat (or house for that matter).
My Dynaplate (on my old 28 footer) was connected to my ham rig via a heavy solid copper 2" strip. I toyed with the idea of keeping a coil of soft copper tubing aboard, to toss over the side when I wanted to work ham radio while at anchor. This would have worked (keep the ends open). I let my bronze through-hulls float unbonded, and I don't like the idea of tying them together. That worked for ME.
Please elaborate. I don't understand why 2 of 3 would be bonded
There are mixed opinions on this. First off, I haven't seen NEW boats with throughulls bonded, although I'm sure some may be. I also recall reading (somewhere) that tying the bronze through hulls together can speed up corrpsion in ALL if just one starts, and that makes sense to me. Others say to bond them only if you have an on-board electrical system.
Why 2 of three on your boat? Maybe one was installed later. Or replaced.
On my own old 28' Pearson, my underwater through-hulls were not bonded. I had this boat for over 20 years. My 2 monel tanks WERE bonded and were also bonded to the bronze rudder via the rudder post.
Otherwise, I don't have the answer to your question.
Thanks for your kind regards as to my leg. Yes, now al I have to do is get down to MD and start to work on the T3.
I went back to an article I read on the Boat/US board. The opinions are that of the writer, and not mine, but they pretty well sum up the issue. The bold face was added my me to highlight the main issue.
Quote:
OK my turn. Oh the myths and traditions that perpetuate.
With regard to gauge, your only concern is mechanical failure and corrosion of the metal. For the former a stranded tinned marine grade wire is the best protecting against vibration failure however the problem is highly exaggerated. With a wire reasonably well attached to the boat along the run, the chance of vibration failure, even with solid wire, is miniscule.
Regarding corrosion, a well tinned marine grade wire is one defense and size is the other. The thicker the wire, the longer it is going to take to corrode through. With regard to corrosion, however, a solid wire or a strap will have greater resistance since the fine wires in a stranded cable tend to hold moisture and present 20 times the surface area for deterioration where as a solid wire will dry off and has minimal surface area.
If you are replacing a stranded wire that has corroded, take Scout's suggestion of replacing the whole run. Capillary action can carry the moisture many feet into the cable and if the end is shot, then the cancer runs well back into the wire.
Current carrying capacity for electrolysis is not a concern - the currents are so small that one strand would carry it. And the emphasis on minimal resistance is unnecessary - at those currents even a couple of ohms resistance are only going to make 0.002 volts difference - big deal. And the only thing wrong with daisy chaining is that if there is a failure early in the chain, you lose the rest of the chain - otherwise there is nothing wrong with it. At electrolysis currents, you could run the daisy chain 100 feet and the voltage loss would be still less than 1/1000 th of a volt.
Now none of this applies to lightning protection. My personal theory is there should be one heavy grounding line, preferably to something like a metal keel, then all the rest of the bonding should be a light enough gauge that it will act like a fuse. I've seen where the bonding wire to a dynaplate was heavy enough to make the main path for a lightning strike and blew the plate right off the side of the boat, leaving a good size hole behind it. The one predictable factor for lightning is its unpredictability.
There is nothing actually wrong with soldering bonding wires to through hulls IF IT IS WELL DONE, which is virtually impossible in the boat and very difficult out. Some modern fittings have a tapped screw hole where you can attach the bonding wire using a crimped ring connector. Always seal any bare wire and the crimp against moisture.
To bond or not to bond? That can be the title of an endless discussion. Some basics on electrolysis can be read at http://www.yandina.com/electrolysis.htm . Many, if not most, of the through hull fittings on a non metal boat do NOT require bonding and bonding them can do more harm. Let me see if I can explain it.
The reason for bonding is to make all the metal the same voltage potential so the zincs can protect them - to provide a ground return, if you like, back to the zinc so the circuit through the water is completed. But without some other external attack, electrolysis doesn't occur. The source of the attack is a different metal in the vicinity that is electrically connected to the under water items, or external current flowing from the dock or an adjacent boat that is trying to pass through your bonding system. Hopefully the protection voltage supplied by the zinc(s) is higher than the local or distant attack and you are protected.
BUT
If there is no "different" metal in electrical contact with a through hull, which is normally the case, then it doesn't need protection from that. If external electrolysis currents are a problem, then by NOT BONDING, they have nowhere to flow at the through hull and the circuit is broken. By INSULATING it, it becomes an entity unto itself and no electrolysis currents can flow - hence no corrosion.
Now I've simplified the situation somewhat by suggesting you can "insulate" the through hull because in the case of a raw water intake, for example, the through hull is connected to the engine block by the salt water inside the tubing between it and the engine. This provides a bonding in itself but perhaps not enough for the zinc to stop currents flowing through it.
The other factor is the radius of protection of a zinc underwater is only about 5 feet in salt water. So bonding a through hull greater than this distance from a bonded zinc is not providing protection anyhow.
My advise is to use common sense. Through hulls with short runs to grounded objects like an engine should probably be bonded. Those that run to heads, galley drains and things like that DO NOT NEED BONDING and bonding can do more harm than good. Instead of going to all the effort of bonding everything in a boat, check each through hull after a couple of seasons. Even if there is electrolysis, very little deterioration will occur in that time and if you do happen to find some, then you can bond it and see if there is a zinc within 5 feet to protect it.
Thanks for the clarification. The one that is not bonded has a bronze ball valve (with a SS handle) connected to it via a brass (I think) threaded coupling. Would the brass-bronze-SS "connections" be considered "different" metals and create a potential source for galvanic corrosion ?
They are different metals. I hope the nipple is not regular (yellow?) brass, which is copper and zinc -- and in salt water it will dezincify. Jamestown Distributors sells RED BRASS (copper-iron-lead) nipples that are much better but not as good as bronze. They have bronze couplings but not nipples. Any alloy, when immersed in an electrolyte (salt water) will be subject to galvanic corrosion, Some alloys, like brass, are much worse than others (like bronze). The closer together the elements in an alloy are on the galvanic table, the less affected the alloy will be.
The 2 that are bonded are bronze seacocks (AC & Waste discharge). The unbonded one is supply for a bait refrig.
I replaced the ball valve on the unbonded one last year b/c the handle rusted off (new handle is SS). In an effort to get it up out of the bilge a little I used the red brass nipple (which I now understand is wrong). I will correct this by removing the coupling and screwing the bronze ball valve directly onto the bronze thru hull. Using a bronze tailpiece in the top of the ball valve, I will connect the rubber hose and therefore eliminate any need for bonding.
If I understand this correctly, even if I bond the ball valve, the brass coupling is a problem.
Earth groundig for smaller boats 
