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OK, now I understand the difference between fuses and breakers, and the good/bad for both...thanks everyone!
I also have a better understanding about the re-wiring project I will be taking on.
Last question...Some of my electronics have a bolt to connect them to the boats ground. I do not currently have a ground...or I am not aware that I do. If I do, where would it be, if I don't do I need it? If I do need it, where and how do I connect it?
If you trace the ground wire from you "house battery" aka the battery most of you stuff runs on, if you trace that wire and find where it terminates you will may find a "ground bar". If not then I would suggest you install one. Its very simple to do. One just takes the terminal end of the ground and connects it to the ground bar. The bar then serves to ground the electronics on your boat. The ground bars come in various sizes which is basically dictated by how many devices or will be grounded to it. Hope this helps. I dont always articulate what I am trying to say on these boards , Good Luck.
Hi Scott, I truely am not trying to be harsh by saying this. See if one of the local schools have a 101 course you can take nights, on electricity. You will learn a ton because you have the interest. And what you learn will go a long way in making your rewiring job easierrrr. You will learn by hands on.
I appauld you in wanting to do it yourself, but not understanding grounds, well you're green. And that's OK but, your effords to save money, could leave you shelling a lot out in the long run.
All devises have grounds. Yes you need them. Yes you have them.
Your question does not reflect "green". It is actually a good and reasonable question. The electronic devices you mentioned will have two types of ground connections. One is the DC power ground, which is very straightforward. That's just to complete the circuit for supplying power to run the unit. The other is a chassis ground, usually a wing nut post on the back of the unit. This ground (which is clearly what you are asking about despite the inappropriate replys you got)serves a different purpose. It is supposed to provide a pathway for the shielding on the case and cables of devices that are potentially susceptible to interference such a fishfinder or radar displays. If you hook up your electronics and do not see anything suggesting that stray signals are a problem -- such as snow or lines on your displays -- don't worry about the chassis ground. Usually they are irrelevant, so I would guess that will be the case in your installation. If you do see evidence of a problem, try running a wire from the chassis ground to the bonding system on your boat. This will be a series of green wires that connect metal through hull fittings. If you don't have bonding wires, just try wrapping the ground wire around a metal through hull and see if your interference problem goes away. If it does, you may want to install a "Dynaplate" or similar ground plate and connect the ground wires to it. That avoids the risk of creating electrolysis and corrosion on you underwater through hulls if there is an electrical "leak" in your boat.
But as I said, in most installations the chassis ground is not needed and you can just ignore it.
For grounding the chassis of a electronics unit, you need a separate ground wire run for just that purpose. Don't use a ground wire that is also being used to power a load. The best chassis ground for boats in general is copper braid that has been tinned.
If you are grounding only a chassis, and not trying to supply a RF ground for a radio, then you can ground directly to the engine. All you are trying to do is keep stray charges from building a voltage on the chassis. Area Lightning (not a direct hit of course), the output from a VHF or a radar are all sources for stray charges.
If you are trying to supply a RF ground for a radio, then you will want to use a dynaplate. Dont use brass thru-hull fittings for grounds in either case.
ClassicGuy and Sea_Dad, thanks. Garet makes some good points, I'm new to the world of 12 V wiring. Although I usually have the answers to my questions before I post (from book references) I like to get "hands on" responses from other boaters who actually have done or know what I am talking about...not an electrical engineer who co-authored a book with a boating buddy.
ClassicGuy was right, I am talking about the chassis ground, not the DC power ground. The negative side of my electrical system is gathered back up into a bus bar and routed to the stern at the neg. terminal on battery 1. I wasn't sure about the stud/wing-nut on the back of the FF, and plotter that are labeled "ground".
Special-K, it is ok if I respond as an avid boater of over 30 years as well as being an electrical engineer with over 25 years experience, isnt it?
Garret could stand to exercise some of his suggestions upon himself. Garret, it's not that I think your a .ick (is that how you did it?), you just need to know more than you do.
[This message was edited by Sea_Dad on 03-08-03 at 01:12 PM.]
Sea-Dad, just wondering if you agree that chassis grounds are usually not necessary since you seem to be professionally qualified to answer the question.
I meant I would like to hear from someone who's actually been on a boat, at least once. Theory and practicality/real world situations do not always mesh. Being a boater and an electrical engineer puts you at lead-dog position.
Saltdog, you wont find a single piece of military equipment without chassis grounds, nor will you find any electronic equipment in your house that doesnt have it's chassis grounded. That should tell you something.
You are grounding the chassis for 2 main reasons.
If it shorts the supply lead to the chassis it wont become hot and try to zap you every time you touch it (12 volts wont hurt, but shore power can kill ya).
The second, if there is lightning around, you dont wanna have metal that you are in contact with at any potential other than ground.
Obviously if it's a plastic case, its tough, if not impossible to ground. But if it's metal, and you can get a screw in it, you would be best served in the long run to ground it.
What I have done on my boat is run a ground strap from the engines to the T-Top. From there I just ground what ever chassis need grounding to the T-Top.
By the way, if you choose to run a ground strap, do it to the engine, and not the battery's negative post. And no tight bends, electricity will leave it and head for something else if its a tight corner.
On the nuts and bolts side, I have a ground plate with two holes in it, am assuming that they are for bolts to attach it with.
what kind of bolts to use (SS?), and does the ground wire just attach under the bolt head on the inside?
Is it ok to put the plate on the transom below the waterline? If so, it wont be submerged at speed, but would create quite a drag if on the bottom.
If you decide to use your engine as your ground, which I would never purposfully do, at least don't ground your LORAN to it. You can fight the other gremlins on your own, but that one is just begging for trouble.
Thom
"More than 25% of US High School Graduates read at the 5th grade level or less" How's your kid doing?
If u really want to take a basic electricity course or basic electronics course, there are several on the internet that you could take for free. Plus im sure your local bookstore has a few (usually on 2 or 3) books on the matter. It will take some time, but will provide you with knowledge that you can use for the rest of your life.
Is the bonding system (green wires) supposed to be connected to the negative battery terminal??And if so, is that supposed to be used for chassis ground. My green wires connect my fuel fill , the engines(outboards), and negative battery terminal of battery. Just purchased boat end of last season so in process of a little re-wiring but want to make sure its right. Thanks
quote:Originally posted by Garett:
Hi Scott, I truely am not trying to be harsh by saying this. See if one of the local schools have a 101 course you can take nights, on electricity. You will learn a ton because you have the interest. And what you learn will go a long way in making your rewiring job easierrrr. You will learn by hands on.
I appauld you in wanting to do it yourself, but not understanding grounds, well you're green. And that's OK but, your effords to save money, could leave you shelling a lot out in the long run.
All devises have grounds. Yes you need them. Yes you have them.
Once bitten, twice shy
Garrett - you are obviously quite ignorant when it comes to 12V systems. The question was regarding a ground, not the 12V negative or return which is what the black (or yellow) wire is for on a 12V system. Most marine electronics will also have a ground terminal which is used to minimize interference generated by other systems on the boat.
Some of your other posts as so bad as to be laughable. Really, how much salt air do you get in Ontario, Canada? How important is hi-fi in a boat that has twin outboards turning 4500 rpm. Why doesn't my stereo work when I disconnect the negative wire from the speakers. From your earlier post I thought that would allow me to use all the electrons to generate sound instead of wasting them down the negative wire.
As anyone with a great deal of boating experience, and particularly on boats that had electrical devices on them, would have noticed over time is that LORAN is the one device with at once is both a great source of electrical interference and also because of the relatively low frequency it operates at also prone to picking up interfernece from other devices. How many times have you had the pleasure of listening to repetitive clicks on the VHF (that could only be removed by using excessive squelch or by turning off the LORAN) or light flashed and vertical scanned bright lines on the fish finder caused by the LORAN?
If you've been around a while and on a good number of different boats the number of time would be in the hundreds. How many time have you been out on a boat with a LORAN that would not lock on or kept dropping the stations, once again due to excessive interference from other stuff on the boat? I've seen it a thousand times. At the same time there is no other thing on the boat that has as great a potential to cause stray electrical flows than the ignition and charging systems on the engine. There are some engines around (mostly old Optimaxes) that are so bad about this that their owner's have given up on reliable use of electronics.
These problems can be traced down and solved in most cases but it is an expensive and time consuming process, and unfortunately some guys never get them solved. Oh, and the problems never get better on their own, they only get worse over time. Moreover while these problems are far to common the power of the stray currents themselves are relatively weak. They are not so weak though that if you connect directly to the engine you won't stand the very best chance available to pick them up on your electronics. A far better way to grond to EARTH is to go to a Dynaplate, ground strap, or similar grounding device. While those stray currents are more than happy to flow up a wire connected at one end to your engine and at the other to each of your pieces of electroncis those same currents, small as they are, have a lot harder time passing though just a few feet of sea water - conductor that it is its still not as good as a copper wire.
And so that is my reason for not attaching the chassis ground from a LORAN (or anything else on our boat) to the engine. It would be connecting the device most suceptable to stray current to the thing most likely to cause them. The second worst thing, at least in the sense that it will provide annoying noises to the user, is to connect a chassis ground from the VHF to the engine. All it takes is a nick in a spark plug wire or a corroded connector somewhere in the charging circuit and you'll be listening to clicks, humms, and buzzes all day long on that radio if you have a direct connection to the engine.
Thom
"More than 25% of US High School Graduates read at the 5th grade level or less" How's your kid doing?
Here is an interesting thread I ran across on another forum this morning. Look at the 5th reply. Think how much worse off this fellow would be if he had a wire connected directly from his engine to the chassis of his radio, or any other electronics on his boat for that matter.
Keep in mind, as you ponder all this, that the connection between your engine's negative side batter cable, through the battery, which also feeds your electronics, is not the same as connecting the chassis of your electronics to the engine. They are not the same circuit, the chassis does not act as the ground in the same sense that it does in your car - where it carrys the negative side of the power, not that is until you connect to the engine. When you connect to the engine you are then tieing your electronics chassis directly to the negative side of your DC negative, and that is something that the makers of the electronics didn't do nor did they intend for you to do.
Thom
"More than 25% of US High School Graduates read at the 5th grade level or less" How's your kid doing?
Thom...Makes sense to me. If you're going to connect 'ground' to the engine you may as well connect it to the battery (negitive side). NO GOOD.
"Never enough time to do it right; ALWAYS enough time to do it over." Boston Whaler, "MUMBLER", 24' Outrage (1996), twin 175 HP Evinrude Ocean Pros. Snowball, the cat...
Grounding plate? 
, Good Luck. 
"Never enough time to do it right; ALWAYS enough time to do it over." Boston Whaler, "MUMBLER", 24' Outrage (1996), twin 175 HP Evinrude Ocean Pros. 
Snowball, the cat... 
