How Do I Know if My Boat’s Electrical Has a Bad Ground?
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- เผยแพร่เมื่อ 3 ก.ค. 2024
- "Jeff, I have been watching all of your videos," writes Gerald. "My question, how do I know if my boat has a bad ground?"
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I'm eyeball deep into this on my boat and your explanation really cleared some issues up for me.
Fantastic way to answer this question
An ohms test is not the best way to test resistance on a circuit, You could have multiple strands of wire and all could be broken but one and it will test good or low resistance.
The best way to test any circuit is under load using voltage drop. I'm in automotive I use it on a daily basis.
There are many good videos on how to perform voltage drop tests, You can go from one end to the other and quickly find resistance in a circuit.
I've chimed in on a lot of channels and most people don't get it, watching someone take their windless off and dissemble and reassemble and reinstall
(which should be done periodically anyways) only to find it still not working then finally find a bad connection elsewhere can be found easily using voltage drop.
Way easy and accurate, works on both voltage feed and ground.........
Hi Ken, great contribution!!! Thanks for sharing your knowledge with others.
You are right Ken
Love your videos. The concept of doing the job Correctly vs "Well we been doing it this way for 20 years and haven't had a problem"
Updating ( replacing lead acid house battery to a 190 ah lithium ion battery). Started noticing how my boat is wired. Many questions, but just one for now. Three batteries. 1 house, 2 starting batteries.(one for each engine). Should all three batteries be grounded to each other and then back to the house grounding block.?
HI Off subject but ive had so many tips from you i thought I’d share one from me - putting in camera systems you often have 2 rca plugs but you want to waterproof but heat shrink won’t seal the wire because allot thinner than plugs so use some glue sticks chop a piece off poke it in on each end of the heat shrink then heat gun it - completely sealed! Can be done with any plugs - nmea power to camera etc. much tidier and better than using gunk!
Thanks for sharing Tania Tait
Using a bronze propeller costing thousands of dollars as a ground seems fine until you have actual current on it. At that point, it becomes a sacrificial lump of metal. The same goes for thru-hulls and seacocks you rely on to keep from sinking. I’d rather ground through a dedicated grounding plate, or a large hull-mounted replaceable anode.
I agree, much argument on this as well as grounding all metal thru-hulls together. Anodes are supposed to protect though they have a limit.
Personal, wooden vessel, exposed bolted lead keel so this is my ground. The rest are uncoupled. The lead keel has two large Anodes directly through bolted. Copper wire from aft anode to rudder ss hinge hardware. Prop can only afford a spinner nut zinc.
Every boats construction should be addressed individually, my opinion.
Thanks for sharing Robert, which grounding plate have you used in the past?
@@PacificYachtSystems I have a large zinc fish I hang over the side.
My propeller shaft connects via a flexible coupler. I cut the ground strap because I don't want to make my shaft and prop the vessel's ground. I'd rather ground through my many bonded bronze seacocks. Opinions on this?
Great video !! I have to ask I'm trying to help fix up an old 1979 cobra 750 and I just wanted to ask was is just DC electrical and is the system very basic ??
Jeff, thank-you for all the knowledge you are sharing! do you have a recomendation on how to connect a bonding wire to a regular bronze thru hull fitted with a pipe thread ball valve?( Not a seacock that has a flange with 3 bolts where you could easily use a ring connector)
That's a tough one, too many metal through hulls don't have a connection point for grounding. You do what you can, and many boaters will connect the grounding connection via a hose clamp.
@@PacificYachtSystems Thank-you
I have a timber yacht with a saildrive which is having electrolisis problems. there is no shore power circuit. Should I ground to the keel with a zinc anode on it? Thanks.
Hi Jeff great video as usual. Q: If on the hard should I have any voltage found at the engine block? Running a test from the house bank's negative DC battery terminal (with bat cable detached) using a voltage meter from that terminal to my block it reads the same as batteries. I fact so does my lead keel, my prop shaft and my propeller, oh my! So, I know my sailboat is grounded successfully through the prop shaft as my Maxprop zincs disappear in a month to six weeks here is the worst part - whether in a marina on shorepower or at anchor with no AC power! I've been watching you vids and reading Nigel's bible as I'm in Mex with no marine electricians available here. Any suggestions? Muchas Gracias!
My fiberglass sailboat has ground wires running to every bronze thru-hull and the mast , also to the engine and a large sacrificial zinc , is this a wrong approach ?
Hi Jeff, I am a big fan from Portugal! Great videos! What is your opinion about devices like Sterling Alternators to battery charges, instead normal isolation like Victron. Any real advantage? Or just one more device to give problems in the future...?
Hi Nuno, thanks for the reach out from Portugal. Unfortunately, not familiar with this specific product from Sterling, and hence cannot compare.
Hi there, thanks for the video! I'm having an issue with my boat, that I'm hoping you can put to rest. I recently bought a new, NOCO 4 bank charger for my 16' Aluminum Lowe boat. When plugged into the wall and charging, I noticed that while standing barefoot in my garage, if I touch any bare unpainted metal on the boat, I feel a tingle. Is this because the motor is bolted to the hull, so all aluminum is grounded, and it's a non-issue? Or does this require further digging on my end? Thanks!
Great Video. Jeff, I am rewiring a 20ft center console and adding an ACR with switch and 2nd battery for the house. I am really confused about the wire size that goes from the start battery to the engine, does CCA amps mainly used in calculating the wire size or just the stator output amps ?
The outboard is Yamaha 140 2 stroke and the manual states a 430cca and 70Ah 20HR as minimum requirements. Also maximum generator output Is 12V and 10A.
When sizing your starter circuit wire size, base the wire size based on the amps and also the acceptable voltage drop. The starter circuit will draw way more amps then the alternator can output, hence you should worry about the starter draw.
My engine start battery is isolated from the house Battery, inverter and shore power. (alternator only charged engine start batt) To establish ground, I need to run a wire from House DC negative to Engine Start DC Negative. How big of a wire does this need to be? My inverter chassis is grounded back to the House DC negative with 0gauge. Do I need 0gauge from House DC Neg to Engine Start DC Neg??
Voltage drop test is the BEST! The key to a voltage drop test is the circuit must be working/live. A multi meter on the voltage setting measures a potential difference between the two meter leads. We want very little voltage drop on the negative side. The higher the voltage reading on the meter display (voltage drop) the more resistance you have between the two meter leads. I'll bet you are totally confused, sorry!
So... For a DC circuit, make sure the circuit is running. Place the negative lead close to battery negative and take the positive lead and start working your way up the circuit toward the load (light, motor) on the negative side of the circuit. If the meter display jumps up in value at any point your problem is between the last point you checked and the point you just tested. This isn't easy since wiring is not accessible for the most part. Think of a voltage reading on the display as voltage drop. For example. Positive lead on the battery positive post and negative lead on battery negative post. The reading you are seeing on the display is the voltage difference between those two points or in other words VOLTAGE DROP. Resistance on the negative side of the circuit will create voltage drop or a BAD GROUND. Whatever voltage drop you see on the negative side means that voltage isn't working for you and your load is getting less voltage. It was fun to write this, I hope you can understand it. Peace!
Thanks for sharing Tim, really appreciate the info.
I think that there is a question mark over grounding to the body of water through the propeller shaft. Looking at “Sailing Into Freedom’s” lightning strike event where the energy exited the boat via the prop shaft through the side of the boat blowing a hole that nearly sank the boat, we have to understand why that happened, and is “my” boat vulnerable in the same way. I’m guessing here but it looked to me as though the high resistance of the stainless steel prop shaft caused the energy to find an easier path straight through the vey narrow keel well through which the shaft was fitted. If the space around the prop shaft is open and wide, no problem. But if the keel is very narrow making the distance from the shaft to the surrounding water a matter of just a few centimeters, then there is a lightning strike hull blow through.
All good points, can other fellow boaters share their experience of lightening protection systems?
@@PacificYachtSystems Thanks for asking that question, Jeff. We need as much evidence as possible to build a risk and consequences folder in order to develop solutions.
I am here to learn about 12v systems. I don't know anything about boats. But when I listened to this, I thought, does the ship maintenance guy have to turn the boat power off while he is disassembling the shaft/propeller area? If two propeller shafts are grounded, is that a better ground or is that a ground loop? thanks
Great question Donna, in normal circumstances, the ground tie, should not be carrying current, and it's more about getting a common ground voltage. Yes, dual many engine boats have two paths to ground via their respective engine blocks and propeller shafts.
Hi Jeff, thanks again for all the great videos and valuable information!!! I’d like to ask: what about ground in a steel boat? Is that easier because the whole boat is “ground”? Or should we be more careful? I know you don’t have experience with steel boats as there are not any in the America’s but they are thousands here in The Netherlands :) (and Germany actually).
Don't use hull to carry current back to the battery. Galvanic isolated grounds and transformers for shore power are wise.
@@braithmiller I have three grounds on different parts of the hull where many cables lead there. No wonder the hull was like a polka dot design. I installed a galvanic isolator and last season I had a clean hull. I hope I solved the problem of the previous owner… Thanks for your reply!!!
@@anastasiosvanderpas7463 I would improve to all grounds lead back to one buss before reaching the hull anode.
@@braithmiller That is a good tip, I will look into it. Thanks!
Braith provides really good points. Unfortunately, have limited with metal vessels, popular strategy is to completely isolate the hull except for one location, so that the metal hull is non current carrying.
We don't connect AC neutral to DC negative (in the EU) so no need for galvanic isolater as an electrical engineer I would never do what this video says but it is up to you.
The DC ground is not relative to any 'earth' or in this case water ground. It is relative to the battery. Adding in a random reference point into the DC system is a bad idea. We don't ground our car battery to the road under us and we don't ground electronics to the chassis. Ask a radio (SSB/VHF) enthusiast about it. AC is a different scenario but on a boat only because of shore power.
Well, nice explanation Jeff but how is it in case of aluminium boats and their ground and how do I measure that I have no "leak" into the hull? Thanks a lot for your comment on this.
Hmmm, very limited experience with aluminum hulls. Anyone can answer this question?
Not personal experience. To my understanding good practice is to have a meter set up permanently that you regularly test for stray voltage leaks. So even the test circuit must be open other than for testing period. Both wires to any device positive or negative or housing that electricaly leaks even by salt will cause a galvanic corrosive state. This is so important that if you have to ask the question you need a professional that knows aluminum hulls or dive in this rabit hole. Absolutely shore power must be transformer coupled. Ground through a galvanic isolator. Never use the structure to carry Ground return current.
@@braithmiller Thanks for your answer. Yes, you are right - the isolation transformer is a must in this case. Do you know about any stray current meter made for this purpose? I heared that VDO made some in the past but I cannot find any. Thanks.
@@jakubkuzel8064 galvanometer, I am not sure that helps. Outside of my professional experience. Cruisers forum may be a source for advice. Sv Panope on TH-cam has an aluminum vessel if he doesn't know likely would know where to direct you.
Most specific devices mentioned in (my)reading are obsolete.
@@braithmiller Look up the Bender Isometer IR425 Insulation Monitor.
All totally separate from all these grounds would be the lightening grounding system right? Like connecting the metal outriggers to the copper strip going to the thru hull ground to water.
H mentions this as the 'bonding' system
The most critical issue during a lightning strike is to avoid the extremely high difference in potential caused by lightning, which causes destructive arching inside anything that is plugged in (even if turned off). The best way to protect would be a surge protection device (electronic fast acting circuit) that shorts all wires (phase, neutral and ground) during the mili seconds of this event. A good subject to talk about would be what ratings to use for surge protection devices (consult the manufacturers).
Thanks for sharing!
The protection against lighting strikes is insurance nothing else is going to work.
Jeff, thanks for the best explanation of grounding on a boat I've seen! However, I still don't understand the actual purpose of grounding a DC system. In a house, as you mentioned, it's a safety feature to have a path to ground. Is it the same on a boat with a low voltage system?
By grounding the electrical system on our boats, we not only provide a common reference point (i.e. ground) but we also get a short path to ground.
I think I’ve already touch this subject. In Europe DC is not grounded. Neither they are in electric power plants and substations. Cars, planes and rockets don’t have their DC grounded and they work pretty fine. Nigel Calder answer my question about this issue saying that they are reviewing the subject.
Thanks for sharing and the reminder.
How do you do it on a steel or alu boat?
Good question, but don't have any experience on steel boats. Can anyone chime in?
OK I hope someone can help me I bought a boat it’s a 1970 model it’s got a Johnson 70 horse outboard motor on it took it out today if I’m touching the throttle and I make contact with the steering wheel metal area it will shock you but not constantly and only if you’re touching both but neither individually will shock you and I actually try to get a floaty out of the water without touching anything and got electrocuted as soon as I touch the water what could possibly be causing this Could my boat be passing electric current through the water around it
12v should not be shocking you. If you grab both battery posts nothing happens to you. Does it happen if the motor is off? A bad alternator can produce AC power. I would be concerned something was in the water in your area. Was this a fresh water lake or ocean?
Hi Jeff, In most US marinas, 220V supply to a boat is usually given by connecting 2 hot wires from a 3 phase input to the life and neutral cables of the boat. Each of these wires is 110 volts relative to the 3 phase neutral but 220 v between them. What happens if you connect the boat's AC ground to the boat's 220 V neutral cable? Would this make a big puff? .
yes also you would get electrocuted and die
220v is 2 phase. I’d be shocked if any marine anywhere in the world provides 3 phase power to the docks.
how do you check for stray voltage in the water for safety
You need to clarify whether you are talking about AC or DC voltage. Big differences there. An AC voltage will come from shore and can cause paralysis and thus a form of drowning. DC voltages will usually come from a vessel (including your own). Where it comes from dictates what is the anode and what is the cathode.
Hi Larry, you'll need a really good DC/AC mulitmeter and silver silver chloride reference anode.
My question is my moomba just shuts off out of no where once it’s ran approx 2 min. Before this happened I was pulling a heavy load of teenagers on tubes . I’m begging someone to plz help me .
What is the effect on 12 volt DC electronics when stray 120 volt AC current leaks to ground?
Depends where in the system it happens. Ideal system nothing.
No branch of ac or dc should share a ground.
Ac and dc are supposed to not be co-run or bundled. Use gfci/afgci.
What ground, DC does not require nor use a ground. Just because we have used the term ground to refer to battery negative for the last 100 years or so, does not make it correct nomenclature. There is no ground in DC circuits. There is only the battery negative. In answer to your question; AC at 50 or 60 hertz is not impacted by a DC negative circuit at zero hertz.
My guess is nothing, as a leak to AC ground just completes the AC circuit. Recall that AC neutral and AC ground are connected together.
@@PacificYachtSystems our AC “hot” and ground are connected only at the pier’s main breaker panel. That’s a few hundred feet from our boat. I understand that in some circumstances an inverter or generator will bridge AC ground and DC negative. I think this also differs depending on whether your boat was wired per European, or ABYC standards.
I for one am concerned (and frustratingly confused) about this talk of American standards ( if I've understood correctly) about making/ bonding a common AC earth and DC earth (ie negative). It's a case of "the more I know, the less I understand". I am talking about a standard GRP yacht setup here - metal fittings in the seawater (props, P brackets etc), 16A shore power via a galvanic isolator and then consumer unit, two or three circuits at most, and the rest all DC run via breaker switches, plus or minus solar input (via a fused interface box and a solar controller). It (sharing earths) sounds potentially very disasterourous and dangerous to me for anyone who works on the DC system (ie the main thing most skippers do) in the boat as any AC fault will potentially leak to the DC system. Dangerous. Keep them totally separate. This why well specified battery chargers (ie with inbuilt isolation) are worth their investment as they represent THE direct/ main point of interface between the AC and DC systems on a normal small boat. Keep AC and DC separate.
Great video. However could someone please explain in layman terms the difference between AC and DC? Like, what is the battery? Apologies for a novice question. I am pretty sure I’ve got a ground issue on my 98 whaler.
AC and DC are different voltage types. Direct current is a current that stays constant, while AC produces a positive and negative wave. An AC voltage on a boat motor could be produced by magnets passing by each other. One magnet would create a positive wave, while another magnet would cause the wave to go negative. Therefore, the voltage in the AC unit would pulse back and forth in the wire. A DC voltage would come from your battery, where it's just a constant voltage.
How do you ground a sailboat with no motor. The only metal in the water is a stainless rudder shaft.
Some boaters use a grounding plate.
love your boating power videos. We will donate thru Paypal. Dwayne First Power Generators Toronto, Ontario Canada
Ha .. yep .. an absolute minefield of a topic. Its nearly in the "dark arts" realm. Thanks for the Video.
Glad you enjoyed it
The only reason it is is that so many people have insane ideas about it due to Ignorance of basic electrical principles. I still remember the absolute panic at the marina when someone dropped a stainless bolt and it sunk below a steel boat. The owner completely freaked out because he'd heard about galvanic corrosion being caused by dissimilar metals. He was actually calling a diver to come retrieve the bolt and no amount of talking could convince him otherwise. I always wonder if he did end up suing for damages. That would have made for an interesting court case!