GFCI at docks for boats

[mitiempo]

... and so if im NOT standing in seawater, and I get in contact with the bare circuit, then im just going to be electrocuted??.... how is this safe unless we all boat around with the decks awash with water?

Standing in water has nothing to do with it. A GFCI works on the difference between hot and neutral. Single circuit GFCI's trip at 5ma and ELCI's (whole boat GFCI's) trip at 30ma. If one wire - hot or neutral - is touched there is an imbalance and the device will trip. The only time a working GFCI will not trip is if BOTH hot and neutral are contacted together. As that doesn't create an imbalance it will not trip. This is not very likely with the GFCI installed without exposed wiring.

The ground wire is not necessary for a GFCI to operate.

 

[Davidasailor26]

in my boat, mine will trip whenever there is a short within the appliance itself, without the need for an external ground to seawater or other pathway. or so it seems. I had a heater short and it tripped it... replaced the heater and no more problems. the main circuit is protected by the main breaker, but from the outlet to the appliance and back, it seems like the GFCI protects it. im not sure if it works this way at home, but I assume it would... EDIT... and so if im NOT standing in seawater, and I get in contact with the bare circuit, then im just going to be electrocuted??.... how is this safe unless we all boat around with the decks awash with water?

There are a couple of different things going on here. Likely the reason your shorted heater tripped your GFCI is because the short was from hot to ground, not hot to neutral. This then put current out on the hot that was coming back through ground rather than neutral, so the GFCI sensed the low neutral return current and tripped. If the heater was shorted from hot to neutral then it would have tripped the regular over current protection device (eg circuit breaker) instead. As for how the GFCI protects you if you're not grounded - You're right that it doesn't really offer you anything if you provide no path to ground. A regular circuit breaker may provide some protection if you touch the hot and neutral ends of a bare wire concurrently, but I don't want to guess whether you or the breaker would pop first. The advantage of the GFCI is the many times when you are at least somewhat grounded. I've been shocked just by having a bare knee on a dry concrete floor when touching a shorted electrical motor. A GFCI would have likely sensed the current through me not going back through neutral and tripped.

 

[uncledom]

Stop the music! This is all as clear as mud. What is a ELCI? Also as I under stand it.....I am NOT an electrian...a GFIC, ground fault interruption circuit breaker only works if you are grounded. You are not grounded standing on a wood dock or fiberglass boat. Other than a wiring fault, what does a GFIC do an a dock. Confused.

ELCI and GFCIs work exactly the same but at different leakage settings. Equipment Leakage Circuit Interrupt and Ground Fault Circuit interrupt both sense an imbalance between Hot and Neutral. When you use a device the, lets say one amp of power it uses (hypothetical), must return to ground through the Neutral. If the one amp of power does not return through the Neutral the ELCI or GFCI opens the circuit. It is assumed that the one amp has found a new path to ground and now has the potential to hurt some one and the circuit needs to be opened for safety.

 

[mitiempo]

.....lets say one amp of power it uses (hypothetical), must return to ground through the Neutral. If the one amp of power does not return through the Neutral the ELCI or GFCI opens the circuit. It is assumed that the one amp has found a new path to ground and now has the potential to hurt some one and the circuit needs to be opened for safety.

5ma is 5/1000 of an amp for a GFCI. 30ma is 30/1000 of an amp for an ELCI.

 

[uncledom]

5ma is 5/1000 of an amp for a GFCI. 30ma is 30/1000 of an amp for an ELCI.

I was trying to keep The concept simple for a newbie. If you'd like to be more accurate and we stay with 1 amp theoretical it would go more like this. GFCIs, class A, trip between 4 and 6ma so we use 5 as the example. If a device is using one amp and the Neutral sees less than .995 amps return it will open the circuit. ELCIs come in more flavors. Blue Sea offers them in 10, 15, and 20ma trip ratings I believe. This allows a bit wider latitude for equipment leakage to ground before a trip. Out of that hypothetical one amp it would be .990, .985 and .980 respectively before it opened. And just to be clear neither ELCI nor GFCI relies on the ground that is attached to the it. It simply looks for the balance between Hot and Neutral and opens the circuit based on allowable loss of amperage. Hope that helps

 

[walt]

This is a dock side ELCI (or GFCI) install required by a sort of HOA because you own the dock. This is the best place for ELCI.. not a bad idea to do this.

I am skeptical that the ELCI or GFCI products are as unreliable as you might get the impression from the internet. ELCI on the dock is the simplest way to protect for all sort of faults that can happen or bad wiring on the boat. But the way they insure that nothing bad can happen on a boat is to not supply power in the first place if something is not right. You are forced to fix the problem on the boat - or no power (unless you take the easy way out and just get rid of the ELCI).

Say you went to an ELCI breaker on the dockside (hopefully the HOA allows ELCI or GFCI?) and it trips. You could assume the ELCI is bad but in case we will assume the problem is actually with the boat.

A nice thing about "rms" AC current and voltage numbers is that you can use ohms law same as you would for DC. For example, the ELCI voltage and current trip are in rms so you can calculate the resistance required to create the trip current.

For a 30 ma trip and 120 VAC, the resistance is 4k ohms. (i.e., 120/.03 =4K)

For a 5 ma trip and 120 VAC, the resistance is 24K ohms.

This resistance can be measured with a hand held ohm meter.

You can also create the trip currents with capacitance (about .66 uf for 30ma and .11 uf for 5 ma) but this is more complicated to measure and probably not the problem anyhow.

If we just consider the resistance, you may be able to trace down your problem with a hand held ohm meter.

On the boat, the green ground AC wire should always have a high resistance to either the hot (black) or the neutral (white). So simply unplug the powercord going to the boat and check the resistance from hot to ground and from neutral to ground. If you measure less than 4K ohms from the hot to the ground, you will blow the ELCI when you connect the plug to AC.

If you do measure less than the 4K ohms with this simple test, you can go through the boat and remove/ unplug stuff until you find out what caused the less than 4K ohm resistance and isolate what is causing the problem.

However.. if you did that initial test just described with the ohm meter with the power cord unplugged and saw a high resistance (i.e., too high to trip the ELCI), you may still have a problem where the current that is tripping the ELCI is returning through the water.

In this case what I would do (carefully) is to connect the earth green wire of the dock side to the earth green wire of the boat - and ONLY connect the green ground wires - NOT the current carrying black and white wires. Now with the ohm meter, check again the hot to ground and neutral to ground. If you measure less than 4K ohms, that will trip the ELCI and once again you can go and start isolating stuff in the boat to see when the resistance measurements goes to high impedance and this should identify what is causing the problem.

If you still don’t find anything doing the above, the problem could still be parasitic capacitance and now it gets more complicated. But it’s just not likely that you can create a parasitic capacitance high enough to trip ELCI on the boat. You can create parasitic capacitance to trip the 5 ma GFCI however with for example a very long extension cord.

 

[walt]

In this case what I
would do (carefully) is to connect the earth green wire of the dock side to the
earth green wire of the boat - and ONLY connect the green ground wires - NOT the
current carrying black and white wires. Now with the ohm meter, check again the
hot to ground and neutral to ground

Just thought of a different maybe safer way for the second test described above. Unplug the boat AC from the dock side. Ie, do this test with the power to the boat disconnected. One lead of the ohm meter goes to the DOCKSIDE ground/green. The other lead of the ohm meter goes first to the BOATS hot and then neutral. This method will also find the too low of resistance if the path for the leackage current is through the water (of course assuming the boat is in the water for the test).

 

[mitiempo]

ELCIs come in more flavors. Blue Sea offers them in 10, 15, and 20ma trip ratings I believe. This allows a bit wider latitude for equipment leakage to ground before a trip.

Blue Seas offers 7 different ELCI models - all trip at 30ma.

They offer one branch circuit GFCI that trips at 5ma.

Your suggestion of 10,15, and 20ma ELCI's would offer less latitude than a 30ma ELCI if they existed.

 

[uncledom]

Blue Seas offers 7 different ELCI models - all trip at 30ma. They offer one branch circuit GFCI that trips at 5ma. Your suggestion of 10,15, and 20ma ELCI's would offer less latitude than a 30ma ELCI if they existed.

If your so knowledgeable why don't you explain it rather than pick on the minuesha of other peoples comments. Do you stay up all night trying to find fault in others? Get a life. Go a head and delete me Phil, but I had to say it.

Had my vendors mixed up.
http://trci.net/products/shock-shield/gfci-or-elci
ELCIs are available in different trip levels just not from Blue Sea.

 

[Maine Sail]

ELCI and GFCIs work exactly the same but at different leakage settings. Equipment Leakage Circuit Interrupt and Ground Fault Circuit interrupt both sense an imbalance between Hot and Neutral. When you use a device the, lets say one amp of power it uses (hypothetical), must return to ground through the Neutral. If the one amp of power does not return through the Neutral the ELCI or GFCI opens the circuit. It is assumed that the one amp has found a new path to ground and now has the potential to hurt some one and the circuit needs to be opened for safety.

Some early marine specific ELCI's from Carling / Blue Sea also look for a bonded neutral. If they don't see a grounded neutral they will also trip. This has been a problem for those trying to run a portable generator through a marine specific ELCI...

 

[mitiempo]

If your so knowledgeable why don't you explain it rather than pick on the minuesha of other peoples comments. Do you stay up all night trying to find fault in others? Get a life. Go a head and delete me Phil, but I had to say it.

Had my vendors mixed up.
http://trci.net/products/shock-shield/gfci-or-elci
ELCIs are available in different trip levels just not from Blue Sea.

If advice and information is given it should be accurate.

 

[JoeSailer10]

I am not an electrician, but I don't think that article is correct. Theoretically, it would work that way, but it does not take into account the fact that our bodies are not perfect conductors, they have some resistance to the flow of electricity and that resistance will be enough to trip the GFCI. The article is correct in that a GFCI is not an excuse to be careless.

 

[walt]

Problems of getting shocked on a boat are pretty much covered if you have proper fusing and proper safety earth grounding. If there is a fault on the boat where something that should not be energized gets energized, if there is proper grounding and fusing, at the moment the fault occurs, a lot of current flows through the safety ground and it blows the fuse. This also why anything to do with the safety ground (including diode ground isolations) are hefty... they need to handle enough current to blow the fuse. The fuse and ground handle almost every condition except the hair dryer getting dropped into the bathtub while your in the bathtub (don’t all boats have a bathtub?).

But.. boats are not always wired "perfectly".. which is where the dock side GFCI or ELCI come into play as almost every condition that fusing and grounding take care of, the dockside ELCI also takes care of.

This brings up two questions for me..

First, if for some reason you boat doesn’t have a proper ground and something in the boat become hot and you contact this, what happens?

If you are not at all grounded to any sort of return path, nothing happens. It’s like a bird sitting on a power line. As long as there is no return path, no current flows and you would not even know you are touching something hot.

Now if there is a return path somehow - like you touch something hot with one hand and the other hand is on a ground and the only thing protecting you is ELCI, what happens? You will get shocked and if the current is over the trip point, the power gets shut off in the "thousands of a second" time frame. Is this dangerous? I don’t know but most of us have been shocked with 110 AC at least a few time and we are still reading this. I would think in most cases if you trip ELCI with your body your going to jump.. but live to complain about it.

 

[walt]

the second question is if you have dockside ELCI and are in fresh water, will the ELCI trip if a dangerous in the water condition occurs? I.e., we know that the swimmer shock death occurs in fresh water but since the resistance of fresh water is high, will enough current be generated to trip the ELCI? Note.. Its electric field that kills in the water, not current. Salt water would have much higher current but the shock problem doesn’t happen in salt water.

I couldn’t find anything on this so several years ago did a little experiment using Denver Colorado tap water. Resistance in water is three dimensional and depends on the number of charge cariers plus their mobility so what I did is an approximation but I think ballpark. The three dimensional part of this means that as you move away from an object in water (like a hot conductor), the number of charge carries goes up with the cube of distance simply because the volume of a sphere goes up with the cube of distance. My experiment had less volume of water than in the real world so actually probably underestimates the real current.

Anyhow, I put an electrode about the size of a half dollar in Denver Colorado tap water and had a very simple circuit composed of an 11 ohm resistor in the line to measure the current (measure the rms voltage accross the resitor, use ohms law to find rms current). The attached pictures show the setup.

In this simple experiment, I measured 1.6 volts across the 11 ohm resistor which is a current of .145 amps. As I mentioned before, I think my experiment underestimates the current that would happen in the real world. Regardless, if the ELCI tripped at .03 amps, for my experiment, the actual current was nearly a factor of FIVE times what was required to trip the ELCI.

Denver tap water is also likely to be less conductive to what you would see in a typical lake. So.. based on my simple test, my conclusion is that its safe to assume that even a 30 ma dockside ELCI would eliminate any swimmer shock drownings.

I think its also safe to assume that whomever picked the 30 ma threshold probably knew what they were doing..

 

[uncledom]

Problems of getting shocked on a boat are pretty much covered if you have proper fusing and proper safety earth grounding. If there is a fault on the boat where something that should not be energized gets energized, if there is proper grounding and fusing, at the moment the fault occurs, a lot of current flows through the safety ground and it blows the fuse. This also why anything to do with the safety ground (including diode ground isolations) are hefty... they need to handle enough current to blow the fuse. The fuse and ground handle almost every condition except the hair dryer getting dropped into the bathtub while your in the bathtub (don’t all boats have a bathtub?). But.. boats are not always wired "perfectly".. which is where the dock side GFCI or ELCI come into play as almost every condition that fusing and grounding take care of, the dockside ELCI also takes care of. This brings up two questions for me.. First, if for some reason you boat doesn’t have a proper ground and something in the boat become hot and you contact this, what happens? If you are not at all grounded to any sort of return path, nothing happens. It’s like a bird sitting on a power line. As long as there is no return path, no current flows and you would not even know you are touching something hot. Now if there is a return path somehow - like you touch something hot with one hand and the other hand is on a ground and the only thing protecting you is ELCI, what happens? You will get shocked and if the current is over the trip point, the power gets shut off in the "thousands of a second" time frame. Is this dangerous? I don’t know but most of us have been shocked with 110 AC at least a few time and we are still reading this. I would think in most cases if you trip ELCI with your body your going to jump.. but live to complain about it.

Hey Walt, if the current is flowing through you to ground the fuse won't trip. In actuality if you are "stuck" on the circuit, it will stop conducting when all the fluids that are part of the path through your body have been evaporated and the tissue that housed that fluid is cooked and no longer conductive. That's where the ELCI or GFCI come into play. They see X current passing through the Hot wire and as soon as they see X-.003 amps or less coming back on the Neutral the circuit opens. (at least for a GFCI, ELCIs require a bit more loss of current).

By the way, this discussion has been going on for a while in some form or another. If there is a GFCI or ELCI on your dock power pedestal AND you have an isolation transformer, it will only protect you up to the primary side(input) of the transformer. You need to put a GFCI or ELCI on the secondary side(output) of the transformer to actually protect you on your boat. Any draw on the secondary side of the transformer will appear balanced on the primary and no imbalance will be seen by the fault device.

 

[walt]

If there is a GFCI or ELCI on your dock power pedestal AND you have an isolation transformer, it will only protect you up to the primary side(input) of the transformer. You need to put a GFCI or ELCI on the secondary side(output) of the transformer to actually protect you on your boat. Any draw on the secondary side of the transformer will appear balanced on the primary and no imbalance will be seen by the fault device.

I think you are correct..

The only thing missing from your first paragraph is a technical description of what that would smell like..

 

[zeehag]

doesnt matter what ye run, if you stand in water and mess with 120v circuitry you will be zapped.
sometimes even without the water, in which case, best learn why. strange how 120 works like in a house.
gfi aint gonna prevent a shock, it will short out preventing completion of circuit. they arealso hard to find when out of country. ask me how i know...and you will sustain a goodly shock before it does that job of shorting out. my finger still doesnt feel right , after the recent zapping i got, thanks to an inept or otherwise alleged knowledgeable alleged sailor. i hope inept, as opposed to deliberately shoddy work..
shock prevention is finding where you need to ground stuff and doing it, just like in your home on land. ...and keeping the fork or knife etc out of the socket.

 

[CharlieSea]

Did anyone figure out why the dockside GFCI tripped? If anyone is still looking for an answer, I may have one.

 

[Crazy Dave Condon]

Many sailors are not as savvy to understand the electronic terms which is why one respondent was asking for. As a dealer for example I told my customers if you saw a reverse polarity light go on it equals electrocution which got their attention. That got them to be more aware and to have that problem resolved quickly.

In the old days I called it GFI for ground fault interface which basically was saying if you were around water touching anything with a live current, it should shut off or trip that circuit breaker so no one is electrocuted. Very true you hav to be aware of your surroundings but don’t forget all the dummies running around who don’t think that way. So can someone actually respond to this in layman’s terms.

I can tell you it was no fun seeing a friend’s son being electrocuted on a new dock coming out of the water when he touched that metal post with a electric receptical attached. The dock builder first wired the dock wrong and did not build to code adding GFI as well. I saw that happen so sometimes speak in simple terms so us dummies understand. The above has haunted me for a long time

 

[CYQK]

Ordered a ELCI from blue seas
Noted the discussion above about an isolation transformer. Is this the galvanic isolator?
So getting ready to install the smart plug, ELCI,and galvanic isolator. So do i install the ELCI downstream fron the galv iso??
So smart plug,galv iso, and then ELCI
Thks