Getting shocked

[Mac2]

A couple days ago, my wife called to tell me she kept getting shocked when she touched things around our steel boat that are metal. I was skeptical till she said she would be on the dock until I got home-a big clue. When I got on the boat, I touched the aluminum railing and “zap!” I got a shock similar to rubbing your feet on carpet and touching metal. My wife said this started at three pm. Weird. I got out my ohm meter and started testing. I have since learned how to use the meter more accurately-one lead in the water and the other into the ground of an outlet (ac volt setting). I eventually isolated the voltage to the area of my dock power box (highest readings). I discovered the power line to the nav light, at the end of the dock, had been run between the dolphin and piling. The wires and insulation had been crushed. When they raised the water in the ship canal today (at 3 pm!) the wires were submerged. They always raise the water level a couple feet this time of year in preparation for the drier summer months. Electrician fixed the problem and all good now.
Wondering if anyone else has ever had the happen, and if there is a better portable solution to testing current in the water? Please don’t say stick one finger in the water and the other in a socket!

 

[Fleming]

And that's the reason why marinas everywhere are upgrading to GFCI protected dock power! Potential lawsuit if someone got hurt.

 

[Mac2]

And that's the reason why marinas everywhere are upgrading to GFCI protected dock power! Potential lawsuit if someone got hurt.

They have been planning a remodel for several years now. I’m on the “temp” dock after the original boathouse burnt down.

 

[Comodave]

On a Sunday night about 2 hours before we had to leave for the airport to catch our flight home I had this happen. It was 12 boats ago I was working in the engine room and happened to put my hand in the bilge water while touching one engine. I got a shock. Broke out the meter and found 48 volts AC. Started troubleshooting and found that the PO had reversed the hot and neutral from the inlet to the electrical panel. Also had used brown wire instead of white. Also used 14 gauge wire on the 30 amp inlet. I finally found that the brown wire was originally white but had turned brown due to the overheating. So off to WMP to buy a new inlet and some 10 gauge wire. The inlet had melted inside due to the overheating but was difficult to see because it was mounted very low. I replaced the inlet and ran new wire to the electrical panel. During this process I happened to look at the overhead of the cabinet and there was black charred wood. Apparently had a fire and it looked like the fire died out due to lack of oxygen. Tight fitting cabinet. After I was done I checked the bilge water and no more AC voltage.

 

[Mac2]

Comodave: you got lucky in multiple ways! Nothing more disturbing than finding charred wood and wondering what could have happened. You just confirmed my thinking of installing a smoke detector in the enclosed cabinet where the shore power enters the boat. I have one in the pilot house, but it would take time for the smoke to exit the cabinet.

 

[Comodave]

Yes, it happened before I bought the boat but it was tough to see because I had to lay down and look up to see it. On our ladt boat we only had a bridge helm so we were a distance from the engine room and the electrical system. I installed about 5 or 6 smoke detectors. I used the ones that networked together since I wasn’t sure I would hear them up on the bridge with the engines running. I put a detector up on the bridge so it would alarm if any others went off. It was just a remote alarm for the others, not much up there to catch fire. I had them in the staterooms, engine room, electrical cabinet and salon.

 

[Marco Flamingo]

I was a liveaboard years ago on the ship canal between Lake Union and Lake Washington. One day one of the finger piers came loose and floated out at an awkward angle. It had been chained to a piling, but the chain had dissolved except for some fuzzy crumbles. Further investigation showed that another liveaboard had run a hidden extension cord from shore underwater to his boat, but it had fallen in. Apparently the freshwater or maybe the length of the cord kept the breaker from popping until the conductors had eaten away and shortened the cord. Nobody hurt, but I wondered about the fastenings and through hulls on all the wooden boats sitting a few feet above the cord.

My marina has occasionally had somebody come by to test the electrical system (I think for their protection, not for the boat's). I haven't been able to get a set date and time, but I would love to be there when she/he poked around my boat.

 

[SteveK]

@Mac2
Glad no one was hurt.
Do you have an Aluminum boat and/or your bonding system connected to the ground wire of the shore AC?
Since your boat did not cause this what could you/we do to prevent it. ELCI on your pedestal, would that have tripped in this case? Or would the aluminum rail still be charged? Scary.

 

[Greg QS]

Count your blessings. This happened near us at my buddies marina in NY when a dock got electrified. I believe the jet skier came into the ramp and as soon as he touched it bam.

 

[Mac2]

I was a liveaboard years ago on the ship canal between Lake Union and Lake Washington. One day one of the finger piers came loose and floated out at an awkward angle. It had been chained to a piling, but the chain had dissolved except for some fuzzy crumbles. Further investigation showed that another liveaboard had run a hidden extension cord from shore underwater to his boat, but it had fallen in. Apparently the freshwater or maybe the length of the cord kept the breaker from popping until the conductors had eaten away and shortened the cord. Nobody hurt, but I wondered about the fastenings and through hulls on all the wooden boats sitting a few feet above the cord.

My marina has occasionally had somebody come by to test the electrical system (I think for their protection, not for the boat's). I haven't been able to get a set date and time, but I would love to be there when she/he poked around my boat.

Pretty amazing what you see in marinas. Can’t tell you how many power cables I see purposely run under water.

 

[Mac2]

@Mac2
Glad no one was hurt.
Do you have an Aluminum boat and/or your bonding system connected to the ground wire of the shore AC?
Since your boat did not cause this what could you/we do to prevent it. ELCI on your pedestal, would that have tripped in this case? Or would the aluminum rail still be charged? Scary.

My boat is steel, but the aluminum handrails are bolted to the steel. I have an isolation transformer for the boat, but I still cut off the shore power at the box and still got a reading, so I knew the source was elsewhere. I turned off the power to the entire dock, confirming no readings at my boat. After knowing the source was ac, I walked the dock and found the source. I have since seen alarms, that are connected to the dock/water, that sound off when power is sensed in the water. My pedestal is directed to a GFI breaker. Not sure how much stray current it takes to trip the breaker, if at all.

 

[Mac2]

Count your blessings. This happened near us at my buddies marina in NY when a dock got electrified. I believe the jet skier came into the ramp and as soon as he touched it bam.

I heard of that along with others being harmed when they jumped in to save the drowning “swimmer”.

 

[SteveK]

My boat is steel, but the aluminum handrails are bolted to the steel. I have an isolation transformer for the boat, but I still cut off the shore power at the box and still got a reading, so I knew the source was elsewhere. I turned off the power to the entire dock, confirming no readings at my boat. After knowing the source was ac, I walked the dock and found the source. I have since seen alarms, that are connected to the dock/water, that sound off when power is sensed in the water. My pedestal is directed to a GFI breaker. Not sure how much stray current it takes to trip the breaker, if at all.

This is disturbing. You have an isolation transformer, which is good as it separates hot and neutral, but not ground (or does it).

So how can you avoid this from occurring again.
I do not expect the same with the glass boat and stainless rail is not bonded (as far as I know). But you and others with steel or aluminum boats must have a way to avoid this. I wonder if an in boat ELCI would have tripped, (again does it trip ground). Does not matter as the boat metal will conduct the stray current.

 

[Mac2]

Does not matter as the boat metal will conduct the stray current.

That is my thinking as well. I also believe it will be spreading the load through the boat to limit a concentrated shock point-similar to the idea of connecting all your thru hulls with a grond wire.

 

[Bmarler]

This shouldn’t happen with an isolation transformer. The dockside ground shouldn’t be directly connected to the ships ground.
If it’s a polarization transformer the ground will be connected. In that case, a good quality galvanic isolator should be installed.

 

[Fleming]

This shouldn’t happen with an isolation transformer. The dockside ground shouldn’t be directly connected to the ships ground.
If it’s a polarization transformer the ground will be connected. In that case, a good quality galvanic isolator should be installed.

I think because he has a steel boat, in what sounds like freshwater, the dock power was using his boat hull as a path back to shore (ground) through the water. If he didn't have an isolation transformer, the current would have had a direct path back through the ground connection with much lower resistance that might have allowed the dock pedestal's overcurrent protection to trip. His boat is still "grounded" by virtue of being in the water next to shore, which allowed him to measure that voltage even though he didn't have a 'ground wire'.

 

[Bmarler]

But if he cuts the shore power off, as he says he did, and still gets a reading, where is the connection?
Also, with the isolation transformer, his return path is to the boat.
I have to believe his ground isn’t proper, or the transformer isn’t wired right and has a neutral connection somewhere.
There has to be two sides to get a reading. A boat disconnected from shore connection sitting in charged water is only seeing one side of the line. Like a bird on a wire.

 

[Fleming]

But if he cuts the shore power off, as he says he did, and still gets a reading, where is the connection?
Also, with the isolation transformer, his return path is to the boat.
I have to believe his ground isn’t proper, or the transformer isn’t wired right and has a neutral connection somewhere.
There has to be two sides to get a reading. A boat disconnected from shore connection sitting in charged water is only seeing one side of the line. Like a bird on a wire.

His boat is not a bird on a wire because it's floating in water that is connected to shore where the ground is, so he's part of the circuit as the broken wire tries to send its electrons back to shore through the water. It's just the connection is high resistance between the broken wire and his boat, short circuit through the boat, and then high resistance as it finishes the path through the water back to shore.

If it had been in saltwater the breaker on shore would have tripped, the saltwater would have allowed for an easy path back to shore and the electrons wouldn't have cared about his boat. If it had been a fiberglass boat the electrons also would not have cared about using the boat as a path back to shore.
There was voltage drop between the source and his boat, that's how he was able to find the source because the closer he got to it the less the voltage drop through the water. His entire boat and AC electrical ground were part of the circuit, and he measured a voltage because of the voltage drop in the circuit. So close to the source was X voltage, and on his boat was X voltage minus the voltage drop in the water between the source and his boat.
He felt the small shock because his body then became a part of the circuit with a different resistance than the boat when he touched the boat with two parts of his body.

 

[Bmarler]

Interesting, I'm always in salt water, so haven't really studied the differences. I'm wrapping my head around it now, thanks

 

[SteveK]

Interesting, I'm always in salt water, so haven't really studied the differences. I'm wrapping my head around it now, thanks

Thankfully no one was swimming in the water.

 

[Mac2]

Great points above. To add additional information, I got readings on my aluminum dinghy parked at the bow of my boat. I also got a reading on my neighbors steel boat (less voltage) that is about 20 feet away. I am in fresh water. The fiberglass boat, one slip in front of me, had no reading (20 feet from exposed wire). My steel boat was less than 10 feet from the exposed wire). The main power is attached to a fixed dock and transitions to my floating dock. It needs slack, 2-3 feet, for the fluctuation of water levels in the ship canal. The slack at the transition found its way between the piling and dolphin. One in a million, right!

 

[SteveK]

IMO a power cord from a moving platform to a fixed object should not jump the gap down low as pictured but from an elevated point that will always be in the air, not water. With the 3 foot level change, even a 3 foot dock pole would work.

 

[Mac2]

The electrician opted for a slack loop in the water….

 

[boomerang]

I've had the problem of stray current at the dock due to otters chewing through the AC lines I have running under the dock. When the tide got abnormally high and the wires were submerged, the underwater hardware started taking a beating, which I didn't find out until a haul out and my zincs were gone plus the prop was showing signs of the dreaded pink color. That was several boats ago and thankfully the wires finally burned through and I lost (had greatly reduced)power which was a red flag for me to go looking for a problem. I didn't see any dead otters but I would imagine he literally bit off more than he could chew when he finally reached the hot wire while floating in the creek...
I'm getting ready to run an entire new 240v service to the dock to accommodate our current boat so I guess I'll run conduit under the dock to the while I'm at it.

 

[Mac2]

I've had the problem of stray current at the dock due to otters chewing through the AC lines I have running under the dock. When the tide got abnormally high and the wires were submerged, the underwater hardware started taking a beating, which I didn't find out until a haul out and my zincs were gone plus the prop was showing signs of the dreaded pink color. That was several boats ago and thankfully the wires finally burned through and I lost (had greatly reduced)power which was a red flag for me to go looking for a problem. I didn't see any dead otters but I would imagine he literally bit off more than he could chew when he finally reached the hot wire while floating in the creek...
I'm getting ready to run an entire new 240v service to the dock to accommodate our current boat so I guess I'll run conduit under the dock to the while I'm at it.

Ive heard rats/mice chew on pex because there is soy in the material.
That was my first concern when I discovered the stray current. I even got out a spare anode and wire to hang off the boat before the neighbor, who works in a boatyard, convinced me otherwise. He advised me the metal erosion only happens with DC current. AC current is alternating back and found, so it doesn’t concentrate on one spot to wear down. Maybe there is a difference in salt water?

 

[boomerang]

Ive heard rats/mice chew on pex because there is soy in the material.
That was my first concern when I discovered the stray current. I even got out a spare anode and wire to hang off the boat before the neighbor, who works in a boatyard, convinced me otherwise. He advised me the metal erosion only happens with DC current. AC current is alternating back and found, so it doesn’t concentrate on one spot to wear down. Maybe there is a difference in salt water?

Maybe so and maybe the pink metal was a coincidence but I did add an isolation transformer to the boat later so it definitely should've been protected and never had a problem after that. I just reasoned that the AC current that was going into the water from under the dock found a ground at my prop (pre isolation transformer) but who knows.
A couple of years ago the darn critters ate through the transom mounted transducer cable on my friends boat who was keeping it at my dock. I really don't want them chewing through the cable for my side scan transducer on our Carolina Skiff. That wouldn't be cheap. I wish they would find a neighbors dock more tasty.

 

[Mac2]

Maybe so and maybe the pink metal was a coincidence but I did add an isolation transformer to the boat later so it definitely should've been protected and never had a problem after that. I just reasoned that the AC current that was going into the water from under the dock found a ground at my prop (pre isolation transformer) but who knows.
A couple of years ago the darn critters ate through the transom mounted transducer cable on my friends boat who was keeping it at my dock. I really don't want them chewing through the cable for my side scan transducer on our Carolina Skiff. That wouldn't be cheap. I wish they would find a neighbors dock more tasty.

Definitely possibly without the isolation transformer. Did you have the galvanic isolator?

 

[SteveK]

Ok I will say it.
Bonding the under water metal and negative battery to AC ground so someone on board does not get shocked because a misdirected AC hot touches say an engine block and causes electrocution is enough reason to bond. Not convinced only DC causes erosion of anodes. Sorry, ABYC

 

[Mac2]

Ok I will say it.
Bonding the under water metal and negative battery to AC ground so someone on board does not get shocked because a misdirected AC hot touches say an engine block and causes electrocution is enough reason to bond. Not convinced only DC causes erosion of anodes. Sorry, ABYC

How does this apply to my steel boat, or are you just referring to a fiberglass boat?

 

[SteveK]

How does this apply to my steel boat, or are you just referring to a fiberglass boat?

No, it is not specific to your boat but in this case to all boats bonded as per standard would feed into the dock pedestal thru ground wire. Maybe the ELCI dock breakers would catch this imbalance as well and trip. It has already been shown that bonding has allowed DC current to travel thru the AC ground from boat to boat.
I do not see a way to prevent a metal boat from repeating this shock hazard without a dock breaker tripping.