Very Strange Electrical Hazard/Problem

[walt]

And.. in order to get a shock from AC, you somehow have to be contacting two points at different potentials. As an example, Ross had a great story about the aluminum siding of a house being energergized with AC when a light was turned on. But if you were well insulated from earth ground, you could go up to the house and touch it and not even know it was energized because you would be at the same potential as the house. If you were barefoot on wet soil and did the same thing.. zzzzzttttt.

Corona current due to a lightning storms electric field is different in that it charges any thing that resembles a capacitor - such as an ungrounded mast. If you take two charged capacitors - but charged to different potentials, and bring the leads close, charge will hop from one capacitor to another which then equalizes their voltages - ie, a spark. But you then have to wait for Corona current to re-charge the capacitors before a spark can happen again. The two leads of the capacitors involved in the spark were both insulated from ground - but the spark still occured.

 

[rgranger]

Its still a mystery

So today I did the following...

1) I set it all up again and still got the tingle... so not a corona effect.
2) I checked the polarity of the line coming from my shed. It was okay. So that is not it.
3) I cut the power at the breaker in the boat. Problem went away so that means it is someplace beyond that point. Bummer
4) The outboard is mounted on a cut away directly on the transom... which is fiberglass. And the only lines I could see going aft were for the nav. light.

I don't get it. How could I possibly be getting AC leakage through my outboard. I guess I'm going to have to wedge myself up into that small space and see if there is a bonding wire connected at the transom. I could not see anything obvious sticking my head into the hatches. Maybe someone in the past tried bonding all the metal components in the boat and then grounded through the outboard. And then since then I've somehow gotten a chafe or some other hot lead in contact with that bonded circuit.

Ah the joys of an old boat. As soon as this trip is done I'm going to rip all of the old electrical out of this boat and start over.

Fair winds, all and I'll see you on the water.

 

[nolasafari]

Are you using yourself to test for the tingle? You may test for that tingle one to many times. You said you were not using shore power then talk about turning it on and off.

 

[Chris Patterson]

Hmm. Have you checked continuity between the motor and the boat ground, ie: negative battery? Maybe even unmount the motor altogether and do the same continuity check between mount and ground. It is a strange one, no doubt. It seems, just seems; that there has got to be some 'bonding' in there somewhere..

 

[JohnShannon]

Sounds like two failures, I think your charger is bad, by bad I mean the insulation in it that isolates the 12V output from the 120VAC input is breaking down. So now your 12V output has some connection to the line voltage (with some significant resistance still otherwise you would be using more colorful language than "tingle"). Change the charger/borrow a buddies should go away. The second issue is there should still be a safety ground to provide a safe path for stray currents. You should have continuity between the engine block and third prong on your power cord. Also your power cord should be plugged into a grounded outlet and preferably one with ground fault protection, apparently that isn't the case cause a ground fault detector would notice that the current going out the hot wire was not matched by the current returning in the neutral and would shut down the outlet. In your case that slight mismatch of current going through you and tingles.

 

[Allan12210]

If the polarity checked out that cord may still not be off the hook. Check the voltage between the neutral and the third prong on the female end of the cord. If its polarized then thats rhe larger of the two slots. Its always possible if a cord end was replaced that a strand or few could escape from its proper terminal and be touching the ground screw. You still need to measure from either the charger case or the outboard metal to the earth. If you felt tingling you need to measure that voltage. And don't touch it any more. Eventually you will find a low resistance path to ground and then it won't be a tingle you feel. As John says make sure there is a GFI outlet. If not, put one on and if it pops this is pretty serious and dangerous.

 

[LloydB]

1. Measure The Voltage

 

[centerline]

I don't get it. How could I possibly be getting AC leakage through my outboard. I guess I'm going to have to wedge myself up into that small space and see if there is a bonding wire connected at the transom. I could not see anything obvious sticking my head into the hatches. Maybe someone in the past tried bonding all the metal components in the boat and then grounded through the outboard. And then since then I've somehow gotten a chafe or some other hot lead in contact with that bonded circuit.

you seem to be straying from the main point.... now that you have found it is not static and that killing the circuit breaker will make it go away, it makes no difference in all the world as to how the voltage is getting to the outboard bracket and outboard. it makes no difference if it is bonded or not at this point....
what does make a difference is, what leg of AC voltage is leaking to the hull or ground circuit.... im sure you wont find any AC wiring directly connected to the outboard bracket. if the bracket IS in fact bonded, it will be a DC ground.

you need to find where the AC leak is either to the hull, or the dc ground.... im positive you wont be finding it at the outboard bracket. so even if the bracket is bonded, I would conclude there is little need to crawl in there to look at it....

there is probably 2 legs of AC power, one running to starboard and one running to port..... one of these has a leak.... disconnect them to see which one it is...

and/or, it has already been suggested to unplug the charger to see if that makes the problem go away. Try it!... but if you had an AC leak thru the charger to the DC side, you would have some big battery troubles by now...

in fact, unplug every appliance in the boat to see if you have an issue with a power cord at an unseen location .... or maybe the appliance itself. chect to see if the problem goes away.

when you are inside the boat, touching the appliance while standing on the fiberglass liner, probably on a rug, with rubber soled deck shoes on, you are kind of insulated. if the appliance has a voltage leak, you may not notice it until you become a ground path..... such as you are when standing on terra firma with your body being the only direct path to ground from an otherwise insulated, yet electrified object.

dont over look the fact that the fiberglass itself CAN, in some cases, carry a small amount of current.... enough to give a tingle.

its my thoughts that you should focus your efforts on finding the source of the leak and not for how its getting to the outboard bracket.... that will kind of take care of itself as soon as you can find where the leak is and repair it

 

[rgranger]

Are you using yourself to test for the tingle? You may test for that tingle one to many times. You said you were not using shore power then talk about turning it on and off.

Thanks Nolasafari

Of course, you are right. It is a very slight tingle (way way less than a 9V battery on the tongue) but like you said.... one too many times. And there is no guarantee that it will stay slight.

 

[rgranger]

Sounds like two failures, I think your charger is bad, by bad I mean the insulation in it that isolates the 12V output from the 120VAC input is breaking down. So now your 12V output has some connection to the line voltage (with some significant resistance still otherwise you would be using more colorful language than "tingle"). Change the charger/borrow a buddies should go away. The second issue is there should still be a safety ground to provide a safe path for stray currents. You should have continuity between the engine block and third prong on your power cord. Also your power cord should be plugged into a grounded outlet and preferably one with ground fault protection, apparently that isn't the case cause a ground fault detector would notice that the current going out the hot wire was not matched by the current returning in the neutral and would shut down the outlet. In your case that slight mismatch of current going through you and tingles.

Thanks JohnShannon

I have a car battery charger in the shed. I can try connecting that to my batteries and see if the "tingle" is still present. I don't have a "third prong" continuity to an engine block. This boat has an outboard. And I'm guessing because it is on a trailer, I became the ground. There is a ground fault protected outlet in the boat but I guess the battery charger is not part of that circuit or what you said about GFP would have been correct. Thanks for the suggestion and I'll let you know what happens.

 

[rgranger]

you seem to be straying from the main point....

Thanks centerline....

I'll start with the charger. The only other "appliances" on my boat are the VHF and Chartplotter. Both of those were in the off position when this happened so I doubt that is the source. I guess you could consider the AC outlets in the boat an "appliance". So running each of those down at at time should not take too long. I'll let you know.

r

 

[Crazy Dave Condon]

Rob;

Have you tried tying a sacrificial zinc to a line and throwing it overboard leaving it in the water to see if electrolysis is going on at or near your dock? Could it be the dock wiring if you have any? Not sure about set up but when feeling a tingle around water, I would be cautiouis. I knew of kid electrocuted at a new dock years ago at a resort. I can tell you about it later.

 

[rgranger]

Rob;

Have you tried tying a sacrificial zinc to a line and throwing it overboard leaving it in the water to see if electrolysis is going on at or near your dock? Could it be the dock wiring if you have any? Not sure about set up but when feeling a tingle around water, I would be cautiouis. I knew of kid electrocuted at a new dock years ago at a resort. I can tell you about it later.

Dave

This is happening on my trailer. The O.B. was in a trash can full of water for a test fire. I put my hand in the water to see if it was getting warm and that is when I felt the tingle. And I know about ESD.

 

[centerline]

Thanks centerline....

I'll start with the charger. The only other "appliances" on my boat are the VHF and Chartplotter. Both of those were in the off position when this happened so I doubt that is the source. I guess you could consider the AC outlets in the boat an "appliance". So running each of those down at at time should not take too long. I'll let you know.

r

you are right... it wont be leaking thru a DC component.

and yes, if you have no microwave, tv, light fixtures, battery charger or other AC power-using components ATTACHED to the AC circuit, then it will be found in one of the circuits... not sure if you have regular outlets or GFCI's installed, but i have had GFCI failures where the hot leg shorts to ground.... without going into detail, thats kinda what makes them work, only they arent supposed to stay that way.

 

[rgranger]

you are right... it wont be leaking thru a DC component.

and yes, if you have no microwave, tv, light fixtures, battery charger or other AC power-using components ATTACHED to the AC circuit, then it will be found in one of the circuits... not sure if you have regular outlets or GFCI's installed, but i have had GFCI failures where the hot leg shorts to ground.... without going into detail, thats kinda what makes them work, only they arent supposed to stay that way.

I had not considered the GFCI outlet but now that you mention it.... I've owned the boat now for two seasons and have never had to reset it. Considering all of the rewiring, and power tools I've plugged in through my boats outlets... it seems it should have popped a few times by now. I will run down the charger first and if that is not it... then I'll look at the GFCI outlet.

I really appreciate all of the brain power this forum has "lent" to me. I think I would have just started tearing out all of my wires and replacing everything from scratch. And if it turns out the be the charger of GFCI I would have still not fixed it....

 

[walt]

Centerline, I may be missing something but am wondering if you can give more detail and backup on this

dont over look the fact that the fiberglass itself CAN, in some cases, carry a small amount of current.... enough to give a tingle.

A link maybe? I think the fiberglass in a sailboat has more in common with the fiberglass used in electronic circuit boards or ladders used around high voltage. They dont use fiberglass because it conducts a small amount of current. Certainly you could add something in the fabrication process to intentially make fiberglass slightly conductive (or use carbon fiber) but I dont think this is the case. Just wondering..

Also.. nit picking a little here but GFCI circuits generally fail either on all the time or off all the time. I attached a typical circuit, it uses a relay to connect the line in and line out. The relay and circuit can fail either on all the time or off all the time. There is no mechanism for the hot to short to ground (almost, there is a MOV on the input and these can look like a low impedance if the device is involved in a ightning strike)

If the shock always showed up on the outboard and only the outboard (I think that is what you said), did you ever figure out how it was connected back to AC power somehow

 

[rgranger]

If the shock always showed up on the outboard and only the outboard (I think that is what you said), did you ever figure out how it was connected back to AC power somehow

Walt, Did you switch from talking to centerline back to me? If so, the answer is NO. I'm totally befuddled. This makes no sense to me. BUT! I also don't know for certain if it is AC or DC. I'm going to hook up my volt meter tomorrow and see if I get a reading from the engine cowl to ground. I'm also going to disconnect the battery charger and see if it goes away. And last I might bypass the GF plug and see if the problem goes away (and replace if necessary).

What a pain in the patoot

 

[walt]

yep, that was a question for you - about getting shocked on the outboard. The other thing about the outboard is that you would have been standing on the ground when you touched it. Inside the boat, you would be standing on fiberglass. Were you well insulated from earth ground when you touched the outboard (ie, weaing shoes, on a concrete driveway, etc).

FYI, you can have current across fiberglass insulator but its capacitive current. Fiberglass is a dielectric and of course could be used between the plates of a capacitor and would follow the standard capacitor equations. If you run any numbers, almost no way this is involved in what you are seeing.

 

[rgranger]

FYI, you can have current across fiberglass insulator but its capacitive current. Fiberglass is a dielectric and of course could be used between the plates of a capacitor and would follow the standard capacitor equations. If you run any numbers, almost no way this is involved in what you are seeing.

Yep! This is a weird one. I was standing in grass. b
It would have to be AC then.... but I am stumped on how the current is getting to my engine mount in the first place.

The only electric lines I have going aft are the rear nav. light and the starter cables to the outboard. I've disconected the starter cables and the nav. light line is not touching the transom as far as I can see.... and I don't think the transom has any metal in it..... so who would I get capacitive current....

I'll post something as soon as I figure it out.

r

 

[Ron20324]

Metal throttle or shift cable?