Phantom voltage question

[1haz]

If you bond the metal case of the charger to any piece of the network of bonded metal parts of the boat, hopefully the phantom voltage you see will go away.
If it does not, then the most likely thing is that there is no EGC in the AC line feeding the charger or that EGC is for some reason at an elevated voltage with respect to the water around the boat.

Sorry for any confusion with this but the case of the charger is plastic and the boat is sitting on concrete on the trailer. So this is really the most strange thing. Fiberglass center console boat sitting on a aluminum trailer and the voltage is also showing on the trailer. The EGC in the AC is fine. Everything is 3 wire with good ground and correct polarity. Again I can plug anything else into the plug using the same extension cord and e erything is fine.

 

[GoldDigger]

Sorry for any confusion with this but the case of the charger is plastic and the boat is sitting on concrete on the trailer. So this is really the most strange thing. Fiberglass center console boat sitting on a aluminum trailer and the voltage is also showing on the trailer. The EGC in the AC is fine. Everything is 3 wire with good ground and correct polarity. Again I can plug anything else into the plug using the same extension cord and e erything is fine.

So the voltage difference (and current flow) that you feel as a shock is between the metal parts and trailer and the concrete you are standing on?

Have you tried sticking a screwdriver into the earth outside the concrete and using that as one pole of three voltage measurements: to the AC EGC, to the trailer frame, and to the - side of the boat battery?

 

[1haz]

So the voltage difference (and current flow) that you feel as a shock is between the metal parts and trailer and the concrete you are standing on?

Have you tried sticking a screwdriver into the earth outside the concrete and using that as one pole of three voltage measurements: to the AC EGC, to the trailer frame, and to the - side of the boat battery?

No I haven't tried that. Are you thinking the earth outside the concrete is energized?

 

[ptonsparky]

No I haven't tried that. Are you thinking the earth outside the concrete is energized?

Think of stray Voltage and dairy barns. It could be Voltage drop from an undersized or overlong service neutral. Could be your neighbors neutral. A faulted buried conductor. Where are you in relation to the overhead primary. Lots of things enter into it.

Have fun.

 

[kwired]

No I haven't tried that. Are you thinking the earth outside the concrete is energized?

Earth away from your grounding electrodes and other items bonded to it are at "ground" potential. If you have voltage drop on the service grounded conductor or any other point between your where you are measuring and the source, you will have a rise in voltage to true ground. If that is what the problem is, then other loads especially of similar current draw, should cause similar symptoms.

 

[mike_kilroy]

I have listed some questions below for you to answer so we can help identify where your issue is. I put YOUR comments in quotes with question following each.


But first, have you done any research on this issue? For instance, I googled the words "stray voltage on boats" and got lots of good info, INCLUDING what recommended quasi CODE is for USA - it is totally different than Europe. Over 90% of US boat manufacturers follow this ABYC spec. In USA the code is ABYC and states: connecting the AC green wire to the DC Ground.
YOU APPARENTLY DO NOT HAVE THIS DONE. Ie;, the missing ground wire I keep mentioning.


Some good finds:


http://www.rjwsurvey.com/uploads/Grounding.pdf


http://www.samsmarine.com/forums/showthread.php?11736-How-to-test-for-stray-electrical-current


http://www.cruisersforum.com/forums/f14/stray-voltage-in-a-marina-142433.html


http://abycinc.org/?page=standards


NOW TO QUESTIONS FOR YOU TO HELP YOU FIND THE MISSING OR CORRODED GROUND WIRE:


"one lead on the metal building and the other lead on any metal part of the boat I get 36 volts"


what volts do you get from metal building to the ground terminal on the AC outlet with the charger plugged in?


what volts do you get from metal building to the ground terminal on the AC outlet with the charger NOT plugged in?


"If I plug other metal items into the same plug with the same extension cord I do not have any voltage."


What does this mean? What kind of metal things are you pluggin into an AC outlet??


"There is no continuity between cord on charger and metal on the boat."


Cord on charger has 3 pins; are you saying no continuity from metal on boat to ANY of the 3 120v charger pins? If not, tell us the continuity from that metal rail to EACH of the 3 terminals.


Goldigger said "The - terminal of the battery is very likely grounded to the engine and eventually to all of the bonded metal on the boat"


IS IT?


"The charger is a Genius Noco Genn3" sg-1 said "The 36 VAC could be ripple from the DC output." Reading your manual, this is a PWM output with max ripple of 2%. So if NOT hooked to your batteries, this is only 2.8vac: hooked to battery is is 0.0% ripple. So DC output is NOT an issue.


"Again I can plug anything else into the plug using the same extension cord and eerything is fine."


what does this mean? Does it mean:
A) if charger is plugged in and I am measuring 36vac from building to railing and I then plug in a SECOND device - say a 60watt light, the 36vac goes to 0vac?
-or-
B) I am measuring 36vac from building to railing and UNplug charger so the 36vac goes to 0, and then plug in a SECOND device - say a 60watt light, the 36vac stays at 0?


Your manual on that charger does not go into much technical detail, just keeps saying how great it is, and it does not state if built to ABYC standards or not. You MUST check continuity from the ground pin on the 120ac power plug to the charger's - output. If this is open circuit, that charger is not built to normal USA ABYC specs. If it were me, I would get a refund and buy a better unit. If nothing else, if this continuity is missing, I would immediately call that mfgr and find where a GROUND terminal is that IS tied to the 120vac power plug so you can put a ground wire on it and run it to the - terminal of the charger - with their approval of course. If they do not approve, get a refund. Just tell them they do not meet USA boating standards - refer them to the ABYC.org site listed above if they do not believe you.


Post your answers so we can help you identify your issue; it may still be you have an open neutral or open ground or some other issue in your home as the experts here have considered. The above questions are geared toward helping determine if one of those are your issue, or if you simply are missing a crucial ground wire and how to find and rectify it.

 

[AJElectric]

connecting the AC green wire to the DC Ground.
YOU APPARENTLY DO NOT HAVE THIS DONE. Ie;, the missing ground wire I keep mentioning.
.

I didn't read every single detail in this whole thread, but I would agree it is really this simple. Think of the charger as a "separately derived system" (it does have a transformer, no?) but secondary isn't grounded. Once you bond secondary (battery neg.) to EGC the problem should go away.

From what others are saying this should already be done internally in the charger. Maybe you find it already bonded, then search for B- connection problem from there to boat "frame".

If that is all legit, and still you have a problem, then investigate for a "real" stray voltage problem not related to the boat or charger. (By testing voltage N<>G and N<>dirt and G<>dirt near the boat)

 

[1haz]

OL from charger ground to DC -. I would think the charger is grounded inside the plastic case being that it has a 3 prong cord. The corroded ground wire just doesn't make sense as to why it energized the metal parts of the boat and trailer being a fiberglass hull. I plugged a metal skill saw into the same plug/cord and check from earth to saw and from metal building to saw and no voltage. Again I plugged a portable charger into each battery individually and I have no voltage on the metal parts. This is a brand new charger as I thought the old one may of had a crack or something in it.

 

[K8MHZ]

http://assets.bluesea.com/files/resources/technical_briefs/grounding_circuit_protection.pdf

Good info in the above.

This is just one part, there is also a good diagram.

1. Before installing a charging device, confirm that there is a good connection between AC
and DC grounds. If there is not a good connection, the charger/inverter grounding,
when it is installed, may become the main connection between AC and DC grounds and
must be sized for the boat's entire electrical system in order to avoid the risk of shock
or fire. The AC grounding system and the DC grounding system should be firmly
connected at a main grounding bus or at the engine block.

 

[AJElectric]

OL from charger ground to DC -.

Not clear on OL, do you mean "infinite ohms" ?

I would think the charger is grounded inside the plastic case being that it has a 3 prong cord.

But is the ground/green wire BONDED to the DC- inside the charger? If meter reads infinite ohms then it's not bonded, and that needs to be corrected.

OR if meter reads ~any~ volts (AC or DC) measured between DC- and ground/green then it's not bonded, and needs to be corrected.

This is a brand new charger as I thought the old one may of had a crack or something in it.

Make no assumptions - just because it's new doesn't mean it's infallible, just because it's old doesn't mean it's broken.

 

[mike_kilroy]

OL from charger ground to DC -

haz, I apologize: I was never in the military. I never caught on to the shortcuts like OL...

Please

tell us what OL means.

 

[1haz]

haz, I apologize: I was never in the military. I never caught on to the shortcuts like OL...

Please

tell us what OL means.

Sorry, "open line". No continuity. I think it must be the charger like some have said previously. I have disconnected all DC + and - from each battery one at a time with the exception of charging leads so there were no grounds or hots to boat equipment and still get the voltage on the metal items when the charger is plugged in. What's weird is if no other wires are touching the batteries except the charging leads and the charger is on a fiberglass boat how does it energize the metal? I thought this would be a simple problem to find but it's really confusing me

 

[mike_kilroy]

Sorry, "open line". No continuity. I think it must be the charger like some have said previously. I have disconnected all DC + and - from each battery one at a time with the exception of charging leads so there were no grounds or hots to boat equipment and still get the voltage on the metal items when the charger is plugged in. What's weird is if no other wires are touching the batteries except the charging leads and the charger is on a fiberglass boat how does it energize the metal? I thought this would be a simple problem to find but it's really confusing me

I can be. Let us help you. Begin by answering ALL the questions in post 26.

 

[K8MHZ]

I can be. Let us help you. Begin by answering ALL the questions in post 26.

He has already stated there is no continuity from AC ground to DC -. That means the charger is not suitable for being used on a boat. If he wants to perform a simple experiment, I suggest bonding the DC- to the AC ground and then check for errant voltages. If the bonding takes care of the problem, then a properly configured charger needs to be installed.

While doing so, I would also check the charger mounting screws to see if one of them has poked into some wiring. He may have more than one problem, with the improperly bonded charger magnifying said problem.

 

[cowboyjwc]

Probably is going into metal. Important structural things like rails are not just screwed into fiberglass, they would break out way too easy. They often build a metal stick frame first, then the hull gets laid up over it, then the rails are bolted to that frame afterward. It's that frame that should be grounded.

I'm thinking that this a portable charger, not one designed to be mounted in the boat (or it WAS a portable charger that someone mounted permanently because it was cheaper, not fully understanding why). The difference would be that a portable charger would not have a bonded connection of the DC negative / frame and the AC ground conductor, as it should (per Coast Guard regulations by the way). That's because if there is a short in the AC hot to the DC negative or boat frame and there is no bonding connection, the entire boat metallic frame goes to 120V potential, waiting for some poor soul to touch it. The breaker would not trip because with no ground return path yet, there's no current flow until that person makes connection.

On some types of boats, like commercial fishing vessels with aluminum hulls, where bare metal is in contact with the water, they isolate on purpose to avoid galvanic corrosion when the boat is plugged into the charger while in the water. But when a boat charging system is designed like that, there are all kinds of warning stickers about this because of exactly what you are experiencing and that danger of shock.

Well just showing my age, I was thinking wood frame. :ashamed1:

 

[Jraef]

Well just showing my age, I was thinking wood frame. :ashamed1:

LOL, it used to be, but wood is too expensive now!