Shore power electrical shock

pbyrne · August 31, 2020, 08:59:55 PM

Plugged into shore power I got a good shock when my hand connected the midship cleat and the holding tank stantion.

I used a voltmeter to investigate and I measured 130V AC.

This only happens when the breaker on shore power is On. Panel is still set to off for AC.

Any thoughts? The wiring is factory no mods to AC.

KWKloeber · August 31, 2020, 11:08:35 PM

130vac from cleat to to the stanchion? Using your meter, determine which one is grounded and which is hot.

Does the 12v negative portion of the terminal strip behind the panel have a bond over to the shore power green wire on the AC portion of the terminal strip?

Do you have any hardware, thru hulls, etc., that are bonded to earth, i.e., the 12v negative?

Get an adaper to the 30a shore stanchion if you don't have one and a tester, and check the polarity of the shore power.

Let us know!

Stu Jackson · September 01, 2020, 08:21:29 AM

Mark I or II? Always a good idea to add to your signature, 'cuz the inlet power wire connections and details are different.

Have you looked at your shorepower inlet?

pbyrne · September 01, 2020, 09:45:11 AM

MK II 2001

I've tried a lot of things so far. I have a number of photos that won't upload due to size so I have created this album.

If any better photos are needed I'll take them and add to album!

Photos here: https://photos.app.goo.gl/ynh8UTzWWP4KPzmK9

I did attach the pic of the voltmeter showing the 130 AC reading.

I could really use some help with this. I'm at a loss.

Quote from: Stu Jackson on September 01, 2020, 08:21:29 AM
Mark I or II? Always a good idea to add to your signature, 'cuz the inlet power wire connections and details are different.

Have you looked at your shorepower inlet?

pbyrne · September 01, 2020, 09:46:50 AM

I've added a number of photos. Hopefully they are helpful? If you need a specific one let me know.

I replied to Stu first and there is a photo attached to that post that shows just the meter.

https://photos.app.goo.gl/ynh8UTzWWP4KPzmK9

Quote from: KWKloeber on August 31, 2020, 11:08:35 PM
130vac from cleat to to the stanchion? Using your meter, determine which one is grounded and which is hot.

Does the 12v negative portion of the terminal strip behind the panel have a bond over to the shore power green wire on the AC portion of the terminal strip?

Do you have any hardware, thru hulls, etc., that are bonded to earth, i.e., the 12v negative?

Get an adaper to the 30a shore stanchion if you don't have one and a tester, and check the polarity of the shore power.

Let us know!

pbyrne · September 01, 2020, 09:48:48 AM

I should have mentioned that there is only power showing when the stern breaker is 'ON' and shore power is connected to the boat.

When the stern breaker is 'OFF' there is no power reading. Boat has house batteries to ON at the time too. I know that's 12V but thought I'd mention the state of the other systems.

Stu Jackson · September 01, 2020, 11:16:29 AM

Quote from: pbyrne on September 01, 2020, 09:48:48 AM
I should have mentioned that there is only power showing when the stern breaker is 'ON' and shore power is connected to the boat.

When the stern breaker is 'OFF' there is no power reading. Boat has house batteries to ON at the time too. I know that's 12V but thought I'd mention the state of the other systems.

So there is a loose wire somewhere between that stern breaker and the AC master breaker on your panel. You need to do some digging. Good luck.

Ron Hill · September 01, 2020, 03:24:57 PM

Pby : The factory has been known to crimp or run a screw/bolt thru the decking and break the insulation on the shore power wiring from the 30amp AC plug to the main electrical panel!!

Personally I'd rewire from the shore power plug to the main panel!!

A thought

mainesail · September 01, 2020, 04:46:55 PM

If you do not understand marine AC wiring, please, please, please bring in a professional who does. AC, boats, and water can kill. This is nothing to take lightly. Please do not plug your boat in until this is rectified. The AC side of your system should comply with the ABYC standards.

KWKloeber · September 01, 2020, 06:39:55 PM

I don't readily see that your 12v negs are bonded to the AC grounds. That may be a good thing (otherwise you might not have discovered the leak.)
I'd start isolating potential causes, but first need to determine which is hot (stanchion?) and which is grounded. ONLY if you are comfy doing this.
isolate the stanchion (remove the hose - 'tricity can move thru dampness.)
Again, check for correct/reversed polarity.
Follow the shore inlet to see if it is compromised and energizing the track.

scgunner · September 02, 2020, 08:32:17 AM

Pbyrne,

The only way that stanchion and or cleat can be hot is if it's(undesireably)connected to a power source, with the power disconnected I'd look for that path between the two.

Mainsail also makes a good point, if you're not comfortable with this bringing in a marine electric guy wouldn't be a bad idea.

J_Sail · September 02, 2020, 10:26:33 AM

I would like to reiterate what MaineSail said, DO NOT PLUG IN YOUR SHORE POWER CORD UNTIL YOU ARE CERTAIN IT IS FIXED. One can and should debug this UNPLUGGED. (Sorry for yelling, but stray AC can be deadly)

While it may be tempting to use an AC voltmeter to trace it out with it energized, that is not the safe way, and is usually unnecessary. Disconnect the shore power connecter and use an ohmmeter to look for stray paths that should not exist (could be a dead short or a high-resistance leakage path). If your electrical understanding is insufficient to do so, you should engage someone who has the necessary knowledge and skill. I am not trying to be elitist about it, just recommending appropriate caution. For example, it is possible that your boat is also leaking stray 120v current into the water and could kill someone who falls overboard near your boat. Better safe than sorry when dealing with 120v problems.

Jeremy

Ron Hill · September 02, 2020, 01:29:40 PM

Pby : Stray current will do some real damage so stay unplugged from shore power until you get that circuit rewired.
I know of a friend that had his stainless rudder column eaten away by stray current!!

A few thoughts

pbyrne · September 02, 2020, 01:41:46 PM

Noted! I'm thinking of continuity checks.

Quote from: scgunner on September 02, 2020, 08:32:17 AM
Pbyrne,

The only way that stanchion and or cleat can be hot is if it's(undesireably)connected to a power source, with the power disconnected I'd look for that path between the two.

Mainsail also makes a good point, if you're not comfortable with this bringing in a marine electric guy wouldn't be a bad idea.

pbyrne · September 02, 2020, 01:46:13 PM

I agree. Power is not required as I can do continuity checks.

Can someone suggest the logical places to start? I will plug the cable into the boat and then use the meter between... which pins and parts of the boat?

I'm comfortable handling a meter, but I'm not sure where the best places are to start testing.

Maybe I should visually inspect the cable from the stern 30A to the panel? Anyone know if that's accessible enough?

Quote from: J_Sail on September 02, 2020, 10:26:33 AM
I would like to reiterate what MaineSail said, DO NOT PLUG IN YOUR SHORE POWER CORD UNTIL YOU ARE CERTAIN IT IS FIXED. One can and should debug this UNPLUGGED. (Sorry for yelling, but stray AC can be deadly)

While it may be tempting to use an AC voltmeter to trace it out with it energized, that is not the safe way, and is usually unnecessary. Disconnect the shore power connecter and use an ohmmeter to look for stray paths that should not exist (could be a dead short or a high-resistance leakage path). If your electrical understanding is insufficient to do so, you should engage someone who has the necessary knowledge and skill. I am not trying to be elitist about it, just recommending appropriate caution. For example, it is possible that your boat is also leaking stray 120v current into the water and could kill someone who falls overboard near your boat. Better safe than sorry when dealing with 120v problems.

Jeremy