Electric shock

SKIPPERJON · 11-01-2009, 07:50 PM

I needed to measure the shaft size on my boat today so that I could order new zincs, when I touched the shaft with my calipers, I got a good jolt of electricity.
Wow, where did that come from!!!!??

Took the voltmeter and attached one end to the bonding plate on the transom and stuck the other in the ground. THAT GAVE ME A READING OF 94 VOLTS. No wonder I got zapped.
Just prior to that, I pluged the shorepower cable thru an extention chord to an outlet in the garage.
I checked the power cables, took off both breaker panels thinking there was a short someplace, I found the reverse polarity LED leads broken off but nothing obvious that would give me such a shock. Both breakers were on initially, but after I unplugged and then reconnected the cables, both breakers tripped off.
Still no clue as to what the problem was. Until I got this bright idea. I have an extension chord which is missing the ground plug, so I reversed the position of the plug at the receptacle and voila, no more zapping current at the ground.
Had the LED reverse polarity light been working, I would have cought it sooner. Good thing too, the boat was in my yard and not in the water where it potentially could have been a disaster.

My next project is to fix the light and also use the plug-in tester.

John

BajaFeeling · 11-01-2009, 09:11 PM

Quote:

Originally Posted by SKIPPERJON

I have an extension chord which is missing the ground plug
John

Falls into the same category as disconnecting the CO Carbon Monoxide alarm because the noise keeps one from sleeping.

Throw that extension cord away.
But you still have another wiring problem on your boat that needs to be checked.

SKIPPERJON · 11-01-2009, 09:22 PM

It's gone.

John

rwidman · 11-02-2009, 06:31 AM

Quote:

Originally Posted by BajaFeeling

Falls into the same category as disconnecting the CO Carbon Monoxide alarm because the noise keeps one from sleeping.

Throw that extension cord away.
But you still have another wiring problem on your boat that needs to be checked.

And I suggest you hire someone who knows what they are doing to check the boat's wiring.

SKIPPERJON · 11-02-2009, 05:06 PM

It's not the boat's wireing, it was the receptacle in the garage that was wired incorrectly.

rwidman · 11-02-2009, 07:53 PM

Quote:

Originally Posted by SKIPPERJON

It's not the boat's wireing, it was the receptacle in the garage that was wired incorrectly.

Now you know why electrical codes call for GFCI receptacles in garages, kitchens, outside, etc. And why there's a label on the extention cord cautioning against removing the ground prong on the plug.

At least you weren't seriously hurt. Get the outlet rewired ASAP.

yandina · 11-04-2009, 09:37 AM

No you have STILL something else wrong that could KILL you.

The hot and the neutral in you boat wiring should not connect to anything to give you a shock even if they are reversed. You should be able to reverse the hot and neutral on the line cords and still not get a shock so something is wrong on the boat.

First thing to check is that the neutral on the boat is not connected to the ground. This is a very common error. Normally if the ground is functioning it will protect you from a shock and blow the breaker but the combination of BAD ground and REVERSED polarity can KILL you if the neutral is connected to ground on the boat. Wiring rules require the ground and neutral to only be connected together at the primary source, not on the "appliances".

You can take an ohm meter with the shore power unplugged, but with all 120 volt items switched on, and measure the resistance to ground metal anywhere on your boat from both the HOT and the NEUTRAL. Both should read more than 100,000 ohms although on older salt water boats it may be less. But it should not show continuity.

If you find there is a connection between the AC hot/neutral and items on the boat, and you don't have a breaker box on board where the neutral and ground have been bonded in error, then unplug the items on board one at a time until you find the culprit and fix it.

rwidman · 11-04-2009, 11:22 AM

Home centers and electrical supply houses have inexpensive plug in testers that can be used to check for incorrectly wired receptacles. I would start with the garage, then using a properly wired three wire extention cord, check the boat.

Phil/Fill · 11-06-2009, 10:24 AM

I agree there could be something miss wired on the boat. You should not been shocked because of reverse polarity. Have you re check with a new cord and the out let rewired?

mulberryg · 11-06-2009, 05:33 PM

lack of a bonded neutral at source?

rwidman · 11-06-2009, 06:08 PM

Quote:

Originally Posted by Phil/Fill

I agree there could be something miss wired on the boat. You should not been shocked because of reverse polarity. Have you re check with a new cord and the out let rewired?

His garage outlet may have had more than "reverse polarity".

Trouble shooting is a step by step process.

1. Get the garage outlet wired correctly and test it with a tester.
2. Get a known good extention cord, plug it in to the garage outlet amd test the female end with a tester.
3. Plug the boat in and use the tester on the boat's electrical outlets.
4. Use a volt meter to test for voltage from the boat's shaft (that he received a shock from) to a known ground.

sickcat · 11-07-2009, 05:59 PM

I have seen the issue happen due to a moist/wet plug which was leaking current from the hot to ground. From AC ground to the bonding system to me - OUCH!

rwidman · 11-08-2009, 07:11 PM

Quote:

Originally Posted by sickcat

I have seen the issue happen due to a moist/wet plug which was leaking current from the hot to ground. From AC ground to the bonding system to me - OUCH!

A functional GFCI would have taken care of that without you even knowing it.

Steve G · 11-10-2009, 02:13 PM

The problem is that your neutral should be floating. Someone wired the neutral with your ground as in a home. Also the neutral going back to the outlet must have been compromised to cause the power to search for a path to ground through your caliper and you. Get it corrected now.

sickcat · 11-12-2009, 05:27 PM

Quote:

Originally Posted by rwidman

A functional GFCI would have taken care of that without you even knowing it.

Thanks for the info but I understand that Ron. The boat was on the hard in the yard on an extention cord. I was out there in what we in SoCal call rain. I was supprised that the outlets in the yard were not GFI protected thou.

rwidman · 11-13-2009, 06:16 AM

Quote:

Originally Posted by Steve G

The problem is that your neutral should be floating. Someone wired the neutral with your ground as in a home. Also the neutral going back to the outlet must have been compromised to cause the power to search for a path to ground through your caliper and you. Get it corrected now.

Floating in the sense that the boat would be wired as an appliance, say a washing machine, and the only neutral to ground connection is at the service entrance to the house or building.

It's possible but it's difficult to tell for sure without inspecting it. I agree, get it corrected ASAP.

rwidman · 11-13-2009, 06:24 AM

Quote:

Originally Posted by sickcat

Thanks for the info but I understand that Ron. The boat was on the hard in the yard on an extention cord. I was out there in what we in SoCal call rain. I was supprised that the outlets in the yard were not GFI protected thou.

Two suggestions:
1. Buy the tester in the photo above and use it when working around strange places.

2. Buy an extention cord with a built in GFCI circuit and use it when there's any question of electrical safety.