Getting stray current

[nasdaqsam]

I did a search but could not find anything related to this topic for my circumstances.

I have a 110 volt Dock/shore power set up. This is all 20 amp.

It starts at the house with a standard 20 amp breaker running to a dedicated 20amp GFI outlet. I then run a heavy duty marine lead cord through the dock (aluminum) to a hard wired marine single shore power outlet and split out of their to a GFI weather proof box.

The Shore power runs from there through a Marine shore power cable to the pontoon boat shore power inlet. The only thing this runs is a trickle battery charger and an AC/DC refrigerator. All this works fine no stray voltage.

The split to the GFI runs a 110 volt liftmate that has it's own GFI inline breaker. And anything on the dock I run off the GFI outlet works perfectly and no stray power. Typically an air compressor to blow up my hoist lift bags.

The problem comes in when using the lift mate. If I am using it and not touching the boat even in the pouring rain it is fine no stray voltage. But if you touch the boat while using it you will get a little shock (yes I know this can be fatal thats why I am tying to solve the problem.) All GFI's check out and trip as they should. They do not trip when this happens.

I am at a lose as to why this is happening. If the lift mate was grounding out it should trip one of the three GFI's and if there was an issue with at the boat it would trip one of them. The only thing I can come up with is the switch for the liftmate is a cheap little plastic switch which is not grounded. Not sure I can even get a grounded switch but if this was a neccessity I would think it would have come with one but either way it should trip one of the GFI's.

I am looking for ideas of where to look next.

Regards
Scott

 

[glenn property of pam]

Re: Getting stray current

gfci only trip out when the leak is 4ma or above. a person can sense less than 1ma (0.001 amp) so its possible to detect power thats below the threshold required to trip the gfci. One of your items has a bad or lost refrence to ground. In simple terms one of the items is not grounded. You will need a volt meter then start testing the neutral to ground voltage starting at the house/dock then check every connection as you go. Also for good measure check the live to ground and live to neutral

live to ground should be 120v
live to neutral should be 120v
neutral to ground should be 0v

boat metal to lift metal should be 0v

addition: if you have a large boat with a built in 120v panel you will need to test the Galvanic isolators if the cables to the boat/dock lift pass the above test

 

[Thalasso]

Re: Getting stray current

Delete

 

[Thalasso]

Re: Getting stray current

First of all your GFCI needs to be in the breaker panel.(NEC code) There is nothing protecting you or anyone else from getting shocked from the house to the current gfci breaker.You can put two or three regular plugs on the same line after the GFCI. No need for all those gfci's. If the lift was grounding out it wouldn't trip the gfci. It should trip the 20 amp breaker in the panel.Gfci's only recognize a load imbalance.Example: If you have 10 amps coming in and only 9 coming back is when it trips.
As glenn said, you must have a bad ground on one of your items.

 

[kahuna123]

Re: Getting stray current

Perhaps you have a motor that's looking for a better neutral or internally has an issue. One GFI upstream will protect everything past it. I almost got hurt pretty bad in the rain on my dive platform like that. Code also is the in a subpanel that neutral and ground are not bonded just for this reason.

 

[nasdaqsam]

Re: Getting stray current

Thank you for all the reply's. I will swap out the breaker this morning to a GFCI and start tracing the ground issue. I wasn't thinking about the lower voltage not creating enough of a problem to trip the one of the outlets.

Best regards
Scott

 

[nasdaqsam]

Re: Getting stray current

Ok so spent the better part of Friday tracing grounds and connections. They all work and tested as they should. But I still had the stray voltage to the boat when using the liftmate. It came down to the only thing left, the switch. The switch itself is not grounded. The only thing that made sense was the switch is bleeding though to my hand when using it by touching the boat I am carrying the ground. I swapped the switch for a new one and the problem is gone.

However after listening on here about the way I have it set up I was no longer comfortable leaving the system as is. The system now has a GFCI at the panel box, new wire to the exterior outlet, new cords from there to the shore power and box on the dock, new shore power cable to the boat and of course new switch for the liftmate and new box to seal the switch in.

Thanks for all the help.
Scott

 

[Thalasso]

Re: Getting stray current

Thumbs up.