30 amp Shore Power Cord Short?

Did a little cleaning on the boat today and then wanted to reorganize placement of the 30 amp shore power cord since it is much longer than necessary and cluttering up the deck with current placement. I am using a 30 amp to 3 prong adapter to plug in, which has been past practice with no problem. After hauling much of the 30 amp cord to the pier and coiling it up, when plugging back in, it tripped the GFI. After a few tests, etc, I found that a) plugging in the 3 prong to 30 amp adapter did not trip the breaker but as soon as I plugged the 30 amp into the adapter, the GFI tripped and this was without the 30 amp cord being plugged into the boat. I conclude that there must be a short in the 30 amp cord. My confusion is that there has been no problem with the 30 amp cord so far and there is absolutely no sign of damage. Would welcome any insight/similar experience before I invest in new 30 amp shore power cord.

Capnal
THXKIDS III, 32 Island Gypsy Europa, Orange Beach, Al

Was the GFCI at the shore power pedestal and was it recently upgraded?


Is your shore power cord burned at the ends? If not it is highly unlikely the cord is the fault. The fault may be a new GFCI that is now tripping on your boat or a new internal fault in your boat.



David

NO visible damage to cord and the cord was NOT connected to the boat.

I have seen them go bad with an internal short. Do you have an ohm meter? If so ohm between the 3 leads, 2 at a time. They should show infinite resistance. If they show less than infinite then you do have a short. Buy a new cable. I had a 15 to 30 amp adapter brand new with hot and ground reversed internally. Sent it back for a new one and the new one was fine. You probably had some water get inside one of the plugs and is shorting 2 of the leads together.

There are places which test, and tag electricals incl cords as tested ok. Probably should be done regularly, but who does? If it tests bad replace it, if good the problem lies elsewhere.

If a little water got into it that could be enough to trip a GFCI outlet

kchace said:

If a little water got into it that could be enough to trip a GFCI outlet

Click to expand...

That’s what I was thinking. One of the ends found its way into the water.

My guess is sometime in the past the end of the cord was dropped in the water.

Sea water, fresh water , doesn't matter much the guts will corrode.

Take off the plug on the boat end first and take a look.

If the cord is long a 2-4 ft trim usually gets back to clean wire.

This is a common problem and the best reason to spend a few bucks more when purchasing a cord that can have the terminal ends removed with out damage..

WE use Hubbell .

Sounds like when you coiled up the cord, it shorted internally. If you disconnect the cord at both ends and ohm into it between any two pins, you might pick up a short on the meter when you move the cord around. Concentrate on the last 3 feet of the ends at first, then work your way systematically through the cord.
Good luck and be safe!

I had a situation where I needed to replace a relatively new cord and shore power inlet because salt water had gotten in and corroded things. Even after cleaning, it kept causing my ELCI to show reverse polarity, which I know is a strange warning light to come on, but can show up with this type situation because the leak is on the supply side of the ELCI, not the load side. It was a relatively new cord and a neighbor cut the end off of it, put a new one on, and he used it going forward. (Out of an abundance of caution, I replaced the cord -- and he claimed and fixed the old one).

In any case, I'd advise caution if it is an older cord and the problem isn't likely to be isolated, e.g. corrosion at the end, or a point where it got goodnecked, or where it got slammed in the dockbox, etc. These things can carry a lot of current, e.g. 30+A

There was just a small fire at my old marine that was the result of a bad 30A dock cord. It burned up the breaker box and a dock box. If it hadn't been an active, well-managed marina, with people to notice and respond, it could have gotten out of hand and burned the whole place down.

I don't know for sure why, in that case, the breaker didn't prevent the fire, but I think people sometimes expect too much from simple breakers. They don't trip immediately at the marked current level. Instead, they have a curve where they trip sooner at higher current levels and can say over-current for a long time, even forever, if it is just a modest amount over. Arcing, such as from frayed wires, can also cause sufficient heat to start a fire in a way that won't cause them to trip.