From the Forums: GFCI Mini Splits

September 2017 Multimedia

Recently, one of our readers asked a question about a newly installed mini split. Here are some tips and solutions offered by other readers:

bullseye:  We finally got our mini split AC installed. It's a 120 volt system and is designed to be on a 15 amp breaker. Our dock has a 30 amp GFCI breaker and when ever the outside unit comes on it trips that breaker. Inside the boat it's connected to a 15 regular breaker and it doesn't kick. The fan on the outside unit will only turn about 5 revolutions so I'm sure it's a GFCI issue not an over load.

We have #10 wire running to the outside unit and after problems we hooked up a second ground. Nothing fixed the problem. I'll be headed back down later today with a generator to see how it runs when I hook it up to that. The inside unit gets its power from the outside unit and we can run the fan as long as we want. I've been told because it's an inverter unit this creates issues with GFCI breakers. Any thoughts?? Everything runs with the generator, the unit only pulls 6 amps.

easttnboater: There have been many reports out on the Internet of marinas installing GFCI breakers that trip constantly. You are going to have to talk with the marina.

Endurance: I don't know it it's available at your marina, but it would be an interesting troubleshooting exercise to plug into other 30A GFCI breakers. Perhaps using a neighbor's power or another dock you could find one.

Ike: GFCIs are designed to trip if there is an imbalance between the input and the output. In English that means, if the current in the black hot wire is not the same as the current in the white neutral wire then the GFCI trips. The reasoning behind this is that if an imbalance occurs then current is leaking somewhere in the system. If the GFCI on the dock trips the imbalance can be on the dock, or on the boat. It also means that the current is leaking into the water surrounding the boat or the dock and this is an extremely dangerous situation. So, the leakage needs to be isolated. How is that done. Unplug from the shore tie. Turn off everything on the boat. Plug in. If the GFCI trips the problem is on the dock. If not, then, one at a time, turn on the circuits on the boat. When the GFCI trips you have found the circuit that has the problem. Unplug. Turn everything off again. Turn off each individual appliance on the faulty circuit. Plug in. turn the circuit breaker for the faulty circuit on. If the GFCI trips it is the wiring. If not, turn on each item one at a time. When the GFCI trips you have found the culprit.

Also, a lot of marinas are installing these on old systems that have not been adequately tested for leakage. If the problem is on the dock the marina needs to get an electrician in to troubleshoot the entire dock electrical system. That is a big job and not cheap to do. But it needs to be done. Boat owners at the marina should insist on it, or go somewhere else.

Inverters can be an issue. Some inverters have been found to be wired incorrectly in regards to ground. The grounds for the AC side of the inverter and the DC side should not be connected inside the inverter. Unfortunately some have been found to be connected. This will trip your GFCI. Why. If the grounds are connected you have just connected the water around your boat to AC. Make sure your inverter is wired correctly. see (see the last question) see also

Have any more tips? Jump over to our forum and let us know. OR share your expertise on some of the other topics in the forums at

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