The ELCI breaker tripped again. This is the third or fourth time it’s happened. The good news is we have more clues, but the bad news is it’s still going to be hard to troubleshoot.


  1. This happened early on when the boat was being commissioned, so it started happening before I brought any of my devices aboard.
  2. It’s happened on both the forward and aft ELCI breakers. The errors were slightly different, though. The last time, it was the forward breaker and the green light was flashing, indicating an over current. This time, it was the aft breaker and the red light was illuminated, indicating a ground fault condition.
  3. It’s happened with both the 50-amp cable and the modified 30-amp cable. The bridge between the poles on the 30A was a culprit, but we can rule that out.
  4. It’s intermittent, so it’s likely from something that’s cycling.
  5. The batteries were fully charged – I know this from a prior check on the boat. For some reason, the charger hit the 12 hour max charge time limit, which was weird, but I had been mucking around with the settings recently, so it was likely related to that. In other words, the shore charger would only have been running float cycles – no bulk or absorb cycles.


  1. It’s the battery charger. This is my top guess since there are some weird interactions between the shore power charger and the solar charger. The shore charger will cycle on and the conditions that it cycles on in will vary due to the battery state of charge, the relays to other banks being opened or closed, and the input from the solar charger.
  2. It’s the fridge. This is my second guess – only because household appliances are often implicated in these errors. The fridge has a compressor that cycles on and off. If it is losing a very small amount of current and occasionally surging over the 50mA threshold, it could cause this.
  3. Inverter. Even though the inverter was off in all cases, it’s still in the circuit between the shore power and the boat. The inverter switches its ground depending on whether it’s passing the AC power through or creating AC power from the batteries. This seems less likely to me since it’s a brand new modern inverter, but it’s possible.
  4. Watermaker. This is the only other item that is cycling. It comes on once a week to flush the prefilters. It’s a very small draw and seems unlikely.
  5. The 24V charger. This is a separate charger that runs off AC to charge the thruster/windlass banks. There’s no reason for it to cycle on after the boat has been hooked up to shore power for a week. Unlikely.
  6. There is some kind of fault in the wiring causing a bridge between the neutral and ground. This seems unlikely as it is a new boat and the problem is so intermittant (and happens when we’re away and the boat isn’t being used). I can’t think of a reason for a wiring fault to randomly manifest like this.

Troubleshooting and next steps

Bill and Duncan are going to help. The first step is to measure the AC devices and see if any of them are leaking. Maybe more than one is and it’s the two combined that are causing this (e.g. the water maker cycles on at the same time as the fridge or battery charger). The unfortunate part is, what do we do if something is leaking? Is it worth replacing an entire fridge – especially if the replacement has the same issue? I really like the full sized fridge, and none of the other NP owners have had this issue. If it is just a leaky system we could in theory install an isolation transformer. This would prevent the shore power from tripping – which at best spoils my food in the fridge and at worse could kill my batteries if I’m away for a while. But, it also just masks a problem we probably don’t want to ignore.

I actually hope it’s a wiring issue, since that can be fixed most easily (though extremely difficult to track down). Alternately, it could be a configuration issue with the battery charger. Not at all sure, so stay tuned.

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