I swapped the aft ELCI breaker with a replacement sent by BlueSea. Once I got one of the senior technicians on the phone, he said I’d gone way beyond the required troubleshooting for a replacement and sent me two new units. I still would have preferred they help me troubleshoot, since it’s so unlikely that both units failed. I know it’s possible to more precisely test a breaker’s trip profile. I’d really like to understand what’s going on. But, swapping it out is the next best thing. My working theory is some kind of manufacturing defect making them sensitive to quickly changing high or low ambient temperatures. Virtually all trips have been associated with these conditions (very cold winter days or very hot summer days). While the operating range is way bigger (-35C to 60C), quickly rising or falling ambient temps are a failure mode for breakers in other applications. In other words, when the temperature drops quickly (45 in the day to 25 at night) is when they trip (that’s exactly what happened Sunday night). But, when the temperature stays steady or changes more slowly, the breaker stays closed. The 3104s are Magnetic / Hydraulic, though, which kind of blows my theory (?).

Working with AC always makes me nervous, so I took my time and locked everything down. We currently have shore power plugged into the stern, so I first took apart the forward panel (in the chain locker) to see how it was assembled and wired. After making sure I had all the tools, I replaced the aft one. The whole job took about an hour.

The forward breaker, removed from the enclosure
Took several pictures as reference for the wiring
The aft breaker
There were several smaller wires for the enclosure lights and other stuff
Instead of taking everything apart and labeling the wires, I just transferred them directly to the new breaker
New breaker, ready to go
All done

Job Notes

  • The enclosure is attached to the breaker by tiny screws running down either side of the rocker switch. The bottom two aren’t attached to anything and are held on with nuts
  • There were no torque specs for the wire nuts, but I paid attention to the feel when disassembling. Don’t overtighten.
  • There were several small wires attached to all but one terminal. Some were bundled, so I could not trace them easily. I just moved them without knowing what they are. Honestly, I don’t like missing out on an opportunity to dive deep and learn something, but sometimes you just need to swap the part and see if it helps.
  • Like a home outlet, getting everything back into the enclosure was a bit of a tight fit
  • The chain locker is a damp area. Even though the breaker is at the top under the deck, it doesn’t seem like the best place for a sensitive breaker. The enclosure door has a gasket and latches tight, so just watching for now.
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