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ELCI Breaker with an Inverter/Charger

 

Equipment Leakage Circuit Interrupter (ELCI) breakers are fairly new in the North American marine industry.  Older boats are not equipped with them however they are now in the ABYC standards for new boats and refits. They are similar to a GFI outlet (like in your bathroom) but they protect the whole boat and trip at a higher level, 30mA instead of 5mA. 

ELCI breakers are great for overall safety on a boat but can cause headaches with an improperly wired inverter/charger.  So if you are adding an ELCI breaker to your boat it may or may not work.

For safety reasons, a proper marine rated inverter/charger joins its ground and neutral output wire when inverting.  Normally they also have this bond with no shore input even if the inverter is off.  It removes it after you plug the boat in.

What I often see on inverter/charger installs is one common neutral bus for the whole boat.  This is not proper.  What happens when the boat is not plugged in, is the inverter connects the Neutral and ground together.  Which means anywhere on the boat, including at the shore input plug, main breaker, etc., there is a ground to neutral connection.  When the boat is plugged in this connection stays for ~10 secs as the inverter checks the power and then accepts it.  During this time, if you have an ELCI breaker, it sees this neutral to ground bond.  Every time there is a boat AC load it will see an imbalance of current, and will trip.  If nothing is turned on when plugging in, likely it won’t trip. If you wait, you can turn things on after the 10 sec period.  So you have a breaker that sometimes trips and sometimes doesn’t when you plug into shore power.  You likely won’t know why.  There are also other negative effects from this improper wiring.  When you plug in, during those 10 secs the galvanic isolator on your boat is being bypassed leading to increased galvanic corrosion.  If you turn off the inverter/charger breaker while plugged in, this G-N inverter bond happens, and your galvanic isolator is bypassed until you turn the inverter/charger breaker back on.

The proper way is a separated shore Neutral bus and inverter load bus, if you have separate neutral buses.   Only the inverter loads see this bond.  The ELCI or dock does not see it.  And it will not trip when plugged in, nor will you have a bypassed galvanic isolator from this cause.

 


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