First, Happy New Year to all! I had a reader query just before the holidays having to do with using a portable generator on a boat equipped with an ELCI device installed at the shore power inlet. For those not familiar with the ELCI device, check out my article in the EBT archives:
As for the type of generator we’re talking about here, it would look something like this one:
So, the query reads like this: “Please discuss how the use of a portable generator not built into the boat’s charging system but rather plugged into the AC inlet is not functional with an electrical panel having an ELCI due to the use of an isolated ground on the portable generator not having a neutral-ground bond as would be found on a marine genset at the power source on the boat.”
Basically, there are a few things that we have learned about ELCI’s in the last several years and more to the point, what things can make them trip mysteriously. In this case its kind of difficult to be absolutely positive because we don’t have a complete wiring diagram for the entire installation available, but based on some history, we can be reasonably certain the ELCI in the above case is reacting to what it sees as an “open ground” situation. This means a break in the grounding circuit between the generator and the ELCI at the shorepower inlet.
To reiterate a point I’ve made here in the past, the generators like the one shown above simply have no place on boats. They were never intended for use on boats, even though you and I have all seen vendors at boat shows hawking these generators, they are a cause for concern when people use them on their boats. In this case the tripping ELCI is a good example. Other examples have been mysteriously glowing reverse polarity lights on the AC panels when the generator is running and the constant worry over carbon monoxide poisioning from the gasoline engine these things are running with.
Blue Sea ELCI Box. Great for system retro-fit on older boats without an ELCI integrated into the main AC panel board
Without getting into the esoteria of why at this point, a brief rundown of the things we know today that can cause nuisance tripping with ELCI devices is:
“False” grounds on board, i.e. neutral wire and grounding wires connected at appliances or panel bus bars.
Swapped neutral scenarios in dual load groups.
Vessels equipped with auto-trip devices for reverse polarity.
Electronic “noise” issues from loads on the boat or dock.
VHF emissions in close proximity to the ELCI CT coils.
Green grounding conductor routed through the ELCI sensing (CT) coil.
Open in grounding circuit.
Depending in the specific ELCI, very sensitive to back feeding. They cannot be used as part of a source selector and may also be polarity sensitive.
So to answer our reader query, I’m thinking the device is sensing an open ground in this case. But, without a bit more info, I can’t be sure about back-feeding or reversed polarity issues either.
Hope this helps.