HI Everyone - I have a 1980 410 Commander. We got new docks this spring. The new electrical code apparently requires a more sensitive ground-fault system and as a result the boat will pop the breakers on the dock if I plug in both 30-A cords and set the switch in the boat to "Both Inlets" I can use one cord and "Inlet 1" on the switch and that works fine (except of course I only have 30 amps to work with).. I'm told that "somewhere" the neutrals from both sides are connected. They are not supposed be. Anyone had this problem?
I found on my 410 that the FB and the rear deck outlets were wired - hot to one 30 amp feed and the neutral to the other 30 amp feed - BIG no no . I thought this was a build error on my boat, but maybe not . Any way I made mine right .
Here's an update! Inlet 1 continues to work ok. Changing the selector switch to "Both Inlets" produces good results (everything works) except: 1. Turing on the inverter 2. Turning on one of the two Air conditioner/Heat units and 3. Turning on one of the two lights in the engine room. By "turning on" I mean switching the breaker on the panel in the boat to "on"for that circuit. When these breakers are turned on both circuit breakers on the pedestal on the dock pop.
The inverter powers the refrigerator, microwave, lights and some outlets. It charges the batteries - dedicated for the inverter - and will pass thru AC to the appliances if AC is available.
I would try completely disconnecting the inverter from the 120VAC. The inverter 120VAC present sense circuit might be the problem. You might have other issues also such as the problem light in the engine room.
The AC unit that causes a trip might also have an issue with its control. Not necessarily a wiring issue but a design feature that improperly allows leakage current onto the boat ground system.
The underlying issue is that the new NEC code requirements have reduced the GFCI trip current to 30ma. A 4000 ohm resistance or impedance is enough at 120VAC to cause a trip.
Not splitting the inverter neutrals off separate from the remainder is known to trip the dock side GFIs. I had found this recommendation online and a respected marine electrician I know confirmed this is a common problem for boats with inverters installed. When I installed my inverter I was able to separate the neutrals easily by adding a third neutral bus bar to the panel.
Here is the link to the article:
Doug Maclean said:
google " marina safety upgrades " boatus Char - it would be good info for the library
Update! I am posting with all my fingers crossed hoping not to Jinx myself! I did find two circuits - the aft air-conditioner and the inverter - had the hot coming from inlet 1 and the neutral going back to inlet 2. I changed the neutrals to match the hots and it is working! Thanks you guys for your help. All suggestions got me thinking about the type of problem and led me to look at it correctly!
The GFI or GFCI trip condition is created by a difference between what goes out on the hot and what comes back on the neutral. Any deviation (30 milliamps) between the two will cause the circuit to trip on a GFI fault. GFI's will not work properly with branch circuits ie two hot legs sharing a common neutral or spliced neutrals as someone earlier found. The GFI portion doesn't even care if there is a ground wire attached to the circuit. ( YES you do need it!!!!.) GFI breakers do not trip in the GFI trip mode based on over current. That is handled within the breaker as it always has depending on the size of the breaker and the load it either holds or trips and this can be influenced by many factors, heat being one of the main culprits as more heat creates more amperage draw and can result in the same circuit with the same connected load that does not trip at night but trips in the daytime due to sun heating the shore power cords and increasing resistance.
Great explanation Kevin - thanks!