Connecting 120V grounding to DC negative

flapbreaker":1396retl said:
Mike,

I had the wrong 30 amp adapter pictured. I've updated my original post. Here is what it looks like now. Notice that my CGFI/breaker box has a 15 amp cord and I was planning on running it to the power inlet. Then the 15amp side of the adapter plugs into the CGFI. If I understand correctly the cable from the CGFI is the unsafe part since it's only a 15 amp chord? Even though marinco makes an adapter to downgrade (maybe it doesn't do what I think it does?) the 30 amps to 15 amps? Sorry for all the pesky questions just want to make sure we understand each other.
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It could be sort of safe: it depends on what breakers are installed. Think
of it this way: what is going to happen if you plug a 16 gauge
extension cord into an outlet that has 30 amp breakers, and the cord
gets caught between the dock and your rubrail? The cord will probably
burn before the breakers will trip.

There is nothing magic about the adapters. They do not, in so far
as I know, have integral breakers, fuses or current limiting devices.
At least not the ones we're talking about here.

Mike
 
This is probably an appropiate place to mention a common problem with boat wiring systems. Mike mentioned a fire--and I don't have any idea what caused that fire. But one of the most common reasons for 110 V over heating/fires is at the plug to the boat (female cord/boat recessed male). The boat fitting often gets some salt/corrosion and increases resistance. Often the shower power is not turned off properly before this plug is disconnected--and arcing occurs. With carbon formation, detiorration of these plugs, heat builds up--and the plug plastic softens and eventually causes a short--or enough heat build up to cause a fire. Often these plugs don't have the ring which tightly holds the plug to the boat fitting, or the ring is not tight, and the fitting works, increasing the potential of arcing.

Always turn off circuits in the boat, and on the dock breaker before unplugging the cord at the boat (and at the plug). Inspect both the male and female fittings regularly to be sure that there is no carbon build up, sign of increased corrosion and resistance, or melting of the plastic.
 
I've had exactly that problem with one of my boats! Noticed the amperage and voltage meters bouncing around (surging) and traced it to that connection and a loose threaded lock ring.

Also, be sure you have the plug twisted in the lock position not the release one, or the connection will be shaky.

As a side note, I noted that with 110 volts registered on the electrical panel voltmeter, my upolstery stapler seems to work at 1/4 strength. Back at home with 125 volts, it pumps them babies in like a pneumatic tool! Amazing what the loss of 10-15 volts can do to some voltage sensitive appliances and tools.

Joe.
 
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