Most inverters sold now (I know, not all) are isolated from the ground, and
should NOT have one side grounded, but the new GFCIs are not dependent on
the existence of an earth ground. It is legal to install 3 pronged GFCI
receptacles in older houses without separate ground wires where I live,
because the GFCI works by detecting any difference in the current flowing in
the 2 wires. There is no separate earth ground available in that situation.
The GFCI circuits might also be affected by the harmonic content of the
"quasi" sinewave inverters, but I have not tried it. The waveform from these
inverters is a rectangle, tuned to minimise the third harmonic. Not all
loads like that sort of power, but everything I have tried so far seems to
work ok.
Steve Thomas
----- Original Message -----
From: "Syerdave--- via CnC-List" <cnc-list@cnc-list.com>
To: <cnc-list@cnc-list.com>
Cc: "syerd...@gmail.com" <syerd...@gmail.com>
Sent: Wednesday, September 23, 2015 12:17
Subject: Re: Stus-List GFCI Outlet
worked for Hubbell for 21 years.... There is no standard specifying what
constitutes marine grade, so, the difference could simply be the label.
The GFCI, despite being a safety device, is built offshore to a price,
driven that way by the residential construction market. The marine
variant might be upgraded in some basic ways (visible plating) or might
not, and this will vary by manufacturer. Years ago, manufacturers
built better stuff and did not focus so much on standardization and cost.
To be fair, most customers are not willing to pay for better, when good
enough will do.
GFCIs have provision to protect downstream devices, but they must be wired
accordingly. The GFCI first, and the downstream receptacles connected to
the purpose-specific terminals on that GFCI. Note that this means that
the cumulative ground leakage for the downstream portion are now "seen" by
the GFCI, and "nuisance tripping" could be a result.
Are you worried about safety or compliance?
I think the biggest safety issue is not in the head but somewhere else,
probably when working on the boat. (how often do you use 110v appliances
concurrent with the presence of standing water in the head? At home
sure, but in the boat? In two years I have never used the receptacle in
the head. )
IMO to do this right, install a GFCI receptacle or module as far upstream
as possible, but after the 15A branch circuit breaker (in the 33ii there
are two circuits, port and starboard, I think.) protecting as a priority
the receptacles where you are most likely to be using 120v - fans, tools.
.
One thing to check, and I don't know the answer, is whether or not you are
protected on circuits energized by an inverter. GFCIs don't or at least
didn't always work without a real ground reference. (Gensets as an
example - years ago this created a great deal of confusion WRT workplace
safety practices.)
Dave
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