Date:         Sat, 11 Apr 2009 01:41:01 -0400
Reply-To:     David Beierl <dbeierl@ATTGLOBAL.NET>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         David Beierl <dbeierl@ATTGLOBAL.NET>
Subject:      Re: gfci outlet buzzes with inverter
Comments: To: pickle vanagon <greenvanagon@GMAIL.COM>
In-Reply-To:  <91c8f9760904101728s5e314101ofdedd298d493f2fb@mail.gmail.co m>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 08:28 PM 4/10/2009, pickle vanagon wrote:
>I'm concerned about whether the buzzing is something to be worried about
>otherwise.  It's faint enough that you don't really hear it unless you get
>down on all fours right next to the outlet.  But is the vibration creating
>an unsafe situation?

The maker of the GFCI should know better than we do whether that
stepped square wave is ok for his device...

...but we can say that the vibration is not going to hurt anything.

Whether the rest of the installation is safe is a different
question.  Tentatively, it sounds ok to me, *with the transfer
switch.*  Keep in mind that normally neutral and ground are tied
together somewhere nearby, which would probably destroy the inverter
if it connected to such a situation; but with the outlet isolated I
think you're all right unless you plug in a device with a hot-ground
or neutral-ground short in it, which will take down the inverter.

The inverter doesn't really have a neutral -- both terminals are hot
w/ respect to chassis ground, just like a (US) household 220 vac
circuit.  Some inverters use a dummy ground terminal on their socket(s).

Another point -- I'm quite sure I've read that modern GFCIs do not
measure current flowing in the ground leg, but instead algebraically
sum the hot and neutral legs and trip when the difference exceeds 5
ma.  Thus they don't care where the missing current is going, and can
operate fine with a two-wire hookup.


  --
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'89 Po' White Star "Scamp"