Date:         Thu, 20 Apr 2006 08:22:44 -0700
Reply-To:     John Bange <jbange@GMAIL.COM>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         John Bange <jbange@GMAIL.COM>
Subject:      Re: battery-inverter-charger-battery loop
In-Reply-To:  <6.0.3.0.0.20060419220746.04a7f0f8@buncombe.main.nc.us>
Content-Type: text/plain; charset=ISO-8859-1

>
> I plugged that into my inverter today and it said "open ground."  I opened
> the inverter, and the ground does go to the inverter case, and is not
> common with the neutral pole.  I read with a meter, and got about 40 volts
> between ground and neutral.  I did a little test of wiring the ground and
> neutral into the van's AC system and left hot disconnected.  As i
> expected,
> I was seeing that 40 volts throughout the system including the male plug
> on
> the outside of the van.


Actually, that's normal.  Since inverters are not considered "permanent"
installations, the National Electrical Code doesn't apply, but instead just
UL458. The UL regs are more relaxed and allow them to supply half the
voltage from each side ("hot" and "neutral") rather than forcing the NEC's
strict "single phase 120V hot to ground bonded neutral" rules.

I have a beefy DPDT switch I was going to use for this project, but I was
> hoping to use one pole to turn the inverter on when I switch to it.  Now
> where is that drawing board...


If you're going to leave the inverter turned on and you think people might
be fiddling with the shore power connection, yeah, I suggest switching both
poles. Anything below 50V is considered "low voltage", but it can still give
you a quite unpleasant shock. Also, if you plug in with the inverter powered
up, even if the single pole switch is thrown, you'll likely get a "ground
fault" alarm from the inverter as shore power has neutral tied to ground.

As for controlling the inverter through the switch, are you switching the
inverter power leads, or does your inverter have a remote power switching
option? If the former, that'd have to be one hefty switch...

--
John Bange
'90 Vanagon - "Geldsauger"