Date: Sat, 22 Apr 2006 10:10:46 -0400
Reply-To: Mike Collum <collum@VERIZON.NET>
Sender: Vanagon Mailing List <vanagon@gerry.vanagon.com>
From: Mike Collum <collum@VERIZON.NET>
Subject: Re: battery-inverter-charger-battery loop
In-Reply-To: <6.0.3.0.0.20060422091912.0487ee30@buncombe.main.nc.us>
Content-type: text/plain; charset=ISO-8859-1; format=flowed
Have you thought about installing a separate AC outlet or outlets just
for the inverter ... then using a manual switch for putting the fridge
on the inverter? Just a thought.
Mike
Edward Maglott wrote:
> I'll have to do a few more tests on the inverter to see how it behaves in
> various failure scenarios. I am pretty safety conscious, and this project
> is starting to raise some flags for me.
>
> I'm not sure where the voltage potential you describe would come from. The
> scenario where a failing component on the van would allow some AC current
> to leak to the chassis. How would that translate to potential to earth
> ground? Seems like the potential would be to the ground of the inverter
> directly through the chassis rather than through the high resistance route
> of wet tires to ground back to gas station pump, back up wet hose to filler
> neck.
>
> My goals for this project are to get away from having to manually
> disconnect the fridge plug under the sink to reconnect it to the inverter
> under there, and turn the inverter on. Then have to reverse that process
> later to go back to shore power. Have to remove the pots and pans and
> stuff to do that. Secondly, I'd like to have an outlet with easy access to
> occasionally plug in a cell phone charger, camera battery charger, or other
> small consumers of AC power. So maybe switching the whole AC system of the
> van from shore to inverter is not the way to go. I'm open to suggestions!
>
> Somebody asked how I was going to switch the inverter on and off. I was
> just going to put another switch in parallel with the power switch of the
> inverter. It's a low current switching situation.
>
> Edward
>
> At 12:15 PM 4/20/2006, you wrote:
>
>> However, Once you hard wire that inverter into the Vanagon, it is now a
>> permanent installation and it should meet NFPA and RVIA reqiurements
>> including being UL listed for the application. The floating potential can
>> cause all sorts of safety issues. Imagine this scenario: you are using
>> the
>> inverter to power the refrigerator while driving. The heater element is
>> starting to fail and you are getting some current leakage or voltage
>> potential to the vehicle chassis. You then pull into a gas station and it
>> is raining, wet tires. You place the filler nozzle into the van filler
>> and
>> you complete that circuit and create a spark right at the filler. If you
>> had a proper inverter, with a neutral properly wired, that ground would
>> have become a short and tripped the circuit breaker or blown a fuse or at
>> least ripped a GFCI. This is what grounded wiring systems are all about.
>> How about that same scene with the defect and you pull into a campground
>> and go to connect the water? That could be ni
>> ce shock.
>>
>> Cheap inverters are designed for appliances to be connected directly to
>> them. And those appliances should be the double insulated or isolated
>> type. Laptops, cell phone chargers, and things of that nature are fine.
>> Even TV's with some of the power supply connected to chassis ground can
>> present problems.
>> Use them as intended and avoid getting fancy unless you are ready to
>> spend
>> the money to do it right.
>>
>> Dennis
>>
>>
>> ----- Original Message -----
>> From: John Bange <jbange@GMAIL.COM>
>> Date: Thursday, April 20, 2006 11:22 am
>> Subject: Re: battery-inverter-charger-battery loop
>>
>> > >
>> > > 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
>> > "groundfault" 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
>> > switchingoption? If the former, that'd have to be one hefty switch...
>> >
>> > --
>> > John Bange
>> > '90 Vanagon - "Geldsauger"
>> >
>
>
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