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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
Comments: To: Edward Maglott <emaglott@BUNCOMBE.MAIN.NC.US>
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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