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Date:         Thu, 20 Apr 2006 12:15:55 -0400
Reply-To:     dhaynes@OPTONLINE.NET
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dennis Haynes <dhaynes@OPTONLINE.NET>
Subject:      Re: battery-inverter-charger-battery loop
Comments: To: John Bange <jbange@GMAIL.COM>
In-Reply-To:  <6da579340604200822y4a13aad8q876b98113d8c9c0b@mail.gmail.com>
Content-type: text/plain; charset=us-ascii

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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